Human growth hormone is considered one of the three major anabolic hormones in the body, with the other two being testosterone and insulin. GH is of special interest to bodybuilders and athletes for several reasons.
The first is its reputed anabolic property. GH aids in nitrogen retention and also helps to transport animo acids into muscle for use in muscle protein synthesis.GH has also engendered a reputation for speeding bodyfat loss, since it promotes the sparing of carbohydrates, while at the same time fostering the use of stored fat as an energy source.
Over the years it has become apparent that GH is not as anabolic in actual practice as it appears to be on paper. In fact, most studies suggest that GH doesn’t offer any anabolic benefits to healthy young athletes who are still able to secrete GH at a normal rate. Conversely, GH production drops by 15 percent for each decade of life past age 30, and many older people show unmistakable GH deficiencies. When they’re given supplemental GH injections, they respond by making definite gains in muscle mass, along with a significant reduction in bodyfat stores.
The fact that GH may not be as anabolic in younger people as was originally thought hasn’t lowered its popularity among athletes and bodybuilders, many of whom have added insulin to their anabolic regimens. While the primary purpose of insulin is to treat diabetes, it also has some anabolic effects. In relation to muscle, it exerts mainly a permissive effect in that it prevents excessive muscle breakdown while promoting amino acid uptake into muscle. Some studies show that insulin can convert from being mainly anticatabolic in muscle to anabolic if a large amount of amino acids are also present.
Bodybuilders use insulin because it appears to be synergistic when combined with anabolic steroids and GH. A major side effect of GH is hyperglycemia, or elevated blood glucose. It’s tempered by simultaneous use of insulin, which also adds to the GH’s anticatabolic effect.
Let’s face it: Using drug forms of insulin and GH, as well as anabolic steroids, is not without risk. One obvious effect of this drug triumvirate is an enlarged, or bloated, abdomen. In recent years the odd appearance of some professional bodybuilders, who display both deep abdominal muscle definition and, when they’re not flexed, bloated abdomens, has been blamed on the combination of insulin and GH. Many other side effects are possible, depending how much and how long the drugs are used.
Natural bodybuilders, in their efforts to add muscle and lose bodyfat, look for ways to boost their various anabolic hormones without taking drugs. The most potent nutrients known to boost GH are amino acids, with arginine and ornithine leading the way, although several others can also do it to a lesser degree. Testing of the branched-chain amino acids showed that leucine and valine boosted GH by 10 percent, but the third BCAA, isoleucine, had no effect.
The idea of using arginine as a GH-booster is controversial, since most studies show that the usual oral dose for that purpose is not effective. Arginine is effective when administered intravenously—at doses of 30 grams. In fact, that route is so effective, it’s often used as a test to determine whether patients are deficient in GH. Giving intravenous arginine leads to an average 800 to 2,200 percent increase in GH above baseline, or resting, levels.
The I.V. route works because of not only the greater arginine uptake but also the insulin that’s secreted due to the presence of that much arginine. The lowered blood glucose that results leads to the GH release, as GH opposes low blood glucose. Attempting to take 30 grams of arginine orally would lead to rapid nausea and likely vomiting. Arginase enzymes located in the liver and intestine would degrade most of the ingested high-dose arginine, so you would be left nauseated but without a significant GH release.
Ornithine is a metabolite of arginine that plays a major role in helping the body produce urea, the major nitrogen waste product of protein metabolism. That’s an important function, since without significant urea production, ammonia would build up in the body, leading to toxic consequences. Ornithine is said to be about twice as effective as arginine in stimulating a GH release, although that isn’t saying much when you consider that oral arginine is not too effective for that purpose. As with arginine, the studies that have examined ornithine’s GH-releasing effects have shown mixed results. One study did turn up a significant GH effect from ornithine with an oral dose of 170 milligrams per kilogram of bodyweight, but the dose led to gastrointestinal distress in more than half of the subjects. Both arginine and ornithine taste awful, so that may have played a role.
Some have suggested that experienced bodybuilders who train intensely have already reached their maximum GH release, so using a supplement purported to boost it would be like trying to add more water to a glass filled with water. A recent study seemed to confirm that.1 Ten young men, average age 22, who had never lifted weights got either 0.1 grams of ornithine per kilogram of bodyweight or a placebo. Their blood was drawn and tested for GH both before and after they performed biceps curls using a weight equal to 60 percent of maximum, which is fairly light.
Although ornithine is said to peak in the blood within an hour, the subjects in this study had high blood levels—500 percent above baseline-—two hours after they took it. Those using the ornithine also had GH levels that were 200 percent higher than the placebo group 30 minutes after exercise. Again, however, most published studies of experienced trainees show little or no response from oral supplementation with amino acids, unless they’re taking large doses, which often leads to extreme nausea. It may be similar to what occurs with other supplements, such as HMB, amino acids like ornithine and arginine—it may work more effectively for beginners than advanced trainees.
Another recent study examined whether other nutrients besides aminos can affect GH release.2 It featured a two-part design. The first involved 108 men and women, while the second used 12 men. Both groups initially were tested to determine basal, or resting, GH, as well as body responses. The ages of the subjects in the first part ranged from 18 to 55, while those in the second part ranged from 18 to 60.
Part one found several nutrient associations with GH release, including vitamin C, dietary fiber and two saturated fatty acids. All appeared to promote GH release. Substances that blocked GH included dietary cholesterol and trans fats. Vitamins D and E and omega-3 fatty acids were not associated with peak GH release. All other carbs, amino acids and fatty acids were also not linked to GH release. Low levels of insulinlike growth factor 1, which is a product of GH, were linked to age and bodyfat but higher levels were associated with dietary fiber intake. No other nutrients were shown to affect IGF-1, although higher levels are associated with protein intake.
In the second part of the study that featured 12 men, one type of saturated fatty acid decreased the amount of time GH existed in the blood while another seemed to interfere with nighttime release of GH, which normally peaks at night. The one nutrient that showed the greatest relationship to GH release was vitamin C. The question is why.
Vitamin C is well-known as an antioxidant, but it also works with various enzymes in the body. One example is that vitamin C is required as a co-factor for enzymes that synthesize L-carnitine from amino acids in the body. Vitamin C also plays an important role in the production of collagen, a primary protein in connective tissue. In relation to GH, vitamin C acts as a co-factor in the activity of an enzyme called peptidylglycine alpha-amidating monooxygenase, or PAM, which activates various neuropeptides, or brain proteins.
It turns out that PAM exists in great amounts in both the hypothalamus of the brain, where growth-hormone-releasing hormone is produced, and the pituitary gland, where GH is produced. The thought is that vitamin C, through its actions on PAM, activates growth-hormone-releasing hormone from the hypothalamus, which then triggers the release of GH from the pituitary gland.
So should you take in massive doses of vitamin C to promote GH release? That would not be feasible, since blood levels of C peak after an oral dose of only 200 milligrams. Although the Recommended Dietary Allowance of vitamin C is 75 milligrams a day for women and 90 milligrams for men, in this study 44 percent of the 108 part-one subjects did not meet even those levels. The thing to keep in mind about these findings regarding vitamin C and GH release is that it optimizes normal release of GH.
Editor’s note: Jerry Brainum has been an exercise and nutrition researcher and journalist for more than 25 years. He’s worked with pro bodybuilders as well as many Olympic and professional athletes. To get his new e-book, Natural Anabolics—Nutrients, Compounds and Supplements That Can Accelerate Muscle Growth Without Drugs, visit www.JerryBrainum.com. IM
1 Demura, S., et al. (2010). The effect of L-ornithine hydrochloride ingestion on human growth hormone secretion after strength training. Adv Biosci Biotechno.1:7-11.
2 Denny-Brown, S., et al. (2012). The association of macro and micronutrient intake with growth hormone secretion.Growth Hormone and IGF Res. 22(3-4):102-7.