Body cells are constantly barraged with chemical signals that pester them to respond. Miraculously, they do a pretty good job of filtering out the "noise" and staying on purpose. But some cells lose the ability to regulate these signals and they react before they should. Researchers now believe this loss contributes to chronic diseases, such as cancer and heart disease. For example, if an order to divide gets "heard" by too many cells, it could lead to unrestrained growth as in cancer or an overactive immune system. Test-tube studies more than a decade ago showed that a phytonutrient in soy foods—genistein—dampens communication from the cell's surface to its interior. How well does it work in the animal? For 4 weeks, an ARS scientist fed young rats diets containing soy protein with high or low levels of genistein. Then she measured how the animals' blood platelets responded to chemical signals. Platelets are quite sensitive to outside signals and so are a good model for studying cell signaling. In three different tests, the platelets from the animals receiving the high-genistein diet were less activated, suggesting that genistein and other isoflavones may reduce over-responsive signaling that produces chronic disease. The genistein-rich diet had the equivalent of twice the average Japanese genistein intake. And the Japanese have a lower incidence of cancer and heart disease. The genistein-poor diet contained the equivalent of the U.S. intake. Tofu, tempeh, and miso are some soy foods rich in genistein and other isoflavones.

Nutrient Requirements and Functions Laboratory, Beltsville, MD
Norberta W. Schoene, (301) 504–8388, schoene@307.bhnrc.usda.gov

A little extra cholesterol in our diets may render the "bad" LDL cholesterol in our bloodstream more susceptible to oxidation. That was the outcome of a study with 13 older men and women with moderately high cholesterol—that is, greater than 130 milligrams per deciliter. Evidence suggests that oxidized LDL cholesterol is more apt to provoke the plaques that build up in arteries and increase risk of heart attack and stroke. The volunteers ate 30-percent-fat diets that differed only in the type of fat and the amount of cholesterol. Otherwise the foods were identical. One diet was rich in polyunsaturated fat from corn oil; the other was rich in saturated fat from beef tallow. To compare the effect of increasing dietary cholesterol on blood cholesterol, the researchers added around 220 to 330 milligrams of cholesterol—depending on the volunteer's total calorie intake—to each diet. The type of fat didn't significantly affect the susceptibility of the volunteers' LDL cholesterol to oxidation in a test-tube assay. But the extra cholesterol increased oxidation susceptibility by 28 percent during the corn oil diet and 15 percent during the beef tallow diet. It also prompted a further rise in the volunteers' total—as well as LDL—cholesterol, regardless of the type of fat in the diet.

USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA
Alice H. Lichtenstein, (617) 556–3127, lichtenstein@hnrc.tufts.edu

Are your blood lipids higher than your doctor would like? If you are also overweight—with a body mass index (BMI) between 25 and 30—you'll probably benefit more from cutting those extra pounds than from cutting dietary fat. That's the gist of a study done in Spain by researchers at the University of Cordoba Medical School and at the ARS center in Boston. Two different heart-healthy diets were less effective at improving the cholesterol profile of overweight men than of normal-weight men. Total cholesterol in the overweight men dropped less than half that of the lean men—7 versus 16 percent—after switching from a diet high in total fat and saturated fat to one recommended by the National Cholesterol Education Program (NCEP). Likewise, artery-damaging LDL cholesterol dropped 9 percent in the overweight group versus 21 percent in the lean group. The NCEP diet is low in fat—28 percent of total calories—with only 10 percent saturated fat. A second heart-healthy diet also had less impact on total and LDL cholesterol in the overweight men. Although this diet was high in fat—38 percent of total calories—more than half of it (22 percent) was monounsaturated fat, the predominant fat in olive or canola oils. However, this diet produced a much bigger drop in triglycerides in the overweight group, compared to the lean group: 26 percent versus 4 percent. High triglycerides are associated with reduced glucose tolerance, the earliest stage of diabetes. And evidence is mounting that high trigylcerides independently increase risk of heart disease, say the researchers.

Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA
Jose M. Ordovas, (617) 556–3102, ordovas_li@hnrc.tufts.edu

Tortillas and other foods made with flour from an unusual ARS-developed corn may help combat iron-deficiency anemia. That could benefit not only people in developing countries where tortillas are a part of nearly every meal, but also people in developed countries who don't get enough iron. The unique corn is low in phytic acid, or phytate. Phytic acid is thought to reduce the body's ability to use iron and certain other nutrients. The ARS corn lines have up to about 66 percent less phytic acid that most common varieties. A study with 14 healthy men showed that iron absorption by those volunteers was about 50 percent greater if they ate tortillas made with flour of the low-phytic-acid corn than if they ate tortillas prepared with normal corn flour that contained about two-thirds more phytic acid. Scientists from the Institute of Nutrition of Central America and Panama and from the University of California's Berkeley and Davis campuses conducted the tortilla test, in collaboration with ARS. Now, scientists from the University of Colorado are leading an investigation that will determine if the low-phytic-acid corn boosts absorption of zinc in a group of Guatemalan villagers. The research is perhaps best known for its environmental benefits. One-stomached animals like pigs, chickens, or farm-raised fish that are fed the low-phytic-acid corn have significantly less phosphorus in their manure, because the corn provides a form of it they can readily digest and use. The corn thus helps reduce the load of unused phosphorus that could leach into rivers and streams, perhaps contributing to algal blooms and fish kills. ARS has patented the corn and licensed it to three companies.

Small Grains and Potato Germplasm Research Unit, Aberdeen, ID
A. Victor Raboy, (208) 397–4162, ext. 151, vraboy@uidaho.edu

A new study to define the antioxidant needs of people with spinal cord injuries should also help clarify the nutrient requirements of other, less severely injured individuals. The investigation, apparently the first of its kind, will determine whether paralyzed people need more antioxidant nutrients, such as vitamins A, C, and E, or beta-carotene, a compound that the body uses to make vitamin A. The findings could also be applicable in determining the antioxidant requirements of people who have injuries that leave them sedentary for months at a time or who are gradually losing their mobility because of worsening arthritis, for example. ARS and University of California-Davis scientists aim to work with 75 northern California adults with spinal cord injuries to learn about their eating habits and to test their antioxidant levels. The findings may help paralyzed people live longer and healthier lives. Right now, Americans with spinal cord injuries live only about 80 percent as long as their peers. Though America's dietary guidelines address the needs of many groups, including the young and the elderly, very little research has been done on the special nutrient requirements of those with paralysis. Gunshot wounds and car, motorcycle, or swimming pool accidents are among the leading causes of spinal cord injuries in the United States today. The Paralyzed Veterans of America Spinal Cord Research Foundation, Washington, DC, is funding part of the study.

Western Human Nutrition Research Center, Davis, CA
Betty J. Burri, (530) 752–4748, bburri@whnrc.usda.gov