Testing the level of nicotine in your toenail - whether or not you are a smoker - is a significant indicator of possible coronary heart disease ahead. Non-smokers can also have high levels of nicotine in their bodies as a result of passive smoking.
Toenail analysis has been tested on a group of 62,641 nurses who provided toenail clippings in 1982. Between 1984 and 1998, 905 developed coronary heart disease, and there was a direct match to the levels of nicotine found in their toenails. Those who had the most nicotine also had a 3.4 times higher risk of heart disease, and each increase in the scale used to measure nicotine levels correlated to a 42 per cent increased heart risk.
The analysis remained accurate even after the researchers adjusted for smokers and non-smokers.
(Source: American Journal of Epidemiology, 2008; 167: 1342-8).