Hair follicles have stem cells called melanocytes that produce a pigment called melanin, which gives hair its color. Melanocytes turn over to continue making melanin for a set amount of time. There are two types of melanin: eumelanin and pheomelanin. Diversity in hair color comes from the quantity and ratio of black-brown eumelanin and red-brown pheomelanin. A mutation in a certain receptor (melanocortin-1 or MC1R) leads to red hair.
As we age, these melanin producing cells go through a phenomenon called apoptosis, or programmed cell death, causing the hair to turn gray or white.
Apart from age, other factors can determine when a person’s hair will start to change color. The first is genetics — if your parents started to gray at an early age, there is a chance you will, too. Ethnicity also plays a role. It has been shown that graying occurs earlier in Caucasians compared with African Americans. A study showed that the average age of graying in Caucasians is 34 compared with 44 in African Americans.
Another reason is stress. The graying of hair most of the time is unrelated to stress, but stress can worsen the graying. Chronic stress can have multiple effects on the body, and the hair is no exception. A 2013 study showed a correlation between stress and graying of hair in mice. The theory is that melanocytes are depleted when under stress. While genetics seems to be a larger factor in when one grays, stress can contribute to it.
A good diet, however, may be able to reverse some of the negative effects of stress on the hair. A diet high in sources of antioxidants, such as fish, olive oil and fresh fruits and vegetables, can reduce oxidative stress.
Other factors known to cause graying include smoking and nutritional deficiencies (such as vitamin D, B12, or ferritin). In these cases, correcting the deficiency has been shown to restore some of the pigment or color to the hair.
To keep hair healthy, eat a balanced diet that is rich in protein and includes lots of fruits and vegetables; and reduce stress with exercise or meditation.
Shilpi Khetarpal is an associate professor of dermatology and a dermatologist at the Cleveland Clinic who specializes in hair disorders and laser and cosmetic dermatology.