What is collagen? And what you should know about how to increase it.

Though some beauty "secrets" are only skin deep, and beauty fads come and go for a reason, the products that usually garner the most attention are the ones purported to be rooted in science.

In many cases, any scientific connections are ambiguous at best or deceitful at worst; but sometimes between the two exist a host of oral and topical wellness products pushed by both manufacturers and users alike. High among them are ones containing collagen because of the many known benefits associated with the protein.

Fortunately, one doesn't have to turn to specific beauty products to experience such benefits since collagen is produced naturally in the body and is also available in many food sources.

What is collagen?

In its natural form, collagen is a fibrous, supportive protein stored throughout one's body. Proteins are made up of amino acids. "It's found in skin and other connective tissues like tendons and ligaments," explains Jesse Bracamonte, MD, DO, a family medicine physician at Mayo Clinic in Arizona. There are 29 types of collagen, says Carly Sedlacek, RD, a registered dietitian from Cleveland Clinic’s Center for Human Nutrition.

She says collagen is also present throughout one's organs, blood vessels and musculoskeletal system and accounts for about 30% of the body’s total protein. But its presence in skin and bones is where the protein is most concentrated. "It accounts for 70% of the protein in our skin and about 80% of the protein in our bones," says Josh Redd, NMD, the founder of RedRiver Health and Wellness and author of "The Truth About Low Thyroid."

Regardless of where collagen is found in the body, "it plays a huge role in general health," says Sedlacek.

What does collagen do?

While its role changes slightly across various organs and connective tissue, collagen's primary purpose is to maintain function and provide structure.

In one's skin, collagen is found between the upper and lower layers, and provides support and structure between both. "Think of it as the springs in the mattress, it keeps our skin plump and firm," offers Mary Stevenson, MD, associate professor of dermatology at NYU Langone Health.

It also provides strength and flexibility throughout one's skin and hair. "This is why we associate it with youthfulness," says Redd. He explains that a loss of collagen that occurs as we age is behind skin wrinkles and diminished hair luster. "By age 40, collagen starts vanishing faster than the body can reproduce it," he says. "By age 60, more than half of the body’s collagen has been depleted."

More important than improving one's physical appearance, however, collagen also reduces one's risk of injury by keeping bones strong and tendons elastic. "This is especially important to help us maintain muscle mass as we age," says Sedlacek. Indeed, low collagen is linked to osteoarthritis, osteoporosis, and cardiovascular disease.

Like many proteins, collagen also plays a role in blood clotting. "When the blood vessels become damaged, collagen plays a role in helping to stop bleeding," says Sedlacek. Redd adds that a lesser-known benefit associated with collagen is that it also "keeps the lining of our intestines healthy, so we suffer from fewer gut problems."

What are the best sources of collagen?

Because of such important functions, it's helpful to include collagen as part of a healthy diet. Animal proteins such as chicken, eggs, fish, and bone broth are good food sources of collagen. Foods rich in vitamin C are also important because vitamin C plays an important role in collagen production.

Nearly as important, especially as we age, is eating foods that also prevent the loss of collagen. "Consider eating foods with antioxidants to prevent the breakdown of collagen," recommends Stevenson. Antioxidant-rich foods include blueberries, apples, beans, cranberries, pecans, and dark leafy greens. Stevenson also advises avoiding "direct sun exposure, smoking, and pollutants" because they are known to affect one's collagen levels.

And when such diet choices aren't enough, Redd says collagen supplements may also be helpful, especially for the elderly and anyone dealing with gastrointestinal or autoimmune disorders. "I always advise such patients to eat foods rich in collagen and to consider supplementing with a high-quality hydrolyzed collagen manufactured in the United States," he says.

Do collagen supplements work? Experts weigh in on popular anti-aging pills, creams.

This article originally appeared on USA TODAY: What is collagen? Benefits and best sources to get collagen