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.

Serum creatinine as an indicator of lean body mass in vegetarians and omnivores.

Growing numbers of Americans are adopting vegetarian or vegan diets. While risk for some chronic conditions may be lower when following these diets, concern remains over the ability to consume adequate amounts of various nutrients, notably, protein. Knowing that serum creatinine is a reliable marker of muscle mass, this study examined the relationships between serum creatinine, lean body mass (LBM), handgrip strength, and protein intake in healthy vegetarian (n = 55) and omnivorous (n = 27) adults. Significantly higher protein intakes (+31%), LBM (+7%), serum creatinine (+12%) and handgrip strength (+14%) were observed for the omnivore participants compared to vegetarian participants. Positive correlations (p < 0.001) were noted between creatinine and LBM (R2 = 0.42), creatinine and handgrip strength (R2 = 0.41), protein intake and LBM (R2 = 0.29), and handgrip strength and LBM (R2 = 0.69). These data show that serum creatinine concentrations were lower in vegetarian women and men in comparison to their omnivorous counterparts and that serum creatinine concentrations correlate with LBM and strength in healthy adults, regardless of diet.

Three minutes of moderate-intensity stair walking improves glucose and insulin but not insulin sensitivity or total antioxidant capacity.

BACKGROUND AND AIMS: This study examined the effect of moderate intensity stair stepping exercise on the glycemic response, and antioxidant capacity (TAC) during an oral glucose tolerance test (OGTT). METHODS AND RESULTS: Thirty participants (women = 12) completed 4 OGTTs during rest or stair walking bouts of 1, 3, and 10 min in a randomized order. Blood was collected at baseline and 30 min during the OGTTs and analyzed for glucose, insulin, TAC, and lactate. Glucose concentrations were decreased following the 10 min (-22.69 (-34.66 to -10.72) mg/dL, p < 0.002) and 3 min (-15.37 (-25.05 to -5.69) mg/dL, p < 0.004) bouts but not the 1 min bout (-6.18 (-19.54 to 7.18) mg/dL, p = 0.352). Insulin concentrations were decreased following the 10 min (-6.11 (-8.86 to -3.36 µIU/dL), p < 0.001) and 3 min (-2.589 (-4.54 to -0.63) µIU/dL, p < 0.012) bouts but not the 1 min bout (-0.37 (-1.87 to 1.13) µIU/dL, p = 0.616). Insulin sensitivity index values showed a significant increase in the 10-min trial (1.81 (0.03-3.58), p < 0.048), but not during the 3 min (0.65 (-0.66 to 1.96) p = 0.317) or 1 min trial (0.13 (-1.58 to 1.84) p = 0.878). There was no omnibus effect for trial in TAC (p = 0.132, η2 = 0.07). There was no interaction between trial and time for blood lactate (p = 0.621, η2 = 0.02). CONCLUSION: This study provides evidence bouts as short as 3 min decrease postprandial blood glucose and insulin levels but longer bouts are needed to affect insulin sensitivity.

Effects of chronic decaffeinated green tea extract supplementation on lipolysis and substrate utilization during upper body exercise.

BACKGROUND: Decaffeinated green tea extract (dGTE) can increase fat oxidation during leg exercise, but dGTE is unsuitable for many people (e.g., those with injuries/disabilities), and its effects on arm exercise and women are unknown. METHODS: Eight adults (23-37 years old, 4 women) performed an incremental arm cycle test to measure peak oxygen uptake (VO2peak), followed by four 1-h trials at 50% VO2peak. Subjects were randomly assigned to 650 mg of dGTE or placebo (PLA) for 4 weeks followed by a 4-week washout and crossover trial. Blood samples were obtained pre-exercise and post-exercise for glycerol and free fatty acid analysis. Respiratory gases were collected continuously. RESULTS: VO2 showed no differences across trials ((0.83-0.89) ± (0.19-0.25) L/min, p = 0.460), neither did energy expenditure ((264-266) ± (59-77) kcal, p = 0.420) nor fat oxidation (dGTE = 0.11 to 0.12 g/min vs. PLA = 0.10 to 0.09 g/min, p = 0.220). Fat oxidation as percentage of energy expenditure was not different for dGTE vs. PLA (23% ± 12% to 25% ± 11% vs. 23% ± 10% to 21% ± 9%, p = 0.532). Glycerol concentration increased post-exercise in all trials, independent of treatments (pre = (3.4-5.1) ± (0.6-2.6) mg/dL vs. post = (7.9-9.8) ± (2.6-3.7) mg/dL, p = 0.867, η2 = 0.005 for interaction), as did free fatty acid ((3.5-4.8) ± (1.4-2.2) mg/dL vs. (7.2-9.1) ± (2.6-4.5) mg/dL, p = 0.981, η2 = 0.000). CONCLUSION: Chronic dGTE supplementation had no effect on lipolysis and fat oxidation during arm cycle exercise in men and women.

Postprandial glucose response moderation by cardiorespiratory fitness following short exercise bouts.

BACKGROUND: Previous reports indicate that postprandial glucose (PPG) responses to exercise may depend on cardiorespiratory fitness (CRF), such that less fit individuals have greater reductions in PPG with exercise. Our aim was to investigate moderating effects of CRF on PPG response following exercise of progressively shorter durations and sedentary rest. METHODS: Thirty-four participants (14 female) completed a 75-g oral glucose tolerance test (OGTT) at seated rest. On three subsequent visits, participants completed additional OGTT with either 1, 3, or 10 minutes of stair-climbing. Fingerstick blood glucose measurements were taken every 15 minutes for 1 hour. CRF was determined using a treadmill ramp test. RESULTS: There was a main effect of condition F(3, 93)=13.07, P<0.001, ηp2=0.30. Stair-climbing reduced PPG iAUC compared to control by -3±27% (P=0.546), -11±29% (P=0.091), and -28±22% (P<0.000) for the 1, 3 and 10 min bouts, respectively. There was no trial by CRF interaction for glucose iAUC F(2.4, 73.8)=0.69, P=0.532, ηp2=0.02. Linear mixed model regression analysis revealed that CRF was not significantly associated with glucose iAUC, b=-14 (-45, 16), P=0.339. CONCLUSIONS: Contrary to previous reports CRF did not moderate PPG responses for either sedentary or exercise conditions in healthy men and women. Short, single-bout stair stepping exercise at a self-selected pace is equally efficient for all fitness levels.

Mung Bean Protein Supplement Improves Muscular Strength in Healthy, Underactive Vegetarian Adults.

Although vegetarian diets are considered generally protective against chronic disease, nutrient deficiencies, including protein, are possible due to low bioavailability from plant-based sources. The consequences of inadequate dietary protein include reduced lean body mass (LBM) and muscle weakness. This study examined relationships between protein intake, strength, and LBM in 37 underactive vegetarians and recorded the impact of protein supplementation (18 g/day mung bean protein) on these indices utilizing an eight-week, randomized, controlled, feeding trial. Both handgrip and knee flexor and extensor strength were measured at baseline and week eight. At baseline, LBM was significantly related to grams of protein consumed daily. LBM was also correlated to grip strength (r = 0.569, p < 0.001) and lower body strength (r = 0.763 to 0.784; p < 0.001). Twenty-five vegetarians completed the feeding trial, including 11 in the protein supplementation group (PRO) and 14 in the control group (CON). At the end of the trial, LBM and strength did not differ significantly between groups. However, the average percent change for grip, flexor, and extensor strength did differ between PRO and CON participants (+2.9 ± 7.2% and -2.6 ± 7.3% respectively, p = 0.05). Thus, there were strong associations between dietary protein, LBM, and strength in vegetarians and an indication that supplementary vegetarian protein increased strength in the absence of exercise and independent of LBM.

Sex differences in postprandial glucose response to short bouts of exercise: A randomized controlled trial.

OBJECTIVES: The objective of this study was to assess sex differences in PPG responses to short stair stepping bouts, and to describe their intensity and metabolic cost. DESIGN: Crossover trial. METHODS: 34 participants (age: 25.9±5.5y; women=14) underwent 4 oral glucose tolerance tests (OGTT) during rest or with stair-stepping bouts at self-selected, moderate pace for 1, 3, and 10min. Blood was collected every 15min during the OGTTs and assessed for glucose. Participants also underwent maximal aerobic capacity assessment. Expired gases were collected during capacity testing, and each stair-stepping bout. RESULTS: Normalized to body weight there was no significant interaction for sex with stair-stepping trials (p=0.445, ηp2=0.03), or time (p=0.069, ηp2=0.09), or trial by time (p=0.264, ηp2=0.04). Women had higher mean glucose values than men (15(CI=3, 27)%, p=0.015). iAUC also showed no interaction of sex*trial (p=0.059, ηp2=0.09). Women had higher iAUC values (meanΔ=-29(-48, -11)%, p=0.003). There was a main effect for trial with 10min showing the largest reduction from control for women (e.g. AUC -10(-6, -13)%, p<.001) and men (-8(2, 13)%, p=.010). Metabolic cost of the stair stepping bouts showed no interaction of sex*trial (p=0.715, ηp2=0.01) and no difference between sexes (meanΔ=-1.3(-5.9, 3.4)%, p=0.571). Intensity was higher for women for the 3min (60±11 vs. 48±9%VO2max, p=0.003) and 10min (67±8 vs. 54±12%VO2max, p=0.002) bouts. Moreover, both sexes underestimated the true intensity of stepping. CONCLUSIONS: Both sexes had similar responses to short bouts of exercise, which they perceived as less intense than indicated by objective assessment. Stair stepping reduces postprandial glucose response with similar effectiveness for both sexes. ClinicalTrials.gov Identifier: NCT03400774.

Reducing Glycemic Indicators with Moderate Intensity Stepping of Varied, Short Durations in People with Pre-Diabetes.

Investigate the effects of short duration stair climbing/descending at a self-selected pace on post-prandial glucose responses in adults. Thirty participants (10 female) completed 4 oral glucose tolerance tests on separate days. Following glucose consumption, participants underwent seated rest (control) or walked up/down 21 stairs at a self-selected comfortable pace for 10, 3, and 1min in randomized order. Blood glucose was measured by capillary sampling from finger sticks every 15min until values for all trials converged. Area under the curve (AUC) was calculated by trapezoidal rule. In addition, cardiometabolic measurements were taken during stair exercise with a mobile metabolic cart. Results are presented as mean (SD) unless stated otherwise. All stair-climbing trials reduced peak (30min) postprandial blood glucose levels compared to the control [(1 min = 12(31), p = 0.026; 3 min = -15(25), p = 0.003; 10 min = 35(32) mg/dL, p < 0.001]. At 45min, there were significant reductions only for the 3 and 10 min trials [13(29) and 23(31) mg/dL, p = 0.023 and < 0.001 respectively], but not the 1 min trial [6(33) mg/dL, p = 0.317]. There were significant differences in AUC compared to the control only for the 3 and 10min trials [502 (1141) and 866 (1123) mg/dL·min-1, p = 0.023 and < 0.000] but not for the 1min trial [353 (1265) mg/dL·min-1, p = 0.110]. Median (interquartile range) RPEs reported for the 1, 3, and 10min trials were 1.0 (1.5), 2.0(2), and 3.0 (2.0) respectively, while VO2 was n/a, 54(12), and 59(13)% of peak, respectively. Total metabolic cost was 1.4 (0.5), 4.0 (1.0), and 11.9 (2.1) L O2, respectively. A single 1min bout of low-moderate intensity stair stepping can significantly lower peak glucose concentration, with longer bouts being more effective.