Insufficient activity of the key neurotransmitters serotonin and
norepinephrine is now recognised as a major part of the aetiology of
depression; nearly all drugs used to treat depression enhance these
neurotransmitter systems. Neurotransmitters are chemical messengers sent
between neuronal cells, they have a profound effect on how we feel.
Serotonin is known as the “feel good” neurotransmitter; it is
synthesised from the amino acid tryptophan, which is converted to
serotonin’s immediate precursor 5-hydroxytryptophan (5-HTP). Serotonin
regulates mood and modulates pain perception, it is used to synthesise
melatonin which regulates the sleep/wake cycle; thus serotonin is
associated with a sense of well-being. The amount of the biochemical
precursors in the brain influences the rate of serotonin synthesis.
During the 1970s and 1980s a lot of research was conducted into the
efficacy of using tryptophan and 5-HTP as a treatment for depression.
Tryptophan is found in especially high levels in poultry, tuna, eggs,
cheese, milk and tofu. Serotonin production can be increased two-fold by
consuming tryptophan; however the transport of tryptophan to the central
nervous system and it’s final conversion to serotonin can be compromised
by factors such as vitamin B-6 deficiency and cortisol excess.
Supplementing with 5-HTP bypasses the conversion of tryptophan to 5-HTP;
in addition 5-HTP crosses the blood-brain barrier and does not need to
One of the pilot studies, a placebo- controlled trail using 200mg of
5-HTP, found that depressive symptoms reduced in 60% of patients in the
active treatment group while no change was observed in the placebo
group. Further studies by the same research group produced similar
results, for example, one study with four groups of ten patients found
that 200mg of 5-HTP was not only more effective than placebo but almost
as effective as clomipramine (a tricyclic antidepressant, this group of
medications is associated with a range of devastating side effects).
A 1991 Swiss study divided 36 patients into two groups, one receiving
5-HTP (300mg daily), the other receiving fluvoxamine (an SSRI
anti-depressant); after six weeks both groups had an equal number of
patients showing a 50% improvement. Several other studies have shown
similar results suggesting the efficacy of 5-HTP.
A recent systematic review concluded “available evidence does suggest
these substances are better than placebo at alleviating depression.
Further studies are needed.”
Conventional anti-depressant medication is widely acknowledged to be
associated with a number of severe potential side effects. Raising
physiological levels of neurotransmitters by natural means looks
promising to offer safe symptomatic relief to depressed patients.
It is important to recognise that depression is a multi-factorial
condition and all aspects, including nutritional deficiencies and
psycho-social factors, must be addressed as part of a treatment
Tryptophan is not obtainable for general sale in the UK following deaths
among it’s users in 1989 from eosinophilia-myalgia syndrome. The deaths
were the result of one particular batch only and tryptophan is now
freely available in many countries.