Organic foods generally deliver no more nutrients and arent even completely pesticide free. Thats the surprising conclusion of a new four-year analysis of 237 studies comparing organic versus conventionally produced foods-the largest such scientific review to date. So should consumers skip the organic section of the supermarket, where choices often cost more?
Not necessarily, says Irwin H. Rosenberg, MD, editor of the Tufts Health & Nutrition Letter. “In saying organic foods are no more nutritious, you have to consider the definition of nutrition,” Dr. Rosenberg explains. “If youre comparing nutritional advantages, its not good enough to simply measure relative nutrient content-how much vitamins and minerals.
“Nutritional advantages might also include factors such as better taste, safety and more attractive foods,” Dr. Rosenberg goes on. These factors could also encompass considerations such as pesticide contamination, the presence of antibiotic-resistant bacteria and even global environmental and sustainability issues. “I would tend to define nutrition more broadly, recognizing that nutrition is more than nutrient content.”
NUTRIENTS: NOT MUCH DIFFERENCE. In the new analysis, published in Annals of Internal Medicine, Crystal Smith-Spangler, MD, and colleagues at Stanford University crunched the numbers on four decades worth of studies of organic produce, meats and dairy products. They found no significant differences in levels of vitamins and minerals between organic and conventional produce, except for phosphorus. Organic fruits and vegetables were higher in phosphorus, a difference the scientists called not clinically significant, since most people already get plenty of dietary phosphorus. Organic produce also contained more antioxidant compounds called phenols, though that apparent difference varied widely between studies.
Although most previous individual studies have similarly concluded that organic produce is generally no higher in nutrients, a few exceptions stand out. Earlier this year, University of Barcelona researchers published findings that organic tomatoes were higher in polyphenols than those grown conventionally. In 2010, Washington State University scientists reported higher levels of vitamin C and antioxidants in organic strawberries, compared to conventionally grown fruit. Organic advocates have suggested that these growing techniques lead to more nutrients in the soil, which boost levels in the crops.
When picking fruits and vegetables, however, ripeness may be more important to nutrient content than whether you choose organic produce: Riper produce tends to be richer in nutrients.
WHAT ABOUT PESTICIDES? Dr. Smith-Spangler and colleagues did find a substantial difference in detectable pesticide residue between conventional and organic produce. While 38% of conventional produce contained traces of pesticides-almost always below government safety limits, however-only 7% of organic fruits and vegetables contained detectable pesticides. (How could organic produce, supposed to be grown without the use of pesticides, nonetheless contain these chemicals? Pesticides can drift from neighboring fields or transfer to produce during transport and processing.)
If youre concerned about pesticide contamination, going organic still makes sense. Among those most likely to be affected by pesticide residue are older adults with chronic health conditions, young children and pregnant women. When balancing pesticide worries with budget concerns, consider skipping organic produce with thick peels or rinds you wont eat, anyway-like bananas-and concentrate on fruits and vegetables at greatest risk of actual pesticide ingestion. (See box.) In any case, even the pesticide-conscious Environmental Working Group agrees, “The health benefits of a diet rich in fruits and vegetables outweigh the risks of pesticide exposure.”
BACTERIA AND HORMONES. Organic produce was no less likely than conventional choices to be contaminated by dangerous bacteria, such as E. coli, the Stanford study concluded. The same was true for organic meats. When contaminated with bacteria, however, conventional chicken and pork were at substantially higher risk of contamination with bacteria resistant to multiple antibiotics compared to organic products. But scientists noted that these bacteria wouldnt survive proper cooking.
As for dairy, some people prefer organic milk because of worries about health effects of bovine growth hormones, which conventional farms add to stimulate milk production. The US Food and Drug Administration (FDA), noting that these hormones also occur naturally in cows, maintains that use of added hormones does not affect the milk.
Organic milk is also believed to be higher in heart-healthy omega-3 fatty acids and lower in omega-6 fats, because the cows are allowed to graze and this diet affects the fats in their milk. A higher ratio of omega-3s to omega-6s may be associated with a healthier heart, and new research has even suggested a benefit against the effects of aging. The Stanford study did find that organic milk was modestly higher in omega-3s, although the sample size for this data was small.
GLOBAL CONCERNS. Why do people buy organic foods? A 2010 Nielsen survey put the belief that organic foods are healthier at the top of reasons to choose organic, cited by 76% of respondents. Other reasons included avoidance of pesticides and other contaminants (53%) and an expectation that organic foods are more nutritious (51%). Nearly half of those surveyed, 49%, also said they opt for organic foods because organic farming is better for the environment.
Even that environmental argument, however, is not as clear-cut as you might expect. The US Environmental Protection Agency (EPA) has banned many of the most toxic pesticides, limiting the health and environmental downsides of conventional growing. And earlier this year, scientists at the University of Minnesota and McGill University in Canada reported in the journal Nature that, overall, organic farming produces 25% less food per acre than conventional methods. Even though organic farming has less environmental impact per acre, that advantage may be more than offset by the greater acreage required to yield the same amount of food. Growers of organic fruits, tomatoes, oil seeds such as canola and sunflower, and legumes such as beans and peas produced as much per acre as conventional farmers, but organic grain and vegetable growers were significantly less productive.
Despite such question marks, the market share of organic foods is expected to keep growing. Already, organic fruits and vegetables account for 12% of all US produce sales, and organic dairy products total 6% of the market. Overall, the US Department of Agriculture, which certifies products as organic (see box), says organic foods make up 4.2% of retail food sales.
How much you want to contribute to that market share is as much a personal as a nutritional issue. “There are valid reasons for choosing organic foods beyond their nutrients,” says Tufts Dr. Rosenberg. “Research can help, but consumers have to make up their own minds about what to prioritize.”