Despite what Mom said, eating dirt may be good for you, according to Utah State University researchers.

Eating clay, for example, may provide many of the benefits found in some over-the-counter medicines that help clean the intestines. But only if you eat clay in small amounts.And USU anthropologist Carol Loveland, soil scientist Thomas Furst and nutritionist Georgia Lauritzen conclude that eating dirt may contribute to the success of humans, both biologically and psychologically.

The three recently teamed up to review what is known about the human dirt-eating habit - known as "geophagia" - and to speculate on the possible reasons for the practice.

In America, clay eating generally has been perpetuated as an African custom brought to the country by black slaves.

"Famine is frequently cited as the reason for the behavior, especially during the North American slave period," Loveland said.

The practice persists in the rural South, and researchers said some people now eat starch, which may be more acceptable while providing the same physical sensation but have different physiological effects.

The USU researchers discuss in detail, in a future issue of Food and Food Ways, a "menu" of minerals found in dirt, possible reactions in the digestive tract and the relationship of particle size to effects.

Clay does not supply proteins, calories or vitamins. But analysis shows that it may, depending on the chemical nature of the soil, provide the mineral "micronutrients" of magnesium, phosphorus, potassium, calcium, manganese, iron, nickel, copper and zinc.

Many of these minerals are needed by the body only in small amounts, but are components of enzymes that are used again and again in chemical reactions in body cells.

Study of the medical consequence of eating dirt has focused on the view that it relieves the effects of famine and malnutrition, Loveland said. The other theory is that it interferes with absorption and contributes to certain deficiencies and malnutrition.