Collagen is the most abundant protein in your body and helps make up tendons, ligaments, and your skin ().

Your body produces collagen, but you can also get it from supplements and foods, such as bone broth.

It may offer a variety of health benefits, such as promoting healthy, strong hair.

Here are 5 evidence-based ways that collagen may improve your hair.

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Hair is primarily made up of the protein keratin.

Your body uses several amino acids to build keratin — some of which can be found in collagen (, 3).

When you consume collagen and other proteins, your body breaks them down into amino acids that are then used to build new proteins and compounds ().

There are 11 nonessential amino acids that your body can make and 9 essential ones that you need to obtain from your diet. Collagen is primarily made up of 3 nonessential amino acids: proline, glycine, and hydroxyproline (, , ).

Proline is also the main component of keratin. Therefore, consuming proline-rich collagen should provide your body with the building blocks it needs to create hair ().

However, human studies in humans on the effects of collagen on hair are lacking, making it difficult to know if this protein promotes hair growth.

Summary Collagen is rich in amino acids that your body needs to build keratin, the protein that makes up hair. Still, human studies on the use of collagen to increase hair growth are lacking.

Collagen can act as an antioxidant and fight damage caused by free radicals.

Free radicals are compounds that develop in your body as a result of stress, air pollutants, smoking, poor dietary choices, alcohol, and other environmental influences. Too many free radicals can harm your cells, proteins, and DNA ().

Research shows that free radicals may also damage hair follicles. Since your body’s defense against free radicals decreases with aging, older adults are especially susceptible to hair damage ().

To fight free radicals and promote healthy hair, your body needs antioxidants.

Several test-tube studies have shown that collagen — especially from fish scales — may have powerful antioxidant activity (, , ).

One study found that marine collagen was able to fight four different free radicals, while another study observed that the protein may be a more effective antioxidant than a well-known compound found in tea (, ).

Still, keep in mind that research has only been performed in isolated cells in labs. Thus, the antioxidant potential of collagen in your body is unclear.

Summary Hair follicles can be damaged by free radicals. Collagen may act as an antioxidant that can fight free radicals and prevent hair damage, but research is limited.

Collagen makes up 70% of your dermis, the middle layer of your skin that contains the root of each individual hair (12).

In particular, collagen contributes to the elasticity and strength of your dermis. With age, your body becomes less efficient at producing collagen and replenishing cells in the dermis. This may be one of the reasons why hair gets thinner over time (, , , ).

Therefore, providing your body with collagen may help maintain a healthy dermis and prevent hair thinning.

One eight-week study in 69 women aged 35–55 found that taking daily collagen supplements significantly improved skin elasticity compared to a placebo ().

Another 12-week study in more than 1,000 adults found that a daily collagen supplement improved the amount of this protein in the skin and reduced signs of skin aging ().

Since hair grows out of your skin, the potential of collagen to counteract the effects of skin aging may contribute to better hair growth and decreased thinning. However, research on the impact of collagen on hair thinning is unavailable.

Summary Since collagen protects the layer of skin that contains hair roots, it may help prevent age-related hair loss and thinning — but research on these effects is currently unavailable.

Due to its antioxidant properties, collagen may be able to fight cell damage and slow graying.

Age-related hair graying is largely influenced by genetics, but free radical damage to the cells that produce hair color may also play a role ().

As you age, the cells that produce the melanin pigment that gives your hair its color naturally begin to die. However, free radicals that result from poor diet, stress, and environmental pollutants can damage melanin-creating cells as well ().

Without enough antioxidants to fight free radical damage, your hair may begin to gray. In fact, one test-tube study found that the antioxidant activity of gray hair follicles was much lower than that of hair follicles that still contained pigment (, ).

Since collagen has been shown to fight free radicals in test tubes, it may, in theory, help prevent damage to cells that produce hair color. As a result, it may prevent premature graying or slow down age-related graying (, ).

Nevertheless, research on the antioxidant effects of collagen in humans is currently lacking.

Summary Free radical damage to cells that produce hair color may accelerate graying to some extent. Since collagen can act as an antioxidant, it may be able to fight this damage and slow graying.

You can add collagen to your diet through foods or supplements.

Since it makes up the connective tissue of mammals, it’s found in the skins, bones, and muscles of chicken, beef, pork, and fish.

Broth made from animal bones contains both collagen and gelatin, a cooked form of collagen. This bone broth can be sipped as a drink or used as the base for soups ().

In addition, eating foods high in vitamin C may boost your body’s natural collagen production. Oranges, bell peppers, Brussels sprouts, and strawberries are excellent sources of this vitamin ().

Lastly, collagen can be taken as supplemental pills or powder. Most collagen supplements are hydrolyzed, meaning they’re already broken down and easier to absorb ().

Collagen powder is flavor- and odorless and can be added to smoothies, coffee, and other hot or cold liquids. Flavored varieties are available as well.

According to current research, collagen supplements appear to be safe for most people. However, some reports suggest that supplements may cause a lingering aftertaste, stomach discomfort, or heartburn ().

Summary Collagen can be found in foods, such as bone broths and animals meats, including the skin. Collagen supplements are available as well, many of which contain collagen that has already been broken down, making it easier to absorb.

Collagen may promote healthy hair in a variety of ways.

For one, your body may be able to use the amino acids in collagen to build hair proteins and strengthen the skin that contains your hair roots. It may also prevent hair follicle damage and graying.

However, research on the effects of collagen on human hair is limited.

If you’re interested in trying collagen to improve your hair, consider bone broth or supplements that can be mixed into food or drinks.

You can purchase collagen supplements at local retailers or online.