Antinutrients may need a new name.

Antinutrients may need a new name

Certain chemically active, plant-derived food ingredients--such as enzyme inhibitors, saponins, lectins and phytic acid--have come to be known as antinutrients. At high concentrations, some are toxic. Others bind nutrients, preventing their digestion and use by the body. The value of antinutrients has been so questionable, says University of Toronto nutrition scientist A. Venket Rao, that many nutritionists have recommended either removing them or destroying them by overcooking. However, new evidence is indicating that at relatively low levels, some of these compounds can be beneficial.

Rao says recent studies involving enzyme inhibitors and saponins, for instance, indicate they may be useful in managing a number of diseases, including cancer, diabetes and hypercholesterolemia. And human studies reported last week by his colleague, Lilian U. Thompson, show that by retarding starch absorption, low levels of lectins and phytic acid may benefit those, like diabetics, who can't regulate blood glucose well.

In one study, Thompson rotated 10 healthy and 10 diabetic individuals through 16 different breakfasts--each containing 50 grams of starch. Every morning they ate legumes, potatoes or a cereal-grain food. "We found that the higher the intake of phytic acid and lectins, the lower the blood-glucose levels," she says. Invariably, the potatoes and grains (including breads, oats, rice and bran) caused a rapid, high peak in blood sugar. The seven legumes (including beans and chickpeas) initiated a slower, lower rise in blood sugar. The legumes' sugar-release pattern is desirable, especially for people who have trouble managing blood sugar.

Though some have interpreted low blood-glucose levels after meals as evidence that much of the meal isnot being used by the body, Thompson says her data from in vitro and other studies suggest otherwise: Food is being used; the pace of its absorption has simply been slowed.

In a follow-up experiment, 10 healthy volunteers ate unleavened bread made from navy-bean flour--with and without the beans' usual phytic acid. Their blood-glucose responses were 52 percent higher after they had eaten the bread without phytic acid.

Because high levels of lectins and phytic acid can be toxic, Thompson is quick to caution against adding either to the diet. However, her preliminary studies suggest they should not be removed from the diet either, because the amounts found in a varied, balanced, high-fiber diet may have subtle benefits. She believes that like fiber, which for decades was considered an antinutrient, these compounds deserve serious reevaluation in terms of dietary importance.