Walk into a health food store these days and chances are you won’t find much food. But you will find a bewildering array of dietary supplements, often shelved in alphabetical order. One of the first ones you’ll encounter is L-Arginine. The label won’t be very informative. It may say something like “dietary supplement,” or “conditionally essential amino acid,” or “support for healthy cardiovascular function” or “supports circulation.” However, if you stroll over to the aisle where books, magazines and brochures are displayed, you’ll quickly find far bolder claims about the benefits of taking arginine supplements. There will be claims about helping with heart disease, erectile dysfunction, cramps due to blocked arteries in the leg, wound healing, high blood pressure, migraines, senile dementia, athletic performance and interstitial cystitis, a painful bladder condition. On top of all that, it is supposed to treat herpes simplex infection and prevent the common cold.
Anytime such an abundance of claims are made on behalf of a single substance, a degree of skepticism is warranted. If something sounds too good to be true, it usually is. But there is only one way to check it out. Forget the books, the magazines, the brochures, the ads on the web or the compelling stories from the neighbour. The thing to do is to turn to the peer-reviewed literature. And since arginine has been extensively studied, there is plenty of it. Much of it is confusing, but about one aspect of arginine’s role in health there is no doubt. This amino acid is a building block of various essential proteins in the body and therefore we cannot live without it. But a deficiency is unlikely since arginine occurs widely in meat, dairy products, soy and nuts. Furthermore, our body can synthesize it from other amino acids in the diet.
But what about all the other health claims? Are they supported by proper evidence? That depends on where one draws the line for “proper evidence.” The most interesting therapeutic connection is arginine’s role as a precursor to nitric oxide, a compound that relaxes blood vessels, and thereby improves blood flow. This would explain claims of benefit for high blood pressure, coronary heart disease, congestive heart failure, leg pain, erectile dysfunction and decreased mental capacity in the elderly, all conditions that would be expected to improve with enhanced circulation. These claims are indeed substantiated by some peer-reviewed studies, but while the results are statistically significant, they are not very compelling. Best description would be that arginine is “possibly effective.”
Some limited evidence supports arginine’s role in the formation of L-proline, an amino acid that is essential for the synthesis of collagen, a protein needed in would healing. And a few studies have indicated help with interstitial cystitis. The usual dose for any of these conditions is around five grams per day. Side effects are rare, but stomach irritation due to increased acid secretion is possible. In some cases, especially in combination with blood pressure lowering drugs, arginine may cause blood pressure to fall too low. The same may happen when taken with nitrates or sildenafil (Viagra). However, the most significant problem that has cropped up involves taking arginine after a heart attack. A clinical trial found an increased risk of death! In patients who suffer from kidney or liver disease, arginine can cause a life threatening rise in potassium. Bottom line is that arginine may help with some conditions, but not in a dramatic fashion. Whether it is worth the usual cost of roughly three dollars a day is debatable.