Is Organic Food Really Healthier?

Don't ask the US federal government whether there are any health benefits to eating organic food. It won't tell. No mere coincidence, then, that no pictures of farmers or farms (or fertilizers or pesticides) appear in the USDA food pyramid logo. The federal government encourages the consumption of more fruits, vegetables, and grains, but stops short of evaluating the farming systems that produce these same foods. An apple is an apple regardless of how it has been grown, the USDA food pyramid suggests, and the only take-home message is that we should all be eating more apples and less added sugars and fats.

But this message may be too simplistic. Over the past decade, scientists have begun conducting sophisticated comparisons of foods grown in organic and conventional farming systems. They're finding that not all apples (or tomatoes, kiwis, or milk) are equal, especially when in comes to nutrient and pesticide levels. How farmers grow their crops affects, sometimes dramatically, not only how nutritious food is but also how safe it is to eat. It may well be that a federal food policy that fails to acknowledge the connection between what happens on the farm and the healthfulness of foods is enough to make a nation sick.

The Results Are In

In the late 1990s, researcher Anne-Marie Mayer looked at data gathered by the British government from the 1930s to the 1980s on the mineral contents of 20 raw fruits and vegetables. She found that levels of calcium, magnesium, copper, and sodium in vegetables, and of magnesium, iron, copper, and potassium in fruit had dropped significantly.

The 50-year period of Mayer's study coincides with the post World War II escalation of synthetic nitrogen and pesticide use on the farm. These powerful agri-chemicals allowed farmers to bypass the management-intensive methods of maintaining soil fertility by replenishing soil organic matter with cover crops, manure, and compost, and of controlling pests with crop rotation and inter-cropping. Reliance on chemical fertilizers and pesticides became a defining characteristic of conventional farming, while farmers who eschewed the use of agri-chemicals came to be considered organic.

In 2004, Donald R. Davis, a research associate with the Biochemical Institute at the University of Texas, Austin, published a similar analysis of data collected by the USDA in 1950 and again in 1999 on the levels of 13 nutrients in more than 40 food crops. Davis found that while seven nutrients showed no significant changes, protein declined by six percent; phosphorous, iron, and calcium declined between nine percent and 16 percent; ascorbic acid (a precursor of Vitamin C) declined 15 percent; and riboflavin declined 38 percent. Breeding for characteristics like yield, rapid growth, and storage life at the expense of taste and quality were likely contributing to the decline, Davis hypothesized. The "dilution effect," whereby fertilization practices cause harvest weight and dry matter to increase more rapidly than nutrient accumulation can occur, probably also played a role, Davis suggested.

Meanwhile, researchers at the Rodale Institute in Pennsylvania were seeing a tradeoff between use of synthetic fertilizers and food nutrient values in the Institute's Farming System Trial (FST). The FST is the longest-running side-by-side comparison of organic and conventional farming systems in the US.

"We looked at the major and minor nutrients of oat leaves and seeds, grown after 22 years of differentiation under conventional and organic systems," says Paul Hepperly, research and training manager at the Institute. "The organic matter in the conventional system did not change over the 22 years, but we got about a one percent increase in organic matter over the baseline every year in the organic system. We found a direct correlation between the increase of organic matter and the amount of individual minerals in the oat leaves and seeds. The increase in minerals ranged from about seven percent for potassium, up to 74 percent for boron. On average, it was between 20 and 25 percent for all the elements we looked at, and we looked at nitrogen, phosphorous, potassium, calcium, magnesium, sulfur, iron, manganese, copper, boron, and zinc. The production practices used on these oats was completely the same the year they were planted -- the plots varied only by the legacy of what had happened to the soil as a result of the previous farming practices. This showed how dramatic the soil change had been and its effect on the nutrient content of the plant. We've done these tests not only on oats but also on wheat, corn, soybeans, tomatoes, peppers, and carrots, and we consistently find that the organic heritage improves soil and improves the mineral content of the food products."