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Animal study: L-theanine extends life expectancy

The amino acid L-theanine, which is found in small amounts in tea, extends the lifespan of the worm Caenorhabditis elegans, a favourite lab animal of anti-aging researchers. The extent of the effect, which nutritionists at the University of Jena report on in the European Journal of Nutrition, is limited however.

An average cup of green tea contains about 8 mg L-theanine; an average cup of black tea contains 25 mg. Supplements usually contain several hundred milligrams. Manufacturers suggest that these supplements reduce feelings of stress in a natural way and improve brain function.

In addition to this, there are several studies that suggest that L-theanine has other effects too. Animal studies have shown for example that L-theanine makes beta-amyloid plaques less toxic. [Free Radic Biol Med. 2009 Dec 1; 47(11): 1601-10.] This would suggest that L-theanine supplementation might help inhibit Alzheimer's.

Animal studies have also shown that L-theanine, along with caffeine and catechins, is one of the compounds in green tea that have a slimming effect [In Vivo. 2004 Jan-Feb; 18(1): 55-62.] and that can lower blood pressure. [Biosci Biotechnol Biochem. 1995 Apr; 59(4): 615-8.] Moreover, there are human studies which have shown that supplementation with cysteine and L-theanine protect the immune system of athletes who do intensive training.

The researchers tested the life-extending effect of L-theanine on nematodes in a laboratory. They did this by adding the amino acid to the worms' food. The graph below shows the effect of the most effective concentration. The maximal lifespan increased by 4.4 percent as a result of supplementation and average lifespan increased by 3.6 percent.

Animal study: L-theanine extends life expectancy

Animal study: L-theanine extends life expectancy

The graph above shows the life-extending effect of L-theanine on nematodes that had also been exposed to the toxic pesticide paraquat. Only the highest concentration of L-theanine was capable of extending the lifespan of the nematodes by a statistically significant amount.

"Taken together, these findings indicate that L-theanine extends Caenorhabditis elegans lifespan suggesting that this compound may be worth evaluating in mammals and potentially humans in regard to prevention of aging and age-associated diseases", the researchers summarise.

The study was partially financed by Coca-Cola Germany.

Eur J Nutr. 2012 Sep; 51(6): 765-8.