The following article is part two of a three part series on the importance of muscle strength as it relates to one’s health and longevity. The first article discussed the relationship between muscle strength and maintaining healthy body functions as one ages, along with tips and advice for how to start an exercise-training program to increase muscle strength. This second article will discuss how aging changes one’s response to exercise training and nutrition, and explain how diet and nutrient supplementation can be modified to improve exercise training adaptation. The third article will discuss the role of nitric oxide in muscle function and development, and explain the need to maintain adequate nitric oxide levels to bring about desired training adaptations. It is not exaggerating when I say that following the simple recommendations provided in these articles can have a profound effect on your quality of life.
Muscle Mass, Strength and Function with Aging
From birth until about 30 years of age, there is a continued development in strength, muscle mass and quality. After age 35, a gradual decline in muscle mass and strength begins and is associated with a reduction in strength, power and speed of movement. This decline accelerates at about 50 years of age and then again at 70 years of age. After the age of 70, this decline continues to accelerate 25-30% per decade.
Aside from a loss in muscle mass and strength, other alterations in muscle occur with age include reductions in mitochondrial and capillary density. Mitochondria are the power plants of the cell. They are responsible for aerobic (in the presence of oxygen) energy production in the form of adenosine triphosphate (ATP). ATP is the energy currency of the cell and is required to run all energy requiring metabolic processes in the body including muscle contraction. The capillaries surrounding the muscle fibers are where the transfer of oxygen and nutrients pass from the circulatory system into the muscle fiber, and where metabolic waste products are transferred out. As muscle mitochondrial and capillary density increases, the ability of the body to perform prolonged endurance exercise increases and efficiency of exercise recovery improves. Conversely, as mitochondrial and capillary density decrease, exercise endurance decreases.
The decline in muscle mass and strength with age is genetically controlled. However, a decline in physical activity with age also contributes. If muscle is not physically challenged regularly, it will atrophy. Think “ if you don’t use it you loss it.” This is why, as one ages, it is important to participate in a regular resistance exercise training program. Another reason for the decline in muscle mass and strength is due to “anabolic resistance”. Characteristics of anabolic resistance include a blunted protein synthesis response to resistance exercise and dietary protein including protein consumed immediately post exercise.
Therefore, with advancing age the amount of dietary protein necessary to maintain muscle mass increases.
Dr. John Ivy on connection between aging, protein, and muscle mass.
Dietary Protein Requirements
Dietary protein is a vital nutrient that supplies needed amino acids that are used to make enzymes, hormones, neurotransmitters, antibodies, and serve as the building blocks for repair and growth of all tissues of the body including muscle. There are 20 amino acids that the body requires for these purposes. Of these 20 amino acids, 11 can be produced in the body itself and are referred to as non-essential amino acids, while 9 are referred to as essential amino acids because they have to be obtained through dietary means.
Not all dietary proteins are equal in nutrient value. As mentioned above, protein is made of amino acids and each protein has a unique amino acid profile. Proteins can be classified as complete or incomplete proteins.
- A complete protein is one that has an adequate proportion of all 9 essential amino acids necessary for the dietary needs of humans. Complete proteins are typically animal-based proteins such as meat, fish, milk, cheese and eggs. However, there are some plant sources of protein that are considered complete such as soy, quinoa, buckwheat, hemp, and spirulia.
- An incomplete protein is one that lacks one or more of the essential amino acids or does not have an adequate proportion of one or more of the essential amino acids. However, just because a protein is incomplete does not mean that it is not beneficial. Meals are not generally made from a single food item, and combining the right combination of incomplete proteins can provide the necessary essential amino acids required by the body. Proteins that are combined to provide a complete amino acid profile are known as complimentary proteins. Examples are brown rice and black beans or kale and almonds.
As mentioned above, the RDA for protein is 0.36 g per lb. of body weight, and represents the quantity of protein that should be consumed daily to meet population needs and to prevent deficiency. However, factors including physical activity pattern, body type and age can have a significant influence on protein need. For example, young individuals competing in sports who are likely involved in a rigorous training program require a greater amount of dietary protein than the RDA. Likewise, as individuals approach 45 to 50 years of age there is an increased requirement for dietary protein. In fact, once one reaches middle age, the requirement for dietary protein approximately doubles to between 0.55 to 0.68 g of protein per lb. of body weight.
Increasing protein consumption in middle-age provides many benefits for both men and women. It has been found to slow muscle loss with age, increase skeletal muscle mass and strength, and to enhance training adaptation when combined with a resistance or aerobic exercise training program. Consuming additional protein while lowering carbohydrate and fat consumption when dieting has also been found to reduce muscle loss while increasing fat loss in overweight individuals.
Timing Protein Consumption for Best Results
The timing of protein consumption is also an important consideration as it can have a significant impact on how effective whole body protein synthesis can be activated. Protein that is consumed at daily meals should be spread out evenly. That is, the protein at breakfast, lunch and dinner should be about the same volume.
Research indicates that consuming a moderate amount of protein at each meal stimulate muscle protein synthesis more effectively over a 24 hour period than skewing protein intake toward the evening meal.
In addition, eating a well balance breakfast consisting of an adequate amount of protein reduces appetite and is associated with a reduced caloric intake over the course of the day.
Consuming a protein snack such as Greek Yogurt, turkey breast, or low fat chocolate milk or a sports protein supplement before bedtime can also be beneficial. During sleep there is usually a loss of muscle protein as muscle is broken and the amino acids released are converted by the liver to glucose in order to prevent blood glucose from falling. Recent research indicates that taking a protein supplement before bedtime will actually promote protein synthesis while sleeping and increase muscle mass. Moreover, subjects who participated in a 12-week resistance exercise training program and who received a pre-bedtime protein supplement were found to had significantly greater increases in muscle mass and 20% greater increase in total body strength than subjects that received a non-caloric placebo.
Post exercise is another important time to consume protein. Following a workout, the body is highly sensitive to certain nutrients. Consuming a protein supplement within 30 minutes post exercise has a much greater effect on stimulating muscle protein synthesis than at any other time. This is because after exercise the muscle is better able to take up amino acids from the blood due to an increase in amino acid transporters on the outer membrane of the muscle. Taking up more amino acids, particularly L-leucine, results in a greater activation of muscle protein synthesis. Stimulating protein synthesis post exercise accelerates muscle tissue repair, reduces muscle soreness and increases the rate of training adaptation. For individuals preforming resistance exercise this translates to an increase in muscle mass and strength. For individuals training aerobically, it translates to a greater increase in muscle mitochondria and capillarity.
Type of Protein Post Exercise
The type and quantity of protein consumed post exercise is also important. Proteins that are easily digested and high in L-leucine produce the highest rates of protein synthesis. The single best protein for a post workout supplement is whey. In comparison tests against other quality proteins such as soy and casein, whey accelerated protein synthesis significantly faster. However, other vegetable proteins such as pea or rice are also beneficial. The amount of protein required to maximize protein synthesis post exercise is between 20 to 25 grams for adolescents and young adults. For middle aged and older individuals it appears to require as much as 35 to 40 grams of protein. However, it is possible to maximally stimulate muscle protein synthesis in older individuals with 20 to 25 grams of protein if about 2 to 3 grams of L-leucine is added to the supplement.
To summarize, individuals who are physically active, competing in sports or middle-aged or older should increase their daily protein intake to 0.55 to 0.68 g of protein per lb. of body weight. Protein consumption should be evenly distributed across the 3 basic daily meals. Taking a protein snack or supplement containing 20 to 25 grams of protein 30 to 45 minutes before bedtime should also be considered as this will help to limit muscle loss while sleeping. If engaged in a regular exercise-training program, it is important to also consume a post exercise protein supplement as soon after the completion of each exercise session. This will limit muscle damage and soreness, promote muscle protein synthesis and enhance the rate of training adaptation. Protein supplementation post exercise should be about 20 grams for young individuals and 30 to 40 grams for middle-aged and older individuals. The amount of protein post exercise for older individuals can be reduced by adding 2 to 3 grams of L-leucine. If weight reduction is a goal, caloric restriction should be accompanied with an increase in protein consumption. This requires that the percentage of protein in the diet be increased to about 35% of total macronutrients.
Suggested Daily Protein Consumption
Distribution of Daily Protein Consumption Based on a 2,500 Caloric Diet with Protein encompassing 30% of the Total Macronutrients:
- Basic 3 meals of the day
- Breakfast – 40 grams
- Lunch – 45 grams
- Dinner – 55 grams
- Post Exercise Workout
- Within 30 minutes post exercise – 25 grams
- Approximately 30 to 45 minutes before bedtime – 25 grams
Total Daily Protein Consumption – 190 grams
- Beasley JM et al. The role of dietary protein intake in the prevention of sarcopenia of aging. Nutrition in Clinical Practice 28:684–690. 2013.
- Beelen M1, et al. Protein coingestion stimulates muscle protein synthesis during resistance-type exercise. American Journal of Physiology: Endocrinology and Metabolism 2008,295:E70-77. doi: 10.1152/ajpendo.00774.2007.
- Cribb PJ and Hayes A, Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy. Medicine and Science in Sports Exercise 38:1918-1925, 2006.
- Cuthbertson D, et al. Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. FASEB Journal 19:422-424, 2005.
- Esmarck B, et al. Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans. Journal of Physiology 535:301-311, 2001.
- Ferguson-Stegall L, et al. Aerobic exercise training adaptations are increased by postexercise carbohydrate-protein supplementation. Journal of Nutrition and Metabolism 2011,2011:623182. doi: 10.1155/2011/623182.
- Ferguson-Stegall L, et al. Postexercise carbohydrate-protein supplementation improves subsequent exercise performance and intracellular signaling for protein synthesis. Journal of Strength and Conditioning Research 2011,25:1210-24. doi:10.1519/JSC.0b013e318212db21.
- Garaulet M and Gómez-Abellán P, Timing of food intake and obesity: A novel association. Physiology & Behavior xxx (2014) xxx–xxx
- Mamerow, MM et al. Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. The Journal of Nutrition 29:2014 doi: 10.3945/jn.113.185280.
- Moore DR, et al. Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. Journal of Gerontology 2014,70:57–62. doi: 10.1093/gerona/glu103.
- Norton C, et al. Protein Supplementation at Breakfast and Lunch for 24 Weeks beyond Habitual Intakes Increases Whole-Body Lean Tissue Mass in Healthy Older Adults. Journal of Nutrition 2016,146:65-9. doi: 10.3945/jn.115.219022.
- Res PT, et al. Protein ingestion before sleep improves postexercise overnight recovery. Medicine and Science in Sports Exercise 2012,44:1560-9. doi: 10.1249/MSS.0b013e31824cc363.
- Snijders T. et al. Protein ingestion before sleep increases muscle mass and strength gains during prolonged resistance-type exercise training in healthy young men. The Journal of Nutrition 2015,doi: 10.3945/jn.114.208371.
- Tang JE, et al. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. Journal of Applied Physiology 107:987-992, 2009.
- Wennberg M, et al. Poor breakfast habits in adolescences predict the metabolic syndrome in adulthood. Public Health Nutrition 2014, doi:10.1017/S1368980013003509.
- Wilkinson SB, et al. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. American Journal of Clinical Nutrition 85:1031-1040, 2007.
- Wolfe RR, et al. The role of dietary protein in optimizing muscle mass, function and health outcomes in older individuals. British Journal of Nutrition 2012,108 Suppl 2:S88-93. doi: 10.1017/S0007114512002590.