ISSN健身營養指引更新 : 蛋白質與碳水的攝取策略

文：減重醫師 蕭捷健

到底該怎麼攝取蛋白質和碳水化合物，才能讓增肌或減脂達到做好的效果？這一直是運動營養學追求的終極答案。ISSN ( 國際運動營養學會）每隔幾年就會根據最新的研究 update 一次飲食建議，讓我們來看看最新版的增肌飲食，內容做了什麼更新。JJ整理了和健身運動相關的建議，和耐力型運動（如鐵人或馬拉松）相關的就不說了。

JJ的風格，一向是帶給大家確定而不模擬兩可的答案，讓我們繼續往下看。

訓練完不用急著補充蛋白質

我們一直以來都有這樣的觀念：運動完要趕快補充優質蛋白，讓肌肉組織能夠修復 。難道這樣的鐵律還能夠被打破嗎？營養學是一個巨型迷宮，人體的反應往往超乎預期，科學研究更是常常讓人跌破眼鏡。讓我們來回溯一下，「運動完要馬上補充蛋白質」這樣的觀念，是從哪裡來的。

2006年，Cribb教授發表在運動科學與醫學期刊 (Med Sci Sports Exerc.) 的這篇研究，要求兩組男性受試者完成數週的重量訓練，而他們攝取完全相同的營養素。兩組唯一的區別在於:

• 一組在每次運動前後攝取營養素
• 另一組則在早晚攝取

結果發現，這兩組受試者的肌肉都發達了，但是在運動前後攝取營養的組別，肌肉量和力量顯著增強。從此，肌力訓練前後要馬上攝取營養，就成了行為的準則，普世的價值。

就在大家都認為這是不可能錯誤的真理大廈時，Jay Hoffman 在這個研究裏，發現了兩朵烏雲：Cribb的實驗設計有一個不完美的地方，就是他們所攝取的熱量和營養素，並不是我們現在所建議的量。也就是說，在Cribb的研究裏，受試者吃的不夠。於是，Jay Hoffman的團隊做了一個幾乎一模一樣的研究，唯一不同的地方，就是兩組的營養素攝取符合今天的建議量，結果發現，兩組受試者的肌肉都變強壯了，沒有誰比誰壯。

這告訴我們，只要一整天的營養素攝取量足夠，我們就不用把飲食集中在運動前後吃掉。

這不代表Cribb的研究是錯誤的，但我們必須要重新定義他原本的研究結果：當一整天的蛋白質和碳水化合物攝取不足的時候，運動前後吃東西，增肌的效果還是會比較好。大部分的老百姓，一整天下來吃得都是不夠的，所以運動前後吃東西，還是很重要。

代謝窗口(Metabolic window)其實不存在？

這幾年，我們一直有代謝窗口的概念（Metabolic window)。所謂的代謝窗口，就是指鍛煉後15分鐘到30分鐘內，攝入足夠的營養素，是肌肉合成的關鍵。研究發現，這個窗口沒有這麼短，如果運動前有攝取優質蛋白和澱粉，只要在運動完兩小時內吃東西，就能有效促進肌肉合成。所以，運動完可以慢慢洗澡然後回家，不用急著在健身房泡乳清蛋白啦。

近幾年的研究，更是指出：肌肉是每分每秒都在代謝耗損的，而蛋白質的補充能愈平均愈好。以下，就是ISSN對蛋白質攝取的建議：

ISSN的蛋白質攝取建議

我把原文放在本文的最下面，大家可以參考著看。

最重要的是滿足每天的攝取總量。

• 每日 1.4 - 2.0 g 蛋白質/每公斤體重 

• 在減脂期間，可能需要更高的蛋白質攝入量 2.3-3.1 g /kg

均勻間隔攝取，例如每三小時攝入一次20-40g的蛋白質，其中每份包含 10 g的EAA (必須氨基酸），0.7 - 3 g 的亮氨酸（Leucine) 。

運動後兩小時內攝取蛋白質，有助於刺激肌肉合成。

建議在睡覺前攝取30g的酪蛋白。

碳水化合物該怎麼吃？

攝取碳水的目的，在於給肌肉和肝臟裡的肝糖系統充電，讓我們提高運動表現。所以，ISSN只給出了全天建議的攝取量，沒有建議一定要少量多餐。只不過，以ISSN的建議量，不多餐我看也吃不完。

建議攝取量

• 娛樂性健身的民眾：每天攝取每公斤體重 3-5g 碳水。 
• 每天運動2-3小時的運動員，每週運動5-6次，需要攝取每天每公斤體重 5-8 g 的碳水化合物，以維持肝臟和肌肉的肝糖量。

攝取時機

• 在運動前後攝取碳水＋蛋白質，能改善身體組成。
• 在整個阻抗運動過程中，攝取碳水化合物，能夠維持血糖，並促進更高的肝糖儲備

總之，就是除了運動前後，運動中也要喝碳水。在實際運運用上，每公斤 5-8g 差異很大，以一個70公斤的人來說，每天要吃350克的碳水，還是560克？我們可以發現，這個建議攝取量不實際，因為個體差異太大。想要知道我們到底該吃多少，只有詳實的飲食紀錄，和每天早晨量小便後的體重。

攝取碳水的個人建議

我們吃下去的碳水，會變成肌肉和肝臟中的肝糖儲存裡來，多出來就變成脂肪。肝糖就像是人體中的電池，充越飽我們就越有力量，但是肝糖的儲存量是有限的，基本上肌肉越多，儲存量就越大，每個人也就大約800-2500卡。比方說，我們的肝糖儲存量，還剩下 50g 的碳水，你吃下90 g 的碳水，就會有 40 g 以上的碳水最後變成為脂肪儲存起來。所以實際上，碳水到底要吃多少，只能靠每天量體重去斟酌加減。

• 如果每天吃400g 碳水，一週後體重不變，就改成500碳。
• 如果每天吃400g 碳水，一週後多了一公斤，那就改成350碳。 我們知道身體不會一週長 1kg 的肌肉出來，多出來的體重大部分都是肥肉。但是，這1 kg也有可能是肌肉中的肝糖含量升高，也有可能是你最近吃很鹹，也有可能是便秘。總之，每天做體重紀錄，一段時間後就能找到自己的黃金攝取量了。
• 有些人每天吃大量的碳水，會開始產生胰島素阻抗的現象，這不利於肌肉生長，可以考慮碳水循環的方式增肌。

祝大家吃得開心，練得更開心

2017 ISSN nutrition position stand / 2018 August update

1. 1.

   Nutrient timing incorporates the use of methodical planning and eating of whole foods, fortified foods and dietary supplements. The timing of energy intake and the ratio of certain ingested macronutrients may enhance recovery and tissue repair, augment muscle protein synthesis (MPS), and improve mood states following high-volume or intense exercise.

2. 2.

   Endogenous glycogen stores are maximized by following a high-carbohydrate diet (8–12 g of carbohydrate/kg/day [g/kg/day]); moreover, these stores are depleted most by high volume exercise.

3. 3.

   If rapid restoration of glycogen is required (< 4 h of recovery time) then the following strategies should be considered:

   1. a)

      aggressive carbohydrate refeeding (1.2 g/kg/h) with a preference towards carbohydrate sources that have a high (> 70) glycemic index

   2. b)

      the addition of caffeine (3–8 mg/kg)

   3. c)

      combining carbohydrates (0.8 g/kg/h) with protein (0.2–0.4 g/kg/h)

4. 4.

   Extended (> 60 min) bouts of high intensity (> 70% VO2max) exercise challenge fuel supply and fluid regulation, thus carbohydrate should be consumed at a rate of ~30–60 g of carbohydrate/h in a 6–8% carbohydrate-electrolyte solution (6–12 fluid ounces) every 10–15 min throughout the entire exercise bout, particularly in those exercise bouts that span beyond 70 min. When carbohydrate delivery is inadequate, adding protein may help increase performance, ameliorate muscle damage, promote euglycemia and facilitate glycogen re-synthesis.

5. 5.

   Carbohydrate ingestion throughout resistance exercise (e.g., 3–6 sets of 8–12 repetition maximum [RM] using multiple exercises targeting all major muscle groups) has been shown to promote euglycemia and higher glycogen stores. Consuming carbohydrate solely or in combination with protein during resistance exercise increases muscle glycogen stores, ameliorates muscle damage, and facilitates greater acute and chronic training adaptations.

6. 6.

   Meeting the total daily intake of protein, preferably with evenly spaced protein feedings (approximately every 3 h during the day), should be viewed as a primary area of emphasis for exercising individuals.

7. 7.

   Ingestion of essential amino acids (EAA; approximately 10 g)either in free form or as part of a protein bolus of approximately 20–40 g has been shown to maximally stimulate muscle protein synthesis (MPS).

8. 8.

   Pre- and/or post-exercise nutritional interventions (carbohydrate + protein or protein alone) may operate as an effective strategy to support increases in strength and improvements in body composition. However, the size and timing of a pre-exercise meal may impact the extent to which post-exercise protein feeding is required.

9. 9.

   Post-exercise ingestion (immediately to 2-h post) of high-quality protein sources stimulates robust increases in MPS.

10. 10.

    In non-exercising scenarios, changing the frequency of meals has shown limited impact on weight loss and body composition, with stronger evidence to indicate meal frequency can favorably improve appetite and satiety. More research is needed to determine the influence of combining an exercise program with altered meal frequencies on weight loss and body composition with preliminary research indicating a potential benefit.

11. 11.

    Ingesting a 20–40 g protein dose (0.25–0.40 g/kg body mass/dose) of a high-quality source every three to 4 h appears to most favorably affect MPS rates when compared to other dietary patterns and is associated with improved body composition and performance outcomes.

12. 12.

    Consuming casein protein (~ 30–40 g) prior to sleep can acutely increase MPS and metabolic rate throughout the night without influencing lipolysis.

1. 1)

   An acute exercise stimulus, particularly resistance exercise and protein ingestion both stimulate muscle protein synthesis (MPS) and are synergistic when protein consumption occurs before or after resistance exercise

2. 2)

   For building and maintaining muscle mass, an overall daily protein intake of 1.4–2.0 g/kg/d is sufficient for most exercising individuals

3. 3)

   Higher protein intakes (2.3–3.1 g/kg fat-free mass/d) may be needed to maximize the retention of lean body weight in resistance trained subjects during hypocaloric periods

4. 4)

   Higher protein intakes (> 3.0 g protein/kg body weight/day) when combined with resistance exercise may have positive effects on body composition in resistance trained individuals (i.e., promote loss of fat mass)

5. 5)

   Optimal doses for athletes to maximize MPS are mixed and are dependent upon age and recent resistance exercise stimuli. General recommendations are 0.25–0.55 g of a high-quality protein per kg of body weight, or an absolute dose of 20–40 g.

6. 6)

   Acute protein doses should contain 700–3000 mg of leucine and/or a higher relative leucine content, in addition to a balanced array of the essential amino acids (EAAs)

7. 7)

   Protein doses should ideally be evenly distributed, every 3–4 h, across the day

8. 8)

   The optimal time period during which to ingest protein is likely a matter of individual tolerance; however, the anabolic effect of exercise is long-lasting (at least 24 h), but likely diminishes with increasing time post-exercise

9. 9)

   Rapidly digested proteins that contain high proportions of EAAs and adequate leucine, are most effective in stimulating MPS

10. 10)

    Different types and quality of protein can affect amino acid bioavailability following protein supplementation; complete protein sources deliver all required EAAs