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A new method for the estimation of body composition in humans, called infrared interactance, is discussed. Infrared interactance is based on the principles of light absorption, reflection, and near-infrared spectroscopy. Body composition (percentage fat) was estimated in 53 adults (23 to 65 yr of age) by infrared interactance and compared to results from deuterium oxide dilution (r = 0.94), skinfold (r = 0.90), and ultrasound (r = 0.89) measurements. The method is safe, noninvasive, rapid, easy to use, and may prove useful to predict percentage body fat, especially in the obese.

Of 824 women screened, 410 were enrolled at midpregnancy in a prospective, randomized, controlled nutrition intervention study. Of these, 226 were predicted as likely to have small or large babies, 184 to have average-sized babies. Two hundred thirty eight mothers received USDA Women, Infants and Children (WIC) Food Supplementation vouchers from midpregnancy, 172 did not. Leukocyte protein synthesis (as a cell model) was significantly higher (p = 0.009) by 36 weeks gestation in supplemented mothers. Mean birth weight of their babies was greater, 3254 vs 3163 g, (+91 g) p = 0.039, adjusted for sex, gestational age, prenatal visits, pregnancy interval, smoking, and previous low birth weight infants. Controlling for entry weight obviated the significance of the difference, except for WIC supplemented smokers (greater than 10 cigarettes/day) whose babies were significantly heavier by +168 g (p = 0.017) than those of unsupplemented smokers. WIC partially protects fetal growth in smokers.

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The apparent and true digestibilities of the same preparations of six proteins (spray dried whole egg, cottage cheese, canned tuna, peanut flour, soy isolate, and wheat gluten) were estimated in four to five men and in rats and compared to estimates of digestibility from three different in vitro enzymic digestion procedures. For all six proteins, the correlation coefficient was 0.46 between true digestibility in humans and in rats; with values for tuna excluded, r = 0.96. With all six proteins, none of the in vitro values was significantly correlated with values from humans or rats. However, with either the three animal proteins alone or the three plant proteins alone, correlations were high (r greater than 0.90) between one or more of the in vitro estimates and the observed true or apparent human and rat digestibilities. The differences in the relationship between enzymic digestion estimates and the human digestibility estimates for plant or animal proteins suggest that for accurate prediction of protein digestibility in humans by these enzymic methods, different equations would have to be used for plant and animal proteins. For protein sources containing both plant and animal protein, use of the in vitro enzymic procedures would give only an approximate estimate of digestibility in humans.