US panel warns on excessive antioxidant intake

WASHINGTON, April 11 (Reuters) -- A US government advisory panel warned consumers on Monday against taking large doses of antioxidants such as vitamins C and E, saying only modest increases in current recommended levels were warranted.

The panel of the Institute of Medicine, which identifies concerns in medical care and research for the government, also said that most Americans already were receiving the proposed levels through normal diet without resorting to vitamin and mineral supplements.

The group recommended slightly higher vitamin C levels for smokers but set maximum advisable levels for several compounds.

Panel Chairman Norman Krinsky, a professor at Tufts University School of Medicine in Boston, said people falling short of recommended levels should improve their diets.

``Particularly improving the intake of such things as fruit and vegetables, which we know are rich in these nutrients,'' Krinsky said in a conference call with reporters.

Antioxidants are a wide range of compounds that neutralize free radicals -- charged particles produced by radiation, chemicals and the body's own metabolism that can damage cells.

There are claims that large doses of antioxidants can help prevent a range of ailments including heart disease, cancer, Alzheimer's disease and diabetes.

``After a comprehensive review of the scientific evidence, our panel concluded too little is known at present to provide a definitive answer,'' Krinsky said.

But the panel warned that high levels of vitamin C can cause diarrhea, too much vitamin E can increase the risk of stroke, and excessive selenium, another substance the panel examined, can cause hair loss and brittle nails.

For vitamin C, the panel recommended that adult women consume 75 milligrams per day and men 90 milligrams, up from 60 milligrams currently. Vitamin C's tolerable upper limit was put at 2,000 milligrams per day.

Because smokers are more likely to have oxidative cell damage, the panel said they needed an extra 35 milligrams of vitamin C each day.

For vitamin E, researchers recommended that men and women consume 15 milligrams from food sources such as nuts, seeds, liver, leafy green vegetables and some vegetable oils. Current guidelines are 10 milligrams for men and eight milligrams for women.

At high levels, vitamin E acts as an anticoagulant, or anticlotting agent, and a maximum level of 1,000 milligrams a day was recommended by the panel -- a level only obtainable by taking supplements.

For selenium, the recommended daily level was 55 micrograms for women and men, previously 70 micrograms for men and 55 micrograms for women. An upper limit of 400 micrograms was suggested.

The panel said it looked at beta-carotene and other carotenoids and said the evidence for them as true dietary antioxidants was not available. Their only clear nutritional role was in the formation of vitamin A, the panel said.

Data on excessive intake of beta-carotene was contradictory, so the group set no maximum, Krinsky said.

Stress slows healing of cuts and bruises

LONDON, Apr 14 (Reuters) -- Stress can slow the body's healing and recovery process by lowering levels of key immune system chemicals, American researchers said on Thursday.

Professor Janice Kiecolt-Glaser, a psychologist at Ohio State University of Medicine, told a British Psychological Society conference in Winchester that wounds in stressed people can take as much as 24% longer to heal than those in other patients.

But relaxation techniques, such as guided imagery and visualisation, can help to relieve stress and boost the immune response.

``The line of research we are doing suggests that stress has large effects on wound healing,'' Kiecolt-Glaser told Reuters.

``It may be related to psychological literature that suggests that more stress before surgery is associated with a lower and more troubled recovery.''

Kiecolt-Glaser and her husband, immunologist Dr. Ronald Glaser, compared the healing process and measured immune system chemicals called cytokines in 36 women who were given a small wound on their arm.

Half of the women were caring for relatives suffering from Alzheimer's disease and had high scores on a standard stress test. The other women had average stress levels.

There were no differences between the two groups apart from the stress levels, but Kiecolt-Glaser said the wound of the caregivers took nine days longer to heal than the other group.

The blood samples of the caregivers also had lower levels of cytokines, which can aid the wound healing process by causing inflammation.

In other studies the researchers measured the body's immune response at the site of an open blister and the impact of relaxation techniques.

``The two subsequent studies were designed to examine response at a wound site as it evolves over 24 hours,'' Kiecolt-Glaser said.

By placing a plastic plate with a special solution of blood serum and saline to mimic the body's response over an open blister they were able to watch as cytokines migrated to the serum and to determine if their levels increased.

``Stress was associated with significantly slower secretion of cytokines at the wound site,'' she added.

The husband and wife team suspect that if stress reduces the level of cytokines very early after wounding then all the stages that follow in the healing process are delayed, which explains the longer healing time.

Half of the participants in the third study were also given relaxation sessions to determine if it could reverse the effects of stress.

``There were significantly more cells that migrated into the wound sites among individuals who were given relaxation,'' Kiecolt-Glaser said.

Gardening fights weeds and osteoporosis at the same time

``Those (women) that like yard work can rejoice,'' Dr. Lori W. Turner told Reuters Health. ``This study shows that yard work and weight training are optimal choices for maintaining bone density.''

Turner and colleagues measured the bone mineral density of the thighbone, or femur, of 3,310 women aged 50 or over. They found that 57% of the women had reduced bone density or osteoporosis.

Women who gardened at least once a week had stronger bones than women who were sedentary or participated in other activities such as jogging, swimming, walking or aerobics, according to the study, which was presented at the American Alliance for Health, Physical Education, Recreation and Dance conference in Orlando, Florida.

Weekly weight training, bicycling, aerobics and dancing were also associated with greater bone density than swimming, jogging, or yoga, Turner added.

``Yard work and weight training are strong factors for high bone density,'' Turner said. While just 45 of the women surveyed did weight training, more than 1,000 women reported doing some form of yard work at least once a week, she noted.

``The best thing about yard work is that so many people are willing to do it,'' Turner said in a statement issued by the University. ``People have other motivations for gardening. They take pride in a beautiful yard and pleasure in being outdoors. They'll probably continue to do it as long as they're able.''

The researcher did warn, though, that exercise alone may not help women avoid osteoporosis. ``There are a lot of factors that contribute to osteoporosis,'' Turner said. ``But the more we know, the more we can encourage women to maintain healthy lifestyles and the more power we can give them to prevent this disease.''

Bone loss resumes when calcium intake drops

SAN DIEGO, Apr 17 (Reuters Health) -- To maintain strong, healthy bones, you need to make a ``lifetime commitment'' to getting enough calcium, warn experts from the US Department of Agriculture (USDA). They report that bone loss associated with aging climbs to pre-therapy levels soon after calcium supplements are abandoned.

``Our take home message is 'don't stop,''' said Dr. Bess Dawson-Hughes, of the Jean Mayer USDA Human Nutrition Research Center on Aging, at Tufts University, Boston. She presented her findings at the Experimental Biology 2000 conference, held here this week.

Nutrition and osteoporosis experts have long advocated that individuals meet recommended dietary allowances (RDAs) for calcium -- preferably from food -- in order to build and maintain healthy bone density. Calcium is especially important for adolescents, who are building bone density to peak levels, and for post-menopausal women, who lose bone density at about 1% per year. Loss of bone density can cause osteoporosis and increase the risk of fractures in the elderly.

In the Tufts study, Dawson-Hughes' team examined calcium intake and bone density in nearly 300 men and women over the age of 65 for a period of 2 years. All of the subjects had taken calcium supplements for 3 years previous to the study.

A large number of subjects told the researchers that they had stopped calcium supplementation. Dawson-Hughes reports that ``by 1 year after they stopped treatment,'' women who had stopped the therapy ``had no residual benefit in terms of bone density.''

In other words, they resumed losing bone density at pre-treatment rates. Men who abandoned supplements took a little longer to see treatment effects vanish, but after 2 years of not taking extra calcium, they, too, saw levels of bone loss rise to pre-treatment levels. The bottom line, said Dawson-Hughes, is that there appears to be ``no sustained benefit from calcium'' once treatment stops.

Similar results were found in adolescents. Dr. Steven Abrams, a pediatric researcher at the USDA/ARS Children's Nutrition Research Center, in Houston, Texas, reviewed findings from four 1-to-2-year trials in girls and boys aged 6 to 14 years.

``The benefit from calcium supplementation wasn't really held once you stopped it,'' Abrams said, with bone development (that is, increases in bone density) in adolescents who stopped supplementation slowing to levels similar to those seen in untreated children.

Dawson-Hughes told Reuters Health that ``meeting the calcium requirement should be a lifetime commitment.'' She also believes that individuals need to move ``beyond the concept of pills'' and aim to get most of their calcium intake from foods.

Current US government RDAs for calcium are 800 mg for children aged 4 to 8, 1300 mg for children aged 9 to 18, 1000 mg a day for adults aged 19 - 49, and 1200 mg per day for adults over age 50. Calcium is found in dairy products and in produce such as collards, turnip greens, rhubarb, broccoli and kale.

Cocoa may help fight cholesterol

SAN DIEGO, Apr 17 (Reuters Health) -- Cocoa, the compound that gives chocolate its deep, rich flavor, may also help prevent cholesterol-related damage to arteries, researchers report.

However, they stress that the cocoa they tested was de-fatted cocoa extract, not the high-fat chocolate found in the average candy bar or cup of hot cocoa.

``Biologically active compounds that are present in cocoa (extract)'' appeared to protect rabbit arteries from constricting under the effects of cholesterol, explained researcher Dr. Tissa Kappagoda of the University of California, Davis. His team's findings were presented at the Experimental Biology 2000 conference, held here this week.

Speaking with Reuters Health, Kappagoda explained that cocoa extracts appear to be a good source of antioxidant flavonoids -- plant-based compounds thought to fight the chemical processes that link a high cholesterol level to diseased arteries. Similar compounds found in vegetables, fruits, and tea seem to protect arteries from harm, and the researchers sought to determine if extracts of the cocoa bean might do the same.

To do so, they conducted laboratory tests examining the response to cocoa extract of segments of rabbit aorta (the large artery leading from the heart). Kappagoda explained that healthy aortas retain the ability to relax -- easing blood flow and keeping blood pressure at healthy levels. Cholesterol-related damage to the aorta restricts this relaxation, however, sending blood pressure upwards.

The California researcher reports that exposing aortas to cocoa extract ``produced a relaxation'' in aortic tissues. This response was noted in aortas taken from rabbits fed either low- or high-cholesterol diets. He said the response was ''totally comparable'' to that seen in similar tests of flavonoid compounds from other sources, including fruits, vegetables, and tea.

Although the study received funding from the Mars candy bar corporation, Kappagoda stressed that there is a big difference between the consumption of pure, non-fat cocoa extract and high-fat chocolate bars and hot cocoa drinks. He points out that chocolate manufacturing processes eliminate most natural flavonoids from much of the commercial chocolate available to consumers, and between 40 - 45% of calories in most store-bought coca drinks are from fat.

``As a cardiologist,'' he said, ``I don't recommend (consuming) that, because we usually try and shoot for a much lower fat content, especially for people who have heart disease.''

But cocoa lovers can take heart from the fact that, according to Kappagoda, ``a couple of companies are looking at this, and they (hope) to produce a low-fat, 'lite' cocoa drink which will have all the good things and reduce the fat -- and still be acceptable from a taste point of view.''

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