Organic foods may contain additional antioxidants
As more consumers go organic, a new study has reignited the debate on the potential harms and benefits of organic foods.
Numerous studies have shown that, vitamin for vitamin, organic foods are nutritionally equal to their conventional counterparts. In clinical studies, people who eat organic foods tend not to be healthier than those who don’t. But a new analysis of data from 343 published studies reveals that compared to conventionally grown foods, organic plant-based foods may contain 20-40% more antioxidants and about 48% less cadmium, a metal. carcinogenic. The study appeared June 26 in the British Journal of Nutrition.
âThe body of evidence shows that there are higher levels of nutrients in organic foods,â says study co-author Charles Benbrook, agricultural researcher at Washington State University.
Like some previous studies that drew opposite conclusions, the new work is a meta-analysis. Such studies collect and analyze data from a collection of other studies rather than producing new data. A 2012 meta-analysis included data from 240 studies and found no nutritional benefit in organic foods over conventional foods. The authors say their new study contradicts older analyzes because it includes more data and uses a statistical method they say is better.
Experts warn that meta-analyzes can give erroneous results if they include poor-quality experiments or if they try to compare disparate data sets. The latter issue could hurt the new study, according to food and nutrition researcher Shahla Wunderlich of Montclair State University in New Jersey. The study includes analyzes of organic foods from regions of the world with varying climates, soil types, pests and farming practices. These factors influence the nutrients in foods, says Wunderlich. âRegardless of organic versus conventional, the nutritional value would be different,â she says.
Wunderlich was also concerned about a possible bias in the study: She received part of her funding from the Sheepdrove Trust, a charity that supports organic farming.
Even though the results of this latest meta-analysis are accurate, it is still unclear whether the reported differences are relevant to health. Although organic foods had lower levels of cadmium, the levels found on conventional crops were still below safe limits set by federal agencies.
And the benefits of the additional antioxidants are also unclear, says Benbrook. Researchers have long hypothesized that antioxidants such as vitamin E and beta-carotene improve heart health and fight cancer. But, the clinical studies have been largely inconclusive. The new analysis also found that organic foods contain less protein, amino acids and fiber than conventional foods.
Why organic crops contain less cadmium and more antioxidants is also a puzzle. The authors believe that organic crops can produce more antioxidants because they produce less sugar than conventional crops. Conventional crops can sometimes receive an excess of nitrogen fertilizer, which could alter the metabolism of plants to produce more sugars and fewer antioxidants. The authors also question whether the increase in antioxidants is directly caused by the reduced use of pesticides by organic farming, because plants make antioxidants as a defense against pests, and organic crops may suffer more.
“It’s certainly possible,” says plant microbiologist Gwyn Beattie of Iowa State University in Ames, and further tests may confirm the hypothesis. But she points out that plants produce defensive antioxidants even when not under attack.
For now, nutrition experts like Wunderlich say at least one thing is clear for healthy eating: the importance of eating produce. âI prefer to see people eat all kinds of foods and have lots of fruits and vegetables in their diet, whether they are organic or not,â she says.