Kalman says that people on low-fat and non-fat diets are at risk for nutrition-related hair loss because hair needs essential fatty acids. "Essential fatty acid deficiency causes a drying-up of the scalp and skin," he says. "These are vital nutrients that support follicular health. When the follicle is not healthy, hair loss or thinning occurs."
Omega-3 fatty acids can be found in fatty fish such as salmon and mackerel, and in flaxseed oil and macadamia nuts and walnuts. It's recommended that women, in particular, try to eat a food source of omega-3 fatty acids three times a week to maintain skin and hair health.
Biotin, part of the vitamin B complex, is another nutrient associated with hair loss. According to Kalman, people who are eating adequate amount of protein—which includes most Americans—should not have a problem with biotin deficiency, though vegans may be at risk. Good food sources of biotin are eggs, liver and soy.
Karmally says that it's not known if biotin supplements, which are marketed to help with male- and female-pattern baldness, can help with hair loss, and adds that she is unaware of any research indicating that the biotin in biotin hair products, such as shampoos, can be absorbed through the hair or scalp.
Karmally recommends that people experiencing hair loss see a physician, who can help determine the cause of their hair loss, and registered dietician, who can assess their diet and health status. "When you are looking for symptoms of nutrition deficiency in someone with skin and hair changes, it's difficult to pinpoint the cause," she says. "People should pay attention to all aspects of their diet for their total health, as well as their hair and skin."