Tuesday, January 2, 2007

Stored Calories May Raise Cancer Risk

Cancer Risk Not From Calories Eaten, but From Calories Kept WebMD 1/2/07 "It's not the calories you eat -- it's the calories you don't burn off that increase cancer cancer risk, studies of mice suggest...This study suggests that ... being lean as opposed to being obese has a greater protective effect against cancer," ..."Excess calorie retention, rather than consumption, confers cancer risk."...Fat cells, Nagy and colleagues note, aren't just storage cells that hold extra energy. These cells emit many kinds of chemical signals that have profound effects on the body. One of these signals is called leptin. Leptin promotes some cancers. The heavier mice in the Nagy study had higher leptin levels than the cooler, leaner mice. Another signal is adiponectin, which seems to protect from cancer. The fat cells of obese people don't give off as much adiponectin as fat cells of lean people...The heavier mice in the Nagy study had lower adiponectin levels than the cooler, leaner mice"

Nagy wonders whether exercise might create some of the benefits seen with the cooler mice. The article mentions that

"It's now well known that a restricted-calorie diet cuts the risk of getting cancer and slows the growth of some cancers. Most researchers think this is directly related to calorie intake. But not Tim Nagy, PhD, professor of nutrition sciences at the University of Alabama, Birmingham."

It may cut the risk of various types of cancer but what about longevity? At least with studies involving rodents , exercise lengthens life only modestly - calorie restriction and resveratrol increases it dramatically. Strange isn't it. You'd think exercise would have a more profound effect on longevity but it doesn't appear to. For humans the thinking is exercise might add 3.5years to your life (I bet it's more in the 7-9% for daily exercise - similar to rodents, than 5% - this study isn't as good as it could be). Maybe a better way to look at it is that you might not live much longer, although I'm not sniffing at an extra 3.5 (or 4-6yrs), but those years will be considerably healthier and able (esp. during the latter years). This study noted that most of the 3.5 years gained were from prevention of heart disease, but if Nagy is right, there must be some prevention of cancer as well, including some early onset cancers.

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