Here are Discovery Health Online's guidelines for separating fact from fiction with supplements that purport to be anti-aging elixirs.

  • Human growth hormone (HGH). This hormone, approved by the Food and Drug Administration for use in children whose bodies produce insufficient amounts of the substance to allow normal growth, has been reported to increase strength and stamina and lower body fat percentage in some people who took it. But studies haven't determined if there are anti-aging effects, and at least one study suggests that those with higher levels of HGH might die younger than those with lower levels, according to the National Institute on Aging.
  • DHEA. This hormone, which is produced by the body's adrenal gland but begins to drop after age 20, has been touted for its ability to boost immunity, increase muscle mass, improve memory and send sex drive skyrocketing. Experts warn, however, that the drug hasn't been established as safe for human use.
  • Melatonin. While it helps our bodies measure appropriate sleeping and waking times and is often taken in supplement form to treat insomnia or prevent jet lag, scientific studies don't support melatonin's effectiveness for longevity, and users should take into account the risks of daytime sleepiness and blood vessel constriction.
  • Ginkgo Biloba. Tests are ongoing on this botanical product, which is used by many to boost their memory and is approved in Germany for treating Alzheimer's disease. Different preparations are available, with varying content and active ingredients. Side effects can include excessive bleeding, especially when combined with daily aspirin use.
  • Alpha-lipoic acid. As levels of this potent antioxidant drop with age, supplementation may be helpful to treat some complications of diabetes. And in recent studies, aging rats displayed improved memory, increased pep and cell rejuvenation when fed alpha-lipoic acid in combination with acetyl-L-carnitine, another chemical available as a dietary supplement. Human trials of the combination are ongoing.