A METABOLIC NITROGEN-BALANCE STUDY FOR 40-D AND EVALUATION OF THE MENSTRUAL-CYCLE ON PROTEIN REQUIREMENT IN YOUNG NIGERIAN WOMEN

A long-term N balance study was carried out to determine the adequacy of an estimated protein requirement level recommended for young health y Nigerian women and the effect of the menstrual cycle oa the requirem ent. Eleven healthy young women, 25 (SD 2.6) years, were fed on a diet providing 0.6 g protein (N x 6.25)/kg per d and an average energy int ake of 0.17 (SD 0.012) MJ/kg per d. Urine, faeces, sweat and menstrual fluids were collected for estimation of N balance. Menstrual N loss v aried among individuals ranging from 46 to 124 mg N/d with an average of 89 (SD 21.8) mg N/d. Individual N balance nas found to vary accordi ng to the day of the menstrual cycle. Positive N balances were recorde d at about ovulation while negative balances were observed just before the onset of menstruation. The average N balance ranged from +8.49 (S D 5.64) to -430 (SD 7.84) mg N/kg per d. Nevertheless, an overall cumu lative positive N balance of +5.7 (SD 6.98) mg N/kg per d which did no t change significantly with time was observed for the last 5 d of two consecutive 20 d diet periods, although three subjects were in negativ e N balance. Blood biochemical measurements were stable except for one subject who had elevated serum aspartate aminotransferase (EC 2.6.1.1 ) levels. These findings suggest that our estimate of protein requirem ents was sufficient to achieve N balance equilibrium in a majority (70 %) of young women. However, to satisfy 97.5% of the population, slight adjustments might be necessary ia the energy intake since subjects wh o were in cumulative negative N balance also lost weight.