Most of your hair is made up of protein (with a little bit of fat and a few other components), specifically a protein called keratin. And the protein you get in your diet can help your hair grow and stay healthy, says Shani Francis, MD, MBA, medical director and chief wellness director of Ashira Dermatology.
That's because in order to grow, your hair needs the building blocks of protein, called amino acids. Your body can produce 11 of the 20 amino acids, but that means you have to get the remaining nine amino acids — called essential amino acids — from food.
If your diet is low in complete proteins, which contain all nine essential amino acids, you may experience hair loss, according to a January 2017 report published in Dermatology Practical & Conceptual. Biotin, a B vitamin found in protein you eat, helps metabolize amino acids and can support strong, healthy hair, Dr. Francis says (although you probably don't need biotin supplements unless you're deficient in it, according to March 2019 research published in Dermatology and Therapy).
One of your body's priorities when it comes to using protein, Dr. Francis says, is to support healthy muscle tissue. If your body isn't getting enough protein to maintain basic muscle function, your hair will suffer first, she says. "The body is using everything it can to keep going what's most important," she says.
How Much Protein Do I Need?
Protein deficiency is incredibly rare in the United States, even among those who follow vegetarian and vegan diets, according the U.S. National Library of Medicine. The recommended daily intake is about 46 to 56 grams of protein for adults, or about 10 to 35 percent of total caloric intake, according to Harvard Health Publishing. Dr. Francis recommends her average female patients aim for 40 grams of protein per day.
After about two to three months of not getting enough protein, a person may start to notice hair loss, according to the American Academy of Dermatology (AAD).
The Best Sources of Protein for Healthy Hair
Although she recommends getting your nutrients from whole foods whenever possible, Dr. Francis says what's most important is getting enough protein, period. "Some people choose protein bars or shakes, and if it's easier for them to get protein that way, I don't discriminate."
Nutritious sources of lean protein include fish, eggs, chicken, dairy, nuts, legumes, quinoa and beans; together they'll provide the complete proteins your body needs to perform normal functions, including hair growth. Friendly reminder: A serving size of animal protein isn't very large — about three ounces, or the size of a deck of cards, in most cases.
Dr. Francis points out that even those following a protein-restrictive diet, like a vegan diet, can still meet their protein requirements from plant-based protein but does recommend vegans work with a dietitian.
Keep in mind that while protein restriction can certainly lead to hair loss, Dr. Francis says, there are other factors that might be contributing to thinning hair, according to the AAD. Before loading up on protein, you may need to rule out (with the help of a medical professional) high levels of vitamin A, low levels of iron, thyroid disease, infection, stress or malnutrition from an eating disorder.
- Dermatology Practical Conceptual: "Diet and Hair Loss: Effects of Nutrient Deficiency and Supplement Use"
- Dermatology and Therapy: "The Role of Vitamins and Minerals in Hair Loss: A Review"
- American Academy of Dermatology: "Hair Loss"
- U.S. National Library of Medicine: "Dietary Proteins"
- Harvard Health Publishing: "How Much Protein Do You Need Every Day?"