Garlic powder boosts testosterone production and reduces cortisol production. This discovery was made by researchers at Kobe University and pharmaceuticals company Riken in Japan. Rats given garlic powder in their feed retain more proteins to boot.
It wasn't the first time that these researchers had studied the pharmacological effects of garlic. In the late nineties they published an article on garlic's ability to break down fat. This is because garlic boosts the production of noradrenalin. [J Nutr. 1999 Feb; 129(2): 336-42.] On this occasion, however, the researchers were examining the anabolic effects of garlic.
The Japanese did tests on three groups of rats; each group was given feed that differed in one aspect only: the amount of protein. The rats' feed consisted of 40, 20 and 10 percent protein.
The researchers then split each diet group into two sub-groups. One was given ordinary feed containing 10, 20 or 40 percent protein; the feed for the other sub-group was enriched with garlic powder. Every kilogram of feed contained eight grams of garlic powder. And one gram of that powder contained five milligrams of dialylsulphides.
The rats were given this feed for 28 days, after which the researchers measured how much nitrogen [read: protein] the rats had retained.
They discovered that garlic had no effect in the rats that had been given little or average amounts of protein. But in the group that had the high protein intake, the nitrogen balance was higher in the garlic group.
The concentration of corticosterone was lower in the garlic rats' blood, as shown below. The graph below also shows the amount of testosterone the researchers found in the rats' testes. The higher the protein intake, the higher the testosterone production – in the garlic rats.
The Japanese think that the way the testosterone production rises has something to do with the messenger hormone LH. They base their supposition on an experiment in which they injected dialyldisulphide – the active substance in garlic – into rats and then measured the LH production. The production rose. The more dialylsulphide the rats got, the higher their LH level rose.
The doses used in the table above are interesting. The figures on the left show the number of millimoles per litre of injected fluid. The rats were given just one millilitre. If the Japanese' assertions are true, then dialyldisulphide is pharmacologically interesting.
Riken, the pharmacologists who funded the research, manufactures garlic extracts for supplements.
J Nutr. 2001 Aug;131(8):2150-6.