Organic food and health: The evidence

by Shane Heaton DipION


First published in Positive Health Issue 75 (April '02)

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Public concern about the safety and integrity of our food has intensified in recent years and a heated debate has ensued over the merits of organic food. A comprehensive and careful review of over 400 scientific papers by the author has revealed important differences between organic and non-organic foods and supports the consumer intuition that organic food is better for you.

When the UK Food Standards Agency (FSA) stated in September 2000 that organic consumers were "not getting value for money if they thought they were getting extra safety or nutritional quality",1 they effectively issued a challenge to the organic movement to come up with the scientific evidence supporting their long-standing claims that organic food is better for you. After two years of gathering and carefully sifting through the evidence, I can report that, collectively, the available scientific evidence does in fact, support the view that organically produced foods are significantly different in terms of food safety, nutritional content and nutritional value from non-organic foods. Previous literature reviews have been unable to confirm these differences as they failed to ensure that only studies that properly compare organic and non-organic crops are included in their analyses.2-4 Without even considering the social, environmental and animal welfare benefits of organic farming, there are good reasons to eat organic food...


Fewer Pesticides

Nearly all of the 450 pesticides allowed in non-organic farming are prohibited in organic farming, and the seven that are allowed are generally used on a non- routine basis only, following authorization from the certifying body for a specific reason, and when all other pest control methods have failed. They are generally simpler substances than those used in non- organic agriculture, tending to degrade more quickly in the environment, and therefore residues are rarely found on organic food. When residues are present, they are usually of lower incidence and lower levels than residues in non-organic food, and more often than not come from environmental pollution.2,5-8


In contrast, 25 million kilograms of pesticides are applied to conventional crops each year in the UK9 and residues are found on nearly half of all fruit and vegetables tested.10 Multiple residues of up to seven different compounds are not uncommon on many foods, especially lettuces (7 different pesticides have been on single samples in the last 3 years of testing, pears (6), strawberries (5), oranges (7) and even baby foods (5 different compounds in a single jar!). We know very little about the combined toxicity of multiple compounds although some research suggests they may be hundreds of times more toxic than the same compounds individually.11


Researchers have linked symptoms such as headaches, tremor, lack of energy, depression, anxiety, poor memory, dermatitis, convulsions, nausea, indigestion and diarrhoea with pesticide levels in patients’ bloodstreams.12 Many pesticides are known or suspected hormone disrupters and the US Environmental Protection Agency ranks pesticide residues among the top three environmental cancer risks.13 While the FSA doesn’t consider pesticides to be a food safety issue,14 the British Medical Association is more concerned, stating, “Until we have a more complete understanding of pesticide toxicity, the benefit of the doubt should be awarded to protecting the environment, the worker and the consumer. This precautionary principle is necessary because the data on risk to human health from exposure to pesticides are incomplete.15 Epidemiological evidence suggests that combinations of pesticides can cause an increased incidence of birth defects in the offspring of pesticide applicators and in the local residents of areas of heavy pesticide use,16 and the respected Royal Society recently recommended that exposure of pregnant women to hormone disrupting chemicals (including pesticides) should be minimized in order to protect unborn children.17  


Dr Vyvyan Howard, foetal and infant toxico-pathologist at the University of Liverpool, has found that we each have around 500 accumulated toxic compounds in our bodies — most of them from our diet. Our grandparents didn’t have these chemicals in their bodies because most of them didn’t exist 50 years ago. "From the simple stance of hazard avoidance, organically produced food is the best option that we have.” Dr Vyvyan Howard, Toxico-Pathologist, University of Liverpool.


More Nutrients

According to official data from MAFF and the Royal Society of Chemistry, nutrient levels in fruit and vegetables are lower now than they were 60 years ago. Trace minerals in vegetables have fallen by up to 76%.18 It is worthy of note then that studies comparing the nutrient contents of organic and non-organic fruit and vegetables reveal a strong trend towards higher levels in organic produce. Of 27 studies comparing the mineral and vitamin C contents of organic and nonorganic crops, 14 showed higher levels in organic produce while just one favoured non-organic.19 Potential reasons for the difference include different varietal choices, better soil nutrient recycling (composting and crop rotation to avoid soil mineral depletion, and better encouragement of the soil micro-organisms that improve nutrient uptake by roots.20

American nutritionist Virginia Worthington statistically analysed the available data and quantified the differences.21 While the average levels of all 21 minerals compared in the scientific literature were higher on average in organic fruits, vegetables and grains, most did not attain statistical significance because of the limited numbers of comparisons available, despite the magnitudes of the differences found (see Table 1). However, there can be no dispute over vitamin C, magnesium and phosphorus, all of which, according to the available evidence are significantly higher in organic produce.


While the conventional view is that we are getting enough minerals in our diet, many health issues linked by nutritionists to multiple nutrient deficiencies are on the increase. Official data confirm that many people fail to get the recommended daily allowance for various nutrients in their diet and deficiencies are common - not low enough to cause acute deficiency diseases like scurvy and beri-beri, but low enough to cause body systems to underperform for months, years or decades until symptoms show and it may be too late to do anything about it.


Table 1. Average differences found in organic v. non-organic crops21


Calcium +26%

Chromium +86%

Copper +11%

Iodine +498%

Iron +21%

Magnesium +29%

Manganese +42%

Molybdenum +152%

Potassium +13.6%

Selenium +372%

Vitamin C +27%


The United States Department of Agriculture has estimated that considerable improvements in public health, including declines in cancer, heart disease, diabetes, arthritis, osteoporosis, allergies and infant deaths, would result from small improvements in our intake of vitamins and minerals,25 and Worthington has shown how the sometimes small differences between organic and non-organic produce can mean the difference between getting the recommended daily allowance for a nutrient or failing to.21


More Phytonutrients

Plants contain some 5-10,000 naturally occurring phytonutrient compounds26 that are often involved in the plants own immune system, protecting it from pests and disease. Because organic crops are not artificially protected with pesticides, they tend to produce more of these protective compounds. So far, significantly more lycopene has been found in organic tomatoes,27 more polyphenols in organic potatoes28 more flavanols in organic apples29 and more resveratrol in organic red wine.30 A recent review of this issue estimated that "on the basis of the currently available evidence, organically grown vegetables will tend to contain 10-50% more phytonutrients than conventionally grown.26




Fewer Food Additives

More than 500 additives are permitted for use in conventionally produced foods,31 compared with just 30 or so permitted in organic processing, and only when necessary for the production of the food in question. Additives are present in extraordinary abundance in food today and we each eat up to five kilograms of them a year. Organic standards strictly prohibit many specific additives and ingredients that have been linked with health problems, including hydrogenated fat (heart disease33), phosphoric acid (osteoporosis34), MSG (asthma, headaches35,36), aspartame (neurological disturbances37,38), and artificial flavourings and colourings (allergic reactions, hyperactivity in children31,39,40).


Less Nitrate

Nitrate is a natural constituent in plants, present at low levels in all vegetables, and while not toxic itself, in certain circumstances nitrate can be converted into potentially harmful nitrite and nitrosamines, which are known to cause cancer in animals.41,42 While levels of nitrate in drinking water must be carefully monitored and controlled, similar controls are lacking for vegetables (which contribute far more nitrate to the human diet), and artificial fertilization practices are known to result in much higher levels in vegetable crops.2 While other factors such as season and light exposure also influence the level of nitrate in crops, l4 out of 16 comparative studies found higher levels in non-organic than organic crops, and none found higher levels in organic.19


No Greater Risk of Food Poisoning

Despite recent accusations and media reports,43 there is no evidence linking organically produced foods with an increased risk of food poisoning.44 A recent Public Health Laboratory Service survey of over 3,000 samples gave organic foods a clean bill of health45 and confirmed expectations that organic methods, such as the careful composting of manure, minimize pathogenic risks. Professor Hugh Pennington, a leading UK expert on E-coli 0157, agrees that organic standards are “risk reduction measures that represent a way forward".46


Better Health Outcomes

So can organic food, with fewer toxins and more nutrients, make a difference to your health? Observations, experience and clinical evidence from organizations such as the Nutritional Cancer Therapy Trust and Foresight (the preconceptual care charity) suggest that it can, but it’s very difficult to do any controlled studies with people because of the many other confounding factors like genes and lifestyle.

"This scientific evidence supports our experience that organic food provides the nutrient content and freedom from unnatural toxins necessary for remission from cancer and continued good health." The Nutritional Cancer Therapy Trust

Interesting, then, are controlled animal feeding trials, and the evidence here is clear — animals fed organically produced feed have better health in terms of growth, reproductive health and recovery from illness than those fed on non-organic feed, including over successive generations.47,48

I believe that regulators fail to see the significance of these differences because of a fundamental failure to understand the true definition of health. They often see health as simply the absence of illness, and honestly believe that we are healthier than ever before, citing increased longevity statistics but ignoring the fact that the people living to old age now have benefited from improved disease treatments after growing up before the accelerated declines in crop nutrient contents, the proliferation of food additives, and the dramatic increase in pesticide use (3300% rise in 50 years but higher percentages of crops are lost to pests than ever before49). Also overlooked are such details as (age-adjusted) cancer incidence escalating rapidly over recent decades; allergies, headaches, fatigue and PMS all now commonplace50, infertility affecting around one in four couples (a far more relevant gauge of our current health than the longevity of people conceived before the industrialisation of food production!); and the ages of incidence of many diseases getting lower and lower. Many doctors and nutritionists believe that health is better defined as an abundance of well-being, and is hindered by both an increase in the amount of toxins we are exposed to and a decrease in the amount of nutrients in the food needed to deal with those toxins.


In my opinion, organic food offers those interested in protecting or improving their health an important haven in today’s polluted and processed world. Organic food is not a luxury. It is how food is supposed to be.

As a nutritionist, I am obliged to point out that just because food is organic doesn’t guarantee it's healthy. A diet high in refined, pre-prepared, sweet, salty, fried or junk food, whether organic or non-organic, is not a viable strategy for long-term health. As ever, balance is the key. Choosing organic food does not negate the need to eat a balanced diet, though as we have seen it can reduce your intake of toxins while increasing your intake of vitamins, minerals and antioxidants, thus contributing to your overall health.


More Research Needed

The Food Standards Agency (FSA), which currently asserts that there is no evidence of a difference between organic and non-organic produce, has pointed out that there is considerable variability in agricultural measurements caused by factors other than the method of agriculture. Of course there is — varying weather, soil, climatic and crop conditions all play a part. But the evidence to hand reveals that the average nutrient contents of organic produce are consistently higher than those in non-organic produce. The considerable variability in agricultural measurements makes it necessary to collect and consider a large amount of data in order to identify underlying patterns. We have now analysed the existing data enough. It can no longer be credibly disputed that that there are significant differences in the nutritional quality of organic and conventional produce that demand further investigation. There is an urgent need for more comparative data on the full spectrum of nutrients in organic and nonorganic produce, and an end to the meaningless claims that there is no evidence of a difference. The FSA has committed to investing in research on organic food and farming and is currently consulting with the organic movement as to the form that research should take.

In the Meantime...

·  Vote with your fork. Buy organically produced food wherever possible. Buying organic is not only beneficial to your health; it also sends a message to regulators, farmers and the government about how you would like food and farming managed.

•Write to your MP to ask them to write to the Minister for Public Health at the Department of Health. Ask them to ensure that the FSA fulfils its commitment to commission research investigating the nutritional differences between organic and non-organic food. Ring the House 0f Commons (tell: 0207 219 3000) to find our who your MP is; 

·  Support the Soil Association — the UK’s largest organic membership organization — working with farmers, manufacturers, retailers, consumers, regulators and researchers to ensure the continued success of the organic movement. Members receive the Living Earth magazine every quarter to keep up with organic campaigns. lobbying work, and the latest on environmental, food and farming issues. For more information see

·  See all the evidence for yourself. Read the complete report Organic Farming, Food Quality and Human Health,19 which includes summaries of 99 studies comparing the nutrient contents of organic and conventional foods and lists over 400 scientific references. Also highly recommended is Virginia Worthington’s review.21


“The birthright of all living things is health. This law is true for soil, plant, animal and man: the health of these four is one connected chain. Any weakness or defect in the health of any earlier link in the chain is carried on to the next and succeeding links, until it reaches the last, namely, man.

The undernourishment of the soil is at the root of all. The failure to maintain a healthy agriculture has largely cancelled out all the advantages we have gained from improvements in hygiene, in housing and medical discoveries. To retrace our steps is not really difficult once we set our minds to the problem. If we are willing to conform to natural law, we shall rapidly reap the reward not only in a flourishing agriculture, but in the immense asset of an abounding health in ourselves and in our children’s children”

Sir Albert Howerd, organic pioneer, 1945




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About the Author

Shane Heaton, DipION, is a clinical nutritionist registered with the British Association of Nutritional Therapists. His extensive research on organic food quality has led to the publication of the ground-breaking Soil Association report, Organic Farming, Food Quality and Human Health. Shane has a nutrition practice in west London and can be contacted on