But before arginine became linked to nitric oxide-boosting supplements, it was most associated with growth hormone release. While several other amino acids promote the release of growth hormone, arginine is particularly noted for that effect. In fact, an infusion of arginine at a dose ranging from 12 to 40 grams was often used to determine if a GH deficiency existed, especially in children.
The IV reliably promoted a release of GH in about 20 minutes, except in people deficient in the hormone. That information trickled down to the popular press, with books on longevity declaring that you could effectively promote GH release by taking arginine orally. Several studies appeared to confirm that assertion.
One such study involved 14 men, aged 15 to 30, who took 1.2 grams of arginine polyglutamate and 1.2 grams of L-lysine. That particular combination of amino acids promoted GH release five times greater than when either amino acid was used alone. Lysine and arginine normally compete for uptake in the body, since they both use the same amino acid transport system. Lysine is often suggested as a natural therapy for treating herpes infections because the virus requires arginine for growth and propagation. Lysine displaces arginine, thereby preventing viral replication.
Over the years other studies have attempted to test whether oral arginine is an effective GH releaser. No one questions the effectiveness of infused arginine. The problem with oral arginine is that there are a number of formidable barriers to its absorption, starting with the liver enzyme arginase, which degrades it. Another involves methylated arginine by-products of protein digestion that are inactive analogs of arginine but inhibit genuine arginine functions, including the synthesis of nitric oxide.
A few studies that concluded that oral arginine was ineffective for GH release suffered from flaws. One took only a single blood sample after an oral arginine dose, concluding that arginine showed no apparent GH release. Another was flawed because the researchers used too small a dose of arginine. The fear was that too large a dose would either be degraded in the liver or cause gastrointestinal distress. (Large doses of amino acids draw fluid into the intestine, which can result in nausea and vomiting.)
One study, however, overcame most of the flaws of previous research and found some interesting results.1 Eight healthy men, aged 18 to 33, were examined on four separate occasions. The men reported to a lab after an overnight fast and were promptly fitted with a catheter in their forearm veins. Blood samples were taken every 10 minutes for five hours by the attending physician, Dr. Dracula (just kidding on that last one).
A half hour after catheter insertion the men took doses of arginine in six ounces of water ranging from five to nine to 13 grams—or a placebo. Six drops of lemon juice disguised the considerable taste of the arginine (often described as being like dog vomit). The placebo had just the water and lemon juice.
The five- and nine-gram doses resulted in greater GH release than the placebo, but the 13-gram dose didn’t increase the release beyond that. In fact, the larger dose led to gastrointestinal distress. The GH rise occurred 30 minutes after the subjects took the arginine, compared to 20 minutes after an IV infusion. GH peaked after an hour.
Arginine primes the pituitary gland to induce the hypothalamus to release GH. It also suppresses the brain hormone somatostatin, which suppresses release of GH. Some scientists suggest that somatostatin release increases with age, explaining the drop in GH secretion that occurs in many older people.
The study showed that nine grams of arginine produced a GH release 45 percent greater than the five-gram dose, but that was considered statistically insignificant. More important, however, it showed that the pituitary gland can respond to oral doses of arginine.
The authors suggest that if you want a greater GH release during exercise, you should time your arginine dose with the start of your workout. Begin your workout 30 minutes after taking five to nine grams. They caution that some people don’t respond to any dose of arginine in relation to GH release. Taking a preworkout drink that contains protein or carb, which increases blood glucose, will likely blunt or prevent arginine-induced GH release. Keep in mind, too, that other amino acids compete with arginine for uptake into the body. So take arginine on an empty stomach.
1Collier, S.R., et al. Growth hormone responses to varying doses of oral arginine. Growth Horm IGF Res.2005;15:136-139
©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.
