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Long-Term Validation of 1 g of Protein per Kilogram Body Weight from a Predominantly Vegetable Mixed Diet to Meet the Requirements of Young Adult Males¹

Enrique Yáñez^*, Ricardo Uauy^2,, Isabel Zacarías^* and Gladys Barrera^*

^* Universidad de Chile, Instituto de Nutrición y Tecnología de los Alimentos (INTA), Casilla 15138, Santiago 11, Chile Department of Pediatrics, University of Texas Health Science Center, 5323 Harry Hines Boulevard, Dallas, TX 75235

Eight healthy young men participated in a 90-d metabolic balance study designed to assess the adequacy of 1 g of protein (N x 6.25) per kilogram body weight per day provided by a predominantly vegetable diet. The mean gross energy intake of the subjects was 49 kcal/(kg·d). The individuals received the experimental diet for eleven 8-d experimental periods. Three isoenergetic, isonitrogenous meals were served at 0800, 1200 and 1900. Anthropometric measurements and biochemical determinations in blood were made at the beginning of the study and afterwards at regular 15-d intervals. Body weight was measured daily. The mean overall weight change for the group was -0.8 kg. The mean daily urinary nitrogen output decreased from an initial value of 134.6 mg/(kg·d) to a final figure of 115.1 mg/(kg·d) (P < 0.01), while the daily fecal N decreased from 31.5 to 26.3 mg/(kg·d) (P < 0.05). Mean cumulative nitrogen balances were slightly positive for seven out of the eight individuals with an overall mean nitrogen balance value of +6.7 mg N/(kg·d). Biochemical and hematological values showed no significant changes throughout the study, except for a decrease in serum cholesterol. It is concluded that the "Chilean" mixed diet fed at the level of 1 g of protein per kilogram body weight per day with sufficient energy meets the long-term protein-energy needs of healthy young men, thus supporting the 1984 FAO/WHO/UNU safe recommended daily protein allowance of 0.75 g of reference protein, with a correction for the lower digestibility of vegetable sources.

KEY WORDS: • protein requirement • young adult men • mixed diet • long-term • nitrogen balance

¹ Supported in part by a grant from the United Nations University.

² Reprint requests should be directed to: Dr. Ricardo Uauy, University of Texas Health Science Center, Department of Pediatrics, 5323 Harry Hines Boulevard, Dallas, TX 75235.

Manuscript received 25 January 1985. Revision accepted 23 December 1985.