Lower energy content of human milk than calculated using conversion factors.
Bodyweight gain of formula-fed babies is usually higher than that of breast-fed ones. The energy content of human milk is usually quantified not by direct measurement but by calculation based on The Standard Tables of Food Composition in Japan. For this study, the energy of human milk was quantified in two ways, using a direct measurement and a calculation method. A total of 227 milk samples (192 colostrum, 21 transitional milk, and 14 mature milk) were collected from 114 healthy women. Energy of the whole milk was measured by ballistic bomb calorimetry. The content of protein, fat, and carbohydrate was determined by direct measurement methods. Energy of the milk was also calculated according to the indices in The Standard Tables. The mean value for all milk samples of directly measured energy was significantly lower than that of the calculated energy (58.1 +/- 8.1 vs. 64.5 +/- 10.6 kcal/100 g, n = 227, P < 0.05). Similar results were observed in colostrum and transitional milk but not in mature milk. Measured energy in mature milk was significantly higher than that in colostrum (64.2 +/- 3.6 vs. 57.1 +/- 8.0 kcal/100 g, P < 0.05). Protein concentration in mature milk was significantly lower than that in colostrum (1.4 +/- 0.4 vs. 2.2 +/- 0.7 g/100 g, P < 0.05). The measured energy content of human milk was lower than the calculated energy based upon the Standard Tables, suggesting that formula milk contains excessive energy.