There has been a lot in the news recently about resveratrol, a natural phytoalexin that has powerful effects on health and longevity. Of course, with every new supplement that garners a lot of media attention, claims by hucksters abound. And, of course, with the percentage of overweight Americans now well over 60%, weight loss is a health topic on many people's minds.

Can resveratrol help you lose weight? Possibly. But let's see where this idea came from, and why resveratrol is still a good supplement to consider taking, especially if you are overweight, even if the weight loss claim remains to be proven.

Resveratrol, a naturally-occurring substance found in grape skins, Japanese knotweed, peanuts, and other plants, is used by plants to ward off fungal attack, and is found in higher quantities among plants in damp, mold-friendly environments (this is why wines from Bordeaux in France, Willamette Valley in Oregon, and the Finger Lakes region of New York have higher resveratrol levels in their red wines than those from Napa and Sonoma in California).

Through a mechanism scientists are still struggling to understand, resveratrol triggers the SIRT1 gene in the human body. Activation of this gene has been understood to have the following results:

• improved function of the cellular mitochondria, the organelle responsible for converting foodstuffs into energy.
  
• protection from the loss of neurons (brain cells) through degenerative diseases such as Alzheimer's Disease and Amyotrophic Lateral Sclerosis
• protection from cellular stress, by boosting heat shock factor 1 (HSF1), which prevents cells from degenerating in the face of pollutants, temperature variations, bacteria and viral attack, too little oxygen, and other stressors
• extended longevity (lifespan), in everything from single-celled yeast to mice. Resveratrol specifically has been responsible for the longer lives in test animals.
  
• boosted endurance, in studies of mice.
  

Also, because it can chelate (bind) copper, resveratrol has been shown to reduce amyloid plaques (like those that cause Alzheimer's Disease) in rodent models.

The reason resveratrol is expected by some to help with weight loss is the fact that activation of SIRT1 makes your metabolic system more efficient. In people with naturally higher expressions of SIRT1, scientists found faster metabolisms, suggesting that a natural SIRT1-booster like resveratrol could cause the metabolism to rev higher.

Poking around the Web, naturally, you see plenty of anecdotes, although without the rigor of double-blind studies, it's difficult to separate out the effect of concurrent changes in diet and physical activity from those associated with resveratrol.

However, regardless of whether the impact of resveratrol on weight loss is significant enough to merit attention, it's worth pointing out a few other important facts about resveratrol that pertain to health:

• in studies with mice, obese mice treated with resveratrol lived as long as normal-weight mice, much longer than obese mice without the benefit of resveratrol. The treated obese mice did not suffer from obesity-related diseases such as diabetes and cardiovascular disease than their untreated test subjects contracted and often died from.
• Sirtris Pharmaceuticals, a drug company bought by GlaxoSmithKline, announced in early 2008 that its first drug designed to treat type-2 (adult onset) diabetes, SRT501, was showing encouraging results in early trials. SRT501, like other drug candidates in Sirtris' portfolio, was developed to trigger the SIRT1 gene.
• a study of obese rats found that resveratrol countered the negative effects of a high-fat diet, and reduced systolic (blood pressure) readings.
• resveratrol has demonstrated anti-cancer effects in studies, preventing the growth and, in some cases, causing the retreat, of breast, colon, and prostate cancers. It is believed that resveratrol disables nuclear factor-kappa B, a protein needed for tumor growth, thereby allowing cancer sell apoptosis (tumor cell suicide).

How much should you take? Dr Mehmet Oz, Oprah's doctor, suggests taking up to 500 mg of resveratrol per day. Dr Oz recommends resveratrol, but does not endorse any particular brand. It's best to do your research and buy from a reputable company.