The recommended phenylalanine dosage (including tyrosine) in adults is 15 mg per pound per day. Most people obtain more than this just from dietary sources. However, in some cases, supplementation may be suggested. At this time, there is no recommended phenylalanine dosage for supplements because studies used too wide of a dosing range. When taking supplements, it's best to follow the guidelines on the product label.
Phenylalanine Dosage: An Overview
Phenylalanine is an amino acid sometimes used in dietary supplements. It is important to note that unlike medications, for which the standard doses have been well established, less information is available for determining the best dose for supplements, including phenylalanine.
What Is the Recommended Phenylalanine Intake?
The Recommended Dietary Allowance (RDA) for phenylalanine (plus tyrosine) in adults is 33 mg per kg per day (15 mg per pound per day). Tyrosine is another amino acid included in the RDA for phenylalanine, because phenylalanine is used by the human body to make tyrosine. If you get enough phenylalanine in your diet, you do not need any tyrosine through food. If your phenylalanine intake is too low, however, a dietary intake of tyrosine is important.
Most people get more than the RDA for phenylalanine, and supplementation is not usually necessary or recommended. In the United States, the average phenylalanine intake (for all age groups combined) is 3.4 grams (3400 mg) per day.
It should be noted that these intakes refer to L-phenylalanine (the naturally occurring form found in food products). D-phenylalanine (found only in certain supplements) has no nutritional value.
What Is the Best Phenylalanine Dosage for Supplementation?
It is not known what the best (that is, the safest and most effective) dose for phenylalanine supplementation may be. Studies have used a wide range of doses -- too wide to make any recommendations for phenylalanine dosing. Since little information is available to guide you in choosing a phenylalanine dosage, be sure to follow the directions on your particular supplement.
If you have phenylketonuria (PKU), you should not take any phenylalanine supplements at any dose. People with this condition must limit their intake of phenylalanine.
Written by/reviewed by: Kristi Monson, PharmD;Arthur Schoenstadt, MD
Last reviewed by: KristiMonson, PharmD;
List of references (click here):
Jellin JM, editor. Pharmacist's Letter/Prescriber's Letter Natural Medicines Comprehensive Database Web site. Available at: http://naturaldatabase.com/. Accessed March 6, 2008.
Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, DC: National Academy Press, 2005. Available at: http://books.nap.edu/openbook.php?record_id=10490&page=R1. Accessed March 6, 2008.
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