Next time you clip your toenails, you may hesitate to throw them away. Toenails can tell us about the risk of lung cancer, according to a study just published in the American Journal of Epidemiology (March 2, 2011).
You may even be at risk of the disease if you have never smoked. The point is that nicotine accumulates in certain tissues, including hair and nails, and can be measured accurately.
Comparing the toenails of 210 men with lung cancer and a comparison group of 630 men without lung cancer, researchers found that the men with the highest levels of nicotine were 10.5 times more likely to develop lung cancer.
Even when taking into account reported smoking — that is, when comparing men at similar levels of cigarette use — men with the most nicotine in their toenails were over 3.5 times more likely to get lung cancer than those with the least toenail nicotine.
Why toenails? Researchers were looking for a way to evaluate secondhand smoke exposure. Deposits in hair are well recognized. But hair and toenails are formed of the same kind of tissue, so logically they would show similar levels. And toenails record deposits of nicotine over a whole year.
More than that, in fact; the study showed that toenail nicotine levels are closely linked to smoking status six years prior to collection of clipping samples. Moreover, toenail nicotine levels predict the risk of heart disease in women. Women with the highest toenail nicotine levels have a 42% higher risk of heart disease than do those with the lowest levels.
One thing didn’t need proving is that smoking is harmful and the damage can be measured throughout the body, not just lungs.