Top Institute Food & Nutrition, Wageningen, The Netherlands.
Am J Clin Nutr. 2013 Jul;98(1):121-8. doi: 10.3945/ajcn.112.051201. Epub 2013 May 1.
Older individuals generally experience a reduced food-chewing efficiency. As a consequence, food texture may represent an important factor that modulates dietary protein digestion and absorption kinetics and the subsequent postprandial protein balance.
We assessed the effect of meat texture on the dietary protein digestion rate, amino acid availability, and subsequent postprandial protein balance in vivo in older men.
Ten older men (mean ± SEM age: 74 ± 2 y) were randomly assigned to a crossover experiment that involved 2 treatments in which they consumed 135 g of specifically produced intrinsically L-[1-(13)C]phenylalanine-labeled beef, which was provided as beef steak or minced beef. Meat consumption was combined with continuous intravenous L-[ring-(2)H5]phenylalanine and L-[ring-(2)H2]tyrosine infusion to assess beef protein digestion and absorption kinetics as well as whole-body protein balance and skeletal muscle protein synthesis rates.
Meat protein-derived phenylalanine appeared more rapidly in the circulation after minced beef than after beef steak consumption (P < 0.05). Also, its availability in the circulation during the 6-h postprandial period was greater after minced beef than after beef steak consumption (61 ± 3% compared with 49 ± 3%, respectively; P < 0.01). The whole-body protein balance was more positive after minced beef than after beef steak consumption (29 ± 2 compared with 19 ± 3 μmol phenylalanine/kg, respectively; P < 0.01). Skeletal muscle protein synthesis rates did not differ between treatments when assessed over a 6-h postprandial period.
Minced beef is more rapidly digested and absorbed than beef steak, which results in increased amino acid availability and greater postprandial protein retention. However, this does not result in greater postprandial muscle protein synthesis rates. This trial was registered at clinicaltrials.gov as NCT01145131.
老年人的食物咀嚼效率通常会降低。因此，食物质地可能是调节膳食蛋白质消化和吸收动力学以及随后的餐后蛋白质平衡的一个重要因素。
我们评估了肉质地对老年人体内膳食蛋白质消化率、氨基酸利用率以及随后的餐后蛋白质平衡的影响。
10 名老年男性（平均年龄 ± 标准差：74 ± 2 岁）被随机分配到一项交叉实验中，他们分别摄入 135 克专门制作的、内源性 L-[1-(13)C]苯丙氨酸标记的牛肉，这些牛肉以牛排或肉末的形式提供。肉的摄入与连续静脉内 L-[环-(2)H5]苯丙氨酸和 L-[环-(2)H2]酪氨酸输注相结合，以评估牛肉蛋白的消化和吸收动力学以及全身蛋白平衡和骨骼肌蛋白合成率。
与食用牛排相比，食用肉末后肉蛋白衍生的苯丙氨酸更快地出现在循环中（P < 0.05）。此外，在餐后 6 小时期间，其在循环中的可用性也高于食用牛排（分别为 61 ± 3%和 49 ± 3%；P < 0.01）。与食用牛排相比，食用肉末后全身蛋白平衡更为正性（分别为 29 ± 2 和 19 ± 3 μmol 苯丙氨酸/kg；P < 0.01）。在 6 小时的餐后期间，骨骼肌蛋白合成率在两种处理方式之间没有差异。
肉末比牛排更易消化和吸收，这导致氨基酸利用率增加和餐后蛋白质保留增加。然而，这并不会导致更大的餐后肌肉蛋白合成率。本试验在 clinicaltrials.gov 上注册为 NCT01145131。
