Are organic foods safer and healthier than conventional alternatives? Those are two separate questions. Some consumers are interested in getting more nutrients; others are more concerned about getting fewer pesticides. Let's do nutrition first.
As seen in my video, Are Organic Foods More Nutritious?, hundreds of studies have been reviewed and researchers didn't find significant differences for most of the traditional nutrients like vitamins and minerals. They concluded that despite the widespread perception that organically produced foods are more nutritious, they didn't find robust evidence to support that perception. They did, however, find higher levels of phenolic phytonutrients in organic.
These so-called "secondary metabolites" of plants are thought to be behind many of the benefits ascribed to eating fruits and vegetables. Organic fruits and vegetables had between 19 and 69% more of a variety of these antioxidant compounds. The theory was that these phytonutrients are created by the plant for its own protection. For example, broccoli releases the bitter compounds like sulforaphane when the plant is chewed to ward off those who might eat it. Bugs take one bite and say, "Ew, this tastes like broccoli!" But pesticide-laden plants are bitten less by bugs and so may be churning out fewer of these compounds. Plants raised organically, on the other hand, are in a fight for their lives and may necessarily have to produce more protection. That was the theory anyway, but we don't have good evidence to back it up. The more likely reason has to do with the fertilizer; plants given high dose synthetic nitrogen fertilizers may divert more resources to growth rather than defense.
These antioxidants may protect the plant, but what about us? More antioxidant phytonutrients are found in organic vegetables and so yes, they displayed more antioxidant activity, but also more antimutagenic activity. Researchers exposed bacteria to a variety of mutagenic chemicals like benzopyrene, the polycyclic aromatic hydrocarbon found in barbecued meat, or IQ, the heterocyclic amine found in grilled/broiled/fried meats (as well as cigarette smoke), and there were fewer DNA mutations in the petri dishes where they added organic vegetables compared to the petri dishes where they added conventional vegetables.
Preventing DNA damage in bacteria is one thing, but what about effects on actual human cells? Organic strawberries may taste better, and have higher antioxidant activity and more phenolic phytonutrients, but what happens when you stack them up head-to-head against human cancer cells? Extracts from organically grown strawberries suppressed the growth of colon cancer cells and breast cancer cells significantly better than extracts from conventional strawberries. Now this was dripping strawberries onto cancer cells growing in a petri dish, but as I showed in Strawberries versus Esophageal Cancer, there are real life circumstances in which strawberries come into direct contact with cancerous and precancerous lesions, and so presumably organic strawberries would work even better, but they haven't yet been tested in clinical trials.
Although in vitro studies show higher antioxidant and antimutagenic activity as well as better inhibition of cancer cell proliferation, clinical studies on the impact of eating organic on human disease simply haven't been done. Based on antioxidant phytonutrient levels, organic produce may be considered 20 to 40% healthier, the equivalent of adding one or two serving's worth to a five-a-day regimen. But organic produce may be 40% more expensive, so for the same money you could just buy the extra servings worth of conventional produce. From a purely nutrients-per-dollar standpoint, it's not clear that organic foods are any better. But people often buy organic foods to avoid chemicals, not because they are more nutritious. For more on the best available science comparing the nutritional content, pesticide risk, heavy metal toxicity, and food poisoning risk of organic versus conventionally raised foods )including practical tips for making your own DIY fruit and veggie wash), see:
- Are Organic Foods Safer?
- How to Make Your Own Fruit and Vegetable Wash
- Are Organic Foods Healthier?
- Are the Benefits of Organic Food Underrated or Overrated?
I imagine that the reaction to this series will be similar to that for the one I did on GMO foods, riling up critics on both sides of the debate:
- Are GMOs Safe? The Case of Bt Corn
- Are GMOs Safe? The Case of Roundup Ready Soy
- Is Monsanto's Roundup Pesticide Glyphosate Safe?
- GMO Soy and Breast Cancer
More on the nutritional implications of stressed-out plants here:
- Is Hydroponic Basil as Healthy?
- Xenohormesis: What Doesn't Kill Plants May Make Us Stronger
- Appropriating Plant Defenses
Production method aside, in vitro, Which Fruit Fights Cancer Better?
Michael Greger, M.D.
PS: If you haven't yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:
- 2012: Uprooting the Leading Causes of Death
- 2013: More Than an Apple a Day
- 2014: From Table to Able: Combating Disabling Diseases with Food
- 2015: Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet
- 2016: How Not To Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers
Image Credit: Sally Plank / Flickr. This image has been modified.