Iron levels did not increase in postmenopausal women when they ate several servings of meat and poultry daily for seven weeks. That's good news because epidemiological studies have associated excess iron in the body with increased risk of cardiovascular disease. It is thought that having too much iron--as measured by serum ferritin--raises the chance that free iron ions will be available to damage blood vessels and other tissues. Results of this study indicated that eating meat had little effect on iron stores after seven weeks. Young women regularly lose iron through the menstrual flow. But women past menopause and men tend to accumulate the mineral unless they regularly donate blood. During the five-month study, the 14 women consumed three different diets: high-meat, low-meat and low-meat with mineral supplements to supply missing nutrients. The extra protein in the high-meat diet did not reduce the women's calcium status, as suggested by some research. They did not excrete more calcium or experience a drop in body calcium levels or bone metabolism, which corroborates other findings and indicates that calcium status cannot be used as a rationale for eating less meat. Lastly, the high-meat diet improved the women's zinc absorption. They absorbed more zinc from the high-meat diet than they did from the low-meat diet, even when it was supplemented with zinc.
Grand Forks Human Nutrition Research Center, Grand Forks, ND
Janet Hunt, (701) 795-8328

Evidence is growing that vitamin K--well known for its role in blood clotting--is also crucial for healthy bones. Researchers at ARS' center on aging improved chemical methods for measuring the vitamin K content of different types of foods. They then expanded their database of vitamin K levels by analyzing more than 250 foods collected nationwide by the Food and Drug Administration for its Total Diet Study. Using these data, the ARS researchers estimated the vitamin K intake by 14 age and gender groups, based on the FDA model of typical consumption. With the exception of 25 to 30-year-old men and women, most Americans get the vitamin K daily Recommended Dietary Allowance of about 85 micrograms--that's millionths of a gram. The richest sources of vitamin K are green, leafy vegetables. One serving of spinach or collards, for instance, or two servings of broccoli provide four to five times the RDA. The greener the vegetable, the higher the content, say the researchers, because the vitamin is associated with the chlorophyll. Vegetable oils--soybean, canola and olive--and dressings containing them are the second best source. Animal foods are poor sources unless they are cooked, processed or packaged with one of these oils--but not corn or peanut oil, which are much lower in vitamin K.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
James A. Sadowski/Sarah Booth, (617) 556-3150

Preliminary evidence suggests that people may need more vitamin K than the current Recommended Dietary Allowance to maintain strong, healthy bones. The vitamin activates at least three proteins involved in bone formation. One of them, osteocalcin, needs to be saturated with chemical structures known as carboxyl groups. And the attachment of these carboxyl groups requires vitamin K. Earlier this year, French scientists found that older women with elevated blood levels of the undersaturated protein had lower bone density and a higher risk of hip fracture. So ARS researchers conducted a pilot study, using their newly developed blood test, to see if extra vitamin K could increase saturation, thereby improving the outlook for bone health. It did. When nine healthy, young men and women consumed four times the RDA for vitamin K, their levels of the undersaturated protein were significantly lower than when they consumed the RDA. They also excreted less of the carboxyl groups, indicating that more were being added to protein. The vitamin is well known for its role in blood clotting, and the current RDA--around 85 to 95 micrograms (mcg) per day--is based on the requirement for normal clotting. People can increase their vitamin K intake by adding one or two servings of spinach, kale, collard greens or broccoli to their daily diet--provided they get some fat at the same meal so the vitamin will be absorbed.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
James A. Sadowski/Sarah Booth, (617) 556-3152
Division of Clinical Chemistry, Johns Hopkins Medical Institutions, Baltimore, MD
Lori J. Sokoll, (410) 955-6304

Stomach acid apparently plays an important role in the absorption of beta carotene and other carotenoids recognized for their antioxidant activity in the body. That is according to the results of a recent test. A group of 12 men and women took a drug, omeprazole, for nine days to temporarily block the production of stomach acid. Then they took a 120-milligram beta carotene supplement. Their blood levels of beta carotene rose only half as much, compared to their beta carotene levels when they took the supplement without taking the drug. This helps explain why--in a nutritional status survey of elderly conducted in the early 1980's by this ARS center--the lowest levels of carotenoids were seen in participants who had lost the ability to secrete stomach acid. About 30 percent of people over age 60 have this condition, known as atropic gastritis or hypochlorhydria. The researchers suspect that long-term infection with Helicobacter pilorii, the bacteria that causes stomach ulcers, contributes to the destruction of acid-secreting cells. They theorize that eating more sour foods may increase carotenoid absorption, but have not yet done such tests. Normally, stomach acidity is around a pH of 1. The omeprazole drug raised the study volunteers' stomach pH to between 4.6 and 7.4.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Guangwen Tang, (617) 556-3133

Skeletons made of epoxy resin are helping researchers at the Children's Nutrition Research Center in Houston improve the accuracy of bone mineral content measurements in growing children. Using a dual-energy x-ray absorptiometer, or DXA, is becoming a common tool for measuring bone, fat and lean mass in people because of its precision and ease of use. But others using the DXA have reported a loss of bone mineral content in volunteers who have lost weight. The Houston researchers wondered if this was an actual loss or if the DXA was "seeing" more bone mineral when the subjects had more fat in their bodies. So they filled the skeletons with predetermined amounts of calcium to approximate the content in children and adolescents at ages 4, 10, 15 and 18. With each section of the skeleton encased in plastic cylinders, these "phantoms" resemble distant cousins of the Tin Man in The Wizard of Oz. But they answered the question. Their calcium content, as measured by the DXA, agreed closely with the actual amount of calcium added. When they were made 15 to 20 percent heavier, however, by laying strips of a fat simulating material over the abdomen, hips and thighs, the DXA measured a small but significant increase in calcium content--about 2.5 percent more. The correction will enable researchers to more accurately gauge the true rate of bone growth in children. And they plan to use the epoxy phantoms to calibrate other equipment for measuring minerals in the human body, such as the whole body counter and neutron activator.
Children's Nutrition Research Center, Houston, TX
Kenneth J. Ellis/Roman J. Shypailo, (713) 798-7000

Premature infants who receive small amounts of breast milk or formula within days of birth--in addition to intravenous feedings--may get a much needed boost in intestinal development. This may enable them to more quickly tolerate regular feedings, a prerequisite for release from the hospital. Preliminary findings, based on the progress of 70 premature infants weighing less than 2.5 pounds at birth, indicate that early feedings stimulate production of lactase. That's the enzyme that digests the major milk sugar, lactose. For years, very low birth weight infants have received intravenous (IV) feedings exclusively for the first two weeks. Because these infants didn't produce the enzyme, doctors thought the undigested sugar from breast milk or formula would increase the risk of necrotizing enterocolitis--a serious complication that destroys the intestinal lining. But this ongoing study strongly suggests that the advantages of early feedings outweigh the disadvantages. Half the infants were introduced to less than one-quarter cup of breast milk or formula each day beginning only four days after birth. The other half received only IV feedings for two weeks. A test administered three times during their first month showed that the early feeding group had significantly higher lactase activity for the first three weeks.
Childrens Nutrition Research Center, Houston, TX
Robert Shulman, (713) 798-7145

Oatrim retains its health benefits equally through baking or boiling. That's based on a test of its ability to reduce blood glucose, thereby reducing the risk of middle-age diabetes. Twenty-four men and women had as much improvement in their glucose tolerance after consuming baked or boiled pudding containing Oatrim as they did with instant pudding. The ARS-developed fat replacer contains beta glucans, a fiber component that lowers cholesterol, and is now found in many processed foods. In an earlier long-term study, Oatrim significantly reduced volunteers' cholesterol, blood pressure, glucose and the hormones controlling glucose tolerance. And they lost weight, despite efforts to prevent weight loss. The researchers wanted to know if the cooking method altered Oatrim's efficacy. Judging from the glucose responses of these volunteers, it made little difference. Total dietary fiber was slightly higher in uncooked Oatrim, and it produced a bigger response in one of the hormones that control blood glucose. But there was no difference between the cooked puddings. Oatrim can't be fried.
Beltsville Human Nutrition Research Center, Beltsville, MD
Judith Hallfrisch, (301) 504-8396

It's now possible to take in 5,600 foods at one sitting without gaining a pound. Just download the new USDA Nutrient Database for Standard Reference (SR11) from the Internet or the laboratory's bulletin board. It's free of charge. This eleventh release of the food composition tables lists values for more than 70 food components--such as vitamins, minerals, lipids, amino acids, fiber and energy (calories)--in over 5,600 foods grouped into 22 categories. It replaces SR10, issued three years ago, as well as the printed publication--USDA Handbook No. 8. The nutrient database is a major source of food composition data for epidemiological researchers as well as food and nutrition professionals, and serves as the foundation for most commercial nutrient database programs. In the latest version, laboratory nutritionists have added new food items, such as ethnic foods, brand name candies and infant formulas and foods. There are also updated values for breakfast cereals, new sodium values for canned vegetables and soups, and new data for beef and lamb cuts with external fat trimmed to 1/8 inch, reflecting recent market changes. SR11 is more user friendly than older versions because of its new, relational format. Users with relational database management software--such as Paradox, Access, or Dbase--can retrieve information and generate their own reports. On the Internet, SR11 can be retrieved from the Nutrient Data Laboratory Home Page. Staffers have also added a search tool for locating the nutrient values of selected foods. Those without an Internet connection can retrieve the database from the Nutrient Data Laboratory Bulletin Board by dialing (301) 734-5078. This version does not have a search tool, however. A CD-ROM of the database will be available sometime next year.
Beltsville Human Nutrition Research Center, Beltsville, MD
David Haytowitz/Susan Gebhardt, (301) 734-8491

Evidence that the vitamin folate--known as folic acid on supplement labels--may reduce the risk of colorectal cancer got another boost in a recent study of rats. As the amount of folate in their diet increased, the number of rats that developed tumors of the colon and rectum from high doses of a known carcinogen decreased proportionately. So did the number of tumors per rat. In the human diet, green vegetables, organ meats and citrus are rich sources of folate. Colorectal cancer is the second leading cause of cancer deaths in the United States, claiming 60,000 lives annually. Each year, 150,000 new cases are diagnosed, and up to 90 percent are thought to be related to diet. Epidemiological studies by others repeatedly have found more precancerous growths--or adenomatous polyps--in the colons of people with low folate intakes or blood levels. They also found the converse: Fewer polyps in the colons of people with high folate intakes or blood levels. Looking for a cause-and-effect link, ARS researchers turned to a rat model in which the colon cells go through precancerous changes similar to those of humans. One group of rats was given the recommended folate level for rats in their feed. A second group got four times the recommended level, and a third group got 20 times the recommended level, while the control group got no folate. About 70 percent of the control rats developed tumors after being challenged with high doses of the carcinogen dimethylhydrazine. That dropped to 40 percent of the group given the recommended folate level and to only 10 percent of the group given four times the recommended level. Excessive amounts of folate, however, did not increase protection. In fact, the group getting 20 times the recommended level tended to have more tumors than the rats getting four times the requirement. The same pattern occurred for the number of tumors per rat. The findings extend those of an earlier study in which extra folate protected the colorectal cells of this breed of rats against precancerous changes after challenge with a much lower dose of the same carcinogen.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Joel B. Mason, (617) 556-3194

Getting enough dietary folate can reduce the risk of heart disease and stroke, even in those who have a glitch in their genes for converting the amino acid homocysteine to a less toxic relative. Folate--also known as folic acid or folacin--activates one of the enzymes that promote this conversion. This helps to prevent a backup of homocysteine in the cells, which gets dumped into the blood stream. Studies indicate that elevated blood levels of homocysteine increase the risk of cardiovascular disease, apparently by promoting artery narrowing. In 1988, a group of Canadian researchers discovered a mutation on the gene that acts as a blueprint for this enzyme. That mutation produces a less efficient enzyme. ARS researchers, in collaboration with one of the Canadian researchers, wanted to know if the enzyme's activity depends on the level of folate in the blood. So they tested blood samples from 365 people enrolled in the National Heart, Lung and Blood Institute's Family Heart Study and found that it did--but only in the subjects who had two copies of the genetic variant, one on each chromosome. Twelve percent of the volunteers had this double variant. Among this group, those whose blood folate levels were below the study median--6.8 nanograms per milliliter--had significantly higher homocysteine levels than the volunteers with only one or no copy of the variant. But those whose folate levels were above the median had normal homocysteine levels. This genetic variant is quite common, the study found. Forty-seven percent of the volunteers had at least one copy, while 41 percent had none. It's easy to get enough folate through the diet. Green vegetables and citrus are rich sources.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Paul F. Jacques, (617) 556-3322

Middle-aged women in the military who fail to meet the body fat standard based on tape measurements now have some data to question their score. In a study of women between the ages of 40 and 60, the tape measure method overestimated body fat by nine to 14 percent in some women and underestimated it by seven to 11 percent in others--compared to body fat measurements obtained by the long-accepted standard of underwater weighing. That's because the equations each branch of the military uses to estimate body fat from circumference measurements of arms, legs and abdomen were developed from studies of younger people. The researchers wanted to know if the equations accurately reflect body fat in older personnel, because service men and women who do not meet the standards must undergo a weight control program until they lose the excess fat. Failing that can be grounds for discharge. The cutoffs for body fat range from 26 percent for all women in the Marine Corps, to 36 percent for women over age 40 in the Army. Based on these standards, the Army equation overestimated body fat in the fewest number of women tested--one out of 52, or two percent of the group. The Navy equation overestimated body fat most often--in seven of 35 women tested, or 20 percent. Most of those who met the standards based on tape measurements also met them in underwater weighing. The findings point to the need for a larger study to assess and possibly revise these equations for personnel over age 40. The researchers chose to study older women first because this group is most under-represented in the current equations. But they suspect the equations may also need revision for older men.
Walter Reed Army Medical Center, Washington, DC
Gaston P. Bathalon, (202) 782-2011
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston MA
Virginia A. Hughes, (617) 556-3079

Body builders will find no help in a bottle of chromium supplements, contrary to claims that it boosts strength and muscle mass while reducing fat. A new, well-controlled study of 36 sedentary young men who volunteered for a weight training program found what other studies have been reporting: Those who took an extra 200 micrograms (mcg) of chromium daily gained no more strength or muscle bulk than those who got a placebo. And none of the men had a significant change in body fat, even after two months of working out five days per week. One third of the men took chromium picolinate. Another third took chromium chloride--an inorganic form of the mineral--for comparison, while the rest got a look-alike placebo. Their overall strength increased from 28 to 36 percent, on average, depending on the group. Their scores, however, were not statistically different from one another because of the wide range of body types in each group. The researchers concluded that the benefits of chromium supplements on body composition occur only in people with low intakes. Most Americans consume less than 50 mcg each day--the bottom of the range thought to be adequate--and may be operating on marginal levels. Because the chromium content of foods varies, sometimes dramatically, one insurance against deficiency is to eat a wide variety of foods and choose fortified cereals and whole grain breads over the more refined products. The study also found that the men taking chromium picolinate, but not chromium chloride, showed early signs of iron deficiency in three different assays of iron status. This suggests that extended use may be detrimental, especially in women before menopause, and needs further study.
Grand Forks Human Nutrition Research Center, Grand Forks, ND
Henry C. Lukaski, (701) 795-8353