Anti-Aging: The Hormone Factor
As we age, our risk for numerous health conditions increase. This includes our risk for cognitive decline, heart disease, sarcopenia (muscle wasting), and cancer. While part of our increased risk for these conditions is due to poor lifestyle choices, another part of this increased risk is due to declining hormones as we age. This is particularly true of growth hormone and insulin-like growth factor-1 (IGF-1).
Growth hormone is produced by the pituitary gland and is the master hormone that drives the growth and development of the body. It does this partly through the stimulation of the liver to produce IGF-1, which contributes to the maintenance of lean body mass and the overall health of the body’s vital organs.
Numerous studies in the 1980’s have repeatedly shown that growth hormone and IGF-1 decline as we age. Unfortunately, it has also been consistently shown that as growth hormone and IGF-1 decline, there is a concomitant decrease in muscle mass and immune function and an increased risk for disease conditions.
This observation of a link between declining growth hormone and increased disease risk lead to the idea that growth hormone replacement might help reduce the risk for age-related diseases, thus supporting healthier aging.
A number of pre-clinical and clinical studies have suggested that growth hormone and IGF-1 replacement in growth hormone – deficient adults may have beneficial effects on cardiovascular function, brain function, body composition, and overall well-being in some instances. While these studies showed the promise of growth hormone/IGF-1 replacement therapy for improved quality of life during aging, additional studies demonstrated that growth hormone/IGF-1 replacement therapies can have a number of serious adverse effects. These risks appear to be due to resulting excess levels of growth hormone and/or IGF-1.
For example, both low and high blood levels of IGF-1 have been reported to increase the risk of all-cause mortality compared to mid-levels of IGF-1. Because of these risks, the use of growth hormone/IGF-1 replacement therapy for anti-aging has not been approved by the U.S. Food & Drug Administration.
To alleviate the risk associated with growth hormone/IGF-1 replacement therapy, growth hormone secretagogues have been developed. Growth hormone secretagogues are products or ingredients that promote the normal production and/or release of growth hormone from the pituitary. The most common growth hormone secretagogues include peptide drugs and amino acids. While peptide-based growth hormone secretagogues typically have to be administered intravenously by medical professionals, amino acids can be taken orally in dietary supplements. Some of the best known amino acid secretagogues are arginine, glycine, and glutamine.
Arginine. Arginine is an amino acid found in many foods such as dairy products, meat, poultry, fish and nuts. It supports several processes in the body including cell division, normal healing, immune function, and the secretion of hormones. Early studies demonstrated that arginine infusion stimulates a rise in plasma growth hormone levels. More recent studies have shown that oral consumption of arginine (both 5 and 9 grams) increased blood levels of growth hormone starting 30 minutes after ingestion. A separate study in elderly subjects reported that supplementation with arginine aspartate at a dose that provided 17 grams of free arginine for 14 days increased blood levels of IGF-1, improved nitrogen balance, and decreased total and LDL cholesterol without causing any adverse effects.
Other studies have also reported that the combination of arginine and lysine can increase plasma growth hormone concentrations. A recent study reported that a blend of amino acids (arginine, glutamine, and lysine) increases blood levels of growth hormone and improves memory in mice with beta-amyloid – induced memory impairment. Animal studies suggest that arginine might work by activating nitric oxide synthase signaling to induce growth hormone gene expression.
Glycine. Like arginine, glycine is an amino acid that has been reported to enhance growth hormone secretion. It is the simplest amino acid used to make proteins and works with glutamine to support normal brain function. In one study, supplementation with 250 ml of a glycine solution increased blood levels of growth hormone in both normal individuals and individuals with a partial gastrectomy. In a separate study, infusion of glycine at doses of 4, 8, and 12 grams stimulated growth hormone secretion.
Glutamine. The other primary amino acid that has been reported to enhance growth hormone secretion is glutamine. Glutamine plays a role in a variety of biochemical functions including protein synthesis, regulation of acid-base balance, cellular energy, nitrogen donation for anabolic processes, and more. In one early study, oral glutamine supplementation to healthy subjects elevated blood levels of growth hormone within 90 minutes. A second study reported that the combination of glycine, glutamine, and niacin, given orally twice daily for 3 weeks, increased blood levels of growth hormone in men and women 40 – 76 years of age by 70% compared to the placebo treatment.
It is clear that our hormone profiles change as we age and that the decline in some hormones, particularly growth hormone, is linked to age-related health conditions. Maintaining healthy growth hormone levels can be an important part of our fight for healthy aging. Amino acids may help to support healthy growth hormone levels in an entirely physiological manner by gently stimulating the endocrine system to produce and release its own growth hormone naturally. Therefore, powerful amino acids like arginine, glycine and glutamine might help maintain healthy growth hormone levels and support healthy aging.
Article by Dr. Robert Blair