Telomeres, those protective caps on the ends of your chromosomes, tell tales about your biological aging process. The unhealthier your lifestyle habits, the more premature damage occurs to them, leading to an inability to make more stem cells that repair your cells and organs, an increased risk of disease-causing genetic mutations, and damage to your DNA.

Over time, the length of your telomeres serves as a sort of biological clock that reflects how fast you are aging.

Now a large, four-year study in the American Journal of Clinical Nutrition shows that 2,000 IUs a day of vitamin D supplements protects telomeres from fraying and preserves their length — in turn, protecting you from premature aging and associated chronic diseases such as dementia, cardiovascular disease, osteoarthritis, and diabetes.

But the researchers also stress that you need to embrace healthy, anti-inflammatory nutrition such as the Mediterranean or MIND diet, a regular stress-busting exercise routine, and healthful sleep habits to provide the most protection to your telomeres — and your future.

If you combine those lifestyle habits with time in the sun (using micronized zinc sunscreen after around 15 minutes) and you keep your kidneys and liver healthy (limit sugar, red meats, and alcohol, and don't smoke or vape), you'll be able to maintain beneficial vitamin D levels and slow down aging.