Decreased Appetite for Food in Alcoholism
Long-term alcohol intake can decrease the total amount of food consumed when food is freely available and over time this can promote the development of a severely malnourished state. Alcoholic beverages are high in calories but low in nutrients and how the body uses the energy contained in alcohol is complex and not well understood. Assessment of meal composition has highlighted that the alcohol-induced alteration in food intake may be highly specific and linked to impaired appetite for carbohydrate (in particular). The aim of this chapter is to explore this very specific alcohol effect (i.e. decrease in appetite for carbohydrate). We will begin by investigating whether alcohol is a food for the human body and then briefly look at the biochemical processes associated with regulation of appetite for carbohydrate. It is well accepted that appetite for carbohydrate is largely dependent on the efficient performance of cortisol, a steroid under the control of the hypothalamic-pituitary-adrenal axis, and insulin a pancreatic peptide hormone. In the last section we will look at data from a number of studies aimed at assessing the effect of alcohol on cortisol and insulin under variable nutritional conditions in order to conclude that a decreased appetite for carbohydrate may be a physiological consequence of alcohol consumption.
Red wine alters the glucose-insulin relationship when consumed alone after a meal
The aim of this study was to assess the effect of a small-moderate dose of red wine on the level of serum insulin and plasma glucose before and after a meal. A total of 18 non-diabetic males aged between 19-22 years participated in the current investigation. In the fasting trial participants underwent a 6 hour fast before consuming 4 standard units of red wine (40g alcohol) or the equivalent amount of placebo over a period of 135-min. Food was then presented alone for 45-min. Alternatively, in the feeding trial food was consumed for 45-min prior to participants ingesting 4 standard units of red wine (40g alcohol) or the equivalent amount of placebo over a 135-min period. The serum insulin and plasma glucose level was assessed at regular 45-min intervals across the four 180-min experimental periods. The results showed a significant alcohol-induced decrease in postprandial glucose and no significant change in serum insulin concentration when red wine is consumed alone following a meal. Alternatively, the ingestion of red wine alone prior to food promoted a significant reduction in serum insulin concentration despite preprandial glucose remaining unchanged. It was concluded that red wine may promote an alteration in the feedback mechanism by which plasma glucose controls the insulin rate, which under specific conditions could potentially provide some health benefits to diabetic individuals.
Ingesting alcohol prior to food can alter the activity of the hypothalamic-pituitary-adrenal axis
There is an increasing evidence that long-term alcohol intake can promote damage to most of the body's major organs. However, regular consumption of a small-moderate amount of alcohol is often recommended as being beneficial to health and of concern is that the effect of ingesting commercially available alcohol products on steroid hormone synthesis under variable nutritional conditions has not been thoroughly investigated. Many individuals consume alcohol alone prior to a meal and the aim of the present study was to assess the effect of consuming a small-moderate amount of commercially available alcohol on the level of salivary cortisol and salivary dehydroepiandrosterone sulfate (DHEAS) before and after a meal. A total of 24 males aged 19-22 years participated in the current investigation. The experimental procedure required participants to fast for 6 h before being asked to ingest either 40 g alcohol in the form of red wine (n = 8), low alcohol and high beer (n = 8), white wine (n = 8) or the equivalent amount of placebo over a 135-min period before consuming food for 45-min. The level of blood alcohol, salivary cortisol and salivary DHEAS was assessed upon arrival and then at regular 45-min intervals during the 180-min experimental period. The results showed that the consumption of alcohol and placebo can significantly lower the level of salivary cortisol. However, the effect of consuming a small-moderate amount of commercially available alcohol on the level of salivary DHEAS was dependent on the nutritional content of the beverage with red wine promoting no change, white wine promoting a significant decrease, and beer having a variable effect on salivary DHEAS concentration when compared to placebo. It was concluded that the effect of commercially available alcohol on the HPA axis is not the same for all alcohol products and both the nutritional status of participants and the nutritional content of the alcoholic beverage being administered should be taken into consideration when investigating the effect of alcohol on the HPA axis.