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 males

Nitrogen Balance at the Recommended Dietary Allowance for Protein in Minimally Active Male Vegans

Vegan diets have gained popularity in recent years for reasons including health benefits and concerns for animal welfare. Although these diets are considered to be nutritionally adequate, questions remain over whether the current protein recommendation (0.8 g/kg/d) is sufficient. Protein status is determined through a nitrogen balance analysis when the protein content of the diet is known. A negative balance indicates a catabolic state, and a positive nitrogen balance indicates an anabolic state. In healthy adults, nitrogen equilibrium is the expectation reflecting the net synthesis and breakdown of proteins. Currently, there are no known studies measuring nitrogen balance in strict vegan men fed the protein requirement. Eighteen minimally active vegan men received a 5-day eucaloric diet (protein content: 0.8 g/kg/d). On day five, 24 h urine was collected for nitrogen analysis. Both the mean absolute nitrogen balance (-1.38 ± 1.22 g/d) and the mean relative nitrogen balance (-18.60 ± 16.96 mg/kg/d) were significantly lower than zero (equilibrium) (p < 0.001). There were no correlations seen between nitrogen balance and age, years as vegan, or fat-free mass. Consuming 0.8 g/kg/d of protein is not adequate to produce nitrogen balance in men adhering to typical strict vegan diets for at least one year.

Comparison of three methods for the estimation of total nitrogen losses in hospitalized patients

Since the measurement of total nitrogen output (TNO) is not routinely determined in the clinical setting, its level is frequently estimated using formulas based on the urinary urea nitrogen excretion (UUN). We measured TNO in 124 surgical patients over 990 days (TNO, 19.22 +/- 8.72 g N/day; total urinary nitrogen (TUN) 18.17 +/- 8.70 g N/day; UUN, 15.17 +/- 7.70 g N/day; mean gastrointestinal nitrogen (MGIN) 0.68 +/- 0.49 g N/day; integumental nitrogen (ITGN), 0.34 +/- 0.08 g N/day) and compared the results with the daily estimations using three different formulas: formula A, UUN + 4; formula B, UUN x 1.20 + 1.05, where 1.20 is the reciprocal of the mean ratio UUN/TUN and 1.05 the mean extraurinary nitrogen losses; and formula C, UUN x 1.0986 + 2.55, derived from the regression analysis of UUN vs TNO. TNO estimated by these formulas were 19.17 +/- 7.70, 19.26 +/- 9.24, and 19.22 +/- 8.70 g N/day, respectively. The regression analyses of the estimated TNO from the three formulas versus the measured TNO indicated that formulas A, B and C were equally accurate in estimating TNO over the entire range of UUN. However, when only values of UUN greater than or equal to 30 g N were considered, a modified formula A (UUN + 6) was the best predictor of TNO. Daily audits of the differences between the estimated and measured TNO showed comparable results for the three formulas. In 28.4 to 31.1% of the observed days the differences were higher than +/- 2 g N/day, an error which is not acceptable when estimating the protein requirements in many clinical conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitrogen economy in alcoholic patients without liver disease

Nitrogen balance was studied in five alcoholic patients during alcohol consumption and after 1 or 2 weeks of abstinence, under metabolic ward conditions. Patients had a history of excessive ethanol intake for five years or more. They were intoxicated and otherwise asymptomatic on admission and had been drinking 150 g or more of ethanol daily, for at least one month. Subjects consumed a diet providing vitamins and minerals exceeding RDA values, 45 kcal/kg of body weight and 0.6 g/kg of proteins (as egg protein), for 33 days. During the first 11 days patients received 200 g of ethanol that were isocalorically substituted later by dietary fat and carbohydrates. The results of this study show that, in alcoholic patients while drinking and after seven days of alcohol withdrawal, nitrogen balance is significantly decreased compared to that performed after two weeks of abstinence. Ethanol metabolic rate was found to be increased, compared to controls. It was lower in four of five patients after the second week of abstinence. These results suggest that alcohol abuse increases protein requirements in chronic alcoholic patients even without histologic liver disease or clinical signs of gastroenterologic disorders.