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Smoother skin, shinier hair, stronger nails, healthier joints, and more lean muscle mass—these are just a few of the benefits proponents claim collagen powders, pills, and foods can deliver.

Plenty of people are buying into the idea. Collagen is promoted as an anti-aging compound, as well as a beauty and performance enhancer, says Karen Formanski, an analyst with market research firm Mintel, making it appealing not just to middle-aged consumers but also to younger ones. According to projections by Nutrition Business Journal, collagen supplement sales in the U.S. will reach $298 million this year—up from $73 million in 2015.

Although collagen supplements have been around for quite a while, collagen has more recently popped up as an ingredient in foods. “The category of functional foods and drinks with added collagen has really exploded in the past couple of years,” Formanski says. “We see it as an offshoot of the overall trend of foods and drinks with added protein.” Energy bars, oatmeal, smoothies, coffee creamers, and popcorn are just a few of the foods that tout collagen on their labels.

But is eating more collagen really the quickest route to looking and feeling younger? Here’s what we know.

What Role Does Collagen Play in the Body?

Collagen is a type of protein. The word collagen derives from the Greek word kolla, which means glue. And true to its definition, collagen really is like an adhesive that holds many of the body’s tissues together. Skin, tendons, ligaments, bones, and cartilage—what are commonly known as connective tissue—are made up of collagen, says Keith Baar, PhD, professor of molecular exercise physiology at the University of California, Davis. When your body makes more collagen, these tissues are healthier, thicker, and spongier, he says, so they’re better able to support and protect your joints.

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Where a lack of collagen may be most noticeable is in the skin. “Collagen—along with elastin—is what supports and sustains the dermis [the middle layer of skin],” says Maritza Perez, MD, clinical professor of dermatology at New York City’s Icahn School of Medicine at Mount Sinai and member of the Skin of Color Society board of directors.

As you age, your body becomes less efficient at making collagen, and getting too much ultraviolet light from the sun accelerates the natural decline. “Sun exposure leads to collagen breakdown and results in less new collagen being produced,” Perez says.

In people with fairer skin, collagen breakdown—evidenced by wrinkles and sagging or crepey skin—becomes visible around age 50, but in some people with darker skin (who have more natural protection against UV rays), it may happen a decade later.

How Does the Body Make Collagen?

All proteins are made up of tiny molecules called amino acids. When you eat protein, your body breaks it down into its individual amino acids. It then uses those amino acids, along with amino acids it can produce on its own, to make new proteins.

“Amino acids are like building blocks, and the body puts some of them together in a specific pattern to form collagen,” says Lauri Wright, PhD, an associate professor of nutrition at the University of North Florida in Jacksonville. The three amino acids most prevalent in the formation of collagen are glycine, proline, and hydroxyproline.

Although collagen is found naturally in animal foods, your body can still make it if you don’t eat meat, dairy, or eggs. “As long as you eat a variety of plant proteins—such as legumes, soy, and quinoa—you will get all the essential amino acids your body needs to build collagen,” Wright says.

In addition to protein, your body also needs vitamin C, zinc, and copper to help it form collagen. “Vitamin C is especially important to regulate the synthesis of collagen,” Wright says. Vitamin C is plentiful in citrus fruits, bell peppers, and broccoli. You can get copper and zinc from nuts, seeds, and whole grains.

Does Eating More Collagen Build Your Collagen Reserves?

There’s no doubt that having ample collagen in your body is important. But the question remains as to whether taking supplements or eating foods that contain collagen translates directly to more collagen in your body. All protein you consume, collagen included, is processed by your body in the same way.

“Whether you ingest a collagen supplement or a steak, the body recognizes them as protein and breaks them down into amino acids in the digestive system,” Perez says. “There’s no guarantee that when you eat collagen, those amino acids will wind up in the skin [or ligaments] and produce collagen.”

Supplement proponents argue that in order for your body to make more collagen, it needs more of the specific amino acids (namely glycine and proline) the body uses to build collagen. How do you get more of those amino acids? By consuming more collagen. Many supplements and collagen-enhanced foods use hydrolyzed collagen (also called collagen peptides).

“There is some evidence the body can absorb these and use them to rebuild tissue,” says Donald K. Layman, PhD, professor emeritus in the food science and human nutrition department at the University of Illinois in Urbana. “Collagen also contains unique levels of glycine, an amino acid that may stimulate growth hormone, improving collagen synthesis.”

But even if eating collagen directly does lead to more collagen in your body, you don’t need special collagen foods or supplements to get it. Collagen is found in meat, poultry, fish, egg whites, and gelatin, as well as in stock or bone broth. The latter two are made from simmering animal bones for several hours, which leads to the collagen in the bones being released into the liquid.

It’s not really clear how much collagen you get from foods that contain it. For example, Purely Elizabeth Vanilla Pecan Collagen Protein Oats and Pact Glow With It Snack Bites have 10 grams of protein per serving. But in addition to collagen, protein-containing foods—such as nuts and seeds (in the oats) and egg white powder and pea protein (in the snack bites)—are on the ingredients list.

Does Collagen Really Do All the Things It’s Claimed to Do?

“Currently, we’ve got this huge gap between what protein science tells us and what consumers who take collagen have been saying for years—back to ancient times in Asia,” Layman says. “There’s an amazing amount of subjective evidence saying it’s great, but there’s not a lot of science to prove it.”

There have been small studies looking at the effect of supplemental collagen on ligaments and other connective tissue that have shown some promise. A placebo-controlled study of 20 runners with Achilles tendon injuries found that those who took 2.5 grams of collagen twice daily had greater improvement in Achilles pain at the three-month mark and were able to return to running sooner than those taking a placebo. (This study was financially supported by a manufacturer of collagen supplements.) And another study of just eight people found that consuming a vitamin-C enriched collagen supplement, followed by 6 minutes of jump roping, led to increased collagen synthesis in ligaments. “Exercise is what helps deliver the amino acids into the ligaments,” says Baar at UC Davis.

As for skin benefits, a 2019 review of 11 studies on collagen supplementation published in the Journal of Drugs in Dermatology found that doses ranging from 2.5 to 10 grams per day did increase skin elasticity and hydration.

Still, the research is preliminary, and even studies that hint at positive results from ingesting collagen can’t conclusively prove cause and effect. “There is evidence it is absorbed, and that there is an increase in certain amino acids, but no direct evidence that taking a collagen supplement increases collagen in the skin,” says Natasha Mesinkovska, MD, assistant professor of dermatology at the University of California, Irvine, and author of the review study.

Are Collagen Supplements Safe?

Collagen supplements—as well as the collagen being sprinkled into various food products—are usually derived from the skin, hide, tendons, bones, cartilage, or other connective tissues of cows, pigs, chicken, or fish. Collagen claimed to be vegan is made from genetically modified yeast and bacteria, but there is little evidence that it would have the same potential benefits as animal-derived collagen.

As is the case with all dietary supplements, the Food and Drug Administration doesn’t verify that collagen supplements contain what they say they do or determine whether they’re contaminated with heavy metals, bacteria, or pesticides before they’re sold. Because heavy metals and toxins can collect in animal bones, it’s possible that supplements could be a source of compounds such as arsenic or lead.

For example, a recent analysis of 28 collagen supplements by the Clean Label Project found that 64 percent had detectable levels of arsenic, about one-third tested positive for lead, and 17 percent had cadmium. (Some research has found small amounts of lead and cadmium in bone broths, too.) Although, for the most part, these levels were low, heavy metals accumulate in the body over time, which is one reason experts say there’s no safe intake level for heavy metals.

That said, most studies have not found any serious adverse effects from collagen supplementation (although most involved relatively short-term use). Yet until there’s more conclusive evidence in favor of supplements or collagen-enhanced foods, the best solution may be to focus on eating a healthy diet that supplies adequate amounts of protein, and limiting sun exposure. “Right now, Baar says, “the business component of collagen is further along than the science component.”