一水肌酸

一水肌酸

一水肌酸的功能

肌酸（一水肌酸）是一种无色透明的物质，在肌肉组织中用于产生磷酸肌酸（一种形成三磷酸腺苷的重要物质）。^{[1 2]}

一水肌酸补充剂可以增加大多数人肌肉中磷酸肌酸的水平，尤其是运动状态或摄入碳水化合物时。^{[3 4]}可是，大约30%的人摄入肌酸补充剂却不能保持肌肉中的量，^{[5 6]}这就解释了一些试验中发现的肌酸对运动锻炼的不稳定作用。肌酸可以增加运动相关性瘦肌肉块的体积，^{[7 8 9]}尽管增加的体积中含有多少肌肉、多少水分目前还不清楚。大多数^[10]但不是所有的对照试验发现每天补充20克的一水肌酸5~6天后可以提高运动能力以及延缓短时高强度运动后的肌肉疲劳，如短跑和举重。^{[11 12 13]}可是，年纪较大的人却只能少量获益，^{[14 15]}且运动员在竞技时使用肌酸补充剂并不能稳定获益。^{[16 17 18]}肌酸补充剂并不能增加运动耐量且会因为体重增加而受损。^[19]

目前有少量的试验正研究肌酸补充剂对运动锻炼的长期作用。两个长期的双盲实验对非训练妇女^[20]或训练男性^[21]使用肌酸后发现通过体重训练计划可以提高瘦肌肉的强度和重量。可是，第三个以前的试验却发现在体重训练的足球运动员中并没有明显的获益。^[22]

肌酸在肌肉萎缩的人的细胞内的量会有所缺乏。这种缺乏与肌肉组织的减弱和退化有关。一项病例报道称一例9岁的患有肌肉萎缩的儿童补充肌酸后肌肉功能得到提高。^[23]一项双盲实验发现肌酸补充剂（成人每天补充10克，儿童每天补充5克）可以轻度提高各种程度的肌肉萎缩病人的肌肉强度和运动能力。^[24]肌酸补充剂还能提高一些罕见的肌肉和能量代谢疾病的肌肉强度。^{[25 26 27]}对于先天性心脏功能衰竭的人，静脉注射肌酸可以提高心脏功能，但口服却对心脏毫无效果。^{[28 29]}一项双盲实验发现每天补充20克的肌酸，5天后改为每天10克维持51天后明显降低血清胆固醇和甘油三酯水平，但并不改变低密度脂蛋白和高密度脂蛋白的量。^[30]可是，另一项双盲实验却发现在运动员身上给予肌酸12周后并没有改变血脂水平。^[31]肌酸补充剂在这些阴性结果的试验中使用的量较低，每天只有5克，仅维持11周。

一水肌酸的分布

肌酸可由人类肝脏、胰腺和肾脏产生。在肌肉组织中含量最高，包括心脏。动物蛋白，包括鱼类是每天饮食中的1~2克肌酸的来源。一水肌酸补充剂可被很好的吸收。

一水肌酸已经被应用于与以下疾病的治疗中。（以下所有信息适用于个体化健康情况）：

哪些人可能会缺乏？

进行高强度运动的人，尤其是那些限制肉类摄入的人肌肉中肌酸的储备会降低。一些肌肉性疾病和类风湿性关节炎、慢性循环系统、呼吸系统疾病也会导致肌酸水平降低。^[32]

一般需要多少一水肌酸？

有两种方法衡量肌酸的补充量。在负荷方法中，每天补充20克的肌酸（与暖水混合，分4次服用）维持5~6天。^[33]肌肉中的肌酸水平可以迅速增加，对于短时提高力量有一定帮助，如举重、足球赛或短跑。而在负荷期之后为了维持肌肉肌酸水平，每天可以补充2~10克。^{[34 35]}

另一种方法是每天早加强训练时期补充3克的一水肌酸至少4周，这样可以使肌酸水平逐渐升高，最后达到负荷量。^[36]可是，目前还没有试验对这一方法进行测试。服用肌酸的同时补充糖可以提高肌肉的摄入量。^{[37 38]}

摄入大量的咖啡因对抗肌酸的作用。^[39]

是否有副作用和药物相互作用？

目前还不清楚肌酸的长期副作用，但在肌酸的试验中没有发现毒性作用。在一项关于肌酸的副作用报道中，腹泻是最常见的，其次是肌肉痉挛。^[40]一些报道称肾脏、肝脏和血液功能不会因为短期大量服用或长期小量服用而受影响。^{[41 42 43 44]}在每天摄入5~30克的5年试验中，并未发现肾脏功能受到改变。^[45]可是，间质性肾炎在一例补充每天补充20克肌酸的健康男性中发生，停止服用肌酸后肾脏功能有所恢复。^[46]对这一病例的分析认为是肌酸促发了肾脏疾病的发生。肌酸补充剂对于已存在的肾脏疾病病人有一定的损害作用。在一篇报道中称一例肾病综合征的病人服用肌酸后发展为肾小球硬化，而停用后肾小球硬化得以恢复。^[47]

在三篇以前的报道中称服用肌酸后出现肌肉痉挛。^{[48 49 50]}

到目前为止，还不清楚一水肌酸与其他药物之间的相互作用关系。

参考文献

1. Greenhaff PL, Bodin K, Soderlund K, et al. Effect of oral creatine supplementation on skeletal muscle phosphocreatine resynthesis. Am J Physiol 1994;266:E725-30.

2. Greenhaff PL. Creatine and its application as an ergogenic aid. Int J Sport Nutr 1995;5:94-101.

3. Harris RC, Soderlund K, Hultman E. Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation. Clin Sci 1992;83:367-74.

4. Green AL, Simpson EJ, Littlewood JJ, et al. Carbohydrate ingestion augments creatine retention during creatine feeding in humans. Acta Physiol Scand 1996;158:195-202.

5. Greenhaff PL, Bodin K, Soderlund K, et al. Effect of oral creatine supplementation on skeletal muscle phosphocreatine resynthesis. Am J Physiol 1994;266:E725-30.

6. Casey A, Constantin-Teodosiu D, Howell S, et al. Creatine supplementation favorably affects performance and muscle metabolism during maximal intensity exercise in humans. Am J Physiol 1996;271:E31-E7.

7. Stone MH, Sanborn K, Smith LL, et al. Effects of in-season (5-weeks) creatine and pyruvate supplementation on anaerobic performance and body composition in American football players. Int J Sport Nutr 1999;9:146-65.

8. Earnest CP, Snell PG, Rodriguez R, et al. The effect of creatine monohydrate ingestion on anaerobic power indices, muscular strength and body composition. Acta Physiol Scand 1995;153:207-9.

9. Stout JR, Eckerson J, Noonan D, et al. The effects of a supplement designed to augment creatine uptake on exercise performance and fat-free mass in football players. Med Sci Sports Exerc 1997;29:S251.

10. Kreider RB, Ferreira M, Wilson M, et al. Effects of creatine supplementation on body composition, strength, and sprint performance. Med Sci Sports Exerc 1998;30:73-82.

11. Toler SM. Creatine is an ergogen for anaerobic exercise. Nutr Rev 1997;55:21-5 [review].

12. Greenhaff PL. The nutritional biochemistry of creatine. J Nutr Biochem 1997;8:610-8 [review].

13. Greenhaff PL, Casey A, Short AH, et al. Influence of oral creatine supplementation on muscle torque during repeated bouts of maximal voluntary exercise in man. Clin Sci 1993;84:565-71.

14. Tarnopolsky MA. Potential benefits of creatine monohydrate supplementation in the elderly. Curr Opin Clin Nutr Metab Care 2000;3:497-502 [review].

15. Rawson ES, Clarkson PM. Acute creatine supplementation in older men. Int J Sports Med 2000;21:71-5.

16. Mujika I, Padilla S. Creatine supplementation as an ergogenic aid for sports performance in highly trained athletes: a critical review. Int J Sports Med 1997;18:491-6.

17. Grindstaff PD, Kreider R, Bishop R, et al. Effects of creatine supplementation on repetitive sprint performance and body composition in competitive swimmers. Int J Sports Nutr 1997;7:330-46.

18. Peyrebrune MC, Nevill ME, Donaldson FJ, et al. The effects of oral creatine supplementation on performance in single and repeated sprint swimming. J Sports Sci 1998;16:271-9.

19. Balsom PD, Harridge SD, Soderlund K, et al. Creatine supplementation per se does not enhance endurance exercise performance. Acta Physiol Scand 1993;149:521-3.

20. Vandenberghe K, Goris M, Van Hecke P, et al. Long-term creatine intake is beneficial to muscle performance during resistance training. J Appl Physiol 1997;83:2055-63.

21. Becque MD, Lochmann JD, Melrose DR. Effects of oral creatine supplementation on muscular strength and body composition. Med Sci Sports Exerc 2000;32:654-8.

22. Stout JR, Eckerson J, Noonan D, et al. The effects of a supplement designed to augment creatine uptake on exercise performance and fat-free mass in football players. Med Sci Sports Exerc 1997;29:S251 [abstract].

23. Felber S, Skladal D, Wyss M, et al. Oral creatine supplementation in Duchenne muscular dystrophy: a clinical and 31P magnetic resonance spectroscopy study. Neurol Res 2000;22:145-50.

24. Walter MC, Lochm???H, Reilich P, et al. Creatine monohydrate in muscular dystrophies: A double-blind, placebo-controlled clinical study. Neurology 2000;54:1848-50.

25. Tarnopolsky MA, Roy BD, MacDonald JR. A randomized, controlled trial of creatine monohydrate in patients with mitochondrial cytopathies. Muscle Nerve 1997;20:1502-9.

26. Sipila I, Rapola J, Simell O, et al. Supplementary creatine as a treatment for gyrate atrophy of the choroid and retina. N Engl J Med 1981;304:867-70.

27. Tarnopolsky M, Martin J. Creatine monohydrate increases strength in patients with neuromuscular disease. Neurology 1999;52:854-7.

28. Andrews R, Greenhaff P, Curtis S, et al. The effect of dietary creatine supplementation on skeletal muscle metabolism in congestive heart failure. Eur Heart J 1998;19:617-22.

29. Gordon A, Hultman E, Kaijser L, et al. Creatine supplementation in chronic heart failure increases skeletal muscle creatine phosphate and muscle performance. Cardiovasc Res 1995;30:413-8.

30. Earnest CP, Almada AL, Mitchell TL. High-performance capillary electrophoresis-pure creatine monohydrate reduces blood lipids in men and women. Clin Sci 1996;91:113-8.

31. Volek JS, Duncan ND, Mazzetti SA, et al. No effect of heavy resistance training and creatine supplementation on blood lipids. Int J Sport Nutr Exerc Metab 2000;10:144-56.

32. Silber ML. Scientific facts behind creatine monohydrate as a sports nutrition supplement. J Sports Med Phys Fitness 1999;39:179–88 [review].

33. Greenhaff PL. The nutritional biochemistry of creatine. J Nutr Biochem 1997;8:610–8.

34. Vandenberghe K, Goris M, Van Hecke P, et al. Long-term creatine intake is beneficial to muscle performance during resistance training. J Appl Physiol 1997;83:2055–63.

35. Becque MD, Lochmann JD, Melrose DR. Effects of oral creatine supplementation on muscular strength and body composition. Med Sci Sports Exerc 2000;32:654–8.

36. Hultman E, Soderlund K, Timmons J, et al. Muscle creatine loading in man. J Appl Physiol 1996;81:232–7.

37. Green AL, Hultman E, Macdonald IA, et al. Carbohydrate ingestion augments skeletal muscle creatine accumulation during creatine supplementation in man. Am J Physiol 1996;271:E821–6.

38. Feldman EB. Creatine: a dietary supplement and ergogenic aid. Nutr Rev 1999;57:45–50.

39. Vandenberghe K, Gills N, Van Leemputte M, et al. Caffeine counteracts the ergogenic action of muscle creatine loading. J Appl Physiol 1996;80:452–7.

40. Juhn MS, O’Kane JW, Vinci DM. Oral creatine supplementation in male collegiate athletes: a survey of dosing habits and side effects. J Am Diet Assoc 1999;99:593–5.

41. Sewell DA, Robinson TM, Casey A, et al. The effect of acute dietary creatine supplementation upon indices of renal, hepatic and haematological function in human subjects. Proc Nutr Soc 1998;57:17A.

42. Poortmans JR, Auquier H. Renaut V, et al. Effect of short-term creatine supplementation on renal responses in men. Eur J Appl Physiol Occup Physiol 1997;76:566–7.

43. Earnest C, Almada A, Mitchell T. Influence of chronic creatine supplementation on hepatorenal function. FASEB?J 1996;10:4588.

44. Almada A, Mitchell T, Earnest C. Impact of chronic creatine supplementation on serum enzyme concentrations. FASEB?J 1996;10:4567.

45. Poortmans JR, Francaux M. Long-term oral creatine supplementation does not impair renal function in healthy athletes. Med Sci Sports Exerc 1999;31:1108–10.

46. Koshy KM, Griswold E, Schneeberger EE. Interstitial nephritis in a patient taking creatine. N Engl J Med 1999;340:814–5 [letter].

47. Pritchard NR, Kaira PA. Renal dysfunction accompanying oral creatine supplements. Lancet 1998;351:1252–3 [letter].

48. Hultman E, Soderlund K, Timmons J, et al. Muscle creatine loading in man. J Appl Physiol 1996;81:232–7.

49. Vandenberghe K, Goris M, Van Hecke P, et al. Long-term creatine intake is beneficial to muscle performance during resistance training. J Appl Physiol 1997;83:2055–63.

50. Juhn MS, Tarnopolsky M. Potential side effects of oral creatine supplementation: a critical review. Clin J Sport Med 1998;8:298–304 [published erratum appears in Clin J Sport Med 1999;9:62].