Protein, carbohydrate, and ethanol consumption: interactions in AA and ANA rats.

Female rats of the alcohol-preferring AA line were given a choice between protein, carbohydrate, and fat sources. Subsequent free access to alcohol decreased their intake of carbohydrate but not of protein or fat. The individual alcohol intakes were negatively correlated with the carbohydrate intakes (-0.76) and with the alcohol-induced changes in carbohydrate intake (-0.83), but positively correlated with the concurrent protein intakes (0.78). The alcohol consumption and ethanol elimination rate of AA rats were subsequently found to vary directly with the protein content (5, 10, 20 and 40% by energy) of the premixed diet given to them--they drank more than 9 times more ethanol on the 40% than on the 5% protein diet--but the alcohol intake of the alcohol-avoiding ANA rats was not affected by protein intake. The results clearly indicate that the three macronutrients are related to alcohol consumption in different ways, suggesting that protein intake affects the selection of alcohol of AA rats through a factor correlated to ethanol elimination (but not through a ceiling effect from the rate of elimination) and that the alcohol in turn reduces carbohydrate consumption.