Safety of amino acid supplementation
The addition of amino acids to food and dietary supplements is prohibited in the Netherlands, with the exception of a number of highly specific applications. In response to the increasing demand for dietary supplements containing nutrients, including amino acids, the Minister of Health, Welfare and Sport and the Minister of Agriculture, Nature Management and Fisheries requested the Health Council of the Netherlands to report on the safety aspects of adding amino acids to food and dietary supplements.
Amino acids are the building blocks of protein, one of the components of all living organisms. Some amino acids also act as neurotransmitters or hormones, or as the precursors of one of these two groups. A healthy body can produce sufficient amounts of the following amino acids: alanine, arginine, asparagine, aspartic acid, cysteine, cystine, glutamine, glutamic acid, glycine, proline and hydroxyproline, serine and tyrosine. Other amino acids have to be obtained from the food we eat. These are the essential amino acids histidine, isoleucine, leucine, lysine, methionine, phenylanaline, tryptophan, threonine and valine. In addition to the 22 substances cited above, this report also deals with the amino acids ornithine and citrulline. These are metabolites of the above-mentioned amino acids, and are not incorporated into proteins. They are formed in the intestines, the liver and the kidneys.
The reasons for adding amino acids to food and dietary supplements are many and various. The use of cysteine and cystine, glutamic acid and glycine, together with several of their salts as additives, is permitted due to their technological or sensory characteristics. Another reason for adding amino acids is to improve the ’protein quality’ of food. In some countries, including the United States, the addition of amino acids to improve ’protein quality’ is permitted under strict conditions.
Transport systems, which are shared by the various groups of amino acids, mediate the absorption of amino acids from the gastro-intestinal tract and their uptake by organs and tissues. This means that amino acids can exert an influence on each other’s transport and absorption. While it is essential that this factor be taken into account when assessing safety aspects, there is a lack of quantitative data in this area.
In 1992, a report entitled ’Safety of amino acids as dietary supplements’ was published by the Federation of American Societies for Experimental Biology (FASEB). This report concluded that there was insufficient data available to evaluate the safety of amino acids as dietary supplements. There were some indications of adverse health effects associated with the use of individual amino acids, but it was not possible to identify a safe upper level of intake for any of the amino acids as dietary supplements. The Health Council endorses the conclusions of the FASEB report.
After examining recent literature on this subject, the Health Council found no information upon which to base additional conclusions. The Council has, nevertheless, elected to present maximum acceptable levels for the addition of amino acids to food (including dietary supplements). The Council has opted for a general approach, using the quantity of amino acids present in the amount of protein for women recommended by the former Nutrition Council — now part of the Health Council — as a basis for setting maximum thresholds. The Counsil subsequently verified that, using this general approach, none of the values obtained for the various amino acids (except methionine) are known (within the limits of published research) to produce adverse health effects.