A spermidine-based nutritional supplement prolongs the anagen phase of hair follicles in humans: a randomized, placebo-controlled, double-blind study

BACKGROUND: Spermidine has been shown both in vitro and in mice models to have an anagen-prolonging effect on hair follicles (HFs). OBJECTIVES: To evaluate the effects of a spermidine-based nutritional supplement on the anagen phase of HFs in healthy human subjects in a randomized, double-blind, placebo-controlled trial. METHODS: One hundred healthy males and females were randomized to receive a tablet containing a spermidine-based nutritional supplement or a placebo once daily for 90 days. At the beginning and the end of the treatment period, 100 HFs were plucked and subjected to microscopic evaluation to determine the number of anagen V–VI HFs, and immunohistochemical examination was performed to quantify the Ki-67 and c-Kit levels in the hair bulbs. Pull test was performed after three and six months. RESULTS: The spermidine-based nutritional supplement increased the number of anagen V–VI HFs after three months of treatment, accompanied by increased Ki-67, a marker for cellular proliferation, and decreased c-Kit, a marker for apoptosis, levels. All results were also significantly better when compared to the placebo group. The pull test remained negative after six months in all patients receiving the spermidine supplement, while 68% of the subjects in the placebo group had a positive pull test. CONCLUSIONS: This preliminary study shows that a spermidine-based nutritional supplement can prolong the anagen phase in humans, and therefore might be beneficial for hair loss conditions. Further studies are needed to evaluate its effects in specific different clinical settings.