Does a "moderate" alcohol intake damage the brain?

Abstract

SUMMARY A range of volumetric and neurochemical analyses were carried out on the brains of 14 "moderate" drinkers. These data were compared with previous studies from controls and alcoholics. Volumetric measurements consistently suggest a loss of cerebral tissue although the differences were not statistically significant. Changes in the lipid and water content of the white matter were noted and the significance of these changes in relation to the pathogenesis of reversible brain shrinkage caused by alcohol abuse is discussed.There is a considerable volume of clinical, 1 2 neuroradiological,34 neuropsychological' and neuropathological6 -data concerning the long term effects of alcohol abuse on the human central nervous system. A large proportion of these data, particularly with regard to neuropathological changes, deals with severe chronic alcoholism. The interpretation of such data is difficult because of the frequency of occurrence of attendant disorders such as cirrhosis of the liver and nutritional deficiency disorders (Wernicke's encephalopathy) in the more advanced cases of alcoholism. Of particular interest to the general public is the long term effects of a moderate alcohol intake which many would equate with "social" drinking. Materials and methodsCases for the studies cited in this paper were The procedures and techniques utilised in determining the various parameters have been described in previous papers relating to changes in the alcoholic groups.9 1 -20 Samples from the frontal, parietal and occipital white matter of the right hemisphere were used for the various neurochemical assays. The water content was determined by weighing the tissue before and after drying to a constant weight.2' The dried residue was acid digested and the sodium and potassium concentration determined by flame photometry. Although there is a considerable amount of additional information included in the tabular data the principal aim of this paper is to address the issue of the pathological changes in the brains of men regularly drinking between 30 and 80 grams of alcohol per day. The control and alcohol data are used for comparison.

Wernicke-Korsakoff syndrome

“…Although the difference in various brain measures between the moderate drinkers and the control group was not statistically significant, this autopsy study revealed a consistent trend in the measures suggesting loss of cerebral tissue, as evidenced by reduced cerebral weight, increased ventricular volume and pericerebral space, the main loss being in white matter. 40 White matter is composed of approximately 70% water, 20% lipids and 10% protein. 41 and most of the latter two elements is combined to form membranes (myelin in particular).…”

Aspectos clínicos e neuropatológicos da síndrome de Wernicke-Korsakoff

“…Buscando avaliar o impacto do consumo "moderado" de álcool no cérebro, pesquisadores avaliaram medidas cerebrais como peso cerebral, espaço pericerebral e volume ventricular de bebedores moderados (30-80g de álcool/dia), alcoolistas (mais de 80g de álcool/dia), alcoolistas com cirrose, alcoolistas com encefalopatia de Wernicke e grupo-controle de abstêmios ou bebedores de até 20g álcool/dia. Embora não tenham encontrado diferença estatisticamente significativa entre as medidas cerebrais de bebedores "moderados" e grupo-controle, há uma tendência sugerindo perda de tecido cerebral, com peso cerebral reduzido, aumento do volume ventricular e do espaço pericerebral, sendo maior a perda de substância branca 17 . A substância branca é formada de aproximadamente 70% de água, 20% de lipídios e 10% de proteína 39 , sendo que a maioria destes dois últimos elementos está combinada na forma de membranas (mielina particularmente).…”

“…Lesões desmielinizantes mostram aumento do conteúdo de água e decrésci-mo no conteúdo de lipídio, invertendo o processo que ocorre durante a maturação cerebral 12 . O padrão de alteração dos conteúdos de água e de lipídio da substância branca cerebral de pacientes alcoolistas é semelhante ao padrão de alteração do envelhecimento e ao padrão de lesões desmielinizantes observados no estudo supracitado 17 . Ratos expostos ao álcool por cinco meses apresentaram uma redução significativa das ramificações dendríticas no hipocampo, que reverteu após dois meses de abstinência 37 .…”

“…Estudos clínicos e neuroradiológicos indicam que déficits clínicos e retraimento cerebral ("brain shrinkage") são reversíveis em uma proporção de alcoolistas, preferencialmente jovens, seguindo um perío-do prolongado de abstinência alcoólica 6,47 . Deve haver duas alterações patológicas na substância branca como resultado do abuso de álcool: um componente irreversível devido à morte neuronal, similar ao padrão observado na degeneração walleriana 9 e um componente reversível, caracterizado por alterações sutis, de difícil identificação por exames histológicos de material humano 17 . Em 131 casos de encefalopatia de Wernicke diagnosticados por autópsia, com maioria de alcoolistas, somente 26 pacientes foram diagnosticados durante a vida 16 , levantando a possibilidade de que o dano cerebral tiamina-dependente possa existir em muitos alcoolistas antes de ser suspeitado 31 .…”

Alcohol and the brain: A love and hate relationship

“…However, with consumption of 300 g of ethanol per day, brain volume may shrink over 20%. 7 In alcoholics, brain shrinkage is part of the postalcohol remorse; but in all others, drinking a couple of drinks per day may lead to a lifelong hangover. …”