Author: Anna DeMel‍‍‍lo, MSc. R.D.
‍‍‍Founder, Plant-Based Living Initiative

It is well recognised that different food production methods and systems might have various impacts on human health, and on the health of animals; they may also affect our environment to varying extents.

A comprehensive 2017 review, looking at the human health impacts of organic versus conventionally-produced foods, was recently published in the journal Environmental Health. This post presents a summary of its findings.‍‍‍

The authors define the 'conventional food system' as the prevailing and intensive type, 'typically with high inputs of synthetic pesticides and mineral fertilisers, and a high proportion of concentrate feed in animal production.'

On the other hand, 'organic' production is defined as that which uses farmyard and green manure as fertiliser; that relies chiefly on 'ecosystem services and non-chemical measures for pest prevention and control' and where livestock have 'access to open air and roughage feed.'

Keep up-to-date

Prospective cohort studies, on the other hand, tend to follow large numbers of people over a more extended period of time, and present ‍‍‍a great opportunity to look for health-related associations. It should be understood, though, that studies reporting on chronic disease outcomes are limited.

The 2017 NutriNet-Santé study, for instance, involved 62,000 participants and looked at the relationship between body weight and the amount of organic food being consumed: it was found that people who ate high amounts of organic foods experienced the lowest increase in body mass index (BMI) over time, and 31% reduced risk of obesity, as compared with people who ate low amounts of organic foods. Those who regularly (or even occasionally) ate organic foods were also less likely to have high blood pressure, type 2 diabetes, and, among men, cardiovascular disease; ‍‍they were, however, more likely to have reported a history of cancer than those consuming conventional foods.

You can read about this study here:

Research on the human health impacts of organic foods, versus those grown conventionally, remains quite limited, as compared with other public-health related ‍nutrition topics.

Although some recent reviews have brought together findings from clinical studies, these are few and far between; studies also tend to be short-lived and to involve small population sizes.

Examples include:

• Dangour et al., 2010: Nutrition-related health effects of organic foods: a systematic review.
• Smith-Spangler et al., 2012: Are organic foods safer or healthier than conventional alternatives?: a systematic review.
• Forman and Silverstein, 2012: Organic foods: health and environmental advantages and disadvantages.‍‍

As summarised by Smith-Spangler et al., the evidence from clinical studies points to a lack of significant differences in nutritional status (or in classic health biomarkers) between participants consuming organic vs conventionally-grown food.

January 7 2018

©  2016, Plant Based Living Initiative

One of the inherent challenges with observational studies is that those who regularly consume organic food also tend to eat better overall, choosing to eat 'more vegetables, fruit, wholegrain products and less meat'. They also tend to be more active and are less likely to smoke. These choices are also associated with lower risk of chronic illness, and of death.

If we want to better understand the relationship between organic food intake and health, we need more prospective, long-term studies that involve large numbers of participants; these must be well-designed and must adequately control for other lifestyle factors. The evidence base as it now stands certainly needs expanding and strengthening.

Another 2014 prospective cohort study involving just over 623,000 participants, who were followed-up over 9 years, looked at the risk of cancer in relation to organic food intake among UK women.

Results showed that overall risk of cancer was not associated with a person's intake of organic foods, although for one specific type of cancer (nonHodgkin lymphoma) there was found to be a significant reduction in risk (23%) among those who 'usually' or 'always' ate organic foods.

You can read about this study here‍‍‍:

When foods are produced conventionally, synthetic pesticides are often used. When food is grown organically, on the other hand,  this is not the case; instead, other techniques are commonly used, such as crop rotation, intercropping, the use of pest-resistant plant varieties, biological control with the use of natural 'enemies' of certain pests, steam treatment of cereal seeds in place of chemical treatment, and so on.

Although some 'pesticides', such as spearmint oil, quartz sand, potassium, bicarbonate, etc., are actually used in orga‍‍‍nic production, there is usually little concern in terms of toxicity to humans. This is thus a major benefit of organic food production.

In terms of implications for humans, we are almost certainly guaranteed to be exposed to fewer pesticides, and pesticide residues, if we eat organic products. Similarly, agricultural workers are less likely to be exposed to harmful levels of pesticides if they work on an organic farm.

There are, however, ways in which pesticides can end up contaminating organic products. Pesticide spray may, for instance, drift over from fields that are situated near an organic plot; there might be some contamination of organic foods during transportation or storage; there may also be mislabelling of food products themselves, or outright fraud.

A European Commission study, 2009, looked at the cumulative risk of pesticide exposure among adults consuming organic versus conventional products (based on daily intake of 500 g of fruit, vegetables and berries, and using a method known as the hazard index): it was found that toxicity exposure was, in fact, 70X lower among those consuming a diet based on organic foods.

It should be understood that, although current organic certification systems in places like the EU offer a high level of protection against pesticide exposure, there is still room for improvement.

Interestingly, occupational pesticide exposures, or exposures related to pesticide 'drift', have been linked with certain illnesses within the published research (e.g. Parkinson's, type 2 diabetes, certain cancers). It remains unclear to what extent this relates to exposures from residues within food.

What is most evident at this time is that foetal (especially during the first weeks of pregnancy) or childhood exposure, even if brief, may be particularly damaging, causing long-term impacts on growth, on brain and functional development, and on behaviour.

Unfortunately, epidemiological evidence looking at health impacts in relation to pesticide exposure is often not considered to be reliable enough for inclusion within risk assessments conducted by regulatory agencies. There are certainly major limitations to current approaches that centre around health protection of the general population. Again, larger-scale studies are needed so as to better understand health risks from dietary pesticides.

Pesticid‍‍‍es

A limited number of studies involving children have found that allergies and/or atopic illnesses such as eczema could be improved via the regular intake of organic foods. It ‍should be noted, though, that families who prefer organic foods often tend to have healthier lifestyles in general, and that various behavioural choices (such as healthier eating patterns) are likely to contribute to better outcomes for children.

Some studies that may be of interest:

Kummeling et al., 2008: Consumption of organic foods and risk of atopic disease during the first 2 years of life in the Netherlands.

Stenius et al., 2011: Lifestyle factors and sensitization in children - the ALADDIN birth cohort.

Fagerstedt et al., 2016: Anthroposophic lifestyle is associated with a lower incidence of food allergen sensitization in early childhood.

Health Effects of Pesticide Exposure

Although pesticide regulation may be rigorous in some countries or regions, it may still be difficult to know, with certainty, the level of risk that is associated with, for instance, mixed exposures; this is particularly concerning when it comes to cancer-promoting effects, and those related to endocrine disruption and neurotoxicity. At times, there are information gaps, mainly related to what the effects may be of exposure over the long-term, that are quite troubling.

Consumer Reports has come up with an online tool (above) that depicts the risk of pesticide exposure from 48 fresh conventional fruits and vegetables, across 14 different countries. Analyzing 12 years of data, the tool places each produce-country combination into one of five risk categories. Risk assessment included the number and frequency of residues on each food item, as well as pesticide toxicity. Risk categories correlate with the number of daily servings of that food item.

The Environmental Working Group has also put together a 2017 Shopper's Guide to Pesticides in Produce, which may be easily accessed via their website. The Guide's 'Dirty Dozen' and 'Clean Fifteen' help people to decide which whole foods should best be‍‍‍ bought organically.

Plant-Based Foods

There are just a few systematic reviews to date that report on plant chemical and nutrient makeup in relation to the production method used (i.e. conventional vs organic):

Smith‍‍‍-Spangler et al., 2012: Are organic foods safer or healthier than conventional alternatives?

Dangour et al., 2009: Nutritional quality of organic foods: a systematic review.

Barański et al., 2014: Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses.

These reports reach a similar conclusion, in general, when it comes to macronutrient (i.e. carbohydrate, protein, fat), vitamin, and mineral concentrations within food crops:

...concentrations are either not at all or only slightly affected by the production system.

Vitamin C has received the most attention here, with studies reporting small (positive) effects on food content with organic production.

Makeup of Foods

Animal-Based Foods

By regulation, herbivores in organic production (e.g. cows and sheep) receive at least 60% of their feed as roughage, which may be fresh, dried, or silage. Omnivores in organic production (e.g. pigs, chickens) also receive roughage as part of their feed, and poultry must have access to pasture.

Antibiotics and Resistant Bacteria

Omega-3 Fatty Acids

Most of the research to date around organic production is focussed on the quantity of omega-3 (a type of poly-unsaturated fat) within the animal food product.

The omega-3 content of the animal feed itself is known to determine the omega-3 content of the meat, milk, or egg that is eventually produced. Grass and red clover are common roughage feeds, and contain between 30%-50% omega-3; these are common in organic systems; on the other hand, concentrate feed cereals, soy, corn, and palm kernel cake (typical of conventional production systems) all contain below 10% omega-3 (as a percentage of the total amount of fatty acid).

A recent meta-analysis reported that omega-3 content was ~50% higher in organic vs conventional milk. Another recent meta-analysis considered 67 original studies on meat composition (mainly beef, chicken, lamb, and pork), and found that the content of omega-3 PUFA was significantly higher (47%) in organic vs conventional meats, although reliability of the results is said to be relatively low due to large variations between studies.

Antibiotics are commonly used in conventional animal agriculture (think factory farming) for various reasons. Stressful living conditions (due to restricted space and little exposure to the outdoors, etc.) are known to contribute to a greater likelihood of disease amongst the animals themselves. Aside from this, antibiotics are also used prophylactically, to try and prevent illness and keep production levels as high as possible; they may also be used before transportation, after surgeries, when there are potential disease outbreaks, and so on.

It should be understood that the exact same antibiotics may be used in organic livestock rearing as in conventional rearing, but that the conditions under which these may be used are often quite different.

Organic animal farming is supposed to strive for 'low use' (i.e. only when absolutely necessary), although the definition of this may vary; under EU regulations, for instance, products that were treated with antibiotics more than three times during 12 months, or more than once if their productive lifecycle is less than 1 year, cannot be sold as organic.

Documentation of these practices in some jurisdictions, however, is known to be severely lacking. Nevertheless, studies from Denmark and the Netherlands have shown that antibiotic application is significantly higher in conventional as compared to organic animal production: among dairy cattle, ‍‍‍50% and 300% higher, respectively. A study from Sweden, on the other hand, found no significant differences. It may be worth noting that the general use of antibiotics in agriculture is known to vary greatly by country: New Zealand is known to be among those 'lower level' users, while the USA, Spain, Italy, Germany, Portugal, Belgium, Poland, and Cyprus are among 'higher level' users.

Human Health Impacts‍‍‍

Polyphenols (a type of antioxidant, or phytonutrient) may help to prevent common chronic diseases like cancer, cardiovascular disease, and neurodegeneration. Their concentrations within plant foods can be impacted by various things, such as light, temperature, water and nutrient availability. Meta-analyses thus far have reported modest effects ‍‍of organic production on total plant content of polyphenols (an increase o‍‍‍f 14 – 26%).

Toxic Metals

'Cadmium (Cd) is known to be toxic to the kidneys, may demineralise bone, and is carcinogenic.' Fertiliser usage and low soil organic matter (typical of more conventional farming practices) are known to be associated with greater amounts ending up in crops. Some studies, however, have found no differences in terms of crop content, while others have: Barański et al. report significantly higher concentrations (30%) in conventional vs organic cereal crops. ‍

For other toxic metals, including lead, mercury and arsenic, no concentration differences have been reported in comparing conventional and organic crops.

Fungal toxins: one meta-analysis has reported less fungal contamination of organic cereal crops.

There are known to be important differences between organic and conventional animal rearing in terms of antibiotic usage: organic farming is, generally, known to restrict antibiotic use, while conventional livestock rearing generally uses copious amounts of antibiotic‍‍‍s.

This antibiotic overload is a leading contributor to the development of so-called 'super bugs', or bacteria that develop resistance to certain antibiotics.

The implications for human health are already being felt around the globe, as we too may acquire infections that are difficult to treat. According to the WHO, 'antibiotic resistance is one of the biggest threats to global health, food security, and development today.'

Resistant bacteria have, encouragingly, been shown to be less common among organic pork as compared to conventional pork grown in F‍‍‍rance, Italy, Denmark, and Sweden; similar results have been found for organic chicken. Similarly, it has been shown that, when farms have been altered to meet organic standards, the prevalence of antibiotic-resistant Salmonella bacteria decreases.

Nonetheless, bacteria that are resistant to certain antibiotics can be transferred to humans through animal-based foods like meat, poultry, chicken, eggs, and dairy products. A recent report by the European Food Safety Authority has found that 'in both humans and animals, positive associations between consumption of antimicrobials and the corresponding resistance in bacteria were observed for most of the combinations investigated'.

Aside from transmission between animals and humans, through either food or direct contact, resistant bacterial strains and resistant genes can also enter our environment. The global situation is now extreme: 50 – 80% of all antibiotics are estimated to be used for livestock production. The cost of this problem falls heavily on the shoulders of populations around the world, and something certainly needs to change. Making the change to organic production globally would represent only a marginal part of the solution...

Diet choices and the associated‍‍‍ food production methods have important impacts on environmental sustainability [254].

Consumption patterns of consumers preferring organic food [16, 18, 19, 37, 47] seem to align well with sustainable diets [2]. These consumption patterns show some similarities with the Mediterranean Diet [262–265] and with the New Nordic Diet[266–269], with lower dietary footprints in regard to land use, energy and water consumption, and greenhouse gas emissions compared to concurrent average diets.

Further evaluation is needed to assess the extent to which organic food systems can serve as example of a sustainable food systems

What Should I Take Away F‍‍‍rom This?‍‍‍

Among the general population, the main source of exposure to pesticide residues is food itself, as demonstrated by studies tracking the excretion of pesticides in people's urine. Fruit and vegetable intake is known to be positively correlated with pesticide excretion and, as expected, excretion is considerably reduced with the frequent or exclusive consumption of organic plant foods.

It should be understood that there are considerable overall benefits to health from the intake of fruits, vegetables, and other whole plant foods. People should certainly not be deterred from eating these types of foods. There are, for instance, online resources that can certainly help people to make more informed decisions about whether or not an organic product choi‍‍‍ce is best.