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Consumers who choose organic food are often willing to pay a premium, but it turns out added nutritional benefits may not be included in the hefty price tag.

A new analysis has found organic food has the same nutritional quality as crops grown under conventional methods.

"There's no evidence that organically-produced food is nutritionally superior to conventionally-produced food," said Alan Dangour, public-health nutritionist and senior lecturer in public-health nutrition at the London School of Hygiene and Tropical Medicine.

"You can buy organic for other things, but there's no evidence you should be buying it because there's enhanced nutrient content of organic food."

The analysis - funded by the Food Standards Agency of Britain and considered the largest of its kind - has sparked new controversy in the long-brewing debate over the perceived benefits of organic versus conventionally-grown food.

Proponents of organic agriculture say focusing narrowly on nutritional content overlooks the fact that organic food is produced in a way that reduces harm to the environment.

"There are lots of reasons to support organic and you don't have to go down this health road," said Laura Telford, executive director of Canadian Organic Growers, a national charitable organization that represents organic farmers, retailers and other members of the industry.

Organic food is grown without pesticides, herbicides, genetically modified organisms or other synthetic or chemical substances.

In addition, organic production focuses on promoting the health of soil, water and wildlife through a variety of measures, including the humane treatment of animals and use of high-quality compost.

In order for food to be labelled "organic" in Canada, products must be certified by an accredited certification body, according to federal rules that came into force in June.

In the new study, which will be published in the September issue of the American Journal of Clinical Nutrition, researchers conducted a comprehensive review of 55 scientific studies, known as a meta-analysis, to better understand the nutritional differences between organic and conventional food.

They concluded that levels of major nutrients, including vitamin C, magnesium, calcium, zinc and potassium, were similar in organic and non-organic crops.

But there were some differences that researchers noted. Organic crops tended to have higher phosphorous and acidity levels, while conventional crops were found to have higher amounts of nitrogen, differences researchers said could likely be attributed to variations in fertilizer use and ripeness at time of harvest.

"I think it's important for people to know what the evidence really is," Dr. Dangour said.

"They should not be buying organic food if they believe they're buying something which is nutritionally superior."

But there are many other reasons consumers should be buying organic, according to E. Ann Clark, associate professor of plant agriculture at the University of Guelph, who teaches courses in organic agriculture.

When consumers choose organic, they can be assured the products were not produced with genetically modified organisms. There will also be little or no pesticides, chemical fertilizers and other potentially harmful substances, she said.

But there may be traces of those materials, since they can linger in soil.

"When I think of all of it, organic is the way to go," Prof. Clark said. "It's just about that simple."

Ms. Telford said organic growers in Canada are careful not to make claims of the nutritional superiority of organic food. But she also said there is little high-quality scientific research that accurately examines the differences between organic and non-organic crops.

Prof. Clark said the question over nutrition in organic food should be subject to more research. She highlighted a study published last year by the U.S.-based Organic Center which found higher levels of antioxidants, vitamin C and vitamin E, as well as other nutrients.

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