What is the role of sebum in hair loss?

Sebum is the oily liquid covering the skin surface. Recently, a group of Japanese researcher reported a correlation between excessive sebum in the scalp and hair loss. Excessive sebum often accompanying thinning hair is attributed to an enlargement of the sebaceous gland. They believed excessive sebum causes a high level of 5-alpha reductase, the enzyme that converts testosterone into dihydrotestosterone (DHT), and pore clogging, leading to malnutrition of the hair root and a shift into the resting (telogen) phase. Although this condition could be hereditary, they believe diet is a more likely cause. The researchers note that Japanese hair was thick and healthy, with a small gland and little scalp oil, until large amounts of animal fat crept into their diet after WWII. This change has led to a significant height increase in the Japanese population, but it has also resulted in more Japanese men losing hair. To some extent, their observation makes sense: problems with greasy hair have ...  more