Effects of formula temperature on postprandial thermogenesis and body temperature of premature infants

To study the effect of formula temperature on the thermogenic response to gavage feeding, we fed formula at room temperature (mean 24.0° C, SD 1.1) and at body temperature (mean 36.9° C, SD 1.7) to premature infants in a crossover design while monitoring their metabolic heat production and gastric, rectal, and skin temperatures. After feeding with room temperature formula, stomach temperature fell by 6.9° C, rectal temperature by 0.2° C, and mean skin temperature by 0.6° C, and metabolic rate increased by 16% in the first postprandial hour. After body temperature feedings, mean skin temperature fell by 0.2° C, but stomach and rectal temperatures did not change appreciably. The metabolic rate rose by 12% in the first hour, which was not significantly less than the rise after room temperature feeding. The heat required to warm the formula to body temperature did not result in a detectably greater rise in metabolic rate after cool feeding than after warm feeding. The effects of feed temperatures below room temperature were not studied, but it remains possible that cooler feedings might produce even greater body cooling and a greater thermogenic response.