By Kimberly J. Decker, Contributing Editor
The loss in bone mineral density that baby boomers face gets a lot of press—and for good reason. Less buzzed about, but no less serious, is sarcopenia, the progressive loss of muscle mass and strength that comes with age. According to Matt Pikosky, director of research transfer, Dairy Management Inc.™ (DMI), Rosemont, IL, this inevitable decline generally begins at about age 40, after which adults will lose an average of 10% lean muscle mass with each decade. “That muscle mass is far more important to older adults’ health and wellness than is recognized by most Americans,” he says.
Just why we lose muscle as we age is still an open question, with theories about relative protein breakdown and synthesis, as well as the effects of inflammation, being posed. It’s also possible that at reduced levels of protein consumption, aging muscles exhibit “amino-acid insensitivity”—resistance of muscle cells to take up the nutrients for use in protein synthesis.
Whatever sarcopenia’s cause, weight-bearing resistance exercise and proper nutrition can halt it’s progress. Nutritionally, “protein is one of the primary aspects within total calories that older adults want to be cognizant of,” Pikosky says. “Dietary protein, once it’s digested and broken down into amino acids for use within the body, provides that structural framework for the continuous building and repair of body tissues that takes place on a daily basis. Sufficient protein intake is very important to minimize that muscle loss that’s going to happen as we age.”
Adequate protein intake for an aging adult may be higher than the current minimum recommendation of 0.8 grams per kg of body weight per day—a minimum originally established to prevent deficiency. Boomers, for whom “maximize” is a mantra, aren’t particularly impressed by minimums, and Pikosky contends that “minimum protein requirements to prevent deficiency do not necessarily translate to optimal amounts to promote health.” A protein recommendation that goes beyond solely preventing deficiency, Pikosky suggests, is the Institute of Medicine’s Acceptable Macronutrient Distribution Range (AMDR), which targets obtaining 10% to 35% of total calories from protein. For a person who is consuming 2,000 calories per day, this recommendation works out to be between 50 and 175 grams of protein per day. For a 70 kg person, this would be about 0.7 grams protein per kg of body weight per day (just below the RDA) to 2.5 grams protein per kg of body weight per day (about three times the RDA).
As for where to get that extra protein, a high-quality source rich in essential amino acids is ideal. Dairy foods fit the bill, Pikosky says. “They contain high-quality proteins, casein and whey, and together provide nine essential nutrients, including calcium and vitamin D, which are important for bone health throughout the lifespan,” he says. Whey protein is also rich in the essential amino acid leucine, which he singles out as a “key amino acid initiator” of protein synthesis, as evidence indicates that it plays a “unique role” in turning on the metabolic machinery that leads to protein synthesis.
