If older Americans consumed extra vitamin D along with extra calcium, it might substantially reduce the enormous cost of treating broken bones in the elderly —estimated to be $13.8 billion in 1995. That's the finding of a 3-year study of 389 men and women over age 65. The group that took calcium and vitamin D supplements daily had less than half as many broken bones during the course of the study as the group that got a placebo—11 fractures versus 26. The supplements contained 500 milligrams of calcium and 700 International Units (IU) of vitamin D. This substantial reduction in fractures can't be explained by the small changes in bone mineral density between the two groups, the researchers said. By the end of the study, the supplemented group was only slightly ahead of the placebo group in bone mineral density, according to total body measurements and measurements of the hip and spine. The study is the first to demonstrate that extra calcium and vitamin D can reduce the effect of osteoporosis in men. During the study, participants consumed a little more than 700 mg of calcium daily from their diets. That's at the high end of the typical intake for men and women over 65, which falls between 500 and 700 mg. By adding the supplements, they averaged close to the 1,200 mg now recommended for people age 51 and over. To get that amount from foods, a person would need to consume a well-balanced diet, including three sources of dairy products daily.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Bess Dawson-Hughes/Susan S. Harris, (617) 556-3064/3073; hughesb@hnrc.tufts.edu; harris_si@hnrc.tufts.edu

Findings from a new study support the U.S. government recommendation that pregnant women should limit supplemental iron to 30 milligrams per day unless they have iron-deficiency anemia. Researchers from the University of California at Berkeley, California Public Health Foundation, and ARS collaborated in the 15-month study with 13 volunteers. The study monitored zinc absorption rates before and after pregnancy. Results suggest that nursing mothers who take high doses of iron might interfere with their body's ability to absorb zinc. Scientists already know from animal and human studies that the body's ability to absorb zinc changes dramatically during and after pregnancy. The new study was the first to document the changes at intervals from pre-conception to about 2 months after birth. It also was the first, in humans, to suggest iron supplements might interfere with zinc absorption during lactation. Pregnant women need zinc for normal fetal growth and development. After their babies are born, the mother needs zinc for producing breast milk. Severe zinc shortages can retard growth, impair brain function and reduce the body's ability to fight infection. Many women do not consume the recommended daily intake during pregnancy (15 mg) or lactation (19 mg). The richest food sources include red meat, liver, oysters, beans, whole grains, garbanzo beans, and poultry.
Western Human Nutrition Research Center, San Francisco, CA
Janet C. King, (415) 556-9697, jking@whnrc.usda.gov

Protein-rich foods don't prompt the loss of body calcium through the urine, in contrast to what some health professionals have believed. A new ARS study--along with two other studies--finds no support for the notion that diets containing ample meat, fish and poultry increase the risk of osteoporosis. In the ARS study, 14 postmenopausal women excreted no more calcium when eating 10 ounces of meat, fish, or poultry daily for 7 weeks than when eating only 1-1/2 ounces of these high-protein foods. Researchers attribute this to the phosphorus in these foods, which appears to save calcium. The belief that high-protein foods increase calcium loss came from earlier studies in which people consumed pure protein, which does not contain phosphorus or other nutrients that may counterbalance the protein's effects, say the researchers. The latest findings have an important implication for elderly people, especially those with osteoporosis: They shouldn't limit their intake of protein-rich foods for fear of this disease. In fact, low serum protein has been associated with an increased risk of hip fractures. Many elderly consume too little protein and could benefit from regularly consuming moderate amounts of lean meat, poultry, or fish.
Grand Forks Human Nutrition Research Center, Grand Forks, ND
Janet R. Hunt, (701) 795-8328, jhunt@gfhnrc.ars.usda.gov

High amounts of a natural cancer-fighting compound have been found in Tribute and Delite, strawberry varieties developed by ARS scientists. In an evaluation of 36 strawberry varieties, these two had the highest levels of the compound, ellagic acid. The acid content varies by variety, and the researchers found more of it in the leaves than in the seeds or fruit pulp. Now they can breed for higher levels in the fruit, where it is most needed. Researchers don't yet know how much ellagic acid must be consumed to produce beneficial effects. But studies with the National Cancer Institute and Ohio State's Department of Preventive Medicine suggest that a diet that includes strawberries, raspberries, blackberries, cranberries, walnuts and pecans would be rich in ellagic acid. [Click here for an in-depth story on this subject in Agricultural Research magazine]
Fruit Lab, Beltsville, MD
John Maas, (301) 504-5652, jmaas@asrr.arsusda.gov

Cutting calories may inadvertently slow dieters' reaction times. This effect may continue for weeks after the diet ends, ARS researchers and their British colleagues report. Reaction time lengthened 11 percent in the 14 women volunteers who went on a reducing diet. What's more, reaction time continued to grow for 3 weeks after the diet ended. Scientists want to know if the slowdown lowers dieters' alertness--and thus increases the risk of accidents. They also want to learn if the longer diet regimens sometimes needed to achieve healthful weights might increase this risk. Further study of dieting's effects on reaction time could lead to new understanding of how the body uses calories and nutrients for thought and action. Healthcare professionals could use this information to improve diet and exercise plans for overweight Americans. The new study confirms an earlier finding by the British investigators, who are with the British Biotechnology Sciences Research Council. Scientists measured reaction time at five intervals during the study by determining how long it took the women to hit the space bar on a computer keyboard when a white star appeared on the screen. The overweight but healthy volunteers, age 25 to 42, lost an average of 27 pounds during the 21-week study. For most of this time, they ate only half of the number of calories needed to maintain their beginning weight.
Western Human Nutrition Research Center, San Francisco, CA
Mary J. Kretsch, (415) 556-6225, mkretsch@whnrc.usda.gov

Chromium supplements—in two different formulations—lowered blood pressure in rats bred to spontaneously develop hypertension. The supplements, chromium picolinate and chromium nicotinate, also reduced the formation of damaging free radicals in the animals' tissues, indicating that chromium can act as an antioxidant. The findings confirm and expand on those of an earlier collaborative study between Georgetown University and ARS scientists. In the earlier study, chromium nicotinate lowered blood pressure in the rats after researchers exaggerated hypertension by adding table sugar to their drinking water. In the latest study, the Georgetown University and ARS researchers tested four other chromium formulations and found that three —chloride, acetate and picolinate—also significantly lowered the rats' blood pressure. Earlier human studies have linked hypertension with diabetes and with insulin resistance—the inability of insulin to get glucose into cells. Chromium is essential for insulin to operate efficiently and has been shown to reduce diabetic symptoms and restore glucose tolerance in studies of humans and animals. Two of the chromium formulations, picolinate and nicotinate, reduced blood sugar. That's according to the animals' hemoglobin A1C levels--the most sensitive measure of blood sugar. What's more, both compounds reduced the formation of free radicals in the animals' livers, based on measurements of highly reactive free radicals. The nicotinate formulation was also protective in their kidneys. Free radicals form naturally in cells and are counteracted by antioxidants.
Beltsville Human Nutrition Research Center, Beltsville, MD
Richard A. Anderson, (301) 504-8091, anderson@307.bhnrc.usda.gov
Georgetown University Medical Center, Washington, DC
Harry G. Preuss, (202) 687-1441

Boosting fiber intake can reduce the number of calories your body absorbs from the foods you eat. Results from a recent ARS study indicate that increasing fiber intake decreases digestion and absorption of both fat and protein. Based on actual measurements from the study, the scientists say that American men who double their daily fiber intake from an average 18 grams to 36 grams would absorb about 130 fewer calories per day. Women who increase fiber intake from 12 to 24 grams a day would absorb about 90 fewer calories. The researchers tested nine diets on 17 volunteers for 2 weeks at a time. The diets were combinations of low, medium, and high fat with low, medium, and high fiber. The researchers measured how much carbohydrate, fat, protein, fiber, and energy (calories) the volunteers' bodies used from each of the diets. More news on fiber and calories: The researchers say the calorie counts listed on labels for fiber-containing foods could be more accurate. Because some of the calories in foods don't get digested and absorbed, food maufacturers estimate the available calories in each product.
Beltsville Human Nutrition Research Center, Beltsville, MD
David J. Baer, (301) 504-8719, baer@bhnrc.arsusda.gov

There's good news for people concerned about the safety of taking chromium supplements. In a 20-week ARS study, rats that daily consumed more than 2,000 times the estimated safe limit of chromium for people showed no signs of toxicity. Researchers tested two widely used formulations of the mineral--chromium picolinate and chromium chloride. While neither produced toxicity, the animals stored more of the picolinate in their tissues, indicating that they absorbed more. The findings support earlier reports of very low toxicity in animals. And they bring into question the relevance of a study done 2 years ago using cultured human cells that reported DNA damage. Cultured cells are far more vulnerable than body cells because they lack the body's normal protective mechanisms. People generally absorb less than 2 percent of the chromium in the diet. Years of ARS chromium studies with animals and people have not identified any toxic symptoms, even when chromium was given several times above the suggested daily upper limit of 200 micrograms. In fact, the highest daily exposure considered safe over the course of a lifetime is 350 times this upper limit. This reference dose was established by the Environmental Protection Agency.
Beltsville Human Nutrition Research Center, Beltsville, MD
Richard A. Anderson, (301) 504-8091, anderson@307.bhnrc.usda.gov

A post-harvest vapor heat treatment keeps leaves of kale and collards from yellowing and reduces their loss of sugar and other nutrients in storage. Leafy green vegetables—rich sources of important nutrients and dietary fiber—are highly perishable after harvest. In ARS lab tests, kale treated at 113 degrees F for 30 minutes remained green and crisp after 7 days in storage at 59 degrees F. Collards, more heat sensitive, maintained their freshness for a week at the same storage temperature when first held at 104 degrees F for 60 minutes. Scientists don't know how the heat protects the produce. But they do know that stress from heat promotes the build-up of certain proteins. These same "heat shock proteins" may also provide resistance to deterioration caused by cold storage, when produce later is stored at the lower temperatures. Further research is planned to answer these questions.
Horticultural Crops Quality Lab, Beltsville, MD
Chien Y. Wang, (301) 504-6128

Last Updated: October 27, 1997
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