The Council for Responsible Nutrition (CRN) has authored risk assessments that establish safe upper intake levels for the amino acids taurine (Tau), glutamine (Gln) and arginine (Arg) commonly used in dietary supplements. The paper, published in the April issue of the peer-reviewed journal Regulatory Toxicology and Pharmacology, was co-authored by CRN scientists John Hathcock, Ph.D., and Andrew Shao, Ph.D., and is the latest in a series of such analyses co-authored by them.
“Over the last decade the prevalence of amino acids within sports nutrition supplements and ‘energy boosting’ functional foods and beverages has significantly increased. We chose to assess the safety of taurine, glutamine and arginine because they are among the most widely used and studied of the supplemental amino acids,” explains Dr. Shao, co-author of the paper and vice president of scientific and regulatory affairs for CRN.
Applying the safety assessment method he developed and which has been recognized internationally as a scientifically valid way to quantitatively evaluate nutrient safety in humans, CRN’s Dr. Hathcock, senior vice president of scientific and international affairs, and Dr. Shao, reviewed published randomized, controlled clinical trials conducted in humans involving these three amino acids to determine the safe upper level for supplements (ULS) of each. They relied on uncontrolled trials and animal data as supportive information.
The two co-authors concluded that the absence of adverse effects is strong for Tau at up to a dose of 3 grams per day; for Gln, at up to 14 grams per day; and for Arg, at up to 20 grams per day; therefore these values were selected as the respective ULS for each.
The ULS values were derived using basic elements of the U.S. Food and Nutrition Board’s (FNB) Tolerable Upper Intake Level (UL) risk assessment method as well as the observed safe level (OSL) method, developed by Dr. Hathcock and now used as the as the highest observed intake (HOI) by the Food and Agriculture Organization and World Health Organization. The values noted in the risk assessments are identified as the ULS, since dietary intakes from food sources were not taken into consideration, but consumers should be aware of their intake from all sources.
Upper levels do not suggest that supplements taken above the level identified are unsafe, nor do they constitute a recommended intake. They merely identify the highest quantitative level at which there is no known toxicity, ensuring that science is the deciding factor when it comes to setting and enforcing regulatory guidelines for ingredients used in dietary supplements.
This is the eighth in a series of risk assessments completed by CRN scientists. Previous risk assessments on vitamins C and E were published in 2005 and on vitamin D in 2007 in the American Journal of Clinical Nutrition. Risk assessments on non-essential nutrients including Coenzyme Q10, lutein and lycopene, creatine, carnitine, glucosamine and chondroitin sulfate were published in 2006 and 2007 in the journal Regulatory Toxicology and Pharmacology.
“CRN is dedicated to helping ingredient manufactures deliver the safest products possible to consumers, and risk assessments are the best indicators we have to establish upper limits. These risk assessments, using our expansions of the UL method, represent the first time upper intake levels have been identified for amino acids. As amino acids continue to be more widely used by the general public, there needs to be a scientific method for establishing safety. It is important that we don’t allow for a non-scientific approach such as the use of a random multiple of the recommended daily allowance,” said Dr. Hathcock.
The manuscript for these recently published risk assessments is currently available online through the International Society for Regulatory Toxicology and Pharmacology (ISRTP) and will be published in an upcoming issue of Regulatory Toxicology and Pharmacology, the official journal of ISRTP.
Dr. Hathcock is the author of the CRN publication, Vitamin and Mineral Safety, 2nd Edition, which provides an academic review of safety levels for 28 vitamins and minerals, with methodology, including CRN’s approach, on assessing safety along with a review of governmental and regulatory safety conclusions.
The Council for Responsible Nutrition (CRN), founded in 1973, is a Washington, D.C.-based trade association representing dietary supplement industry ingredient suppliers and manufacturers. CRN members adhere to a strong code of ethics and manufacture dietary supplements to high quality standards under good manufacturing practices.