L & DL Phenylalanine

Description

Phenylalanine is an essential amino acid – meaning that the body cannot synthesize it on its own and we must get it from the diet. The primary dietary sources of phenylalanine are high protein foods such as meat, fish, eggs and dairy products. Another significant dietary source for some people may be through consumption of sugar-free products containing the artificial sweetener aspartame (Nutrasweet), which is formed by a combination of phenylalanine with another amino acid – aspartic acid

Amino acids come in two forms, designated as "L-" and "D-" forms. The "L-" form is the naturally occurring form in foods, whereas the D- form is the synthetic variety. When an amino acid is synthesized commercially, there is usually a mixture of the L- and D- forms. Sometimes the D- form is removed, but in the case of phenylalanine, the combination of the two forms is used to take advantage of the unique characteristics of both forms. The combined form of the supplement is known as D, L-phenylalanine or DLPA.

Claims

Maintains nervous system health

Relieves depression

Elevates mood

Decreases pain

Boosts memory

Suppresses appetite

Theory

DLPA has two distinct fates in the body. The L-form of phenylalanine can be converted in the body to another amino acid – tyrosine. Tyrosine, in turn, can be converted into one of several neurotransmitter molecules (L-dopa, norepinephrine, and epinephrine), each of which have important functions in brain metabolism. The D-form of phenylalanine cannot be converted to tyrosine, but it can be converted to another compound called phenylethylamine (as can the L-form), which may have effects in elevating mood, treating depression and altering pain sensation. 

Scientific Support

DLPA has been used to treat depression, Parkinson’s disease and painful conditions such as arthritis. In one study, phenylalanine supplements were able to elevate mood in 31 of 40 subjects suffering from depression. Doses of DLPA from 75-200 mg/day over 20 days have been shown to be effective in treating depressed mood, agitation and sleep disturbances. In some cases, depressed subjects were discharged without further treatment beyond continued use of the supplement. In another study, 150-200 mg of DLPA was compared to a prescription antidepressant (imipramine). Following 30 days of supplementation, DLPA was found to be as effective as the drug in treating depressive symptoms, indicating that DLPA has powerful antidepressant properties. 

 Safety

Mega-dose intakes of any amino acid are discouraged and phenylalanine is no exception – where nerve damage may result with intakes approaching 2 grams per day. A condition known as phenylketonuria (PKU), in which phenylalanine cannot be broken down, requires individuals to follow a diet low in this amino acid. Do not take DLPA in conjunction with prescription antidepressants. 

 Value

Like 5-HTP, DLPA may have some benefits for people who may be concerned with possible drug/herb interactions reported for St. John’s wort. Rarely used as a stand-alone supplement, DLPA may be better suited as an ingredient in a larger blend of nutrients/herbs targeting pain/depression and appetite/weight loss.  

Dosage

The daily requirement of phenylalanine is probably about 1 gram. Effective DLPA doses are in the 75-200 mg/day range.

 References

1. Anderson GH, Johnston JL. Nutrient control of brain neurotransmitter synthesis and function. Can J Physiol Pharmacol. 1983 Mar;61(3):271-81.

2. Anderson GH. Diet, neurotransmitters and brain function. Br Med Bull. 1981 Jan;37(1):95-100.

3. Ashley DV, Barclay DV, Chauffard FA, Moennoz D, Leathwood PD. Plasma amino acid responses in humans to evening meals of differing nutritional composition. Am J Clin Nutr. 1982 Jul;36(1):143-53.

4. Benevenga NJ, Steele RD. Adverse effects of excessive consumption of amino acids. Annu Rev Nutr. 1984;4:157-81.

5. Candito M, Aubin-Brunet V, Tonelli I, Feuillade P, Pringuey D, Chambon P, Darcourt G. Plasma tryptophan in a protein controlled diet in depressed patients. Encephale. 1994 May-Jun;20(3):327-32.

6. Contino MI, Bausano G. Nutritional approach to the therapy of pain: recent findings. Recenti Prog Med. 1985 Sep;76(9):472-5.

7. Fernstrom JD, Fernstrom MH. Dietary effects on tyrosine availability and catecholamine synthesis in the central nervous system: possible relevance to the control of protein intake. Proc Nutr Soc. 1994 Jul;53(2):419-29.

8. Fernstrom JD. Can nutrient supplements modify brain function? Am J Clin Nutr. 2000 Jun;71(6 Suppl):1669S-75S.

9. Fernstrom JD. Dietary amino acids and brain function. J Am Diet Assoc. 1994 Jan;94(1):71-7.

10. Fernstrom JD. Dietary precursors and brain neurotransmitter formation. Annu Rev Med. 1981;32:413-25.

11. Fernstrom JD. Effects of precursors on brain neurotransmitter synthesis and brain functions. Diabetologia. 1981 Mar;20 Suppl:281-9. Review.

12. Growdon JH, Cohen EL, Wurtman RJ. Treatment of brain disease with dietary precursors of neurotransmitters. Ann Intern Med. 1977 Mar;86(3):337-9.

13. Growdon JH, Wurtman RJ. Nutrients and neurotransmitters. N Y State J Med. 1980 Sep;80(10):1638-9.

14. Haze JJ. Toward an understanding of the rationale for the use of dietary supplementation for chronic pain management: the serotonin model. Cranio. 1991 Oct;9(4):339-43.

15. Hommes FA, Lee JS. The control of 5-hydroxytryptamine and dopamine synthesis in the brain: a theoretical approach. J Inherit Metab Dis. 1990;13(1):37-57.

16. King RB. Pain and tryptophan. J Neurosurg. 1980 Jul;53(1):44-52.

17. Lehnert H, Reinstein DK, Strowbridge BW, Wurtman RJ. Neurochemical and behavioral consequences of acute, uncontrollable stress: effects of dietary tyrosine. Brain Res. 1984 Jun 15;303(2):215-23.

18. Lieberman HR, Corkin S, Spring BJ, Growdon JH, Wurtman RJ. Mood, performance, and pain sensitivity: changes induced by food constituents. J Psychiatr Res. 1982-83;17(2):135-45.

19. Lieberman HR. Behavioral changes caused by nutrients. Bibl Nutr Dieta. 1986;(38):219-24.

20. Lucca A, Lucini V, Catalano M, Smeraldi E. Neutral amino acid availability in two major psychiatric disorders. Prog Neuropsychopharmacol Biol Psychiatry. 1995 Jul;19(4):615-26.

21. Melamed E, Glaeser B, Growdon JH, Wurtman RJ. Plasma tyrosine in normal humans: effects of oral tyrosine and protein-containing meals. J Neural Transm. 1980;47(4):299-306.

22. Nurmikko T, Pertovaara A, Pontinen PJ, Marnela KM, Oja SS. Effect of L-tryptophan supplementation on ischemic pain. Acupunct Electrother Res. 1984;9(1):45-55.

23. Pogson CI, Knowles RG, Salter M. The control of aromatic amino acid catabolism and its relationship to neurotransmitter amine synthesis. Crit Rev Neurobiol. 1989;5(1):29-64.

24. Previc FH. Dopamine and the origins of human intelligence. Brain Cogn. 1999 Dec;41(3):299-350.

25. Seltzer S, Dewart D, Pollack RL, Jackson E. The effects of dietary tryptophan on chronic maxillofacial pain and experimental pain tolerance. J Psychiatr Res. 1982-83;17(2):181-6.

26. Seltzer S, Marcus R, Stoch R. Perspectives in the control of chronic pain by nutritional manipulation. Pain. 1981 Oct;11(2):141-8.

27. Seltzer S, Stoch R, Marcus R, Jackson E. Alteration of human pain thresholds by nutritional manipulation and L-tryptophan supplementation. Pain. 1982 Aug;13(4):385-93.

28. Seltzer S. Dietary control of chronic maxillofacial pain. Endod Dent Traumatol. 1985 Jun;1(3):89-95.

29. Spring B. Recent research on the behavioral effects of tryptophan and carbohydrate. Nutr Health. 1984;3(1-2):55-67.

30. Strain GW. Nutrition, brain function and behavior. Psychiatr Clin North Am. 1981 Aug;4(2):253-68.

31. Thurmond JB, Brown JW. Effect of brain monoamine precursors on stress-induced behavioral and neurochemical changes in aged mice. Brain Res. 1984 Mar 26;296(1):93-102.

32. Warfield CA, Stein JM. The nutritional treatment of pain. Hosp Pract (Off Ed). 1983 Jul;18(7):100N-100P.

33. Wurtman RJ. Food consumption, neurotransmitter synthesis, and human behaviour. Experientia Suppl. 1983;44:356-69.

34. Wurtman RJ. Nutrients that modify brain function. Sci Am. 1982 Apr;246(4):50-9.

35. Zeisel SH. Dietary influences on neurotransmission. Adv Pediatr. 1986;33:23-47.