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Organic nutritional advantages questioned again

By Laura Crowley , 22-Jul-2008
Last updated the 22-Jul-2008 at 13:32 GMT

A debate has ignited over the nutritional benefits of organic produce compared to conventional, with recent analysis disputing claims of its nutritional superiority.

In a report published in March, the Organic Center at America’s Organic Trade Association argued that organic produce is 25 per cent more nutritious than conventional foodstuffs.

However, these claims were unfounded, according to Joseph Rosen, emeritus professor at Rutgers University and scientific advisor to the American Council on Science and Health (ACSH) in his report “Claims of Organic Food’s Nutritional Superiority: A Critical Review”, published yesterday by ACSH.

He criticised the methodology and said the information was carefully selected to support arguments for the nutritional benefits of organic produce. When recalculating the data used in the original report, Rosen concluded that conventional products are actually 2 per cent more nutritious than organic varieties.

The two takes on the data add to the ongoing questions on whether organic produce, which is becoming increasingly popular among consumers, has nutritional benefits.

Amarjit Sahota, director for the UK’s Organic Monitor, said a key component driving this growth is the assumption that organic food is healthier, especially for fresh fruit and vegetables, which make up between 60 and 70 per cent of organic sales.

“Seven or eight years ago, there was much speculation on the benefits of organic produce, but a real lack of any substantial research,” he said.

“But over the last few years, more and more research has shown that there are more vitamins and nutrients in organic food than in conventional food. And there is far more research coming out with this conclusion than vice versa.”

The organic market has been experiencing considerable growth in recent years, as consumers have become ever more aware of the effects diet can have on their health and are turning away from produce grown using pesticides.

The UK Soil Association, also advocates of organic food, expects a healthy 10 per cent growth for sales of organic products this year, which it says if four to five times higher than sales growth for the general food market in a good year.

Differences between reports

The Organic Center’s review, “New Evidence Confirms the Nutritional Superiority of Plant-Based Organic Foods”, looked at peer-reviewed scientific studies published since 1980 comparing nutrient levels in organic and conventional foods.

It identified 236 organic and conventional foodstuffs that were equally measured on nutrient content, and found that in 61 per cent of the cases, the organic versions were more nutritionally dense.

Furthermore, the organic samples contained higher concentrations of important polyphenols and antioxidants in about three-quarters of the 59 matched pairs representing the four phytonutrients.

And, in general, the report said: “Across all 236 matched pairs and 11 nutrients, the nutritional premium of the organic food average 25 per cent.”

However, in yesterday’s report, Rosen wrote that the methodology of the study was flawed as “results that were not statistically significant were used throughout, non peer-reviewed papers were included and much relevant data… not included”.

Examples of Rosen’s criticism include the fact that Organic Center’s report claimed organically grown vegetables had more quercetrin than conventional varieties. Rosen said the organic ones studied had been sprayed with an organic pesticide that would have increased the plant’s production of the nutrient.

Additionally, one study looking at the nutrient content from an analysis of kiwi fruits included the skin, which most consumers do not eat, as well as the pulp.

Previous studies

These conflicting views echo similar scientific debates raging over the advantages of organic over conventional.

For example, a US study published last July in the Journal of Agricultural and Food Chemistry concluded that organically-grown tomatoes contain higher levels of beneficial flavanoids than conventional ones.

The researchers said that organic tomatoes contained on average 79 and 97 per cent more quercetin and kaempferol aglycones than conventionally grown tomatoes.

Meanwhile, a review from the British Nutrition Foundation last June said that the overall body of science does not support the view that organic food is more nutritious than conventionally grown food.

"Organic farming represents a sustainable method of agriculture that avoids the use of artificial fertilisers and pesticides and makes use of crop rotation and good animal husbandry to control pests and diseases," wrote BNF’s Claire Williamson.

"From a nutritional perspective, there is currently not enough evidence to recommend organic foods over conventionally produced foods.”

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