Harvard has collected toenail clippings from more than 100,000 people in the name of science.

Researchers can use the clippings to measure levels of arsenic and selenium in a person's body over several months, according to the Boston Globe. Harvard epidemiologist Shelley Tworoger is using the toenails to examine how stress levels coincide with tumor progression in patients with ovarian cancer.

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To study the tonails, all five clippings need to be ground up into dust and mixed together. The toenail donors also have to be quizzed about their foot health practices.

Though the toenail request may seem odd, one participant said she knew it was important for research. 

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