Several studies have brought to light that too much caffeine can have a detrimental affect on hair. But, a small amount daily can help with hair growth.
Differential effects of caffeine on hair shaft elongation, matrix and outer root sheath keratinocyte proliferation, and transforming growth factor-β2/insulin-like growth factor-1-mediated regulation of the hair cycle in male and female human hair follicles in vitro.
Caffeine enhanced hair shaft elongation, prolonged anagen duration and stimulated hair matrix keratinocyte proliferation. Female HFs showed higher sensitivity to caffeine than male HFs. Caffeine counteracted testosterone-enhanced TGF-β2 protein expression in male HFs.
Another study showed: Caffeine was identified as a stimulator of human hair growth in vitro; a fact which may have important clinical impact in the management of AGA. However, too much caffeine can decrease hair growth.
For caffeine, dose-response experiments showed that a concentration of 0.15% was stimulatory in the MSOCM,13 but suppressive in the hair follicle model. Also concentrations of 0.05% and 0.01% showed suppression.
These high concentrations were regarded as nonphysiologic or toxic, an effect which can be observed in many substances. High concentrations may cause an over-stimulation of hair follicle metabolism resulting in extensive consumption of energy reserves, exhaustion of the proliferation capability and finally lack of hair shaft elongation.
How do we know the exact amount needed for optimal growth? From patient feedback.
After treating thousands of patients for hair loss, patients report typcially one up to two cups daily works optimally for hair growth. Over that amount we see negative effects on the hair.
But we must remember that caffeine is found in coffee and tea and in energy drinks. We must be careful of energy drinks because the amount of caffeine is extremely high and does not always reflect the amount labeled on the bottle.