The anabolic effect of garlic

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.

Garlic as a drug
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.

Study
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.

Results
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.

Dialyldisulphide
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.

Garlic supplementation increases testicular testosterone and decreases plasma corticosterone in rats fed a high protein diet.

Abstract

The effects of garlic supplementation on protein metabolism were investigated by measuring testis testosterone and plasma corticosterone in rats fed diets with different protein levels. In Experiment 1, rats were fed experimental diets with different protein levels (40, 25 or 10 g/100 g casein) with or without 0.8 g/100 g garlic powder. After 28 d of feeding, testosterone contents in the testis were significantly higher and plasma corticosterone concentrations were significantly lower in rats fed 40 and 25% casein diets with garlic powder than in those fed the same diets without garlic powder. Urinary excretion of 17-ketosteroid (an index of testosterone), nitrogen balance and hepatic arginase activity were significantly higher in rats fed the 40% casein diet with garlic powder than in the 40% casein controls. In Experiment 2, the effect of diallyldisulfide (a major volatile sulfur-containing compound in garlic) on the secretion of luteinizing hormone (LH) from the pituitary gland, which regulates testosterone production in the testis, was investigated in anesthetized rats. Plasma LH concentration increased dose dependently after administration of diallyldisulfide (P < 0.01, r = 0.558). These results suggest that dietary supplementation with 0.8 g/100 g garlic alters hormones associated with protein anabolism by increasing testicular testosterone and decreasing plasma corticosterone in rats fed a high protein diet. PMID: 11481410 [PubMed - indexed for MEDLINE] Source: http://www.ncbi.nlm.nih.gov/pubmed/11481410