We’re going to keep this simple: A loss of collagen causes wrinkles. But what does collagen have to do with skin aging, anyway? Well, let’s not forget that your skin is made up of collagen. It’s an essential part of the structure of our skin, bone, cartilage, and muscle that helps tissues to be more elastic and withstand stretching (so, for example, it keeps skin looking young and supple).

While you do make your very own supply of collagen naturally, it declines as you age. Starting in your 20s, collagen levels decrease about 1% each year1 (we know—much sooner than expected). Plus, other lifestyle and environmental factors can reduce your collagen production, such as sun damage, high-sugar diets2, stress, and more—you can read about all of them here.

So when your collagen begins to degrade at a quicker rate than you naturally produce it, whether that’s caused by environmental changes or age, that’s when your skin’s elasticity and tightness become compromised (among other full-body effects). 

The answer: While you can’t apply collagen to your skin and expect it to replenish your internal bank, you can ingest it. Specifically, hydrolyzed collagen peptides have been shown to help promote the body’s natural production of collagen1 and other molecules that make up the skin, like elastin and fibrillin—so keep an eye out for “hydrolyzed collagen peptides” on your product labels.

Not sure where to look? Here’s a curated list of the nine best collagen supplements on the market, (all backed by a nutrition Ph.D.) to get you started.