Chrysin is a dietary flavenoid found in honey, propolis and plants, including the Passiflora. Bodybuilders take chrysin supplements to increase testosterone production, in part through the reduction of estrogen production, according to the University of Hawaii at Manoa. However, chrysin is unlikely to be effective for this purpose, although it might be useful for other purposes.
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Use by Bodybuilders
A 2003 article by C. Gambelunghe published in the "Journal of Medicinal Food" showed that although previous studies done in test tubes or using mice indicated that chrysin was an inhibitor of aromatase enzyme, leading to the theory that its use would increase testosterone levels, human tests showed no increase in urinary testosterone levels after supplementation with chrysin. If chrysin really increased testosterone levels, urine levels of testosterone would also increase. This means that usage for increasing muscle mass and libido is contraindicated.
A study in the "Journal of Medicinal Food" in 2008 by PR Barbosa involved mice and appeared to show that chrysin has an anti-anxiety effect that didn't affecting memory. If further research shows the same effect in humans, this could lessen the need for current anti-anxiety medications with unpleasant side effects.
In 2005, "FEBS Letters" contained a study by KJ Woo showing possible anti-cancer, anti-inflammatory and anti-oxidation effects for chrysin. Further research could lead to development of new cancer treatments.
There is a good reason chrysin supplementation didn't lead to increased testosterone levels in previous studies. According to a 2001 "British Journal of Pharmacology" study by T. Walle, chrysin is not well absorbed when taken orally, and its bioavailability is very low due to the way it is metabolized. Most of the chrysin taken orally is excreted in the feces.
The beneficial studies mentioned above showing the possible effectiveness of chrysin for helping with particular health conditions did not involve human trials. Finding a way to increase the bioavailability of chrysin is important if these positive results are going to be translated into benefits for people since oral supplementation is not effective.
A 1986 study on plant flavenoids and thyroid function done by J. Koerhle that appeared in "Progress in Clinical and Biological Research" found that chrysin can inhibit thyroid function. Chrysin inhibits an enzyme called deiodinase which is involved in thyroid hormone metabolism. An underactive thyroid can lead to increased weight gain, heart disease, joint pain and infertility, according to the Mayo Clinic.