Ethanol: relative fuel value and metabolic effects in vivo.

A nasogastric formula infusion method was used to evaluate the steady-state fuel value of ethanol relative to that of glucose in eight chronically alcoholic men undergoing a 4- or 5-week balance experiment. Each subject received a maintenance infusion of the formula diet throughout the study. When control formula glucose (week 1) was isocalorically replaced with ethanol [week 2, 30% of kcal; week 3 or 4 (5-week experiment) 40% to 60% of kcal], the following was observed: weight loss; zero energy balance and reduced or negative balances of N, K, P, Mg, and Na; increased urinary urea N and 3-methylhistidine; lowered urinary C-peptide; no change in indirectly or directly measured thermal energy losses; and a blood level related rise in breath and urinary ethanol losses. All of these changes promptly reversed during the middle (week 3 in 5-week experiment) and final control weeks. Accounting for all diet-related energy losses (urine, breath, thermal), the fuel value of the ethanol-containing diet relative to the glucose control formula varied between 0.95 and 0.99, depending upon the blood alcohol level. Hence weight loss during short-term (seven-day) ethanol infusion is unrelated to overall negative energy balance, stems primarily from decrements in protein, minerals, and fluid, and may in part be mediated by the reduction in insulin secretion that accompanies switching from dietary glucose to ethanol.