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Utilization of Nitrogen, Energy, and Sulfur by Adolescent Boys Fed Three Levels of Protein¹

Department of Food and Nutrition, School of Home Economics, University of Connecticut, Storrs, Connecticut 06268

Nine adolescent boys were fed three levels of dietary nitrogen between 0.08 and 0.12 g/kilogram body weight. Caloric intakes were 55 to 59 kcal/kg. One year later eight of the original boys were fed the same diets except that caloric intakes were adjusted to current body weights. The mean increase in weight over the 1-year period was 4.6 kg; in height, 4 cm; in lean body mass, 4%; and in surface area, 0.08 m². The daily nitrogen retention necessary to support a weight gain of 4.6 kg was 0.36 g. For dietary protein of Biological Value 100 the minimum protein requirement of these adolescent boys was 26.9 to 29.7 g/day. The calorie conversion factor for protein in the diets fed was 3.46, and apparent digestibility of the protein was 79 to 85%. The percentage of dietary energy excreted in urine was 1 and 2%, when the lowest and highest levels of nitrogen, respectively, were fed; fecal calories were the same, 4%, when the two levels were fed. Total dietary sulfur increased as dietary nitrogen increased; however, urinary total sulfur decreased at the higher sulfur intake while total sulfur in feces was unchanged.

KEY WORDS: • adolescent boys • protein requirement • sulfur utilization • energy utilization

¹ Supported by National Institutes of Health Grant no. R 1 AM 8556, from the National Institute of Arthritis and Metabolic Diseases.

² Present address: Nutrition Program, Center for Disease Control. Atlanta, Georgia 30333.

³ Present address: Department of Public Health, State of California, Sacramento, California 95814.

⁴ Present address: 1103 West Virginia Avenue, Martinsburg, West Virginia 25401.

Manuscript received 20 November 1972.