Lighter training regimens best for immune system

``From the viewpoint of immune function, the optimal training regimen is of low volume,'' reports Dr. Roy Shephard and colleagues at the University of Toronto in Canada. Their findings are published in a recent issue of the Journal of Sports Medicine and Physical Fitness.

Previous research has suggested that an excess of athletic activity can actually depress immune function. ``According to this viewpoint, light training is supposed to enhance the immune response,'' the Canadian researchers explain, ``but larger volumes of training have a depressant effect, leaving the individual temporarily more vulnerable to viral infections.''

The investigators asked 33 healthy but generally inactive men between 19 to 29 years of age to take part in one of two 12-week exercise programs -- 40 minutes of aerobic exercise (jogging or cycling) performed either 3 or 5 days per week.

Blood tests taken before, during, and soon after exercise revealed that levels of ``killer'' CD16 cells rose by 27% in the light training group (3 days/week) compared with just 21% in the moderate-training (5 days/week) group.

Levels of antibody-producing immune B cells dropped by 33% after moderate training, the researchers add, while light training ``had no effect on B cell count.''

The investigators conclude that for ``the sedentary young adult, it does appear that any (immune-) protective advantage of physical activity can be obtained from a light training programme.''

Moderate training did have benefits unrelated to immune function, however. The authors note that only those involved in the moderate exercise program lost weight and fat over the 12-week period. Overweight and obesity have long been associated with an increased risk for developing cardiovascular disease and diabetes.

SOURCE: Journal of Sports Medicine and Physical Fitness 1999;39:1-11.

Protein in diet may reduce heart disease risk

The findings were ``surprising,'' said lead author Dr. Frank B. Hu in an interview with Reuters Health, ``because we thought, from ecological studies, that animal protein is associated with an increased risk of heart disease.'' Those studies compared the diets of people in different countries and found that the lowest rates of heart disease were in areas where the least amount of red meat was consumed.

The research team, from the Harvard School of Public Health in Boston, Massachusetts, used food and heart disease information obtained from over 80,000 women enrolled in the ongoing Nurses' Health Study. The study participants filled out food consumption questionnaires every 2 years, over a follow-up period of 14 years.

After controlling for age, the investigators determined that ``a higher intake of total protein was associated with a lower risk of ischemic heart disease.'' According to Hu, the women who consumed the most protein had an estimated 25% reduction in heart disease.

While the researchers note that ``our findings strongly reject the hypothesis that a high protein intake, including animal protein, is associated with an increased risk'' of heart disease, Hu commented that the study does not make the claim that animal protein needs to be the source of essential dietary protein -- vegetable protein from beans, legumes, nuts, and soy-products can offer many of the benefits of animal protein.

``A moderately high (protein intake) -- up to 24% of your calories -- should be safe for heart disease, and may even be beneficial,'' Hu told Reuters Health.

SOURCE: American Journal of Clinical Nutrition 1999;70:221-227

Vitamin E shows promise in type 1 diabetes

Dr. George L. King of the Joslin Diabetes Center in Boston and colleagues, write in the August issue of Diabetes Care that ''oral vitamin E treatment appears to be effective in normalizing retinal (bloodflow) abnormalities and improving (kidney) function.''

Many diabetics suffer from a degenerative eye condition called diabetic retinopathy, which can cause vision loss. Bloodflow at the retina is also decreased in diabetics. In this clinical trial, patients received large doses of vitamin E for 4 months. The researchers note that at the end of the study period, retinal blood flow increased to a near-normal rate, and kidney function also improved.

In an interview with Reuters Health, King noted that ``there are potentially interesting uses for vitamin E for the treatment of diabetic eye and kidney diseases.''

However, King added that because of the ``small number of patients and (relatively short study period, the) results are not conclusive.'' He emphasized the need for a large clinical trial to be performed as a follow-up.

In an editorial accompanying the report, Dr. Sushil K. Jain, of the Louisiana State University Medical School in Shreveport, observes that the dosage of vitamin E administered in the study was 60 times greater than the recommended daily allowance, and that not much is currently known about potential problems that could arise from so elevated a level of vitamin E consumption.

Because of a lack of sufficient understanding of these results, Jain cautions that ``the recommendation for the widespread use of high-dose vitamin E for diabetic patients is premature.''

SOURCE: Diabetes Care 1999;22:1245-1251.

Call for research into hormonally active agents in environment

There is some indication that exposure to hormonally active agents -- such as polychlorinated biphenyls (PCBs), DDT and some cleaners, pesticides, and food additives -- can increase the risk of breast, endometrial, testicular, and prostate cancers.

But the report notes that the bulk of the research is confined to the effects of these compounds on wildlife and some controlled animal studies. Data on the compounds studied to date fail to show a link between cancer and other disorders and exposure to hormonally active agents.

``Determining the risk to humans from contact with these chemicals in the environment is difficult because ordinary exposure to these agents has not been routinely monitored,'' said National Academy of Sciences panel chairman Dr. Ernst Knobil of the University of Texas Health Sciences Center in Houston, in announcing the release of the report.

``Determining what these exposures actually are is therefore of primary importance,'' he continued.

``There are two ways to look at this,'' Knobil said in a telephone interview with Reuters Health. ``On one hand, whatever data we have does not support a link between exposure (to hormonally active agents) and various cancers and disorders. On the other hand... the database is incomplete.... There are some 50-odd (hormonally active) compounds that have been listed. Only a very small number have been looked at... and we can't generalize (the findings to date) to all of the compounds.''

``Appropriately designed, long-term studies are needed to document the presence or absence of links between (hormonally active agents) and various cancers in humans,'' the report states. ``Research on suitable animal models is also needed to examine the role that prenatal exposure to suspected chemicals plays in inducing cancer later in life or in subsequent generations,'' the panelists add.

Supplement makers fight FDA proposal on health claims

In April 1998, the FDA proposed guidelines on health claims. The agency has received more than 100,000 comments on the proposal, the majority opposed to the criteria, said Janice Oliver, deputy director of the FDA's Center for Food Safety and Applied Nutrition.

Because of the volume of comments, the agency decided to get additional public input, especially on its proposed definition of what constitutes a ``disease,'' and whether the agency should allow manufacturers to make ``implied disease claims,'' such as stating that a product ``maintains healthy function.''

Some of these claims have been allowed under the Dietary Supplement Health and Educational Act (DSHEA) and Nutritional Labeling Acts, but under different criteria. In most cases, manufacturers have been required to provide scientific evidence to back their claims.

The new proposal has a stricter definition of what constitutes a disease, saying that processes such as aging, menstrual pain, pregnancy, and menopause are ``disease states.'' A product aimed at treating disease is considered a pharmaceutical under FDA laws, which means in some cases, supplement makers might have to go through the same rigorous approval process as drugs, a prospect that makes supplement manufacturers unhappy.

At the meeting, several food processing and supplement makers said the FDA should withdraw its new proposal.

The drug industry's trade organization, the Pharmaceutical Manufacturers and Researchers of America, said there must be bright lines between claims of modifying disease and altering bodily function.

``If disease is defined narrowly, dietary supplement manufacturers will consequently be permitted to make what are today generally understood to be 'drug' claims,'' said PhRMA senior VP for regulatory affairs Bert Spilker, adding that they could do so without undertaking clinical trials to prove safety and efficacy.

Douglas Kamerow, a physician with the federal Agency for Health Care Policy and Research, agreed. ``The key question is where is the evidence behind these claims that are being made,'' he explained, adding that supplement makers should be required to document their claims.

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