If you’ve been feeling low energy, dealing with brittle nails, or battling constant brain fog, there’s a good chance your iodine levels might be to blame. Nearly 2 billion people worldwide don’t get enough of this essential mineral.

If your skin feels dry no matter what products you use, your hair seems thinner than it used to be, or your nails have developed strange ridges seemingly overnight—you might be dealing with more than just aging.