Saponin: Natural Steroids

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As any reader of the sports pages knows, some athletes looking for a competitive edge “bulk up” by using synthetic steroids. These anabolic compounds, which are synthetic derivatives of testosterone, have many side effects, including liver damage, mood swings, and impotence. It’s no wonder that these compounds have a bad reputation.

But not all steroids are harmful. In fact, they’re essential to our health. Human sex hormones such as estrogen, progesterone, and testosterone are all classified as steroids, as are cortisone and forms of ­vitamin D. The class also includes the bile acids and sterols such as cholesterol, which our bodies use to make sex hormones.

Plant pretenders

Some plants can affect human hormones, a feat they achieve by producing their own steroids. Although we don’t yet understand why plants produce these compounds, we do know that some plant steroids resemble human steroids in both form and function. For example, plants are rich in beta-sitosterol, a compound that resembles cholesterol. Plants use this compound almost in the same way humans use cholesterol–to make hormones that control cell growth and reproduction.

One class of plant steroids is known as the steroid saponins. “Sapon” means soap in Old German, and refers to the tendency of saponins to foam in water and, perhaps, their tendency to taste like soap. The instructions on a package of quinoa tell you to rinse the grain before cooking. When you do this, a foamy, milky liquid washes off that contains saponins. If it wasn’t rinsed off, the grain would taste bitter.

Some plant saponins can weakly mimic the human hormones that they resemble. For example, yam (Dioscorea spp.) contains variable amounts of a saponin called diosgenin, which can be converted into hormones such as progesterone and estrogen. In fact, Mexican yam (D. composita) has been used to make oral contraceptives. But our bodies can’t convert diosgenin into steroids without some help from a chemist; converting diosgenin into hormones needs to be done synthetically in a laboratory. Because of this, many commercial wild yam creams popular among menopausal women add synthetic progesterone to increase the product’s effectiveness, although the added progesterone may not be listed on the label.

Unprocessed diosgenin does have a very weak estrogenic or progesteronic effect, so weak that it’s hard to say which way the effect goes. This effect may account for wild yam’s long history of use by women for various reproductive system ailments.

Benefit from eating yams

Fenugreek (Trigonella foenum-graecum), an herb used in the cuisines of India and the Middle East, contains seeds that are richer in diosgenin than any yam; it contains other saponins too. Fenugreek is traditionally recommended to increase breast milk production and breast size, although there’s no conclusive research supporting these uses.

Fenugreek saponins resemble cholesterol, and human studies show that they can lower levels of cholesterol and triglycerides, compounds associated with heart disease. In a 1996 study from India, diabetics taking 25 g of fenugreek for 24 weeks lowered their cholesterol by 14 percent and triglycerides by 15 percent. A 1991 French study of diabetic dogs showed that saponins reduced cholesterol absorption from foods and decreased the amount of cholesterol stored in the liver.

The most celebrated saponins are the ginsenosides, found in all ginseng species, especially Korean or Asian (Panax ginseng). Ginseng is sometimes promoted as an aphrodisiac and enhancer of male virility, but this is misleading. Ginsenosides are less like our sex hormones and more like our corticosteroid hormones in that they weakly stimulate the adrenal and pituitary glands, which may account for ginseng’s ability to combat fatigue, help the body adapt to stress, and regulate the immune system. Adrenal and pituitary stimulation may also lead to enhanced sexual desire/ performance, but, again, no conclusive human studies demonstrate this.

In the big picture, we’re lucky that plant hormones are as mild as they are. Plants that could exactly duplicate our steroid hormones would undoubtedly be a commercial success today, but would have been ­disastrous for humans as we evolved. Interfering with our delicate hormonal balance might have kept humans from evolving at all. Imagine the consequences of a food or spice that could have caused infertility, birth defects, mental illness, cardiovascular disease, or other problems. We’re likely better off with these saponin “mimics” for subtler–and safer–effects.

C. Leigh Broadhust holds a doctorate in geochemistry and is a nutrition consultant in Clovery, Maryland.

James Dukeis a member of the Herbs for Health Editorial Advisory Board. His most recent book isThe Green Pharmacy(Rodale, 1997).

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