30 April 2002

Otago Researchers Find No Conclusive Evidence That Organic Produce More Nutritious

Claims that organically produced food has superior nutritional benefits do not appear to be supported by the available evidence, according to a recent University of Otago study which is the first critical review of research comparing organic and conventional foods to be published by a leading international science journal.

Otago's Department of Food Science was commissioned by The New Zealand Institute of Crop & Food Research to undertake an independent review of the nutritive, sensory and food safety qualities of organic and conventionally produced foods. Principal researcher Dr Diane Bourn and co-author Associate Professor John Prescott, published their findings in a recent edition of Critical Reviews in Food Science and Nutrition.

The paper is expected to be of wide international interest to consumers, industry and policymakers interested in organic food production systems, says Dr Bourn.

"From our review of about 100 studies, it is evident that there are few well controlled studies which allow us to make valid comparisons. A substantial research effort into the nutritional value of organically versus conventionally produced foods is needed to back-up claims of any significant benefits in these areas," says Dr Bourn.

"We found no strong evidence that organic and conventional foods differ in concentrations of various nutrients, with the possible exception of nitrate content, which may be lower in some organic crops" she says. And no evidence was found that certified organic foods might be more susceptible to microbiological contamination.

"We also reviewed studies investigating taste and found no convincing evidence of any differences between conventional and organic produce. However studies have not clearly considered factors such as variety, time of harvest, distribution, and storage conditions," she says.

But taste and nutritional value were not the only reasons why people chose organic over conventional food. Other reasons included "no or lower pesticide residues in organic food and environmental benefits such as reducing fertiliser run-off", she says.

Organics is a very fast-growing industry both here and overseas, and consumers deserve to have the "best information possible" to base their decisions on, she says.

"The studies we've looked at were generally poorly designed and did not control for a large range of factors that could influence nutritional value. Pursuing research that goes beyond investigating basic nutrient levels is more difficult, but is an essential component in the evaluation of organic production systems," she says.

"It's possible that the non-use of pesticides in organic food production may lead to higher levels of compounds that help to naturally protect plants against pests and diseases. Some of these may help protect against illnesses like heart disease and cancer. This is an area where much more research needs to be been carried out," she says.

ENDS