Leading nutritional researchers have found that senior citizens are fond of popping handfuls of supplements every morning, but they can't confirm most of the pills lead to any health benefits.
At a recent National Institutes of Health conference in Bethesda, Md., an all-star lineup of policymakers and vitamin researchers announced that in most cases they don't know much about how, or whether, supplements affect the aging human body.
What is clear is that supplement use among the elderly is on the rise. About 40 percent of older men and 50 percent of older women take vitamins regularly. Among women, the majority tend to be Caucasian, higher income, college educated and exercise-conscious. This self-selection presents a thorny problem for researchers because study subjects are often healthier than the population at large.
"The people who least need supplements are the most likely to take them," said Judith Finkelstein, head of the Office of Nutrition at the National Institute of Aging.
A primary concern is the difficulty of conducting rigorous clinical studies with subjects who often forget to take their vitamins or eat foods that counteract a target supplement's effectiveness.
"The questions we want to answer are complex to answer in human populations," Finkelstein said. She added that the only vitamins that enjoy strong clinical supporting evidence are B and D, which are important in maintaining healthy muscles and bone.
The body itself poses another challenge to supplement research because the elderly often have trouble absorbing vitamins, or store them in fat.
"Although many dietary supplements are water soluble, some may be stored or metabolized in body fat," said Tamara Harris, a researcher with the National Institute on Aging. "New data ... suggests that old age may be associated with additional fat deposition, increasing the half-life of fat-soluble drugs even further."
Much has been written recently about antioxidants and their ability to protect healthy cells from turning cancerous. Antioxidants include beta-carotene, vitamin E, vitamin C and selenium. According to Yale University researcher Susan Mayne, the clinical evidence on their effectiveness at preventing cancer is at best conflicting.
Some studies indicate beta-carotene can protect against the occurrence of oral cancerous lesions. A 1993 study from China suggests a combination of vitamins B, K, E and selenium lowered the chances of getting cancer by 10 percent in a sample population of 30,000 subjects. But another study indicated that high levels of beta-carotene actually make lung cancer more likely in smokers.
"There is no consistent evidence to support the general use of antioxidants [to prevent cancer]," Mayne said.
For women taking herbs to alleviate menopause symptoms, the data is also ambiguous. The most promising herbal is black cohosh, which data indicates is as effective as taking estrogen for hot flashes (see "Cool The Menopausal Heat"). Red clover, on the other hand, doesn't have the same level of research behind it.
The central problem is that researchers have little insight into how these substances actually work in the body. "We don't know the method of action for these," said University of Chicago researcher Gail Mahady. "We cannot prove an estrogenic effect of black cohosh at all. We have a lot of potential positive effects for botanicals, but nothing is etched in stone."
Martin Gahart, assistant director of health care for the U.S. General Accounting Office, sounded a note of caution about dietary supplement use by the elderly. He reiterated the findings of a 2001 GAO report which outlined possible dangers of supplement use.
"We weren't making a judgement," he said. But the report entitled "Anti-Aging Products Pose Potential for Physical and Economic Harm" wasn't exactly neutral. Among its key findings:
Dietary supplements can be harmful to seniors with underlying health problems
Some supplements contain harmful contaminants
- Tests of some supplements showed they contained little or none of the active ingredient stated on the label.
Soulful bluegrass singer Randy Barrett is president of The Business Writers Group (www.bizwritersgroup.com).
Natural Foods Merchandiser volume XXIV/number 3/p. 11