Definition: "An ergogenic aid is any substance or phenomenon that enhances performance "

about us





Strength athletes can boost immune system with cystine and theanine

Many strength athletes who push themselves hard are more susceptible to colds and flu. Their training takes a heavy toll on their immunity and this reduces the activity of their natural killer cells, the first line of defence in the immune system. Researchers at the University of Tokyo have discovered that strength athletes can do something about this by taking nutritional supplements that contain 2 amino acids.


When a dangerous organism enters the body, our natural resistance mechanism is activated, starting with the natural killer cells. Call them the body's storm troopers: at the first sign of trouble they spring into action and only afterwards start to ask questions. Their activity is reduced if there's less glutathione in the body, animal and test-tube studies have shown. Glutathione is a tripeptide consisting of glutamine, cysteine and glycine. Antioxidant enzymes need glutathione to function properly.

Supplements manufacturers have been marketing N-Acetyl-L-Cysteine as a glutathione precursor for years. But the Japanese tried a different strategy: a mixture of cystine and theanine [see structural formulas above]. Cystine is a compound of 2 cysteine molecules, and occurs naturally in egg protein. Theanine is an amino acid found in green tea.

The Japanese did an experiment with 18 young strength athletes. Half of them were given a placebo; the other half got 700 mg cystine and 280 mg theanine daily. These are larger amounts than you get from a normal diet. The athletes were given a powder made by the Ajinomoto company [also sponsor], dissolved in water. They drank a glass of this every day after a meal.

The experiment lasted 2 weeks. In the first week the subjects trained 3 times a week, following their normal schedule. The second week they trained 6 times a week.

When the researchers did a natural killer cell count at the end of week 1, they noticed that there had been little decline in the placebo group. But by the end of week 2 their count had gone down.

Strength athletes can boost immune system with cystine and theanine

In the supplement group the natural killer cell activity remained high throughout the 2 weeks.

Strength athletes who train just a couple of times a week have a normally functioning immune system, the Japanese conclude. They don't need supplements. But if they train harder and more often than normal for a period, they can protect themselves from becoming ill by taking extra theanine and cystine.

Forgive our habit of asking irritating questions, but couldn't athletes achieve the same by increasing their protein intake during an intensive training period?

J Strength Cond Res. 2010 Mar; 24(3): 846-51.