A health expert has pointed out that your fingernails can reveal a lot about your overall well-being.

Dr. David Sinclair, a longevity specialist, has shared that he closely monitors his nail growth as a way to gauge how quickly he is aging.

For most people, aging is simply measured by birthdays—each year that passes is another year lived. But according to Dr. Sinclair, who studies aging and genetics at Harvard Medical School, nails can provide a more precise indicator of how fast the body is aging and, in turn, how much time one may have left.

When it comes to health, most individuals focus on areas like heart function, lung capacity, and diet, rarely paying attention to their fingernails. However, Dr. Sinclair argues that nail growth is an essential marker of how efficiently the body is generating new healthy cells. The faster this process occurs, the better the body is at resisting age-related decline.

Biological aging refers to how old the body’s cells and tissues appear based on their functionality, which can differ from a person’s actual chronological age.

Speaking on his podcast Lifespan, Dr. Sinclair explained: “The rate of your nail growth is a really good indicator of how you’re ageing or not ageing. I do pay attention to whether my nails are slowing down in their growth or not. Every time I have to cut my nails, I’m thinking, ‘how long ago did I cut my nails?'”