A lot. Good health has a lot to do with good-looking hair; that is, good health and good hair care practices aren’t strange bedfellows; in fact, they are intertwined and inseparable. Adequate nutrients in diet reflect positively on healthy-looking hair. However, some people do not have access to good nutrition and others have medical illnesses that predispose them to nutritional deficiency which influences scalp / body hair. Nutrition being a complex subject, the effects of correct nutrition is indirect and often slow to appear. Hair in particular, is slow to respond to any stimulus. Trials have corroborated the fact that right nutrition paves the way for healthy hair growth, and conversely many deficiencies correlate with hair loss.
Hair nutrition is, therefore, a vital part of any treatment regime. A truly systematic and rigorous approach must be adopted while formulating a nutritional supplement for hair growth as many factors impact the eventual efficacy of the treatment. Malnutrition, congenital heart disease, neuromuscular disease, chronic illnesses, malignancy, alcoholism, and advanced age can cause hair to change colour, get weakened or lost.