As we age, muscle mass gradually decreases, a process termed sarcopenia. This can hijack a person’s independence and confidence, making even simple daily tasks, such as lifting groceries or opening a jar, difficult. Losing muscle mass can also increase one’s risk of falling, a major cause of disability.
Sarcopenia develops around the fourth or fifth decade of life, although its rate of acceleration varies due to multiple factors, such as chronic illness, inactivity, or poor nutrition, particularly inadequate protein or calorie intake.
After the process starts, a person loses 3 to 8% of their muscle mass each decade while strength decreases by approximately 1.5% per year. The rate doubles to 3% per year after age 60, and affects 30% of people in this age group. By age 80, more than 50% of people are affected by sarcopenia. While it cannot be stopped altogether, sound nutrition choices and regular physical activity can slow its progress and improve quality of life.
Low protein intake is associated with reduced muscle mass and strength throughout life. Healthy elderly adults who consume more protein than their peers or take protein supplements, while still at risk, will lose less muscle mass as they age.
Females are at particular risk for sarcopenia. “Women typically have lower levels of muscle mass to start with compared to men,” points out Gabrielle Lyon, DO, a physician and muscle-centric medicine expert. “In addition, they have lower levels of testosterone and other anabolic hormones which are part of the metabolism of muscle-building. These hormones decrease further as a female ages, negatively affecting the ability to protect and build muscle.”
Research suggests older adults should try to consume 1.1-1.5g of protein per kg of body weight daily, far above the RDA of 0.8g/kg body weight. In addition to focusing on total daily protein intake, the quality of protein consumed and the amount consumed at each meal matters.
High quality proteins contain a sufficient amount of leucine, the key amino acid triggering the initiation of muscle protein synthesis. Though younger adults can get by on 2g of leucine per serving of protein, older adults require approximately 3g per serving due to an age-related decrease in the anabolic response to amino acids.
Higher-leucine proteins, those containing more than 3g per 30g of protein, include whey and pea protein. Casein and soy protein contain approximately 2-2.5g of leucine per 30g serving of protein.
Lyon agrees. In her work as co-director of the Ash Center for Comprehensive Medicine, she prescribes “any ‘gravity-bearing’ protein—anything that walks, runs, or flies.” Chicken, turkey, beef and bison are all on the muscle-building menu. “Getting 30g or 4-6 oz of one of these proteins at a time will actually trigger muscle protein synthesis,” she explains.
Other nutrients Lyon points to as critically important in combating sarcopenia include creatine, vitamin D, and branched-chain amino acids (BCAAs). “All have been shown in studies to help augment muscle health,” she says.
Vegetarians might find it harder to get sufficient bioavailable protein to rebuild depleted muscles. “Eggs are great,” says Lyon, “but you need about five whole eggs per day to meet your needs. An alternative is 25g of whey protein, which yields 2.5g of leucine. This leucine threshold is key for protecting muscle.”
With the current trend toward non-GMO, plant-based foods, pea protein seems like an ideal protein boost for foods and beverages targeted toward aging boomers. Pea protein, however, is an incomplete protein, lacking sufficient methionine and cysteine. Therefore, it must be blended with another protein to provide all essential amino acids in one serving.
“Getting all of the essential amino acids in a meal is necessary to ramp up protein synthesis. If you’re missing one essential amino acid nothing will happen,” explains Doug Paddon-Jones, PhD, of the Department of Nutrition and Metabolism at the University of Texas Medical Branch, Galveston, Texas. “For example, consuming collagen by itself, without any other source of protein, won’t increase muscle protein synthesis.”
Complete proteins, whether from a single source or combined plant proteins, can get the job done. They must meet the “leucine threshold” and yield approximately 30g of complete protein per meal or serving. Still, it must be noted that these are the best recommendations according to current research.
It remains unclear if following this guidance will translate to greater increases in muscle mass, strength, or improvements in muscle quality over longer periods of time.
“We need more data from long-term studies to validate these recommendations,” notes Blake Rasmussen, PhD, professor and chair of the Department of Nutrition & Metabolism at University of Texas Medical Branch, Galveston. “There are few dose-response studies, and therefore, it is possible that more than 30g of protein per meal could lead to a greater anabolic response in some individuals.”
One double-blind, randomized controlled clinical trial recently published in the Journal of Nutrition compared the response to consuming two different beverages that provided different sources of high-quality protein, one hour after a bout of high intensity resistance exercise.
The protein in the study consisted of a blend of soy and dairy proteins (25% isolated soy, 25% whey protein isolate, and 50% caseinate) vs. a single protein source (whey protein isolate).
Results showed that the soy-dairy protein blend “induced amino acid delivery to muscle tissue [as well as] muscle protein synthesis, and activated a recognized pathway that initiates muscle protein turnover.” Rasmussen reported that “the data provide additional support for the use of targeted nutritional interventions to overcome a critical condition of aging, anabolic resistance, to counteract sarcopenia.”
Synergy of Motion
While protein intake is important, resistance training is critical for improving strength and muscle mass.
Over the immediate time period after exercise, a person is breaking down tissue (catabolism) until the next meal. Taking protein immediately after exercise, therefore, is a sensible solution to getting out of catabolism right away.
Although regular exercise improves the muscles’ response to protein intake, older adults need about 40g of a high leucine complete protein to maximize acute muscle protein synthesis. This post-workout serving of protein is especially important for those who do not meet the RDA for protein. This can be helpful guidance for those making foods and beverages specifically targeting the building of tissue (anabolism)—in this case muscle tissue.
Longer-term studies (at least 12 weeks) in healthy elderly adults who habitually consumed adequate amounts of protein suggest there might not be additional benefits to consuming protein right after exercise. More study is needed to clarify this phenomenon.
Adding leucine to protein-poor meals ramps up acute muscle protein synthesis and anabolic signaling in older adults consuming close to the RDA for protein (0.81 ± 0.04g protein/kg body weight per day).
Longer-term supplementation (2.5g at three meals each day for three or six months) did not improve muscle mass, strength or muscle quality in elderly men who were either healthy or diabetic.
“Leucine has a lot of potential, but supplementation is likely to benefit a relatively small number of people. If you are getting about 3g of leucine per meal, adding more is not going to confer much additional benefit, at least for synthesis,” states Paddon-Jones. It is possible that additional leucine can benefit persons on an energy restricted diet, or under conditions of muscle disuse.
Additional BCAAs follow a similar pattern to leucine. They can up-regulate acute muscle protein synthesis when added to meals containing a suboptimal amount of protein. This is an attractive solution for those who need to keep total protein intake and nitrogen load low. However, the addition of BCAAs is only potentially beneficial for those persons not meeting their complete daily protein needs.
One leucine metabolite common in hospital-based nutrition interventions, Beta-hydroxy-beta-methylbutyrate (HMB), purportedly increases protein synthesis and decreases protein breakdown. Studies in seniors suggest HMB could help reduce muscle mass loss in elderly adults on bed rest.
It also has been suggested that HMB can improve some measures of strength, compared with placebo, in sedentary adults. Just 3g of calcium-HMB, consumed twice daily for 24 weeks, led to significantly greater increases in strength and muscle quality compared with placebo in elderly adults.
On the other hand, in a separate, 24-week resistance training phase of the same study, no differences were noted between the calcium-HMB and placebo groups in muscle quality, strength and functional movement. Therefore, it could be that calcium-HMB might be effective only in the absence of resistance training.
HMB might, therefore, be best reserved for an older person on bedrest, or one too frail to engage in much activity. However, some experts question whether there should be a limit to protein degradation. According to experts, protein degradation is physiologically important.
It is estimated that up to 90% of protein degradation occurs as the body’s mechanism for getting rid of abnormal proteins. This turnover is how the body recycles and rejuvenates the building blocks of the components needed for metabolic function.
Vitamins and Muscles
Other nutrients have been shown to keep existing muscle tissue optimized. A recent study found that, among macronutrients, a form of fermented blueberry juice helped stimulate glucose uptakes in the muscle cells. Also, the starches in slow-cooked potatoes convert readily to glycogen, the storage form of glucose energy favored by muscles.
Cheese, seeds, beans and other legumes, including soybeans and peanuts, are good sources of leucine as well as protein. In fact, roasted soybeans have more leucine content than meat or fish. With pre-, peri-, and post-menopausal women at high risk for sarcopenia, there has been some concern about recommending soy for women at risk for estrogen-linked breast cancer. Soy is high in phytoestrogens, plant compounds that mimic estrogen.
“Due to the popularity of soy there has been a considerable amount of research into its safety in this area,” says Lyon. “But soy protein has been shown to have multiple health benefits, including anti-cancer through its estrogen pathways.” There are two base receptors of estrogen in breast tissue, estrogen receptor alpha (ER-a) and estrogen receptor beta (ER-b). “Estrogen that binds to ER-a promotes cell growth, whereas estrogen that binds to ER-b halts breast cell growth could slow the development of estrogen-dependent tumors,” adds Lyon. Soy prefers the ER-b pathway.
As previously described, vitamin D is important for muscle strength. Deficiency leads to muscle weakness and pain, while vitamin D supplementation can improve muscle strength and function in elderly adults.
A systematic review and meta-analysis of randomized controlled trials examining vitamin D supplementation and muscle function found that vitamin D supplementation had a small but significant positive effect on muscle strength. It does not affect muscle mass or muscle power, but it is also critical to bone health, which indirectly impacts muscle health. So, too, vitamin K2 is important for maintaining the bone health needed to allow for activity that helps build muscle tissue.
Supplementation with vitamin D has been studied in seniors specifically. It has been shown to be more effective in people 65 years of age or older, as well as those who were deficient prior to the start of the study.
While critical in sports and athletics, the concerns for seniors and women also present an opportunity for redress by developers of better-for-you products.
Originally appeared in the July, 2017 issue of Prepared Foods as Muscle Bound.