Male or female pattern baldness, known as androgenetic alopecia (AGA), is a common form of hair loss in men and women. AGA is caused by an overproduction of the androgenic hormone, dihydrotestosterone (DHT). DHT is a potent form of testosterone known to stimulate prostate growth and scalp hair loss. An enzyme produced in the prostate, adrenal glands and scalp, called 5-alpha-reductase, metabolizes the male hormone testosterone into DHT.
Certain natural nutrients, such as saw palmetto and L-lysine, act as 5-alpha-reductase inhibitors that block the conversion of testosterone to DHT in the hair follicles. These natural 5-alpha-reductase inhibitors stop the damaging effects of DHT without reacting with testosterone, unlike many prescription drugs. They can reduce and even stop further hair loss. Natural 5-alpha-reductase inhibitors do not have the hormonal side effects associated with many prescription hair loss medications.
Saw palmetto extract, derived from the berries of the Serenoa repens tree, blocks 5-alpha-reductase from converting testosterone to DHT. In a placebo-controlled, double-blind study, 60 percent of male participants with mild to moderate AGA experienced improvement in hair loss when treated with saw palmetto extract and beta-sitosterol (a phytosterol found in many plants and grains).
L-lysine, an essential amino acid, has been shown to inhibit 5-alpha-reductase. A double blind study reports that non-anemic, iron-deficient women with increased hair shedding experienced significant improvement in hair loss when treated with L-lysine and iron therapy.
Life Extension eds., Disease Prevention and Treatment, 4th ed. (Hollywood, Florida: Life Extension Media, 2003), available at:
Burke KE. Hair loss. What causes it and what can be done about it. Postgrad Med. 1989 May 1;85(6):52-73, 77.
Rushton DH. Nutritional factors and hair loss. Clin Exp Dermatol. 2002 Jul;27(5):396-404.