Stinging nettle is available as a dietary supplement in capsules and extracts, and is touted for everything from strengthening your adrenal glands to keeping your blood vessels young, your hair thick and your skin clear. It’s said to have anti-inflammatory, immune-modulating and diuretic properties. But much of the “evidence” of health benefits is based solely on traditional use or comes from limited (and poorly done) research.
For example, though freeze-dried preparations have long been recommended to treat allergies (notably hay fever), the Natural Standard, which evaluates alternative and complementary medicine, gives nettle a “C” rating, meaning there are inconsistent or unclear data to support this use. Stinging nettle is also used, especially in Europe, to treat symptoms of an enlarged prostate, but here, too, it gets only a “C.” More research is needed to confirm these and other nettle uses, the Natural Standard says.
Keep in mind: If nettle does affect various body functions, this means that supplements might have unexpected—and sometimes undesirable—consequences. There’s some indication that nettle can increase blood sugar and decrease blood clotting, for example, so anyone who has a bleeding or blood sugar disorder or takes medication for such conditions should be especially wary of supplements. Pregnant and breastfeeding women should avoid them. High doses of nettle may also lower blood pressure, increase urination and cause gastrointestinal upset.