Are yams an adequate alternative to hormone replacement therapy?

Dear Ana,

Wild yam (Dioscorea villosa) and Mexican yam have been marketed as alternatives to synthetic progesterone (not estrogen), which is a hormone taken by some women during menopause. These yams contain diosgenin, a plant substance that has a chemical structure similar to progesterone. In the laboratory, diosgenin can be converted to progesterone by using specific reagents and enzymes to carry out a series of chemical reactions. This transformation can only be performed in a lab — the same process does not occur in the human body. As a result, it's actually misleading for a manufacturer to term a wild yam supplement as "natural progesterone" because it is not progesterone, nor does it have any impact on a woman's hormone levels. Since diosgenin doesn't have hormonal activity itself, creams containing this substance are not effective.

In the United States, what is commonly referred to as a "yam" is actually a variety of sweet potato (ipomoea batatas). Yams are similar in shape to sweet potatoes, but are drier and starchier in taste, and are rougher and scalier in texture. Sweet potatoes are a good source of beta-carotene, vitamin C, folic acid, and some B vitamins. Predominantly grown in the Caribbean and Africa, yams are a good source of potassium, but contain no beta-carotene, and have lower levels of B vitamins, vitamin C, and folic acid than sweet potatoes. Eating sweet potatoes or yams will provide nutrients, but, as they contain neither progesterone nor estrogen, they won't affect a woman's hormonal balance.