Thiamine is an essential nutrient, a deficient intake of which causes the deficiency disease beriberi (here). Thiamine is absorbed and phosphorylated in the liver to produce the active coenzyme thiamine pyrophosphate (also called thiamine diphosphate). Thiamine pyrophosphate may play an important role in mood because it is required for a number of reactions that can alter the flow and production of neurotransmitters in the brain. For example, thiamine pyrophosphate is an important coenzyme in the main energy producing reactions, which supply the large amounts of energy required for the correct function of the central nervous system. In addition, thiamine pyrophosphate is also required for the synthesis of NADPH, a reducing coenzyme used in synthesis reactions and necessary for the correct function of the tryptophan hydroxylase enzyme, the rate limiting step in the synthesis of serotonin. Further thiamine pyrophosphate may play a role in nerve conduction directly, and thus facilitate the transmission of action potentials in the brain.
The wide ranging neurological problems associated with a thiamine deficiency support the contention that it plays an important role in correct brain function. But what are the implications of a chronic low intake of thiamine, above the threshold for outright deficiency? Evidence suggests that such an insufficient state may cause detrimental mood changes including the development of depression. Animal studies have shown for example, that low intakes of thiamine in the diet of rodents are able to significantly reduce brain levels of serotonin. In a recent epidemiological study1, researchers assessed the association between thiamine nutriture and the presence of depressive symptoms in the general population as a whole. The researchers reported that the prevalence of depressive symptoms was 11.3 %, and that concentrations of red blood cell thiamine (using 3 different biomarkers; thiamine, thiamine monophosphate and thiamine diphosphate) was associated with the presence of depressive symptoms. Those with the lowest intakes of thiamine had a roughly 3-fold increase in the odds of developing depressive symptoms.
Therefore poor thiamine status may cause the development of low mood and depressive symptoms in certain individuals. But is thiamine an effective antidepressant nutrient? It is important to understand that the effects of thiamine on mood are not drug-like in their action. Thiamine is required for the correct synthesis of serotonin and for correct nerve conduction, and a lack of thiamine inhibits these processes in some way, lowering brain levels of serotonin and causing depression. Returning thiamine to the diet corrects the biochemistry of the brain and thus facilitates nerve conduction and serotonin synthesis. But in those with adequate thiamine nutriture, it is very unlikely that additional thiamine will further improve mood, and in those with depression for reasons other than a thiamine deficiency, thiamine will be of no help. This highlights the difference between a drug and a nutrient well, the latter being associated with no side effects because it s a natural part of the normal biochemistry of the body.
Dr Robert Barrington’s Nutritional Advice: Ensuring optimal thiamine intake is important not just for mental health but general health as well. Thiamine is an important co-enzyme in the main energy producing reactions and optimal levels should therefore be obtained where possible as part of a healthy diet. Thiamine is widely available in many foods including animal products, legumes, grains and yeast. Those with alcoholism or those who consume a lot of alcohol should consider a thiamine supplement as alcohol can deplete the body of thiamine and cause Wernicke’s encephalopathy, a condition characterised by neurological problems such as depression and confusion.
RdB
