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Anti-Aging
Supplements Give Hope, but No Proof
By
Timothy Gower
San-Diego
Union Tribune, April 15, 2003
If you surf
the Internet or browse men's magazines in search of strategies for
boosting muscle or trimming fat, you may have come upon a strange phrase:
hormone secretagogues. Advertisements and Web sites claim that these
pills, powdered drinks and nasal or oral sprays will not only buff your
body, but also strengthen bones, sharpen wits and banish wrinkles and gray
hair.
Scientists say there is no solid research to support the hype about these
all-natural products, which are available without a prescription in stores
that sell dietary supplements and over the Internet. However, many of
those same scientists insist that the concept of a hormone secretagogue -
that is, a compound that can trigger the release of vital chemical
messengers in the body - holds great promise. In fact, researchers in labs
around the world are studying how drugs may act as hormone secretagogues
(pronounced suh-KREET-uh-gogz) and, perhaps, one day be used as antiaging
therapies.
So what exactly is a hormone secretagogue? First, a bit of body chemistry.
Scientists know that the pituitary gland (situated beneath the brain)
makes a substance called growth hormone. Several influences seem to
stimulate growth hormone production, including exercise and sleep. In
turn, growth hormone signals the liver to manufacture insulin-like growth
factor I (IGF-I). This cascade of events is necessary for building muscle
and bones, among other things.
Growth hormone levels rise during adolescence, but begin to drop in middle
age; by age 60, a man produces about half as much growth hormone each day
as he did at age 20. An influential study by researchers at the Medical
College of Wisconsin in 1990 showed that injections of growth hormone can
help older men and women restore some muscle and shed fat. However,
because the therapy can cause a variety of side effects, from aching
joints to blood-sugar problems that could lead to diabetes, the vast
majority of doctors do not prescribe it to patients who simply want to
feel and look younger.
The Food and Drug Administration has approved these injections only for
treating specific medical conditions that cause lower-than-normal growth
hormone levels (such as pituitary tumors). That hasn't stopped
"antiaging" clinics from giving costly growth hormone shots to
patients who hope to turn back the clock. Some athletes reportedly use
growth hormone injections to improve performance, too.
But some companies that sell hormone secretagogues claim that their
products offer a cheaper, needle-free alternative. These products, which
are also known as "hormone releasers," contain a variety of
ingredients, but most include arginine and other amino acids. According to
several companies that sell hormone secretagogues, these preparations
signal the pituitary gland to secrete high levels of growth hormone. The
result, they say, are bigger muscles and trimmer waistlines, even without
exercise.
Don't bet on it, say scientists who study hormones. They insist that the
idea of consuming amino acid preparations to beef up and slim down is
flawed and has never been adequately tested. Studies have shown that high
doses of arginine trigger the pituitary gland to produce a small burst of
growth hormone - but only when injected into the blood, says University of
Virginia endocrinologist Mary Lee Vance. "Taking oral arginine has
not been shown to be efficacious" for stimulating the pituitary
gland, she says. The dose of amino acids in an off-the-shelf secretagogues
is about the same as you would find in a steak. The difference? "A
steak tastes better," she says.
I called several companies that sell hormone secretagogues and asked if
they could support claims that their products build muscle and burn fat.
None offered any solid scientific studies as proof.
That's because there aren't any, according to physiologist Michael J.
Rennie of the University of Dundee in Scotland, who has studied growth
hormone for 30 years. Rennie, who criticizes the use of growth hormones to
aid athletic performance in this month's British Journal of Sports
Medicine, said there is "no published evidence" that nutritional
supplements marketed as hormone secretagogues build muscle in healthy
young people.
While the value of these commercial products appears dubious, hormone
secretagogues under study by scientists have been shown to increase growth
hormone in the elderly to youthful levels. The next step is to figure out
whether these synthetic hormone releasers can produce any health benefits.
Vance and her colleagues at the University of Virginia are currently
testing a secretagogue developed by the pharmaceutical giant Merck in a
group of about 70 elderly men and women. The study, which won't be
completed until next year, will measure whether an experimental drug,
known as MK-0677, helps stave off some effects of aging, such as loss of
muscle and bone density.
Synthetic hormone secretagogues may do more than improve physical well
being, says molecular endocrinologist Roy G. Smith, director of the
Huffington Center on Aging at Baylor College of Medicine in Houston. Smith
is experimenting with rats to determine whether various secretagogues can
prevent age-related memory and cognitive problems. He hopes to start human
studies in about five years. Smith believes that secretagogues may help
older people cope better with stress, since growth hormone reduces the
effects of stress hormones. He adds that secretagogues appear to have a
much lower risk of side effects than growth hormone injections.
Yet, despite their promise, secretagogues have their doubters,
acknowledges Smith. Skeptics have accused him of interfering with nature;
they argue that the frailty and feebleness that comes with old age prepare
us for death. Smith disagrees. "Nature is cruel," he says.
"I think if we can intervene, we should."
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