Nettle Leaf

Proposed mechanism

Nettle leaf supplies iron, calcium, and other minerals as part of general nutrient intake; there is no evidence it displaces cadmium, lead, or other heavy metals from the body. In laboratory cell studies, nettle leaf extract and its phenolic constituent caffeoylmalic acid inhibit cyclooxygenase-derived inflammatory mediators — a proposed anti-inflammatory mechanism, not one confirmed in people. Separately, traditional practice presses the fresh leaf against a painful joint so that histamine, serotonin, and acetylcholine in its stinging hairs act as a topical counterirritant, similar in principle to capsaicin creams. The human evidence there is limited and mixed: one small one-week crossover trial reported reduced base-of-thumb osteoarthritis pain against a non-stinging placebo leaf (a sting is difficult to blind), while a later randomized knee pilot, not powered for efficacy, found no difference from placebo, and Cochrane rates topical nettle evidence as very low quality. That counterirritant effect depends on the fresh, actually stinging leaf contacting skin; dried or encapsulated nettle taken by mouth does not produce it.

Mechanisms describe how researchers think a compound may act, often from laboratory work — a proposed mechanism is not proof of a clinical effect in people.