Harriet Hall in Skeptical Inquirer:
Researchers have failed to find a uniform marker for aging. The aging process seems to be different for different individuals; it is varied, chaotic, and idiosyncratic. There is probably no single cause, but many causes have been proposed: collagen breakdown, UV light, oxidation, inflammation, insulin resistance, glycation, free radicals, accumulation of DNA copying errors, telomere shortening, accumulation of waste products, heterochromatin loss, and many others. I suspect that many of these factors are contributory and that they interact with each other.
Ray Kurzweil believes that science will soon discover the key to immortality, and if he can just stay alive until then, he believes he will be able to live forever. He optimistically takes 250 supplement pills a day, gets weekly IV infusions, uses acupuncture and Chinese herbs, and does other things that he thinks might help keep him alive. His approach is nothing but hope and speculation.
More here.