運動訓練的蛋白補充原則：質比量更重要

Protein Supplementation Principle for Training: Quality is More Important than Quantity

郭家驊(Chia-Hua Kuo)

《大專體育學刊》 19卷4期 (2017/12) Pp. i-v

https://doi.org/10.5297/ser.1904.editorial

摘要

運動訓練可增強體能並保持肌肉的健康來對抗人體老化。運動後，不健康的細胞被免疫系統清除後必須再生新細胞來適應新的挑戰，進而提高體能與生存能力。重建過程需要大量的碳與氮資源（合成DNA與蛋白質）用來再生細胞。這個汰舊換新過程實際上是透過發炎反應，將產生疲勞與疼痛感 (Tidball, 2005)。因此，運動訓練如能及時提供同時具有碳與氮資源的蛋白質，將產生加快運動恢復與消除疲勞感的效果。評估適合運動訓練用的蛋白質來源應特別考量它是否能被身體快速吸收，這比蛋白質的含量多寡更重要。提供蛋白質的食物來源很多，乳清蛋白 (whey protein)是目前公認適合運動訓練的蛋白質來源。最主要的原因是它可被人體快速消化吸收。運動後延遲蛋白質攝取時間，可造成恢復時間延長，不利疲勞恢復(Levenhagen et al., 2001)。特別對於超過 70 歲靠運動訓練防止肌肉流失的高齡者(Esmarck et al., 2001)與經常挑戰肌肉的年輕運動員(Cribb & Hayes, 2006; Levenhagen et al., 2001)，蛋白質補充時間與吸收速度對運動訓練的效果很重要。來自於牛奶分離出來的的乳清蛋白在此目的上提供最佳的選擇。蛋白質補充不僅對正在進行運動訓練的人很重要，任何處於細胞再生需求很大的生理狀況下，例如兒童成長與成人生病時，都比較需要蛋白質。但蛋白質應攝取多少是一 個非常重要問題。蛋白質攝取不足顯然會阻礙成長與體能恢復，蛋白質攝取過多卻加速老化同時增加癌症死亡風險(Levine et al., 2014)。目前世界衛生組織對 19 歲以上的每日建議量(recommended dietary allowance)為每天每公斤體重應攝取 0.75公克，即70公斤體重每天建議吃約53公克的蛋白質才足夠；美國標準則訂在每天每公斤體重應吃到0.8公克(National Research Council [US] Subcommittee on the Tenth Edition of the Recommended Dietary Allowances, 1989)。過去這些標準的訂法並不太具有說服力。因為他們不是根據壽命（或死亡率）的結果來訂。而是用短期或長期的氮平衡這個間接指標，作為判定好壞的標準。最新的大樣本長期追蹤研究顯示當人處在生命期體重下降的階段（69歲後），蛋白攝取量高者壽命較長，但對於年齡體重處於成長期介於 50 ~ 65 歲間的成人，蛋白攝取量高者壽命反而較短 (Levine et al., 2014)。動物研究結果顯示減少熱量攝取使壽命增長的原因主要透過蛋白質攝取減少，而非醣類與脂肪的因素(Solon-Biet et al., 2014)。因此適量蛋白質攝取是決定健康與體能很重要的因素，應取得平衡。對於中年人蛋白質攝取占總熱量攝取的10%以下，在壽命與癌症風險降低上有最佳的結果，但生病時要攝取增加以加速恢復。運動訓練後乳清蛋白需要吃多少？對於86公斤進行重量訓練的人，蛋白質攝取量增加到20公克即達到促進蛋白質合成的最大極限。多吃並無法產生更好的效果(Moore et al., 2009)。類似的研究顯示運動後攝取類似的量（每公斤體重吃0.2公克）在5小時之後全身蛋白合成率可維持高於空腹狀態(Moore et al., 2009)。這些結果很清楚的顯示即使對於經常挑戰肌肉的年輕人，並不需要攝取達到世界衛生組織與美國訂定給一般人的攝取標準。然而，對於肌肉處於減少期的高齡者則須加倍攝取。以71歲的高齡者為例，重量訓練後須攝取每公斤體重0.4公克才能達到跟年輕人相同的蛋白合成增加效果(Moore et al., 2014)。

並列摘要

One of the best benefits of exercise training is to increase physical fitness by preserving muscle health against aging. After exercise, regeneration of new cells after muscle damage helps adaptation of the body against new challenge for survival. This recovery process demands carbon and nitrogen sources for reconstructing new cells in the tissue. It is noteworthy that the cell regenerative process during recovery is part of inflammation program (Tidball, 2005), which generates subjective fatigue feeling and pain. Therefore, providing sufficient protein to challenged muscle in time around workout is crucial in preventing fatigue feeling and ensuring fast recovery. To evaluate the quality of dietary protein source should base on its adsorption efficiency, which is more important than the amount of protein provided. There are many dietary sources, which can be used for protein supplementation. Whey protein isolate is generally considered the best source for training individuals. The main reason is that whey protein can be quickly digested and absorbed in human body. Any delay in protein delivery to challenged muscle will prevent fast recovery for regenerating cells. Therefore, supplementation timing is important for optimal training effect in muscle growth. This is particularly important for both the individuals aged above 70 yrs, when muscle loss is the main concern (Esmarck et al., 2001), and the young individuals under sport training (Cribb & Hayes,2006;Levenhagen et al., 2001). Protein is not only important for individuals under exercise training. It is essential for any individual who has high cell proliferation rate, such as during acute illness and fast growing age. However, how much protein should be taken is an important question in human health. Too little protein intake inhibits growth; yet too much protein intake accelerates aging, in particular, increases cancer mortality (Levine et al., 2014). Recommended dietary allowance of 0.75 gram per kilogram body weight according to WHO and 0.8 gram per kilogram body weight according to USDA for those aged older than 19 yrs are considered maximal (National Research Council [US] Subcommittee on the Tenth Edition of the Recommended Dietary Allowances, 1989). These values are not provided based on human longevity data (all-cause mortality), but nitrogen balance outcomes as indirect evidence. Furthermore, high protein supplementation for elderly in the weight falling phase (> 69 years old) shows increased longevity, but the same supplemented quantity for middle-aged individuals in the weight rising phase (50 ~ 65 years old) is associated with shorter longevity (Levine et al., 2014). A lifespan animal study (Solon-Biet et al., 2014) confirms the causal relationship between protein and longevity. In a human training study, ingestion of only 20 g protein for men weighted -- 86 kg is sufficient to maximally stimulate protein synthesis and albumin protein synthesis after resistance exercise (Moore et al., 2009). Similar result has also been reported with approximately the same protein quantity (0.2 g per kg), which can sustain higher protein synthesis rate for at least 5 hrs above fasted condition (Moore et al., 2009). These results clearly indicate that even for someone who challenges the muscle regularly, protein supplementation does not need to supplement to a level suggested by WHO or USDA. Yet, we must stress again that elderly should be considered as different case. For men aged -- 71 yrs, ingestion of 0.4 g per kg is required to maximally stimulate protein synthesis (Moore et al., 2014).

參考文獻

Cribb, P. J.,Hayes, A.(2006).Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy.Medicine & Science in Sports & Exercise.38(11),1918-1925.

Esmarck, B.,Andersen, J. L.,Olsen, S.,Richter, E. A.,Mizuno, M.,Kjær, M.(2001).Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans.The Journal of Physiology.535(1),301-311.

Levenhagen, D. K.,Gresham, J. D.,Carlson, M. G.,Maron, D. J.,Borel, M. J.,Flakoll, P. J.(2001).Postexercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis.American Journal of Physiology - Endocrinology and Metabolism.280(6),E982-E993.

Levine, M. E.,Suarez, J. A.,Brandhorst, S.,Balasubramanian, P.,Cheng, C.-W.,Madia, F.,Wan, J.(2014).Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population.Cell Metabolism.19(3),407-417.

Moore, D. R.,Churchward-Venne, T. A.,Witard, O.,Breen, L.,Burd, N. A.,Tipton, K. D.,Phillips, S. M.(2014).Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men.The Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences.70(1),57-62.