5-hydroxytryptophan (5-HTP) and Satiety
Weight management has been a hot topic for several decades, particularly as dietary guidelines moved away from fats to focus on carbohydrate. Neurotransmitters play a significant role in this area, particularly serotonin. Serotonin has a multitude of important functions. Among them is a powerful role in creating satiety during eating and in reducing appetite.1,2,3 Appetite, satiety, and overeating are important and relevant concepts in weight management. The following is an inquiry into the connection between serotonin, diet, and weight.
Drs. Wurtman and Wurtman have done extensive work in this area. They began by studying the process in which the serotonin precursor, tryptophan, accesses the brain to produce serotonin.* Tryptophan must compete with other amino acids for transport across the blood-brain barrier. As one of the least abundant aminos in the diet, tryptophan often loses out in this competition. In a seminal piece published in 1995, they explain4
Serotonin-releasing brain neurons are unique in that the amount of neurotransmitter they release is normally controlled by food intake: Carbohydrate consumption–acting via insulin secretion and the “plasma tryptophan ratio”–increases serotonin release.
The Wurtmans noticed that consuming a carbohydrate produces insulin, which sends not only glucose into the tissues but also sends amino acids into muscle cells. The only amino which is not subject to insulin’s message is tryptophan, as it circulates in the bloodstream bound to albumin. Inducing insulin thus clears other aminos from the bloodstream, leaving tryptophan unopposed in crossing the blood-brain barrier to form serotonin.*5 High carbohydrate meals favor tryptophan availability while high protein meals instead favor the availability of tyrosine and other large neutral amino acids to cross the blood-brain barrier.6
In summary, carbohydrate-rich diets trigger an insulin response that enhances the bioavailability of tryptophan in the brain. If serotonin falls, the body may initiate carbohydrate craving to restore serotonin status.7,8 Low serotonin can therefore lead to craving for carbohydrates and may impact weight over time. There is, in fact, a correlation between food cravings for sweets/carbs and BMI.9 This is in addition to the fact that high carbohydrate intake produces high insulin output, and elevated insulin itself can impact weight.10,11
One solution to this complex situation is to raise serotonin with the use of 5-HTP (5-hydroxytryptophan).* 5-HTP use has been shown to increase serotonin12 and promote healthy weight.*13,14 Ioannou and Williams report that, in human subjects, 5-HTP triggered cortical responses associated with healthy body weight as well as cerebral preferences for protein-rich stimuli.*15 This is in alignment with the efficacy of serotonin in satiety. When the “tank” of serotonin is full, our preferences move away from carbohydrate toward protein.
L-theanine and Stress-Eating
L-theanine is well-known for its stress-busting effects.* It is often used to reduce anxiousness and stress-associated behaviors.* Though theanine itself has not often been used in weight management studies, its use during stressful times may reduce the tendency to stress-eat.* Additionally, theanine has been shown to support healthy serum triglycerides and non-esterified fatty acids in obese rodent models, contributing to weight management.*16
Prolent™ from Sanesco includes both 5-HTP and L-theanine as Suntheanine® along with glycine. Prolent is one of several Targeted Nutritional Therapy™ formulas included in the Communication System Management™ (CSM) clinical model.
A recent American Society for Nutrition poster presentation provides evidence that the CSM clinical model, in combination with clinician care, positively affects BMI, weight-related quality-of-life markers (comorbidities), and neuroendocrine markers related to weight.
- Shabbir F, Patel A, Mattison C, et al. Effect of diet on serotonergic neurotransmission in depression. Neurochem Int. 2013 Feb;62(3):324-9.
- Halford JC, Harrold JA, Lawton CL, et al. Serotonin (5HT) drugs: effects on appetite expression and use for the treatment of obesity. Curr Drug Targets. 2005 Mar;6(2):201-13.
- Anderberg RH, Richard JE, Eerola K, et al. Glucagon-Like Peptide 1 and Its Analogs Act in the Dorsal Raphe and Modulate Central Serotonin to Reduce Appetite and Body Weight. Diabetes. 2017 Apr;66(4):1062-1073.
- Wurtman RJ, Wurtman JJ. Brain serotonin, carbohydrate-craving, obesity and depression. Obes Res. 1995 Nov;3 Suppl 4:477S-480S. Retrieved from https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.1550-8528.1995.tb00215.x
- Wurtman J, Wurtman R. The Trajectory from Mood to Obesity. Curr Obes Rep. 2018 Mar;7(1):1-5.
- Wurtman RJ, Wurtman JJ, Regan MM, et al. Effects of normal meals rich in carbohydrates or proteins on plasma tryptophan and tyrosine ratios. Am J Clin Nutr. 2003 Jan;77(1):128-32.
- Shabbir, op. cit.
- Chao A, Grilo CM, White MA, et al. Food cravings, food intake, and weight status in a community-based sample. Eat Behav. 2014 Aug;15(3):478-82.
-  Ibid.
- Erion KA, Corkey BE. Hyperinsulinemia: a Cause of Obesity? Curr Obes Rep. 2017 Jun;6(2):178-186.
- Heller RF, Heller RF. Hyperinsulinemic obesity and carbohydrate addiction: the missing link is the carbohydrate frequency factor. Med Hypotheses. 1994 May;42(5):307-12.
- Lynn-Bullock CP, Welshhans K, Pallas SL, et al. The effect of oral 5-HTP administration on 5-HTP and 5-HT immunoreactivity in monoaminergic brain regions of rats. J Chem Neuroanat. 2004 May;27(2):129-38.
- Halford, op. cit.
- Rondanelli M, Klersy C, Iadarola P, et al. Satiety and amino-acid profile in overweight women after a new treatment using a natural plant extract sublingual spray formulation. Int J Obes (Lond). 2009 Oct;33(10):1174-82.
- Ioannou S, Williams AL. Preliminary fMRI findings concerning the influence of 5-HTP on food selection. Brain Behav. 2016 Oct 28;7(1):e00594.
- Zheng G, Sayama K, Okubo T, et al. Anti-obesity effects of three major components of green tea, catechins, caffeine and theanine, in mice. In Vivo. 2004 Jan-Feb;18(1):55-62.