This doesn’t make organic food a cancer cure-all. Other lifestyle factors – like eating lots of plant foods, having a healthy body weight, getting regular physical activity and adequate rest, not smoking and keeping alcohol intake low – probably have a greater bearing on your cancer risk than whether you eat organic food.
But if you are eating as if your life depended on it – and there are many in the cancer community who are – then organics should be part of the picture.
The study in question, a meta-analysis of 237 research papers conducted by a group of Stanford researchers and published this week in the Annals of Internal Medicine, concluded tersely that “(t)he published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods. Consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.”
This prompted many mainstream media outlets to conclude that organic food is largely a marketing gimmick and a waste of money. The New York Times headline read: "Stanford Scientists Cast Doubt on Advantages of Organic Meat and Produce," while CBS news opined: "Organic food hardly healthier, study suggests."
Granted, for a perfectly healthy person already eating a very healthy diet, organic food may offer only marginal benefit. But let’s look at the study’s assertions in the context of cancer protection:
The Stanford group’s first finding was that organically grown fruits and vegetables don’t consistently contain more vitamins and minerals than non-organically grown equivalents.
This finding is at odds with the conclusion of a comprehensive meta-analysis published last year comparing organic and non-organic foods. Essentially covering the same literature as the Stanford team but using different and more rigorous selection criteria, these Newcastle University researchers found that organically-grown produce has on average 12% higher nutrient levels than its chemically grown counterparts, particularly in the form of antioxidant molecules that plants develop to protect themselves from pests, and which boost human health through various mechanisms.
In an in-depth critique of the Stanford study, Charles Benbrook, research professor at Washington State University, says the Stanford team does not define what it means by a food being “significantly more nutritious” than another food. As he sees it, such a food would need to deliver at least 50% higher levels of several important nutrients per calorie or serving.
“But a food does not need to be 50% more nutrient dense to deliver important health-promoting benefits,” he argues. “Achieving even a 10% increase in the levels of key nutrients in commonly consumed foods would bring about tangible health benefits across the U.S. population.”
Next, the Stanford team reports that pesticide residues, while higher in conventional than in organically grown produce, are largely below safety limits set by the U.S. government. That’s OK then, right? Well, not really.
For one, who’s to say that those “safe” amounts of pesticides really are innocuous? Do safety limits take account of “cocktails” of several pesticides and their possible synergistic effects? (While the EPA regulates pesticide residues on an individual basis, they have not been tested in combination, even though conventional farmers routinely use a wide range of products at different times of the growing cycle.)
Putting aside whether pesticide “safety limits” are really safe, organic produce contains significantly lower residues than chemically grown produce. The Stanford researchers found a 30% "risk difference" between organic and conventional food. To the casual reader this sounds like organic foods carries a relatively unimpressive 30% lower risk of exposing you to pesticides – right?
Wrong, says Charles Benbrook. To arrive at the 30% number, the Stanford team used a statistical method that understates the true risk differential, he says. Crunching the authors’ raw numbers, Benbrook finds "an overall 81% lower risk or incidence of one or more pesticide residues in the organic samples compared to the conventional samples."
Moreover, he adds: “People should be concerned about pesticide health risk, not just the number of residues they are exposed to.” Benbrook notes "a 94% reduction in health risk" from pesticides when eating organic foods. This health risk is important during stages of life when humans are particularly vulnerable to the adverse effects of pesticides and animal drugs, for instance before and during pregnancy, through the first years of a child’s life, when battling a degenerative disease and after 60, Benbrook highlights. These individuals may be constrained in their ability to break down and clear pesticides from their bodies and/or deal with the toxic insult caused by the residues, he says.
In the cancer context, some pesticides and drugs used to treat farm animals have hormone-like effects (see, for example, reports here and here) that may imbalance natural hormone levels and increase the risk of certain types of cancer, such as breast or prostate cancers.
Meanwhile, in comparing organically reared chicken and pork, the Stanford team found no differences in the incidence Escheria coli bacteria contamination between organically and non-organically-reared anmials. However, conventional meat was found to have a 33% higher risk for contamination with bacteria resistant to three or more antibiotics than organic products.
I assume that’s because organically-reared animals aren’t allowed to be treated with antibiotics in the first place; nor can they be given synthetic growth hormones, genetically engineered ingredients or anything else to enhance their growth. This is a grave omission: by focusing on bacterial contamination, the study fails to take into account a wide range of other factors that can make animal foods healthy or unhealthy.
Another flaw of the Stanford study is that it includes no long-term investigations of people consuming organic compared to chemically grown food. The studies included ranged from two days to two years. In fact, only 17 of the 237 studies examined by the researchers involved humans at all (the rest examined the nutrient profiles and pesticide levels of various foods). And of those 17, only three involved human health outcomes (eczema, wheezing and atopy), none of them directly related to cancer.
Since cancer can take years – indeed decades – to show up, it is impossible to extrapolate from this study (or any existing study, for that matter) what the consumption of organic or non-organic foods means for our cancer risk; reliable answers can only come from long-term, large-scale population studies.
To anyone unwilling to wait 20 years for such studies to be published, here’s my two cents’ worth.
As even the Stanford paper concedes, organic produce contains more phenols – natural plant chemicals – and a more favorable omega-6-to-3 ratio of essential fatty acids, nutritional factors that are widely thought to lower our cancer risk. It also reveals that organic produce contains fewer pesticide residues. And even though conventional pesticide residues are deemed “safe,” in people whose bodies’ detoxification capacity is impaired by cancer and its treatments, even “safe” levels of pesticides may be too much. As far as I'm converned, the fewer the better.
Most of the people I know who are affected by cancer – cancer patients, survivors or their families and friends – are highly motivated individuals who are willing to do what they can to tip the odds in their favor. Rather than wait for irrefutable proof – which rarely emerges in any area of scientific enquiry – they prefer to adopt the precautionary principle: avoiding a potentially unhealthy food until it is proven harmless.
In my next blog post I’ll talk about ways to eat clean, healthy food – organic and non-organic – without breaking the bank.
This article was first published on September 7, 2012 at PsychologyToday.com.
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