The Contribution of cocoa additive to cigarette smoking addiction

RIVM report 650270002 Page 101 of 207
Tryptophan
activity, leading to increased catabolism of tryptophan and thus making less
tryptophan available to the brain. Allopurinol, an inhibitor of hepatic tryptophan
pyrrolase activity, prevented the reduction in the indole levels induced by 5-ALA
(40).
The tryptophan degradation in the brain is reduced by methamphetamine due to
inhibition of tryptophan hydroxylase (41).
Critical assessment
Chemical
Both the amino group and the carboxy group form potential sites for a wide variety of
reactions. It has been shown that numerous compounds react with tryptophan in
cigarettes during smoking and resulting in complex compounds with potential
hazardous effect in the body.
In vivo
Several compounds affect the tryptophan level in plasma or brain either by inducing
or inhibiting the tryptophan degradation or by interaction with the binding site of
tryptophan in albumin or in the transport system through the blood-brain-barrier.
Conclusion
Chemical
Tryptophan can react with numerous compounds during smoking resulting in
potentially hazardous compounds for the body.
In vivo
Several compounds affect the tryptophan level in plasma and brain.
DEPENDENCY
Effects of smoking cessation
It is known that nicotine enhances the serotonin release in the brain and that nicotine
withdrawal has the opposite effect. 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; protein intake lacks this effect. This
ability of neurons to couple neuronal signalling properties to food consumption is a
link in the feedback mechanism that normally keeps carbohydrate and protein intakes
more or less constant. Hence many patients learn to overeat carbohydrates
(particularly snack foods, like potato chips or pastries, which are rich in
carbohydrates and fats) to make themselves feel better. This tendency to use certain
foods as though they were drugs is a frequent cause of weight gain, and can also be
seen in people who are attempting to give up smoking (42). Serotonin-enhancing
substances, such as tryptophan and high-carbohydrate diets, have been used in
clinical disorders to relieve negative affect, a classic symptom of cigarette
withdrawal. In a study it was investigated whether the use of tryptophan (50
mg/kg/day) and high-carbohydrate diets, together with more traditional smoking
cessation treatment techniques, was able to ameliorate the smoking withdrawal
syndrome and to improve abstinence rates. Subjects were randomly assigned to
receive either tryptophan (n = 16) or placebo (n = 15). Standard smoking cessation
treatment was identical for the experimental and control groups and consisted of four
2-hr weekly sessions of multicomponent group therapy. Smoking behaviour,
symptoms of nicotine withdrawal, and negative effect were assessed during a 2-week