What is collagen? How this supplement may strengthen skin, bones, and joints

• Collagen is the main protein in all the connective tissues in our bodies.
• Collagen supplements may improve the skin's appearance, strengthen bones, and prevent joint pain.
• Side effects of collagen supplements include allergic reactions and stomach upset.

These days, it's common to see celebrities touting collagen supplements as the key to their smooth skin. But collagen isn't just used to get a dewy glow, it's also important for your bones and joints.

Here's what you need to know about what collagen actually is, how it may benefit you, and the risks involved in using it.

What is collagen?

Collagen is the main protein in the structural and connective tissues in our body, including skin, bones, muscles, ligaments, and tendons. Its fibrous structure gives these parts of the body their shape and strength.

There are four main types of collagen:

• Type I is the most common. It's found in skin, bone, teeth, tendons, and ligaments.
• Type II is in cartilage.
• Type III is in the skin, muscle, and blood vessels.
• Type IV is found in basement membranes, layers of cells that surround all body tissues.

Related Article Module: 17 delicious high protein foods you should add to your diet, according to dieticians

Food sources with the highest levels of collagen include the bones and skin of cows, pigs, and fish. But the body can also build collagen itself from other protein sources, so collagen deficiency is not common among otherwise healthy adults.

Benefits of collagen

• Improves skin's appearance. A small 2018 study among Korean women 40 to 60 years old, found those who took a collagen supplement for 12 weeks had increased skin hydration and smoothness.
• Prevents joint injuries and pain by keeping tendons and ligaments sturdy. In a 2017 study, athletes with sports-related knee pain who took collagen supplements had significantly decreased knee pain.
• Increases bone density. A small 2018 study found 12-month daily supplementation of collage in postmenopausal women with age-related reduced bone mineral density (BMD) improved bone formation and slowed bone degradation.

Collagen supplements

Some people may want to increase their collagen intake through supplementation. However, it's important to note most collagen supplements' primary ingredients are bones and skin from animals or fish, so they are not suitable for vegans or vegetarians.

You can buy collagen supplements online or at most health food stores, and there are a few main types to choose from:

• Powders, pills, and drinks: These typically contain collagen peptides, or hydrolyzed collagen, a type of collagen that's easily absorbed by the body.
• Creams or lotions: Many of these products claim to add collagen to the skin, or to stimulate collagen production in the skin. But collagen molecules are too large to penetrate the skin barrier, making most of them ineffective.
• Gelatin: Gelatin is derived from collagen and may firm and smooth aging skin, build stronger bones, and strengthen cartilage.

Important: The Food and Drug Association does not evaluate collagen supplements for quality or safety. If you're an athlete, look for supplements that are certified to be free of banned substances, says Dana Lis, PhD, a registered dietician and performance nutrition consultant for the Golden State Warriors.

Do collagen supplements work?

Related Article Module: Do collagen supplements work? They may benefit your skin, joint, and bone health

There is some research suggesting oral collagen supplements may help keep skin firm and plump as you age, says Nazanin Saedi, a dermatologist and assistant professor at Jefferson University.

"I tell my patients, 'Don't expect a ton. Can it help? Sure. Can I promise it will help? No.' We can't say for sure what the body absorbs from these supplements, and how much of that goes to the skin," she says. There is more data that peptides in topical applications can stimulate collagen production.

Meanwhile, gelatin supplements containing vitamin C can boost the body's collagen production. It may also help people with osteoarthritis. In a small 2015 study, women with the condition who took supplements had reduced pain and improved knee joint function.

If you do take a collagen supplement, aim for about 2.5 to 15 grams per day. There's no evidence that more than that is helpful, Lis says.

"There's a lot of overhype. There's even collagen popcorn now. We're definitely taking in more collagen than is effective," Lis says.

Collagen side effects

• Allergic reactions, including hives, eczema, and wheezing. People with allergies or who are pregnant or breastfeeding should check labels carefully for potential allergens.
• Stomach upset. Collagen supplements can cause diarrhea and abdominal discomforts, such as an unpleasant feeling of fullness or heaviness.
• Food contamination. Collagen supplements may carry a very low risk of contamination from diseased animal tissues, including those that might transmit bovine spongiform encephalopathy, also known as mad cow disease.

Insider's takeaway

Collagen is the most abundant protein in the body. It provides structure for skin, bone, teeth, ligaments, and cartilage.

Some research suggests collagen supplements may promote firm, smooth skin, and protect tendons and ligaments, but more studies are needed to determine how effective collagen supplements are. Plus, we can't control where our bodies use collagen.

Side effects from collagen supplements can include allergic reactions and stomach upset.

Protein builds muscle, boosts the immune system, and helps with weight loss - here's how much you need a day9 tips to permanently get rid of dark circles under your eyes, according to a dermatologist7 simple tips to get glowing skin with a healthy diet and skincare routineAre you eating enough protein? How to recognize the signs and symptoms of protein deficiency