Arginine: Will it Make You Faster?

It pays to be skeptical. An article from the University of California at Los Angeles showed that cyclists over age 50 who took a commercially available supplement containing the amino acid, arginine, and antioxidants gained a 16.7 percent increase in their anaerobic threshold at three weeks (Journal of the International Society of Sports Nutrition, March 23, 2010).

Muscles need oxygen to convert food to energy. Anaerobic threshold occurs when lactic acid starts to accumulate in the muscles, meaning that a person cannot bring in enough oxygen to cover the amount of fuel muscles use for energy, so the person becomes severely short of breath and has to slow down. Arginine is an amino acid protein building block that can stimulate the blood vessels to increase production of nitric oxide. This dilates blood vessels which can increase blood flow to muscles. The authors demonstrated that arginine did not increase the maximal amount of oxygen that a person can take in and use (VO2max).

1) The only people who can benefit from increased anaerobic threshold are those who are exercising as hard as they can. It does not benefit people who are exercising at less than their maximal capacity. If you take these supplements and do not exercise at your maximum, you are wasting your money. Several studies show that nitric oxide releasers may help athletes exercise longer, but the data are weak, sparse and not very impressive. If you are already exercising as hard and as fast as you can, taking these supplements may let you do more work, which may make your muscles stronger (Medicine & Science in Sports & Exercise, December 2000).

2) Promoters of these supplements recommend doses of 6,000-10,000 mg per day and most athletes who use them take far more than that. Each pill used in this study contained 5200 mg. Side effects include nausea, stomach cramps, diarrhea, gout and a worsening of asthma. High doses may drop blood pressure which could harm performance. During exercise you need higher blood pressures to enhance ciruclation to muscles. A person with resting blood pressure of 120/80 can expect it to rise to 200/80 while jogging.

3) The study subjects took arginine at bedtime. We do not know if arginine taken at night would have any effect whatever on nitric oxide production the next day. Exercise, by itself, raises blood levels of nitric oxide (American Journal of Hypertension, August 2007). So if you want your arteries to make more nitric oxide, go out and exercise.

4) Arginine is so readily available from food that deficiencies of arginine are virtually never reported. Your body can make it and it is abundant in meat, poultry, seafood, diary products, all grains, nuts, legumes and other seeds, and in chocolate.