The Effect of 5-Hydroxytryptophan (5-HTP) on Satiety
Condition: Obesity
Study type: Interventional
Phase: Phase 2

Summary: 
      The aim of the study is to show evidence of the efficacy of 5-HTP to induce satiety and to
      reduce food intake (confirmatory study).

      The primary objective of the present study is to determine:

        -  the effectiveness of a 5-HTP preparation on satiety markers (before intake of a meal and
           during the day)

      The secondary objectives of the present study are to determine the effectiveness of a 5-HTP
      preparation on:

        -  food consumption (amount and composition) during a free meal (dinner);

        -  wellness after one week supplementation;

        -  the intermeal interval;

        -  body weight and waist-hip ratio (WHR).
    

Detailed description: 
      One of the physiological factors regulating the food intake pattern is satiety. Satiety is
      defined as the absence of ingestive motivation, which ends when the next meal is initiated
      (Blundell et al., 1996). Food intake affects a number of physiological objective parameters
      in blood known to be involved in signalling satiety, such as glucose (Melanson et al, 1999;
      Chapman et al, 1999; Campfield et al, 1996), insulin (Speechly et al, 2000) and
      cholecystokinin (CCK) (Gutzwiller et al., 2000; Beglinger et al., 2001; French et al., 2000;
      Degen et al., 2001; Burton-Freeman et al., 2002, 2004). More recently, the gastric hormone
      ghrelin was identified as a marker for hunger and meal initiation (De Graaf et al., 2004).

      Humans do not only eat in response to a metabolic or physiological need. Humans also respond
      to a significant extent to other internal subjective and emotional signals (clues). The exact
      relations between the physiological internal signals and subjective and emotional internal
      signals are not known. Besides also external and social factors modulate
      physiological-derived hunger and satiety signals.

      Though the regulation of food intake has been studied quite extensively, the underlying
      mechanism is not elucidated yet and still new factors involved in this regulation are being
      found. It is known that the macronutrients such as lipids, proteins and carbohydrates affect
      satiety differently, but this mechanism is still not very clear either.

      Nowadays, more and more food supplements become available suggesting to affect hunger and
      satiety sensations, resulting in the long-term in weight loss. For example dietary fibres are
      known for their satiating effect.

      The food supplement 5-HTP is used for this purpose as well. The food supplement, already
      available in the United States and in Italy, has been investigated for multiple indications
      such as migraine, depression, anxiety, fibromyalgia, hypertension, insomnia and obesity.

      Different clinical studies have been performed with 5-HTP for more than three decades now.
      With respect to lowering of food intake, 5-HTP has been studied as well.

      5-HTP is an amino acid produced by the human body from the essential amino acid L-tryptophan,
      which is found in food products. Its clinical value is the ability to increase production of
      serotonin. As a potentially valuable supplement it has been used clinically for more than 30
      years. 5-HTP occurs naturally in two places - the human body and the seeds of the Griffonia
      simplicifolia, a West African medicinal plant.

      5-HTP is the amino acid precursor of serotonin. Normal levels of serotonin are important for
      emotional well-being, may play a role in appetite suppression, and decreased carbohydrate and
      fat intake. Only free plasma tryptophan can cross the blood brain barrier via a carrier
      protein to enter the central nervous system (CNS). Once in the CNS, tryptophan is converted
      to 5-HTP and then is decarboxylated to serotonin. The levels, and possible function, of
      several neurotransmitters can be influenced by the supply of their dietary products. A
      reduction in tryptophan has been correlated to a reduction in serotonin (Curcio et al.,
      2005).

      The 5-HTP metabolism is then influenced by plasma tryptophan levels, which are related to
      food intake. Serotonin synthesis is directly dependent on the availability of the specific
      precursor tryptophan and on the nutritional status.

      The effect of 5-HTP intake on food intake and mood is based on the serotonin production.
      Numerous studies have shown that long-term consumption of 5-HTP (levels up to 900 mg daily)
      reduced food intake and resulted in weight loss.

      In a previous study by Laboratoire Oenobiol with moderately overweight men aged 20-40 years,
      given 50 or 150 mg 5-HTP half an hour before lunch and half an hour before dinner, a reduced
      energy intake with 300 mg 5-HTP compared to placebo was found. This was supplied acutely on
      one day.

      The study reported a linear dose related effect, with significant food intake inhibition
      effect with a 300 mg/day 5-HTP dose. The dose of 100 mg/day did not produce statistically
      significant effects compared to placebo. However, 100 mg of 5-HTP could prove to be
      sufficient if given under chronic administration conditions.

      In the present study therefore subjects will be supplied with 100 mg 5-HTP daily for one
      week. Hunger and satiety feelings, food intake and wellness will be investigated. The study
      will be conducted with overweight women, assuming that this group of subjects will be the
      target group.
    

Intervention name(s): 5-hydroxytryptophan (food supplement)
Intervention type(s): Drug
Intervention MeSH terms: 5-Hydroxytryptophan
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double
Primary purpose: Treatment
Keywords: satiety; food intake; mood; wellness; weight management