Transcript: Are Organic Foods More Nutritious?
Are organic foods safer or healthier than conventional alternatives? Two separate questions: some consumers are interested in getting more nutrients, whereas others are more concerned about getting less pesticides. Let’s do nutrition first. Hundreds of studies reviewed, and they didn’t find significant differences for most of the traditional nutrients like vitamins and minerals, and so 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.
These so-called secondary metabolites of plants are thought to be behind many of the benefits ascribed to eating fruits and vegetables. And 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 compound sulforaphane when the plant is chewed, so as to ward off those who would 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 less of these compounds, whereas plants raised organically are in a fight for their lives, and necessarily have to produce more protection. That was the theory anyway, but we don’t have good evidence to back it up. More likely it 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 found in organic vegetables, and so yes, more antioxidant activity–but also more antimutagenic activity. They exposed bacteria to a variety of mutagenic chemicals like benzopyrene, the polycyclic aromatic hydrocarbon found in barbequed 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? For example yes, organic strawberries may taste sweeter and better, and have higher antioxidant activity and more phenolic phytonutrients, but let’s 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 directly onto cancer cells growing in a lab, but as we saw, there are real life circumstances in which strawberries come into direct contact with cancerous and precancerous lesions, reversing the progression of esophageal cancer, and so presumably organic strawberries would work even better, but they weren’t tested.
So 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 servings' worth to a 5-a-day regimen. But organic produce may be 40% more expensive, so for the same money you could just buy the extra serving's worth of conventional produce. So from a purely nutrients-per-dollar standpoint, it’s not clear that organic foods are any better. But people may buy organic foods to avoid chemicals, not just because they are more nutritious–which brings us to the next question: are organic foods safer? Which I’ll address next.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
Please consider volunteering to help out on the site.