USDA, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND (JJC, LDW, and GFC); the Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA (SMP, LMM, JPM, and AJY); and the School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND (ERS).
Am J Clin Nutr. 2014 Feb;99(2):400-7. doi: 10.3945/ajcn.113.073809. Epub 2013 Nov 27.
Although consuming dietary protein above current recommendations during energy deficit (ED) preserves lean body mass, concerns have been raised regarding the effects of high-protein diets on bone health.
The objective was to determine whether calcium homeostasis and bone turnover are affected by high-protein diets during weight maintenance (WM) and ED.
In a randomized, parallel-design, controlled trial of 32 men and 7 women, volunteers were assigned diets providing protein at 0.8 [Recommended Dietary Allowance (RDA)], 1.6 (2 × RDA), or 2.4 (3 × RDA) g · kg(-1) · d(-1) for 31 d. Ten days of WM preceded 21 d of ED, during which total daily ED was 40%, achieved by reduced dietary energy intake (∼30%) and increased physical activity (∼10%). The macronutrient composition (protein g · kg(-1) · d(-1) and % fat) was held constant from WM to ED. Calcium absorption (ratio of (44)Ca to (42)Ca) and circulating indexes of bone turnover were determined at day 8 (WM) and day 29 (ED).
Regardless of energy state, mean (±SEM) urinary pH was lower (P < 0.05) at 2 × RDA (6.28 ± 0.05) and 3 × RDA (6.23 ± 0.06) than at the RDA (6.54 ± 0.06). However, protein had no effect on either urinary calcium excretion (P > 0.05) or the amount of calcium retained (P > 0.05). ED decreased serum insulin-like growth factor I concentrations and increased serum tartrate-resistant acid phosphatase and 25-hydroxyvitamin D concentrations (P < 0.01). Remaining markers of bone turnover and whole-body bone mineral density and content were not affected by either the protein level or ED (P > 0.05).
These data demonstrate that short-term consumption of high-protein diets does not disrupt calcium homeostasis and is not detrimental to skeletal integrity. This trial was registered at www.clinicaltrials.gov as NCT01292395.
尽管在能量不足（ED）期间摄入超过当前推荐量的膳食蛋白质可以保留瘦体重，但人们对高蛋白饮食对骨骼健康的影响仍存在担忧。
本研究旨在确定在体重维持（WM）和 ED 期间，高蛋白饮食是否会影响钙稳态和骨转换。
这是一项在 32 名男性和 7 名女性志愿者中进行的随机、平行设计、对照试验，志愿者被分配摄入蛋白质含量分别为 0.8 [推荐膳食允许量（RDA）]、1.6（2×RDA）或 2.4（3×RDA）g·kg(-1)·d(-1)的饮食，持续 31 天。在进行 21 天 ED 之前，志愿者先进行 10 天 WM，在此期间，通过减少饮食能量摄入（约 30%）和增加体力活动（约 10%）实现总能量每日减少 40%。从 WM 到 ED，宏量营养素组成（蛋白质 g·kg(-1)·d(-1)和%脂肪）保持不变。在第 8 天（WM）和第 29 天（ED）测定钙吸收（(44)Ca 与 (42)Ca 的比值）和循环骨转换标志物。
无论能量状态如何，2×RDA（6.28±0.05）和 3×RDA（6.23±0.06）组的平均（±SEM）尿 pH 值均低于 RDA 组（6.54±0.06）（P＜0.05）。然而，蛋白质对尿钙排泄量（P＞0.05）或钙保留量（P＞0.05）均无影响。ED 降低了血清胰岛素样生长因子 I 浓度，增加了血清对羟磷灰石酶和 25-羟维生素 D 浓度（P＜0.01）。骨转换的其余标志物以及全身骨矿物质密度和含量均不受蛋白质水平或 ED 的影响（P＞0.05）。
这些数据表明，短期摄入高蛋白饮食不会破坏钙稳态，也不会对骨骼完整性造成损害。本试验已在 www.clinicaltrials.gov 上注册，编号为 NCT01292395。
