Ever feel hungry a few hours after a big meal? A new study may explain why: Chances are you ate carbohydrate-containing foods that caused a rapid spike in your blood sugar. This musters extra insulin into the blood. But the high insulin makes blood sugar crash and suppresses the fat fuels as well, leading to that famished feeling that makes you overeat. That's what happened in a study of 12 obese teenage boys by researchers at Children's Hospital in Boston and the USDA research center at Tufts. The study is the first solid evidence that carbohydrate foods with a high glycemic index (GI)—those which are rapidly digested and absorbed—contribute to obesity. On three separate days that were at least a week apart, researchers fed the boys breakfast and lunch having either a high, medium or low glycemic index. The boys ate almost twice as much after the high-GI meals, compared to the low-GI fare. The researchers concluded that high-GI meals induce a sequence of hormonal and metabolic changes that promote overeating in obese people. About one-fifth of U.S. children and one-third of adults are now overweight, despite a drop in fat intake over recent years. Most starchy foods commonly eaten in North America have a high GI. Moreover, many of the low-fat foods that have flooded grocery shelves are also high in calories. Some starchy foods have GI's up to 50 percent higher than even table sugar. Sources of concentrated sugars, such as sodas and fruit juices, also have a high GI. By contrast, vegetables, legumes and fruits generally have a low GI.
USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Susan B. Roberts, (617) 556-3238.
Children's Hospital, Boston, MA
David S. Ludwig, (617) 355-4878.

Foods that score high in an antioxidant assay called ORAC may protect cells and their components from oxidative damage, according to studies of animals and of human blood. ORAC, short for Oxygen Radical Absorbance Capacity, is a test-tube analysis that measures the total antioxidant power of foods and other chemical substances. Early findings suggest that eating plenty of high-ORAC fruits and vegetables—such as spinach and blueberries—may help slow processes associated with aging in the brain and other parts of the body. In other research studies, consuming high-ORAC foods has so far been shown to (1) raise the antioxidant power of human blood 10 to 25 percent; (2) prevent some loss of long-term memory and learning ability in middle-aged rats; (3) maintain the ability of brain cells in middle-aged rats to respond to a chemical stimulus, a function that normally decreases with age; and (4) protect rats' tiny blood vessels—capillaries—against oxygen damage. The thesis that oxidative damage culminates in many of the maladies of aging is well accepted in the health community. The evidence has spurred skyrocketing sales of antioxidant vitamins. But several large trials have had mixed results. Combinations of nutrients found in foods may have greater protective effects than each nutrient taken alone, the researchers contend. The 10 highest ORAC fruits, in descending order, are prunes, raisins, blueberries, blackberries, strawberries, raspberries, plums, oranges, red grapes and cherries. The 10 highest ORAC vegetables are garlic, kale, spinach, Brussels sprouts, alfalfa sprouts, broccoli florets, beets, red bell peppers, onions and corn.
USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Ronald Prior/James Joseph/Guohua Cao/Barbara Shukitt-Hale, (617) 556-3310.

A study of ferrets explains how high-dose beta carotene supplements may have increased lung cancer rates among smokers in two large intervention trials reported in 1994 and 1996. Excess beta carotene stored in the lungs became oxidized into products that turned the normal control of cell division upside down. These oxidized metabolites decreased a tumor suppressor and increased a tumor promoter in the animals' lungs. Ferrets metabolize beta carotene very much like humans. So researchers tested them with the human equivalent of 30 milligrams of beta carotene daily—the dose given in the large intervention trials. Daily for 6 months, one group was given the beta carotene supplements and exposed to cigarette smoke—equivalent to a person smoking 1.5 packs a day. Two other groups got either the supplement or smoke exposure, while a control group got neither. The group getting both treatments had the strongest precancerous changes. The products of genes that promote cell division were three- to fourfold higher in these animals than in the control group. The findings point out the importance of understanding how the body handles nutrients before high doses are recommended. Beta carotene in amounts obtained from fruits and vegetables is completely safe. Populations that eat more fruits and vegetables rich in beta carotene and other carotenoids have a lower incidence of cancer, particularly lung cancer.
USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Robert Russell/Xiang-Dong Wang, (617) 556-3335/3130.

A profile of U.S. blood homocysteine levels confirms findings of earlier, nonrepresentative studies: This recently recognized risk factor for heart disease increases with age and is higher in males than females. Homocysteine is produced during the conversion of one amino acid into another. Incomplete conversion causes a buildup of homocysteine in the blood, where it is thought to irritate artery linings, encouraging formation of plaque—fatty deposits that cling to artery walls. The researchers used sera from the latest National Health and Nutrition Examination Survey to measure homocysteine for 3,766 males and 4,819 females from age 12 up. Homocysteine levels between the two genders were closest in the young and old, diverging around puberty and converging after menopause. One unexpected finding: Mexican-American females had the lowest homocysteine levels—significantly lower than non-Hispanic African American and white subjects. Low intake of folate, vitamin B12 or vitamin B6 can be a cause for the homocysteine buildup. Orange juice and green leafy vegetables are good sources of folate, which seems to have the most impact on homocysteine buildup.
USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Paul Jacques, (617) 556-3322.

Women who overemphasize being slim at the expense of good nutrition may increase their risk of osteoporosis. ARS scientists in California looked at the eating behavior of 192 women volunteers, ages 18 to 50. The women all were healthy individuals who did not have anorexia or bulimia. Using a standard test, the scientists classified them as either "restrained" or "normal" eaters. The 51 percent classified as restrained eaters had about 12 percent less mineral content in their bones and about 6 percent lower bone-mineral density than the women classified as having normal eating behavior. The test is known as a Three-Factor Eating Inventory. It's already known that not getting enough calcium- rich foods can lead to low bone-mineral density. But the ARS investigation is apparently the largest of its kind to demonstrate a significant association between restrained eating and bone mineral content or density. If the sample is representative, the findings suggest that about half of U.S. women could potentially be restrained eaters who may be increasing their risk of osteoporosis. A thinning and weakening of bone, osteoporosis increases the risk of fractures, particularly of the hip and spine. In the U.S., estimated annual costs of this disease are more than $10 billion for care alone.
Western Human Nutrition Research Center, Davis, CA
Marta D. Van Loan/Nancy L. Keim, (530) 752-4160.

Rett Syndrome, a debilitating disorder that strikes only girls, causes mental retardation and growth failure. There is no cure. But nutrition research may lead to improvement in the quality of life for those with this disorder. Researchers compared energy balance—calories consumed minus calories used—of healthy girls and girls with Rett Syndrome. Both groups had a positive energy balance, but it was lower than average in the Rett girls. Researchers conclude that this subtle, long-running energy deficit plays a role in slowing the girls' growth. Some physicians have had success with a surgically implanted device that allows nutrients to be delivered to the child's body while she sleeps. One girl being studied at these facilities increased her weight from 31 to 48 pounds in a year, allowing her to sit up for the first time. But researchers would like to know why the nighttime feedings seem to increase body fat more than lean muscle mass. The prevalence of Rett Syndrome ranges from 1 in 10,000 to 1 in 23,000 live female births.
Children's Nutrition Research Center at Baylor College of Medicine, Houston, TX
Kathleen Motil, (713) 798-7178.

Dietary variety and the foods' calorie density may be important determinants of body fatness. That's according to a study of 71 healthy men and women aged 20 to 80. Researchers divided foods the subjects reported eating over 6 months into 10 food groups. In a statistical analysis, they looked for relationships between eating habits, energy intake and fatness. In general, those eating the widest variety among several calorie-dense food groups had more body fat, regardless of age or sex. By contrast, those eating the widest variety of energy-sparse vegetables were leaner. Variety among dairy foods, fruit and caloric beverages—milk, orange juice, regular soft drinks or spirits—was not associated with intake or body fat. The calorie-dense food groups were sweets, snacks, condiments, entrees and carbohydrates. Examples of sweets: ice cream, doughnuts, cookies, cakes and candy. Snacks: potato and corn chips, popcorn and French fries. Condiments: gravies, peanut butter, butter, margarine and salad dressings. Entrees: meat, poultry, fish, hamburgers, hot dogs, pizza, mixed dishes, soups and chili. Carbohydrates: rice, potatoes, breads, crackers, bagels, rolls and tortillas. The researchers believe the findings help explain the national rise in obesity, because an enormous variety of calorie-laden foods—particularly snacks and carbohydrates—have flooded supermarket shelves in recent years.
USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Megan McCrory/Susan Roberts, (617) 556-3313/3238.

Getting enough copper during pregnancy may be important for baby's brain development, according to a study of newborn rat pups. The brain has several enzymes that suffer from a shortage of copper. Some of the enzymes contain copper. Others, like PCK, don't contain it but are less active in its absence. Researchers focused on PKC, measuring levels in the rat pups' brains after birth. Throughout pregnancy and afterward, one group of rat mothers got only 1 microgram (mcg) of copper daily—one-sixth the level recommended for pregnant rats. The second group got 2 mcg, and a control group got all they needed. PKC increased in all the pups' brains during the 3 weeks after birth. But compared to the control group, the increase was only about half as much in the group whose moms got 1 mcg of copper. Pups from the 2- mcg group also had a smaller increase—25 percent less overall, with one form of PKC lagging by 50 percent in the cerebellum, which controls motor function. This is significant because poor muscle coordination is a well-known symptom of copper deficiency in baby animals. The findings may have implications for people in the U.S. and other industrialized nations where copper intake is less than desirable. Between 1.5 and 3 milligrams of copper daily is currently suggested for all adults. Rich sources of copper include oysters, liver and cocoa. Whole grains, nuts and seeds are also good sources.
Grand Forks Human Nutrition Research Center, Grand Forks, ND
W. Thomas Johnson, (701) 795-8411.