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Doing farming the organic way - Back to the roots

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Harinath Kasiganesan's TEDx talk is a collective of ideas about organic farming beginning from what the concept is and further details about how it works, the scientific explanations of the betterment it leads to, to a self help guide of setting up a small farm through household kitchen waste and natural material.

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Food Safety: Antimicrobial resistance in the food chain

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Food Safety: Antimicrobial resistance in the food chain

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November 2017

How does the use of antibiotics in food-producing animals lead to antimicrobial resistance in humans?

The high volume of antibiotics in food-producing animals contributes to the development of antimicrobial-resistant bacteria, particularly in settings of intensive animal production. In some countries, the total amount of antibiotics used in animals is 4 times larger than the amount used in humans. In many countries much of the antibiotics used in animals are for growth promotion and prevention of disease, not to treat sick animals.

These bacteria can be transmitted from animals to humans via direct contact between animals and humans, or through the food chain and the environment. Antimicrobial-resistant infections in humans can cause longer illnesses, increased frequency of hospitalization, and treatment failures that can result in death. Some types of bacteria that cause serious infections in humans have already developed resistance to most or all of the available treatments and we are running out of treatment options for some types of infection. WHO recommends an overall reduction in use of antibiotics in food-producing animals to help preserve their effectiveness for human medicine.

Why is antimicrobial resistance important for food safety?

Many of the bacteria (such as Salmonella, Campylobacter and Escherichia coli) carried by animals can also cause disease in people. These bacteria, which are frequently antimicrobial-resistant, can contaminate our food supply from farm to fork, such as through slaughtering and processing. Fruits and vegetables may also be contaminated by such bacteria at the farm or later through cross-contamination. We know about this because we can link drug-resistant bacteria isolated from sick people to an agricultural source through DNA fingerprinting.

Over 400 000 people die each year from foodborne diseases, with over one-third of these deaths occurring in children under 5 years of age. The vast majority of foodborne illnesses are caused by microbes, including bacteria, according to WHO estimates . If these bacteria become resistant to antibiotics, it will become impossible to treat them and more people will die from foodborne diseases.

Why is WHO providing advice to the agriculture sector?

WHO is providing advice to the agriculture sector because the most effective way to prevent the transmission of antimicrobial-resistant bacteria from food-producing animals to humans is by preventing the emergence and dissemination of antimicrobial-resistant bacteria in food-producing animals. WHO's mandate is to build a better, healthier future for people all over the world. This includes protecting people from health threats due to antimicrobial-resistant infections and unsafe food.

Antimicrobial resistance is a major threat to human health. Optimizing the use of antibiotics in both human medicine and animal husbandry will help slow down its emergence and spread. These WHO guidelines were developed to reduce this important public health threat to preserve the effectiveness of antibiotics important for human health. The recommendations are based on WHO's list of critically important antimicrobials for human medicine, with the goal to safeguard all, especially critically important antibiotics. to treat multi-drug resistant infections in humans.

Who are the important actors that can help implement the recommendations in the Guidelines?

These guidelines are relevant to every country, regardless of region, income and setting. The primary audience of these guidelines is policy makers and regulatory officials overseeing the use of antibiotics in food-producing animals. In addition, veterinarians, food animal organizations, food producers, pharmaceutical companies, animal health and public health officials, physicians and other health providers all have a role to play. Consumers also have a strong influence on the way foods are produced and are driving the market for meat produced without routine use of antibiotics in some countries. For example, Namibia has developed a strong export market for its beef since it introduced a ban on the use of antibiotics for growth promotion.

Do the Guidelines call for a total ban of the preventive use of antibiotics in animals?

Recommendation No.3 of the new guidelines says that antibiotics should not be used as a preventive tool in the absence of disease in animals. The use of antimicrobials for disease prevention may be justified when a veterinary professional judges that there is a high risk of spread of a particular infectious disease, if such a judgement is made on the basis of recent culture and sensitivity testing results.

The antimicrobials used should start with those of least importance for human health, i.e. start with classes not used in humans, and then as listed on the WHO List of critically important antimicrobials for human medicine (important and then highly important). Antimicrobials classified by WHO as critically important for human medicine should be used in animals only when the most recent culture and sensitivity results of bacteria known to have caused the disease indicate that the critically important antimicrobial is the only option.

The WHO guidelines address the use of antibiotics used in human medicine. Antibiotics that are used only in animals are outside the scope of the guidelines. All possible means, such as improved hygiene and vaccination, should be taken to reduce the risks of food producing animals contracting infections and therefore reduce the need for antibiotics.

How were FAO and OIE involved in the development of the guidelines?

The Food and Agriculture Organization of the United Nations (FAO), the World Organisation for Animal Health (OIE) and WHO have a long history of collaboration to address health threats at the human-animal-ecosystems interface. A number of expert meetings have been held jointly or in partnership with these agencies since 1997 to address antimicrobial resistance in the food chain, providing a basis for the development of the WHO guidelines. WHO appreciates the important roles played by FAO and OIE in the development of these guidelines.

Recent reviews and data on antibiotic resistance in agriculture provided by FAO and OIE were used by the Guideline Development Group, which was responsible for assessing the evidence and for formulating the recommendations, and are quoted throughout the guidelines. Representatives from FAO and OIE were appointed as special members of the WHO Steering Group and were invited to attend the meetings of the Guideline Development Group as observers and they provided input to the draft guidelines. FAO and OIE were also invited to nominate members of the External Review Group, which provided comments on the draft final guidelines

Why are some of the recommendation made with "low quality evidence"?

WHO's guideline development process uses the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach for assessment of the quality of the scientific evidence upon which the recommendations are based. The GRADE approach is designed to assess the effectiveness of specific interventions, such as a new treatment for a disease. It rates evidence derived from randomized controlled trials as "high quality", while evidence from epidemiological studies, surveillance programmes and other sources of observational data, in which unknown confounders cannot be adequately controlled for, is rated initially as "low quality", which can be upgraded according to specific criteria.

In common with many important public health issues, due to ethical and technical complexity, there are very few randomized controlled studies that have assessed associations between use of antibiotics in food-producing animals and risks of human exposure to and infection by drug-resistant zoonotic pathogens. Most of the supporting scientific evidence - the best available - was collected from epidemiological studies, surveillance programmes and observational studies.

In addition to the quality of the evidence and the balance of benefits and harms of an intervention, a number of other factors are considered when Guideline Development Groups formulate recommendations. These factors include the relative value placed on the potential beneficial and harmful outcomes of an intervention, the acceptability and feasibility of the intervention, resource considerations, and effects on equity across subpopulations. A "strong recommendation" means that after taking all relevant considerations into account, the Guideline Development Group is reasonably certain that the desirable consequences (benefits) of an intervention outweigh the undesirable consequences (risks or harms), such that the intervention should be implemented in most contexts.

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Antimicrobial resistance in the food chain

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The high volume of antibiotics in food-producing animals contributes to the development of antimicrobial-resistant bacteria, particularly in settings of intensive animal production. In some countries, the total amount of antibiotics used in animals is 4 times larger than the amount used in humans.

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Higher antioxidants, lower pesticide residues

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Higher antioxidants, lower pesticide residues

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British Journal of Nutrition

Cited by 202

This article has been cited by the following publications. This list is generated based on data provided by CrossRef.

McCarty, Mark F. and DiNicolantonio, James J. 2014. Are organically grown foods safer and more healthful than conventionally grown foods?. British Journal of Nutrition, Vol. 112, Issue. 10, p. 1589.

Mulet, José M. 2014. Should we recommend organic crop foods on the basis of health benefits? Letter to the editor regarding the article by Barański et al.. British Journal of Nutrition, Vol. 112, Issue. 10, p. 1745.

Shiva, Vandana 2014. Biofortification, Genetic Engineering and Corporate Interests: False solutions to malnutrition. Development, Vol. 57, Issue. 2, p. 268.

Hoffman, Richard and Gerber, Mariette 2015. Food Processing and the Mediterranean Diet. Nutrients, Vol. 7, Issue. 9, p. 7925.

Vecchione, Melissa Feldman, Charles and Wunderlich, Shahla 2015. Consumer knowledge and attitudes about genetically modified food products and labelling policy. International Journal of Food Sciences and Nutrition, Vol. 66, Issue. 3, p. 329.

Baudry, Julia Méjean, Caroline Allès, Benjamin Péneau, Sandrine Touvier, Mathilde Hercberg, Serge Lairon, Denis Galan, Pilar and Kesse-Guyot, Emmanuelle 2015. Contribution of Organic Food to the Diet in a Large Sample of French Adults (the NutriNet-Santé Cohort Study). Nutrients, Vol. 7, Issue. 10, p. 8615.

Hemmerling, Sarah Hamm, Ulrich and Spiller, Achim 2015. Consumption behaviour regarding organic food from a marketing perspective-a literature review. Organic Agriculture, Vol. 5, Issue. 4, p. 277.

Karak, Tanmoy Sonar, Indira Nath, Jyoti Rani Paul, Ranjit Kumar Das, Sampa Boruah, Romesh Kumar Dutta, Amrit Kumar and Das, Kuntal 2015. Struvite for composting of agricultural wastes with termite mound: Utilizing the unutilized. Bioresource Technology, Vol. 187, Issue. , p. 49.

Jones, Andrew D. Fink Shapiro, Lilly and Wilson, Mark L. 2015. Assessing the Potential and Limitations of Leveraging Food Sovereignty to Improve Human Health. Frontiers in Public Health, Vol. 3, Issue. ,

Camargo Abdalla, Fábio da Costa Domingues, Caio Eduardo and Allodi, Silvana 2015. Hepato-Nephrocitic System: A Novel Model of Biomarkers for Analysis of the Ecology of Stress in Environmental Biomonitoring. PLOS ONE, Vol. 10, Issue. 7, p. e0132349.

McCaffrey, Sara Jane and Kurland, Nancy B. 2015. Does "Local" Mean Ethical? The U.S. "Buy Local" Movement and CSR in SMEs. Organization & Environment, Vol. 28, Issue. 3, p. 286.

Bach, Vibe Kidmose, Ulla Kristensen, Hanne L. and Edelenbos, Merete 2015. Eating Quality of Carrots (Daucus carota L.) Grown in One Conventional and Three Organic Cropping Systems over Three Years. Journal of Agricultural and Food Chemistry, Vol. 63, Issue. 44, p. 9803.

Sörqvist, Patrik Haga, Andreas Langeborg, Linda Holmgren, Mattias Wallinder, Maria Nöstl, Anatole Seager, Paul B. and Marsh, John E. 2015. The green halo: Mechanisms and limits of the eco-label effect. Food Quality and Preference, Vol. 43, Issue. , p. 1.

Aleixandre, José Luis Aleixandre-Tudó, José Luis Bolaños-Pizarro, Máxima and Aleixandre-Benavent, Rafael 2015. Mapping the scientific research in organic farming: a bibliometric review. Scientometrics, Vol. 105, Issue. 1, p. 295.

Jimenez, Brígida Sánchez-Ortiz, Araceli Lorenzo, María Luisa and Rivas, Ana 2015. Effect of Agronomical Practices on the Nutritional Quality of Virgin Olive Oil at Different Ripening Stages. Journal of the American Oil Chemists' Society, Vol. 92, Issue. 10, p. 1491.

Vania, Andrea Alleva, Renata and Bernasconi, Sergio 2015. Is organic diet really necessary for children?. Italian Journal of Pediatrics, Vol. 41, Issue. S2,

Baudry, Julia Méjean, Caroline Péneau, Sandrine Galan, Pilar Hercberg, Serge Lairon, Denis and Kesse-Guyot, Emmanuelle 2015. Health and dietary traits of organic food consumers: results from the NutriNet-Santé study. British Journal of Nutrition, Vol. 114, Issue. 12, p. 2064.

Aleixandre, José Luis Aleixandre-Tudó, José Luis Bolaños-Pizarro, Máxima and Aleixandre-Benavent, Rafael 2015. Mapping the scientific research in organic farming: a bibliometric review. Scientometrics, Vol. 105, Issue. 1, p. 295.

Schwingshackl, Lukas Hoffmann, Georg Kalle-Uhlmann, Tamara Arregui, Maria Buijsse, Brian Boeing, Heiner and Triche, Elizabeth W 2015. Fruit and Vegetable Consumption and Changes in Anthropometric Variables in Adult Populations: A Systematic Review and Meta-Analysis of Prospective Cohort Studies. PLOS ONE, Vol. 10, Issue. 10, p. e0140846.

Sørensen, Nina N Lassen, Anne D Løje, Hanne and Tetens, Inge 2015. The Danish Organic Action Plan 2020: assessment method and baseline status of organic procurement in public kitchens. Public Health Nutrition, Vol. 18, Issue. 13, p. 2350.

Abstract

Demand for organic foods is partially driven by consumers' perceptions that they are more nutritious. However, scientific opinion is divided on whether there are significant nutritional differences between organic and non-organic foods, and two recent reviews have concluded that there are no differences. In the present study, we carried out meta-analyses based on 343 peer-reviewed publications that indicate statistically significant and meaningful differences in composition between organic and non-organic crops/crop-based foods. Most importantly, the concentrations of a range of antioxidants such as polyphenolics were found to be substantially higher in organic crops/crop-based foods, with those of phenolic acids, flavanones, stilbenes, flavones, flavonols and anthocyanins being an estimated 19 (95 % CI 5, 33) %, 69 (95 % CI 13, 125) %, 28 (95 % CI 12, 44) %, 26 (95 % CI 3, 48) %, 50 (95 % CI 28, 72) % and 51 (95 % CI 17, 86) % higher, respectively. Many of these compounds have previously been linked to a reduced risk of chronic diseases, including CVD and neurodegenerative diseases and certain cancers, in dietary intervention and epidemiological studies. Additionally, the frequency of occurrence of pesticide residues was found to be four times higher in conventional crops, which also contained significantly higher concentrations of the toxic metal Cd. Significant differences were also detected for some other (e.g. minerals and vitamins) compounds. There is evidence that higher antioxidant concentrations and lower Cd concentrations are linked to specific agronomic practices (e.g. non-use of mineral N and P fertilisers, respectively) prescribed in organic farming systems. In conclusion, organic crops, on average, have higher concentrations of antioxidants, lower concentrations of Cd and a lower incidence of pesticide residues than the non-organic comparators across regions and production seasons.

Cited by 202

This article has been cited by the following publications. This list is generated based on data provided by CrossRef.

McCarty, Mark F. and DiNicolantonio, James J. 2014. Are organically grown foods safer and more healthful than conventionally grown foods?. British Journal of Nutrition, Vol. 112, Issue. 10, p. 1589.

Mulet, José M. 2014. Should we recommend organic crop foods on the basis of health benefits? Letter to the editor regarding the article by Barański et al.. British Journal of Nutrition, Vol. 112, Issue. 10, p. 1745.

Shiva, Vandana 2014. Biofortification, Genetic Engineering and Corporate Interests: False solutions to malnutrition. Development, Vol. 57, Issue. 2, p. 268.

Hoffman, Richard and Gerber, Mariette 2015. Food Processing and the Mediterranean Diet. Nutrients, Vol. 7, Issue. 9, p. 7925.

Vecchione, Melissa Feldman, Charles and Wunderlich, Shahla 2015. Consumer knowledge and attitudes about genetically modified food products and labelling policy. International Journal of Food Sciences and Nutrition, Vol. 66, Issue. 3, p. 329.

Baudry, Julia Méjean, Caroline Allès, Benjamin Péneau, Sandrine Touvier, Mathilde Hercberg, Serge Lairon, Denis Galan, Pilar and Kesse-Guyot, Emmanuelle 2015. Contribution of Organic Food to the Diet in a Large Sample of French Adults (the NutriNet-Santé Cohort Study). Nutrients, Vol. 7, Issue. 10, p. 8615.

Hemmerling, Sarah Hamm, Ulrich and Spiller, Achim 2015. Consumption behaviour regarding organic food from a marketing perspective-a literature review. Organic Agriculture, Vol. 5, Issue. 4, p. 277.

Karak, Tanmoy Sonar, Indira Nath, Jyoti Rani Paul, Ranjit Kumar Das, Sampa Boruah, Romesh Kumar Dutta, Amrit Kumar and Das, Kuntal 2015. Struvite for composting of agricultural wastes with termite mound: Utilizing the unutilized. Bioresource Technology, Vol. 187, Issue. , p. 49.

Jones, Andrew D. Fink Shapiro, Lilly and Wilson, Mark L. 2015. Assessing the Potential and Limitations of Leveraging Food Sovereignty to Improve Human Health. Frontiers in Public Health, Vol. 3, Issue. ,

Camargo Abdalla, Fábio da Costa Domingues, Caio Eduardo and Allodi, Silvana 2015. Hepato-Nephrocitic System: A Novel Model of Biomarkers for Analysis of the Ecology of Stress in Environmental Biomonitoring. PLOS ONE, Vol. 10, Issue. 7, p. e0132349.

McCaffrey, Sara Jane and Kurland, Nancy B. 2015. Does "Local" Mean Ethical? The U.S. "Buy Local" Movement and CSR in SMEs. Organization & Environment, Vol. 28, Issue. 3, p. 286.

Bach, Vibe Kidmose, Ulla Kristensen, Hanne L. and Edelenbos, Merete 2015. Eating Quality of Carrots (Daucus carota L.) Grown in One Conventional and Three Organic Cropping Systems over Three Years. Journal of Agricultural and Food Chemistry, Vol. 63, Issue. 44, p. 9803.

Sörqvist, Patrik Haga, Andreas Langeborg, Linda Holmgren, Mattias Wallinder, Maria Nöstl, Anatole Seager, Paul B. and Marsh, John E. 2015. The green halo: Mechanisms and limits of the eco-label effect. Food Quality and Preference, Vol. 43, Issue. , p. 1.

Aleixandre, José Luis Aleixandre-Tudó, José Luis Bolaños-Pizarro, Máxima and Aleixandre-Benavent, Rafael 2015. Mapping the scientific research in organic farming: a bibliometric review. Scientometrics, Vol. 105, Issue. 1, p. 295.

Jimenez, Brígida Sánchez-Ortiz, Araceli Lorenzo, María Luisa and Rivas, Ana 2015. Effect of Agronomical Practices on the Nutritional Quality of Virgin Olive Oil at Different Ripening Stages. Journal of the American Oil Chemists' Society, Vol. 92, Issue. 10, p. 1491.

Vania, Andrea Alleva, Renata and Bernasconi, Sergio 2015. Is organic diet really necessary for children?. Italian Journal of Pediatrics, Vol. 41, Issue. S2,

Baudry, Julia Méjean, Caroline Péneau, Sandrine Galan, Pilar Hercberg, Serge Lairon, Denis and Kesse-Guyot, Emmanuelle 2015. Health and dietary traits of organic food consumers: results from the NutriNet-Santé study. British Journal of Nutrition, Vol. 114, Issue. 12, p. 2064.

Aleixandre, José Luis Aleixandre-Tudó, José Luis Bolaños-Pizarro, Máxima and Aleixandre-Benavent, Rafael 2015. Mapping the scientific research in organic farming: a bibliometric review. Scientometrics, Vol. 105, Issue. 1, p. 295.

Schwingshackl, Lukas Hoffmann, Georg Kalle-Uhlmann, Tamara Arregui, Maria Buijsse, Brian Boeing, Heiner and Triche, Elizabeth W 2015. Fruit and Vegetable Consumption and Changes in Anthropometric Variables in Adult Populations: A Systematic Review and Meta-Analysis of Prospective Cohort Studies. PLOS ONE, Vol. 10, Issue. 10, p. e0140846.

Sørensen, Nina N Lassen, Anne D Løje, Hanne and Tetens, Inge 2015. The Danish Organic Action Plan 2020: assessment method and baseline status of organic procurement in public kitchens. Public Health Nutrition, Vol. 18, Issue. 13, p. 2350.

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Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses | British Journal of Nutrition | Cambridge Core

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Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses - Volume 112 Issue 5 - Marcin Barański, Dominika Średnicka-Tober, Nikolaos Volakakis, Chris Seal, Roy Sanderson, Gavin B.

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doi: 10.1002/tox.22573. Online ahead of print.

Affiliations

¹ Murtha Cancer Center, Walter Reed National Military Medical Center, Bethesda, Maryland.

² Department of Pharmacology and Toxicology, State University of New York at Buffalo, Buffalo, New York.

³ Clinical Breast Care Project, Windber Research Institute, Windber, Pennsylvania.

⁴ E-squared Genomic Solutions, Johnstown, Pennsylvania.

Show details

doi: 10.1002/tox.22573. Online ahead of print.

Affiliations

¹ Murtha Cancer Center, Walter Reed National Military Medical Center, Bethesda, Maryland.

² Department of Pharmacology and Toxicology, State University of New York at Buffalo, Buffalo, New York.

³ Clinical Breast Care Project, Windber Research Institute, Windber, Pennsylvania.

⁴ E-squared Genomic Solutions, Johnstown, Pennsylvania.

Abstract

Agricultural pesticides are abundant environmental contaminants worldwide, prompting interest in studying their possible detrimental health effects. We examined organochlorine residues by quadrant (n = 245) in breast adipose tissues from 51 women with various stages of breast health to determine patterns of bioaccumulation within the breast and to assess relationships with patient clinical characteristics. Three organochlorine residues-2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), hexachlorobenzene (HCB), and mirex-assayed by high resolution gas chromatography were abundant in breast tissue. p,p'-DDE (745 ± 1054 ng/g lipid) was the most prevalent residue, comprising 97.5% of the total chemical burden. Mean levels of p,p'-DDE and HCB were significantly correlated (P < .001) with patient age at mastectomy, and levels of p,p'-DDE were correlated (P < .05) with BMI. Pesticide concentrations did not differ significantly by breast quadrant and were not different in the quadrant(s) where the primary tumor was located compared to other cancer-free quadrants. In invasive cancer patients, organochlorine levels differed significantly based on clinical characteristics of the primary carcinoma, including stage, grade, ER status, and HER2 status, indicating that body burden of organochlorines may influence the development of specific subtypes of breast cancer. Potentially carcinogenic organochlorines were present at high levels within the human breast warranting further research to determine the impact of organochlorines in the etiology of breast cancer.

Keywords: breast cancer; breast stroma; environmental pollutants; organochlorines; pesticides.

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national center for biotechnology information

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Organochlorine pesticide residues in human breast tissue and their relationships with clinical and pathological characteristics of breast cancer - PubMed

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Agricultural pesticides are abundant environmental contaminants worldwide, prompting interest in studying their possible detrimental health effects. We examined organochlorine residues by quadrant (n = 245) in breast adipose tissues from 51 women with various stages of breast health to determine pat ...

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Food production methods are not always easy to classify. This complexity stems from not only the number and varying forms of conventional and organic agricultural systems but also resulting from the overlap of these systems. In this paper, we use the term "conventional agriculture" as the predominant type of intensive agriculture in the European Union (EU), typically with high inputs of synthetic pesticides and mineral fertilisers, and a high proportion of conventionally-produced concentrate feed in animal production. Conversely, "organic agriculture" is in accordance with EU regulations or similar standards for organic production, comprising the use of organic fertilisers such as farmyard and green manure, a predominant reliance on ecosystem services and non-chemical measures for pest prevention and control and livestock access to open air and roughage feed.

In 2015, over 50.9 million hectares, in 179 countries around the world, were cultivated organically, including areas in conversion [ 4]. The area under organic management (fully converted and in-conversion) has increased during the last decades in the European Union, where binding standards for organic production have been developed [ 5, 6]. In the 28 countries forming the EU today, the fraction of organically cultivated land of total agricultural area has been steadily increasing over the last three decades. 0.1%, 0.6%, 3.6%, and 6.2% of agricultural land were organic in 1985, 1995, 2005, and 2015, respectively, equalling 11.2 million ha in 2015 [ 7, 8, 9]. In 7 EU Member States, at least 10% of the agricultural land is organic [ 7]. In 2003, 125,000 farms in the EU were active in organic agriculture, a number that increased to 185,000 in 2013 [ 10]. Between 2006 and 2015, the organic retail market has grown by 107% in the EU, to €27.1 billion [ 7].

This review details the science on the effects of organic food and organic food production on human health and includes

1. (1)
studies that directly address such effects in epidemiological studies and clinical trials.

2. (2)
animal and in vitro studies that evaluate biological effects of organic compared to conventional feed and food.

Focusing on narrower aspects of production, we then discuss the impact of the production system on

1. (3)
plant protection, pesticide exposure, and effects of pesticides on human health,

2. (4)
plant nutrition, the composition of crops and the relevance for human health,

3. (5)
animal feeding regimens, effects on the composition of animal foods and the relevance for human health.

4. (6)
animal health and well-being, the use of antibiotics in animal production, its role in the development of antibiotic resistance, and consequences of antibiotic resistance for public health.

In the discussion, we widen the perspective from production system to food system and sustainable diets and address the interplay of agricultural production system and individual food choices. The consequences of these aspects on public health are briefly discussed.

Due to a limited evidence base, minimal importance, lack of a plausible link between production system and health, or due to lack of relevance in the European Union, we do not or only briefly touch upon

1. (1)
singular food safety events such as outbreaks of diseases that are not clearly caused by the production system (hygiene regulations for plant production and for animal slaughtering and processing are for the most part identical for organic and conventional agriculture) or fraudulent introduction of contaminated feed into the feed market

2. (2)
historic events and historic sources of exposure, such as the BSE crisis caused by the now-banned practice of feeding cattle with meat and bone meal from cattle, or continuing effects of the historic use of DDT, now banned in all agricultural contexts globally

3. (3)
contaminants from food packaging

4. (4)
aspects of food processing, such as food additives

5. (5)
the presence of mycotoxins in consequence of post-harvest storage and processing which is governed chiefly by moisture and temperature in storage

6. (6)
the use of growth hormones in animal production, which is not permitted in the EU but in several other countries

The literature search for this review was carried out at first using the PubMed and Web of Science databases, while applying "organic food" or "organic agriculture" along with the most relevant keywords, through to the end of 2016 (more recent references were included, when relevant, although they were not identified through the systematic search). We made use of existing systematic reviews and meta-analyses when possible. In some cases, where scientific literature is scarce, we included grey literature e.g. from authorities and intergovernmental organisations. We also considered references cited in the sources located.

Association between organic food consumption and health: Findings from human studies

A growing literature is aiming at characterizing individual lifestyles, motivations and dietary patterns in regard to organic food consumption, which is generally defined from responses obtained from food frequency questionnaires [ 15, 16, 17, 18, 19, 20, 21, 22, 23]. Still, current research on the role of organic food consumption in human health is scarce, as compared to other nutritional epidemiology topics. In particular, long-term interventional studies aiming to identify potential links between organic food consumption and health are lacking, mainly due to high costs. Prospective cohort studies constitute a feasible way of examining such relationships, although compliance assessment is challenging. Considering a lack of biomarkers of exposure, the evaluation of the exposure, i.e. organic food consumption, will necessarily be based on self-reported data that may be prone to measurement error.

In the MOBA birth cohort study of 28,000 mothers and their offspring, women reporting a frequent consumption of organic vegetables during pregnancy exhibited a reduction in risk of pre-eclampsia [ 29] (OR = 0.79, 95% CI 0.62 to 0.99). No significant association was observed for overall organic food consumption, or five other food groups, and pre-eclampsia.

The first prospective study investigating weight change over time according to the level of organic food consumption included 62,000 participants of the NutriNet-Santé study. BMI increase over time was lower among high consumers of organic food compared to low consumers (mean difference as % of baseline BMI = − 0.16, 95% Confidence Interval (CI): −0.32; −0.01). A 31% (95% CI: 18%; 42%) reduction in risk of obesity was observed among high consumers of organic food compared to low consumers. Two separate strategies were chosen to properly adjust for confounders [ 46]. This paper thus confirms earlier cross-sectional analyses from the same study [ 18].

In regard to chronic diseases, the number of studies is limited. In the Nutrinet-Santé study, organic food consumers (occasional and regular), as compared to non-consumers, exhibited a lower incidence of hypertension, type 2 diabetes, hypercholesterolemia (in both males and females), and cardiovascular disease (in men) [ 47] but more frequently declared a history of cancer. Inherent to cross-sectional studies, reverse causation cannot be excluded; for example, a cancer diagnosis by itself may lead to positive dietary changes [ 48].

Only one prospective cohort study conducted in adults addressed the effect of organic food consumption on cancer incidence. Among 623,080 middle-aged UK women, the association between organic food consumption and the risk of cancer was estimated during a follow-up period of 9.3 y. Participants reported their organic food consumption through a frequency question as never, sometimes, or usually/always. The overall risk of cancer was not associated with organic food consumption, but a significant reduction in risk of non-Hodgkin lymphoma was observed in participants who usually/always consume organic food compared to people who never consume organic food (RR = 0.79, 95% CI: 0.65; 0.96) [ 37].

In conclusion, the link between organic food consumption and health remains insufficiently documented in epidemiological studies. Thus, well-designed studies characterized by prospective design, long-term duration and sufficient sample size permitting high statistical power are needed. These must include detailed and accurate data especially for exposure assessment concerning dietary consumption and sources (i.e. conventional or organic).

Experimental in vitro and animal studies

In vitro studies

The focus on single plant components in the comparison of crops from organic and conventional production, as discussed further below, disregards the fact that compounds in food do not exist and act separately, but in their natural context [ 49]. In vitro studies of effects of entire foods in biological systems such as cell lines can therefore potentially point at effects that cannot be predicted from chemical analyses of foods, although a limitation is that most cells in humans are not in direct contact with food or food extracts.

Two studies have investigated the effect of organic and conventional crop cultivation on cancer cell lines, both using crops produced under well-documented agricultural practices and with several agricultural and biological replicates. In the first study extracts from organically grown strawberries exhibited stronger antiproliferative activity against one colon and one breast cancer cell line, compared to the conventionally produced strawberries [ 50]. In the second study [ 51] the extracts of organic naturally fermented beetroot juices induced lower levels of early apoptosis and higher levels of late apoptosis and necrosis in a gastric cancer cell line, compared to the conventional extracts. Both studies thus demonstrated notable differences in the biological activity of organic vs. conventionally produced crop extracts in vitro, which should inspire further research. However, neither of these studies allows for the distinction of a selective antiproliferative effect on cancer cells, and general cell toxicity. Therefore it cannot be determined which of the organic or conventional food extracts, if any, had the preferable biological activity in terms of human health.

Animal studies of health effects

Considering the difficulties of performing long-term dietary intervention studies in humans, animal studies offer some potential of studying long-term health effects of foods in vivo. However, extrapolation of the results from animal studies to humans is not straight-forward. Studies in this field started almost 100 years ago. A review of a large number of studies [ 52] concluded that positive effects of organic feed on animal health are possible, but further research is necessary to confirm these findings. Here we focus on the main health aspects.

In one carefully conducted crop production experiment, followed by a rat feeding trial, the production system had an apparent effect on plasma-IgG concentrations but not on other markers of nutritional or immune status [ 56]. A two-generational rat study based on feed grown in a factorial design (fertilisation x plant protection) of organic and conventional practices revealed that the production system had an effect on several physiological, endocrine and immune parameters in the offspring [ 57]. Most of the effects identified were related to the fertilisation regimen. None of these studies found that any of the feed production systems was more supportive of animal health.

Collectively, in vitro and animal studies have demonstrated that the crop production system does have an impact on certain aspects of cell life, the immune system, and overall growth and development. However, the direct relevance of these findings for human health is unclear. On the other hand, these studies may provide plausibility to potential effects of conventional and organic foods on human health. Still, most of the outcomes observed in animal studies have not been examined in humans so far.

Pesticides

Plant protection in organic and conventional agriculture

Plant protection in conventional agriculture is largely dependent on the use of synthetic pesticides. Conversely, organic farming generally relies on prevention and biological means for plant protection, such as crop rotation, intercropping, resistant varieties, biological control employing natural enemies, hygiene practices and other measures [ 61, 62, 63, 64]. Yet, certain pesticides are approved for use in organic agriculture. In the EU, pesticides (in this context, more specifically chemical plant-protection products; micro- and macrobiological agents are excluded from this discussion due to their low relevance for human health) are approved after an extensive evaluation, including a range of toxicological tests in animal studies [ 65]. Acceptable residue concentrations in food are calculated from the same documentation and from the expected concentrations in accordance with approved uses of the pesticides. Currently, 385 substances are authorised as pesticides in the EU (Table 1). Of these, 26 are also approved for use in organic agriculture [ 6, 66] as evaluated in accordance with the same legal framework.

Table 1 Active substances approved in the EU and important toxicological properties according to risk assessments by EFSA. Data compiled from the EU pesticides database [66] and from Commission Regulation 889/2008 (consolidated version 2016-11-07) Annex II Sections 1-3 [6]

Most of the pesticides approved for organic agriculture are of comparatively low toxicological concern for consumers because they are not associated with any identified toxicity (e.g. spearmint oil, quartz sand), because they are part of a normal diet or constitute human nutrients (e.g. iron, potassium bicarbonate, rapeseed oil) or because they are approved for use in insect traps only and therefore have a negligible risk of entering the food chain (i.e. the synthetic pyrethroids lambda-cyhalothrin and deltamethrin, and pheromones). Two notable exceptions are the pyrethrins and copper. Pyrethrins, a plant extract from Chrysanthemum cinerariaefolium, share the same mechanism of action as the synthetic pyrethroid insecticides, but are less stable. Copper is an essential nutrient for plants, animals and humans, although toxic at high intakes and of ecotoxicological concern due to toxicity to aquatic organisms.

Plant protection practices developed in and for organic agriculture may be of benefit to the entire agricultural system [ 67, 68, 69, 70]. This is of specific value for the transition towards sustainable use of pesticides in the EU, which has a strong emphasis on non-chemical plant protection measures including prevention and biological agents [ 63, 64]. Further, steam treatment of cereal seeds for the prevention of fungal diseases ( http://thermoseed.se/) has been developed driven by the needs of organic agriculture as an alternative to chemical seed treatments [ 71, 72]. These methods are now also being marketed for conventional agriculture, specifically for integrated pest management (IPM) [ 73].

Pesticide use - Exposure of consumers and producers

One main advantage of organic food production is the restricted use of synthetic pesticides [ 5, 6], which leads to low residue levels in foods and thus lower pesticide exposure for consumers. It also reduces the occupational exposure of farm workers to pesticides and drift exposures of rural populations. On average over the last three available years, EFSA reports pesticide residues below Maximum Residue Levels (MRL) in 43.7% of all and 13.8% of organic food samples. MRLs reflect the approved use of a pesticide rather than the toxicological relevance of the residue. There are no separate MRLs for organic products. A total of 2.8% of all and 0.9% of organic samples exceeded the MRL, which may be due to high residue levels or due to low levels but unapproved use of a particular pesticide on a particular crop [ 74, 75, 76]. Of higher toxicological relevance are risk assessments, i.e. expected exposure in relation to toxicological reference values. On average 1.5% of the samples were calculated to exceed the acute reference dose (ARfD) for any of the considered dietary scenarios, with the organophosphate chlorpyrifos accounting for approximately half of these cases and azole fungicides (imazalil, prochloraz, and thiabendazole) for approximately 15%. None (0%) of the organic samples exceeded the ARfD [ 74]. Residues of more than one pesticide were found in approximately 25% of the samples but calculations of cumulative risks were not included in the reports [ 74, 75, 76].

The general population's exposure to several pesticides can be measured by analysing blood and urine samples, as is routinely done in the US [ 80] although not yet in Europe. However, a few scattered European studies from France [ 81, 82, 83], Germany [ 84], the Netherlands [ 85], Spain [ 86], Belgium [ 87], Poland [ 88] and Denmark [ 89] have shown that EU citizens are commonly exposed to organophosphate and pyrethroid insecticides. A general observation has been higher urinary concentrations of pesticide metabolites in children compared to adults, most likely reflecting children's higher food intake in relation to body weight and maybe also more exposure-prone behaviours. The urinary concentrations of generic metabolites of organophosphates (dialkyl phosphates, DAPs) and pyrethroids (3-phenoxybenzoic acid, 3-PBA) found in most of the European studies were similar to or higher than in the US studies. Although urinary metabolite concentration might overestimate the exposure to the parent compounds, due to ingestion of preformed metabolites in food items, several studies have reported associations between urinary metabolite concentrations and neurobehavioral deficits as described below. Besides, the metabolites are not always less toxic than the parent compounds [ 90].

For the general population, pesticide residues in food constitute the main source of exposure for the general population. This has been illustrated in intervention studies where the urinary excretion of pesticides was markedly reduced after 1 week of limiting consumption to organic food [ 91, 92, 93]. Similar conclusions emerged from studies investigating associations between urinary concentrations of pesticides and questionnaire information on food intake, frequency of different foodstuffs and organic food choices. Thus a high intake of fruit and vegetables is positively correlated with pesticide excretion [ 94], and frequent consumption of organic produce is associated with lower urinary pesticide concentration [ 95].

Pesticide exposure and health effects

The regulatory risk assessment of pesticides currently practised in the EU is comprehensive, as a large number of toxicological effects are addressed in animal and other experimental studies. Nonetheless, there are concerns that this risk assessment is inadequate at addressing mixed exposures, specifically for carcinogenic effects [ 96] as well as endocrine-disrupting effects [ 97, 98] and neurotoxicity [ 99]. Furthermore, there are concerns that test protocols lag behind independent science [ 100], studies from independent science are not fully considered [ 101] and data gaps are accepted too readily [ 102]. These concerns primarily relate to effects of chronic exposure and to chronic effects of acute exposure, which are generally more difficult to discover than acute effects. Most studies rely on urinary excretion of pesticide metabolites and a common assumption is that the subjects were exposed to the parent chemicals, rather than the metabolites.

In order to assess the potential health risk for consumers associated with exposure to dietary pesticides, reliance on epidemiological studies of sensitive health outcomes and their links to exposure measures is needed. Such studies are complicated both by difficult exposure assessment and the necessary long-term follow-up. The main focus so far has been on cognitive deficits in children in relation to their mother's exposure level to organophosphate insecticides during pregnancy. This line of research is highly appropriate given the known neurotoxicity of many pesticides in laboratory animal models [ 99] and the substantial vulnerability of the human brain during early development [ 119].

Most of the human studies have been carried out in the US and have focused on assessing brain functions in children in relation to prenatal organophosphate exposure. In a longitudinal birth cohort study among farmworkers in California (the CHAMACOS cohort), maternal urinary concentrations of organophosphate metabolites in pregnancy were associated with abnormal reflexes in neonates [ 120], adverse mental development at 2 years of age [ 121], attention problems at three and a half and 5 years [ 122], and poorer intellectual development at 7 years [ 123]. In accordance with this, a birth cohort study from New York reported impaired cognitive development at ages 12 and 24 months and 6 - 9 years related to maternal urine concentrations of organophosphates in pregnancy [ 124]. In another New York inner-city birth cohort, the concentration of the organophosphate chlorpyrifos in umbilical cord blood was associated with delayed psychomotor and mental development in children in the first 7 years of life [ 125], poorer working memory and full-scale IQ at 7 years of age [ 126], structural changes, including decreased cortical thickness, in the brain of the children at school age [ 127], and mild to moderate tremor in the arms at 11 years of age [ 128]. Based on these and similar studies, chlorpyrifos has recently been categorised as a human developmental neurotoxicant [ 129]. Recent reviews of neurodevelopmental effects of organophosphate insecticides in humans conclude that exposure during pregnancy - at levels commonly found in the general population - likely have negative effects on children's neurodevelopment [ 130, 131, 132]. In agreement with this conclusion, organophosphate pesticides considered to cause endocrine disruption contribute the largest annual health cost within the EU due to human exposures to such compounds, and these costs are primarily due to neurodevelopmental toxicity, as discussed below.

So far only few prospective studies from the EU addressing associations between urinary levels of pesticides and neurodevelopment in children from the general population have been published. Three studies are based on the PELAGIE cohort in France and present results for organophosphates and pyrethroids respectively [ 81, 82, 137]. While no adverse effects on cognitive function in six-year-old children were related to maternal urine concentrations of organophosphates during pregnancy, the concentration of pyrethroid metabolites was associated with internalising difficulties in the children at 6 years of age. Also, the children's own urinary concentrations of pyrethroid metabolites were related to decrements in verbal and memory functions and externalising difficulties and abnormal social behaviour. While this sole European study did not corroborate US birth cohort studies results showing that exposure during pregnancy to organophosphate insecticides at levels found in the general population may harm brain development in the foetus, the exposure levels measured in the PELAGIE cohort were considerably lower for both organophosphates and pyrethroids than those measured in other European studies as well as in studies from the US and Canada. For example, the median urine concentration of organophosphate metabolites in pregnant women in the PELAGIE cohort was 2 - 6 times lower than for pregnant women in other studies [ 85, 122, 138] and the concentration of the common pyrethroid metabolite 3-PBA was only detectable in urine samples from 30% of the women compared to 80-90% in other studies [ 88, 139]. Thus, to supplement the French study and the previously mentioned Danish study of greenhouse worker's children, additional studies that include more representative exposure levels for EU citizens are desirable.

Although exposure levels found in European countries are generally similar to or slightly higher than concentrations found in the US studies, the risk of adverse effects on neurodevelopment in European populations needs to be further characterised. The organophosphate insecticides contributing to the exposure might differ between the US and the EU, also in regard to oral and respiratory intakes. According to the European Food Safety Agency (EFSA), of all the organophosphate insecticides, chlorpyrifos most often exceeds the toxicological reference value (ARfD) [ 74]. A recent report utilised US data on adverse effects on children's IQ levels at school age to calculate the approximate costs of organophosphate exposure in the EU. The total number of IQ points lost due to these pesticides was estimated to be 13 million per year, representing a value of about € 125 billion [ 140], i.e. about 1% of the EU's gross domestic product. Although there is some uncertainty associated with this calculation, it most likely represents an underestimation, as it focused only on one group of pesticides.

Production system and composition of plant foods

In the absence of particular nutrient deficiency, focusing on single nutrients may be of limited value for evaluating the impact of a food or diet on human health [ 49]; studies of actual health effects, as discussed above, are generally more informative than studies of single nutrients.

Overall crop composition

Metabolomics [ 148, 149, 150, 151, 152], proteomics [ 153, 154] and transcriptomics [ 155, 156] studies in controlled field trials provide evidence that the production system has an overall influence on crop development, although there is no direct relevance of these studies for human health. Furthermore, the generally lower crop yield in organic systems [ 146] as such indicates an effect of management strategy on plant development.

Nitrogen and phosphorus

Existing systematic reviews have consistently found lower total nitrogen (7% [ 157], 10% [ 159]) and higher phosphorus (standardised mean difference (SMD) 0.82 [ 25], 8% [ 157]) in organic compared to conventional crops. These findings lack direct relevance for human health. However, considering the differences in fertilisation strategies discussed above, and the fundamental importance of N, P [ 160, 161, 162], and the N:P ratio [ 163] for plant development, this may lend some plausibility to other observed effects of the production system on crop composition.

Vitamins

Polyphenols

Collectively the published meta-analyses indicate a modestly higher content of phenolic compounds in organic food, but the evidence available does not constitute a sufficient basis for drawing conclusions on positive effects of organic compared to conventional plant products in regard to human health.

Cadmium and other toxic metals

A lower Cd content of organic crops is therefore plausible due to a lower Cd content in the fertilisers used in organic farming, and potentially due to higher soil organic matter in organic farmland. The general population's Cd exposure is close to, and in some cases above, the tolerable intake and therefore their exposure to Cd should be reduced. For non-smokers, food is the primary source of exposure, with cereals and vegetables being the most important contributors [ 168].

For other toxic metals including lead, mercury and arsenic, no differences in concentration in organic and conventional crops have been reported [ 25, 159]. Uranium (U) is also present as a contaminant of concern in mineral P fertilisers [ 178], but less so in organic fertilisers [ 179], and consequently manure-based cropping systems have a lower U load than mineral-fertilised systems at equal P load [ 179]. Uranium appears to accumulate in mineral-fertilised soils [ 180], and agricultural activity may increase the U content of surface and groundwater [ 181, 182]. However, no evidence was found comparing uranium contents of organic and conventional products.

Fungal toxins

Regarding fungal toxins in crops, one meta-analysis has reported a lower contamination of organic compared to conventional cereal crops with deoxynivalenol (DON), produced by certain fusarium species [ 25]. Although not fully understood, fungicide applications may alter fungal communities on cereal leaves, potentially weakening disease-suppressive species [ 183, 184]. Also, crop rotations including non-cereal crops may contribute to lower infestation with fusarium [ 185], while N availability is positively associated with cereal DON content [ 186]. These factors give plausibility to the observed lower DON contamination in organic cereals. In the EU, the mean chronic exposure of toddlers, infants and children to DON is above the tolerable daily intake (TDI), with grains and grain-based products being the main contributors to total exposure. The TDI is based on decreased body weight gain observed in mice [ 187]. The production system does not have any observed effect on the concentration of ochratoxin A (OTA), another fungal toxin of importance in cereal production [ 25].

Animal-based foods

Fatty acids

Much of the focus of existing research on compositional differences of organic and conventional animal-based foods is on the fatty acid composition, with a major interest in omega-3 FAs due to their importance for human health. Some studies also address the content of minerals and vitamins.

For cow's milk, a recent meta-analysis reports conclusively an approximately 50% higher content of total omega-3 fatty acids (as percent of total fatty acids) in organic compared to conventional milk [ 192], generally confirming earlier reviews [ 25, 189]. Also, the content of ruminant FAs (a group of natural trans FAs produced in the cow's rumen) is higher in organic milk. The content of saturated fatty acids, mono-unsaturated fatty acids and omega-6 PUFA was similar in organic and conventional milk [ 192].

Dairy products account for 4-5% of the total PUFA intake in most European populations, while meat and meat products contribute another 7-23% [ 199]. The contribution of milk fat to omega-3 PUFA intake (approximated as intake of α-linolenic acid) has been estimated at 5-16% [ 200, 201], while meat contributes with 12-17% [ 201, 202]. The effect of exchanging organic for conventional dairy products on omega-3 PUFA intake while maintaining a constant consumption has not been examined rigorously. From the intake and composition data presented here, it can be estimated that choosing organic products would increase the average dietary omega-3 PUFA intake by 2.5-8% (dairy) and by a less certain 2.5-4% (meat). A recent preliminary estimate based on FAO food supply data resulted in similar numbers [ 198]. For certain population groups and fatty acids, these numbers could be higher, and an increased omega-3 PUFA consumption is generally desirable, as some subpopulations have a lower-than-recommended intake of omega-3 PUFA [ 203]. However, overall, the effect of the animal production system on omega-3 PUFA intake is minor, and no specific health benefits can be derived. Furthermore, other dietary omega-3 PUFA sources, specifically certain plant oils and fish, are available that carry additional benefits [ 204, 205, 206]. The existence of specific health benefits of ruminant trans fatty acids (as opposed to industrial trans fatty acids) is indicated by some studies [ 207] but not strongly supported [ 208]. Taking into account the actually consumed amounts of ruminant trans fatty acids, this is likely lacking public health relevance [ 208].

Trace elements and vitamins

Feed iodine supplementation is not linked by regulation to the production system in the EU, as iodine is listed as approved feed additive, and the maximum amount of supplementation is the same for all milk production. Optimum dairy cow supplementation should be seen in relation to other national strategies for human iodine intake. This should also take into account human subpopulations with low or no intake of dairy products.

For tocopherol, selenium and iron, a higher content is generally desirable, and in the case of selenium milk is an important source. However, the concentration differences between organic and conventional milk are modest and based on a few studies only.

Antibiotic resistant bacteria

Overly prevalent prophylactic use of antibiotics in animal production is an important factor contributing to increasing human health problems due to resistant bacteria. Antibiotic use is strongly restricted in organic husbandry, which instead aims to provide good animal welfare and enough space in order to promote good animal health.

According to EU regulations, routine prophylactic medication of animals in organic production is not allowed. However, diseases should be treated immediately to avoid suffering, and the therapeutic use of antibiotics is allowed, but with longer withdrawal periods than in conventional production [ 5]. Furthermore, products from animals treated more than three times during 12 months, or, if their productive lifecycle is less than 1 year, more than once, cannot be sold as organic [ 6]. This means that therapeutically the same antibiotics used in conventional farming may be used in organic farming, but under different conditions. For example, antibiotics mainly used for sub-therapeutic treatment as prophylaxis are never considered in organic production.

While the organic regulations aim for a low use of antibiotics in livestock production, the actual use of antibiotic drugs in European organic compared to conventional animal husbandry is not comprehensively documented. Scattered studies indicate that the antibiotic use generally is substantially higher in conventional compared to organic systems, especially for pigs (approximately 5 - 15-fold higher) [ 229, 230]. In studies from Denmark [ 231] and the Netherlands [ 232], the antibiotic use in dairy cows was 50% and 300% higher in conventional compared to organic systems, although a Swedish study found no differences in disease treatment strategies between organic and conventional dairy farms, e.g. for mastitis [ 233]. While only sparingly documented (e.g. [ 234, 235]), there is only little use of antibiotics in EU organic broiler production. This is a consequence of regulations prohibiting prophylactic use and prescribing long withdrawal periods before slaughter [ 6, 236], in conjunction with the fact that it is not feasible to treat single animals in broiler flocks. In conventional broiler production, antibiotic use is common (e.g. [ 237, 238, 239]).

Previously, it has been postulated that a reduced need and use of antibiotics in organic livestock production will diminish the risk of development of antibiotic resistance [ 243], and this has also been demonstrated with regard to resistant E. coli in organic pigs compared to conventional pigs [ 244]. It has also been shown that the withdrawal of prophylactic use of antibiotics when poultry farms are converted from conventional to organic production standards leads to a decrease in the prevalence of antibiotic-resistant Salmonella [ 245].

Resistant bacteria may be transferred within the production chain from farm to fork [ 246]. It has been found that organic livestock products are less likely to harbour resistant bacteria in pork and chicken meat [ 25].

In pig production, particular attention has been paid to methicillin-resistant Staphylococcus aureus (MRSA), and in Dutch and German studies, for example, MRSA has been isolated in 30 and 55% respectively of all pigs tested [ 247, 248]. Furthermore, it has been found that healthy French pig farmers are more likely to carry MRSA than control persons [ 249] and that they carry similar strains of MRSA to those found on their pig farms [ 250]. However, the prevalence of MRSA in pig production may differ between conventional and organic farms, and in a meta-study in 400 German fattening pig herds, the odds ratio (OR) for MRSA prevalence was 0.15 (95% CI 0.04, 0.55) in organic ( n = 23) compared to conventional ( n = 373) pig farms [ 248]. Multivariate adjustment for potential risk factors rendered this association non-significant, suggesting that it was carried by other factors, including factors that are regulated in or associated with organic production, such as non-slatted floors, no use of antibiotics, and farrow-to-finish herd types. Furthermore, even if there are considerable differences in antibiotic use between countries, it has been found that antibiotic resistance is less common in organic pigs compared to conventional pigs in France, Italy, Denmark, and Sweden [ 251, 252].

Although it is rare for conventional farms to adopt knowledge about management and housing from organic production except when converting farms in line with organic standards, there may be options to improve animal health and welfare by knowledge transfer to conventional farms in order to reduce the use of antibiotics [ 253].

Within organic production, labelling requires full traceability in all steps in order to guarantee the origin of the organic products being marketed [ 5]. Application of the general principle of organic regulations about transparency throughout the food chain can be used to mitigate emerging problems of transmission of antimicrobial resistance. However, transition to organic production for the whole livestock sector would, on its own, be only part of a solution to the antibiotics resistance issue, because factors outside animal production, such as their use in humans, will be unaffected.

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Human health implications of organic food and organic agriculture: a comprehensive review

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This review summarises existing evidence on the impact of organic food on human health. It compares organic vs. conventional food production with respect to parameters important to human health and discusses the potential impact of organic management practices with an emphasis on EU conditions.