Extracts from the roots of the stinging nettle are used for various alternative medicine treatments, including the reduction of enlarged prostates, according to the University of Michigan Health System. This benefit may be due to the high level of lectins — proteins that bind to sugars — and complex sugars in the plant’s roots. Just because the root extract is natural doesn’t mean it’s safe. Discuss your stinging nettle supplementation plans with your doctor before taking the herb, because it may have several negative side effects.

Pregnancy Problems

If you’re pregnant or trying to become pregnant, avoid using stinging nettle extract products. The herb may affect your menstrual cycle and may even cause you to experience a miscarriage, according to the University of Maryland Medical Center.

Gastrointestinal Discomfort

Every body is different, and yours may not react positively to orally ingesting stinging nettle extract. Gastrointestinal discomfort may occur, according to the University of Michigan, and can include a sore stomach, nausea and vomiting.