Horny Goat Weed inhibits cortisol
Horny Goat Weed, aka Epimedium brevicornum, contains the flavonol icariin, a substance that has been shown to boost testosterone levels in animal studies. According to researchers at Nanjing University, this same icariin prevents the cortisol level from rising under conditions of stress.
Studies have shown that Horny Goat Weed enhances stamina in lab animals, and reduces cortisol produced as a result of exertion. The researchers wanted to know whether icariin can also reduce the rise in cortisol level during chronic stress. They decided to expose rats to chronic, but not extreme, stress for a week.
Every day the Chinese hung a stroboscope above the rats' cage, tilted their cage, introduced a strange animal into the cage, wet their sawdust, took away their food and drink, and exposed them to noise.
Half of the rats were given a placebo daily [vehicle] and the other half were given a small amount of icariin. Administration started 5 weeks before the stress week began.
The figure below shows that icariin suppresses the production of the stress hormone corticotrophin-releasing factor. CRF is produced by the hypothalamus and boosts the production of ACTH by the pituitary gland in the brain. ATCH in turn stimulates the adrenals to produce more cortisol.
The icariin did indeed reduce the production of cortisol – as well as the production of stress proteins like interleukine-6 and TNF-alpha.
A raised cortisol level as a result of chronic stress can lead to depression, and the Chinese believe that Horny Goat Weed may protect against this. If they are right, then Horny Goat Weed may be of interest to athletes who are under stress: life stress raises the chance of injury or illness and reduces the effectiveness of training.
Biol Pharm Bull. 2006 Dec; 29(12): 2399-403.
Grape Seed Extract blocks glucocorticoid receptor 05.08.2009
Quercetin reduces cortisol peak after stress 30.05.2009
Drinking water while exercising keeps cortisol low 20.01.2009
Horny Goat Weed