A deficiency of the B group of vitamins is a common side effect of chronic drinking. It is known that the poor vitamin B status of alcoholics is responsible for many of the neurological difficulties experienced by this group of individuals. Traditionally the poor vitamin B status of alcoholics and other heavy drinkers has been explained by the assumed presence of a poor diet, and there is good reason to believe that this may be a contributory factor. However, the metabolism of certain B vitamins is known to be affected by the presence of high blood levels of alcohol. Folic acid for example, is common in alcoholics and poor folate status may be present in around 80 % of heavy drinkers. This is problematic because the megaloblastic anaemia caused by folate deficiency does not respond to folic acid of 70 μg per day, unless the individual stops drinking. This suggests that the alcohol is able to cause an increase in the metabolism and excretion of folic acid and thus continued drinking prevents stores of the vitamin increasing.
For example, in one study1, researchers administered ethanol to alcoholic patients and measured the excretion rates of folic acid. The results showed that folic acid excretion was 20 to 40 % higher in 4 out of the 5 patients when ethanol was administered compared to a control period. This was despite the researchers ensuring adequate folic acid in the diet. Therefore changes to the metabolism and excretion kinetics of folate may explain some of the poor vitamin status experienced by heavy drinkers. Malabsorption due to changes in the gut mucosal lining may also explain some of the poor vitamin status seen, and this factor should also be considered. However, it is clear that some alterations to the metabolism of folate occurs, even though no impaired liver function is often evident. The authors postulated that the poor folate status in heavy drinker results from a combination of the folate being sequestered into polyglutamate stores in the liver in combination with increased excretion.
Dr Robert Barrington’s Nutritional Comments: Moderate alcohol consumption is associated with improved health outcomes because both ethanol and the polyphenolic substances found in some alcoholic drinks confer health benefits. However, as the amount of ethanol ingested increases beyond moderate levels, detrimental health outcomes become inherent. One detrimental effect of chronic drinking is a deterioration in the vitamin B status of the individual.
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