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Large oral doses of vitamin E or beta carotene do not prevent sunburn
or the skin cell damage that leads to photoaging and skin cancer. But
preliminary evidence suggests that lycopene--a relative of beta
carotene--might help reduce the damage caused by the sun's ultraviolet
(UV) rays. In two separate studies, researchers wanted to resolve
conflicting evidence that antioxidant vitamins taken orally protect the
skin against oxidizing agents generated by the sun's rays. In one study
of 12 men and women, small areas of skin were exposed to a burning dose of
UV radiation after the volunteers had taken either 400 International Units
(IU) of vitamin E or a placebo daily for six months. The supplement did
not significantly increase skin levels of vitamin E. And it did not
reduce skin redness or cell damage compared to volunteers that got the
placebo. In the other study of 16 women, skin levels of vitamin E
increased among those who took beta carotene supplements. But this did
not prevent sunburn. Skin levels of beta carotene didn't decrease after
UV radiation, indicating the nutrient was not being used to protect
against sun damage. By contrast, skin levels of lycopene dropped
significantly. Researchers could not test the effects of giving extra
lycopene, however, because supplements were not available when the study
was done. Lycopene is the red pigment that colors tomatoes, watermelons
and pink grapefruit.
USDA Jean Mayer Human Nutrition
Research Center on Aging at Tufts, Boston, MA
Judy D. Ribaya-Mercado/Mohsen Meydani, (617) 556-3128/3126
When dietary copper was restricted in pregnant and nursing rats, their
pups suffered from retarded development of nerve cells in the part of the
brain that governs learning and memory. This part of the brain,
called the hippocampus, does not finish maturing until after birth and is
therefore especially vulnerable to nutrient deficiencies before and after
birth. Other studies have shown that the brain requires copper for normal
development, but none have specifically investigated if copper was
important to nerve cell maturation in the hippocampus. ARS researchers
concluded that it is, based on the number and size of neurons in a section
of the hippocampus. The degree of retardation in nerve cell development
depended on how much copper was removed from the mothers' diets. The
next question is whether the developing brain can recover if weaned pups
are given adequate copper. Such experiments can't be done on humans for
ethical reasons. But it might be prudent for pregnant and nursing mothers
to include some high-copper foods in their diets, such as whole grains,
oysters, liver, nuts (particularly Brazil nuts), seeds, cocoa and
chocolates. A majority of Americans consume less than the minimum
suggested copper intake, which is 1.5 milligrams daily.
Grand Forks Human Nutrition Research Center, Grand Forks, ND
Curtiss D. Hunt, (701) 795-8423
A lipid discovered by ARS scientists may join the ranks of drugs that
fight inflammation. Such current nonsteroidal drugs--including
aspirin, acetaminophen and ibuprofen--inhibit two biochemical pathways in
the body. But, the new lipid, which could be indirectly produced from
agricultural products, inhibits only one--the lipoxin biosynthetic
pathway. Pharmaceutical companies have been searching for a drug that
blocks only the lipoxin pathway. A drug with these properties would work
especially well on inflammatory conditions associated with asthma and
atherosclerosis. Another plus for the new lipid: It tested negative for
fungicidal, herbicidal and insecticidal properties and was nontoxic to
several types of cancer and HIV-infected cells.
Plant Science and Technology
Research, Philadelphia, PA
Robert A. Moreau, (215) 233-6428
Selenium, the essential trace element known for its antioxidant
prowess, also appears to lift the spirits, according to an ARS study.
During the 15-week study, 30 men reported significant changes in two of
six moods, as measured by a standard questionnaire. The 15 men who
consumed nearly 3.5 times the daily recommended selenium intake felt
significantly more clear-headed and elated toward the end of the study
than they did at the outset. Another 15 men consumed only 40 percent of
the recommended intake. Within that group, researchers found differences
in all six moods based on the activity of a selenium-containing enzyme in
the men's blood platelets. Those with the more active enzymes felt more
agreeable than hostile, more clear-headed than confused, more composed
than anxious, more confident than unsure, more elated than depressed and
more energetic than tired. That's even though enzyme activity was within
the "normal" range for all the volunteers. The findings agree with
another ARS study in which the amount of selenium in men's red blood cells
correlated with two of the mood states. A note of caution: Large doses
of selenium can be highly toxic. The World Health Organization recommends
a daily limit of 400 micrograms. Good food sources include meat, poultry,
seafood, grain products, breads and cereals.
Grand Forks Human Nutrition Research Center, Grand Forks, ND
James G. Penland, (701) 795-8471
Long, easy workouts--the kind typically recommended for
out-of-condition people who want to lose weight--may also be a good choice
for some people of average-or-better fitness. An ARS study evaluated
calorie-burning rates of 32 men who volunteered for workouts on an
exercise bicycle. Preliminary results showed that, among 16 men of
average fitness, those with more body fat hit their best fat-burning rates
when exercising barely hard enough to work up a sweat. Among the other
men of average fitness, those with the least stored fat burned it fastest
when pedaling harder. Researchers rated the fitness level of each
volunteer before he went through increasingly difficult five-minute stints
on the bike. The study was one of the first to suggest a correlation
between the amount of body fat and men's fat-burning rate.
Western Human Nutrition Research Center, San Francisco, CA
Nancy L. Keim, (415) 556-8821
A human virus normally harmless in laboratory mice mutated into a
heart-damaging pathogen when the animals were raised on a diet devoid of
selenium. The virus continued to damage hearts--even in mice that
later got ample selenium in their feed. The findings are the first
indication that a nutritional deficiency can cause a virus to mutate into
a more virulent form. And its importance is not limited to
nutritionally-deprived populations. ARS researchers supplied the
nutritional expertise and diets, and collaborating University of North
Carolina researchers provided the coxsackie viruses--there are 29
different types--which infect more than 20 million Americans annually,
producing a range of maladies from sore throat and cold symptoms to
inflammation of the heart muscle. About 10 percent of infected people
develop serious diseases, such as heart muscle inflammation. Other
nutritional deficiencies also seem to cause viral mutations. University
researchers are now analyzing the genes of another coxsackie virus that
damaged hearts in vitamin E-deficient mice. They expect to find the same
alterations as with selenium deficiency. Both nutrients serve as
antioxidants in the body. If such mutations occur in other RNA viruses,
that may help explain the many new strains of influenza virus in China,
which has widespread selenium-deficient areas.
Beltsville Human
Nutrition Research Center, Beltsville, MD
Orville A. Levander,
(301) 504-8504
Frank Porter Graham Child Development Center, University of North
Carolina, Chapel Hill, NC
Melinda A. Beck, (919) 966-6809
Older women had a significant drop in lean body mass, muscle function
and the ability to fight off infection when their protein intake was only
about half the recommended level. For a 140-pound woman, the
Recommended Dietary Allowance (RDA) is 50 grams per day. While most
Americans consume more than enough protein, some 10 to 20 percent of women
over age 55 eat less than 30 grams daily. That's about the amount in half
a chicken breast, a three-ounce can of tuna or two cups of dried beans.
Researchers wanted to see if such a low-protein intake would compromise
women's immune responses, as well as their ability to get around and
perform normal tasks, even if the women got enough calories. Six
volunteers over age 66 ate about half the RDA for protein for nine weeks,
while six others got a little more than the RDA. The women getting half
the RDA lost an average eight percent of lean tissue, most of which was
muscle. One measure of immune response--a hypersensitivity skin test--was
50 percent lower by the end of the study. And the amount of weight they
could push in a chest press exercise dropped by 12 percent. By contrast,
the six women getting ample protein had no changes in muscle mass.
Moreover, several measurements of muscle function and immune response
improved significantly as did several blood protein measurements,
suggesting that their diet prior to the study may have been a little low
in protein.
Jean Mayer USDA Human Nutrition
Research Center on Aging at Tufts, Boston, MA
Carmen Castaneda/Marilyn C. Crim, (617) 556-3142/3095
Women who carry a genetic marker for low bone density already have less
dense bones in their 20s and 30s than women without the marker.
That's the finding of a study of 155 black and white women age 20 to 40,
and it agrees with what has been seen in women past menopause. Because
low bone density can lead to osteoporosis, the finding points to the need
to identify girls with this marker early in life so that steps can be
taken to help them reach their maximal bone density. The marker,
discovered last year by Australian scientists, results from a mutation in
a gene. This gene makes a protein that regulates the way the body uses
calcium. Women with two copies of the marker (one from each parent) had
between eight and nine percent less bone density in the hip and 6.4
percent less in the spine than those with only one or no mutation. The
study also dispelled the notion that this trait might explain why blacks
generally have denser bones than whites. The percentage of black and
white women with the genetic marker was about equal. Researchers are now
testing to see if people with the genetic marker are unable to adapt to
low-calcium intakes--which are common in the United States. This could
help explain their low bone density.
Jean Mayer USDA Human Nutrition
Research Center on Aging at Tufts, Boston, MA
James C. Fleet, (617) 556-3186
Women shaped more like apples than pears may have more difficulty
losing weight, according to weight-loss studies of 22 women. Those
with more fat around the waist than the hips and thighs--the apple
shape--lost about eight percent of their body weight. That compared to an
18 percent loss in those with larger hips and thighs compared to the
waist--the pear shape. Using sophisticated x-ray equipment, the
researchers also corroborated what others have observed in larger studies
using simpler equipment: Weight loss did not change the waist-to-hip
ratio. The women's basic shape remained the same. Since numerous studies
have associated the apple shape with a higher risk of cardiovascular
disease, diabetes and even cancer, the findings question whether a
weight-loss regimen alone will substantially reduce risk. This study
combined regular aerobic exercise with a 50-percent calorie cut for
optimal weight reduction. Nearly all the weight lost by the women in both
groups was in body fat, not muscle.
Grand Forks Human Nutrition Research Center, Grand Forks, ND
William A. Siders/Henry C. Lukaski, (701) 795-8430/8429
Is 200 International Units (IU) of vitamin D--the current Recommended
Dietary Allowance (RDA)--enough to minimize bone loss in older women?
The latest study suggests that more is better for protecting the hip--at
least in the Northeast where sunshine is sparse during the colder months.
Sunlight prompts the skin to manufacture its own vitamin D. During the
two-year study of 261 women living in the Boston area, half of the
volunteers consumed 200 IU of vitamin D daily, while the other half got
800 IU daily. The group on the higher vitamin D intake lost one percent
less bone at the hip during the first year and 0.5 percent less in the
second, compared to those getting the RDA. Seventy percent of the benefit
occurred in the winter and spring months when the sun's rays are weakest
and exposure is infrequent. The women's average vitamin D intake was only
half the RDA before the study began. All were given extra calcium during
the study to ensure optimal intake. Slowing bone loss at the
hip--actually, the top of the thigh bone where it fits into the pelvic
girdle--could spare many elderly people from painful hip fractures. Good
sources of vitamin D include fatty fish, egg yolks, and milk--because it
is fortified with the vitamin--and fortified breads and cereals.
USDA Jean Mayer Human Nutrition
Research Center on Aging at Tufts, Boston, MA
Bess Dawson-Hughes, (617) 556-3066
Black girls absorb calcium more efficiently and form new bone at a
faster rate than their white counterparts. This difference in calcium
absorption during childhood and adolescence may explain why black women
tend to have lower rates of osteoporosis later in life: They begin with
stronger bones. In the study of 89 girls between the ages of five and 16,
researchers found the greatest difference in absorption rates after the
onset of puberty. But black girls consistently demonstrated more
bone-forming activity throughout childhood and adolescence. The finding
suggests that recommended intakes of calcium may need to be tailored to
particular groups. However, while the black girls absorbed more calcium,
none of the girls in the study met the recommended intakes. Current
recommendations based on a recent National Institutes of Health panel
specify three to four servings of calcium-rich foods for children ages six
to 10, increasing to four to five servings at age 11. A serving could be
one cup of milk, an eight-ounce container of yogurt or one and a half
ounces of natural cheese.
Children's
Nutrition Research Center, Houston, TX
Steven Abrams, (713) 798-7000
Last updated: October 30, 1996
Return to: Quarterly Report
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