Arginine for Sports & Fitness

Some athletes say that arginine helps reduce body fat.

Arginine is a vasodilator; in other words, it increases blood flow so the heart can pump more blood at a lower level. Theoretically, this translates into improved cardiovascular performance. However, more research needs to be done to see if arginine supplementation can enhance athletes’ abilities to perform aerobic activities.

Be aware, when supplementing with individual amino acids, that it is possible to upset the body’s total balance of amino acids by taking just one.

At very high intakes (approximately 250 mg per 2.2 pounds of body weight), the amino acid arginine has increased growth hormone levels,¹ an effect that has interested body builders due to the role of growth hormone in stimulating muscle growth.² However, at lower amounts recommended by some manufacturers (5 grams taken 30 minutes before exercise), arginine failed to increase growth hormone release and may even have impaired the release of growth hormone in younger adults.³

Double-blind trials conducted by one group of researchers, combining weight training with either arginine and ornithine (500 mg of each, twice per day, five times per week) or placebo, found the amino-acid combination produced decreases in body fat,⁴ resulted in higher total strength and lean body mass, and reduced evidence of tissue breakdown after only five weeks.⁵

For most people, arginine has so far appeared to be free of obvious side effects. However, longer-term studies are needed to confirm its safety.

In a double-blind study, supplementation with 9 grams of arginine per day for six months, beginning within 3 to 21 days after a heart attack, resulted in an increase in the mortality rate.⁶ Therefore, people who have recently suffered a heart attack should probably not take large amounts of arginine. Arginine is beneficial for other manifestations of heart disease, such as heart failure and angina. However, because of the potential for arginine to cause adverse effects in heart patients, people with heart disease should consult a doctor before taking arginine.

There have been two case reports of severe allergic reactions following intravenous administration of L-arginine;⁷ however, allergic reactions have not been reported after oral administration.

People with kidney or liver disease should consult their doctor before supplementing with arginine. Some doctors believe that people with herpes (either cold sores or genital herpes) should not take arginine supplements, because of the possibility that arginine might stimulate replication of the virus.

Administration of large amounts of arginine to animals has been found both to promote⁸ and to interfere with cancer growth.⁹ In preliminary research, high intake (30 grams per day) of arginine has increased cancer cell growth in humans.¹⁰ On the other hand, in people with cancer, arginine has been found to stimulate the immune system.¹¹ At this time it remains unclear whether arginine is dangerous or helpful for people with cancer.

Arginine works with ornithine in the synthesis of growth hormone.

Dairy, meat and poultry, and fish are good sources of arginine. Nuts and chocolate also contain significant amounts of this amino acid.