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Protein and Muscle Mass If you are in your 5th decade of life, you may be starting to recognize a decline in your muscle mass associated with the aging process. If you are still in your youth, you may be looking in the mirror wishing for bigger “guns.” Both of these groups may turn to some type of protein supplement to either cease the decline of muscle mass or enhance muscle building, but what should they chose? Elders first: What Happens as you age? As the body ages, a few changes related to muscle take place in the body leading to weight gain, and increased risk for cardiovascular disease and diabetes. As muscle mass decreases, resting metabolic rate slows down because our muscles are the most metabolic part of our body, therefore causing weight gain if intake is not decreased. Muscle is also a large storage site for blood glucose, so with less muscle, there is less storage of glucose and more circulating in the body causing high blood sugars. Muscle also is important for lipid oxidation and decreasing amounts of muscle can lead to increasing cholesterol and LDL (1). What can be done to prevent muscle loss? Exercise and diet are the two keys to maintaining muscle mass as you age. Load bearing high intensity exercises such as resistance training appear to be the most beneficial (1). Intake of protein must exceed protein breakdown. Some protein breakdown occurs naturally with exercise and therefore protein intake along with exercise is important to repair muscle and maintain or create positive protein balance (2). Note here: Don’t go overboard on your protein intake as your body can only store so much protein (about 2g/kg body weight) before it gets excreted or turns to fat inside the body. Whey vs. Soy? Soy protein is a bit unknown when compared to whey protein, but can be the perfect way to supplement the diet with this population. Soy protein offers a few properties that may be appealing as we age. Soy contains isoflavones, fiber, and phytoestrogens, all of which have been known to lower cholesterol, LDL, and triglycerides. While people who exercised and used either protein or whey post-­‐
workout showed no difference in overall cholesterol, people in the soy group had a greater improvement in their LDL:HDL ratio. Participants in the soy group also displayed a greater reduction in triglycerides compared to the whey group (2). Research done on older adults have found minimal or no differences in strength gains between the two supplements when used after a workout (2). Young guns: How do you build muscle? Two things must be in place in order to build muscle: a stimulus and adequate fuel. With exercise, muscle protein synthesis is stimulated up to 100% above resting levels. (1) While muscle breakdown does occur, it is much more minimal when you are in a fed state prior to exercise. When exercising in a fasted state, breakdown is greater. Consuming a combination of carbohydrates and protein, results in a positive nitrogen balance and muscle gain. When do I fuel? It is important to be in a nourished state prior to a workout for the reasons suggested above, using a combination of carbohydrates and protein. Combining carbohydrates and protein enhances protein synthesis to a greater degree than protein alone. While muscle protein synthesis last up to 48 hours after a workout, evidence suggests that consuming a combination of carbohydrates and protein within 30 minutes of a workout enhance muscle hypertrophy and lean body mass to a greater degree (1). Whey vs. Soy? Intact protein coming from milk still appears to have the biggest synergistic effect on building muscle, likely due to the combination of whey and casein. Interestingly, many of the studies find no difference in strength gains between milk supplemented groups and soy protein groups. Research comparing whey supplements to soy supplements have found similar absorption rates, but differing amino acid profiles. The whey protein group typically has higher concentrations of circulating amino acids, in particular leucine. Research on supplementing with leucine alone has had a positive correlation with muscle protein synthesis (3). In conclusion, both soy and whey protein can be beneficial for gaining and/or maintaining muscle mass. The best choice for you would depend upon your personal goals and health history: those wanting to gain muscle mass with no health complications may lean toward whey protein, while people with increased risk for high lipid levels may want to choose a soy based protein. Resources: 1) Phillips, S.M., Tang, J.E., & Moore, D.R. The role of milk and soy based protein in support of muscle protein synthesis. Journal of American College of Nutrition 2009; 28:4 (343-­‐354). 2) DeNysschen, C.A., Burton, et al. Resistance training with soy vs. whey protein in hyperlipidemic males. JISSN 2009; 6:8. 3) Anthony, T.G. et al. Feeding meals containing soy or whey protein after exercise. The Journal of Nutrition 2007; 137:357-­‐362.