Most of the soaring popularity of protein in US supermarkets can be dismissed as marketing hype. Although a new report from Packaged Facts says “protein is currently the hottest functional food ingredient trend in the US,” the truth is that most Americans get plenty of protein without any special dietary boosts.
But an emerging scientific consensus suggests one group of Americans may actually need more protein: older adults at risk of the gradual loss of muscle mass and function that Tufts experts have labeled sarcopenia. Evidence also is mounting that the timing of older adults’ protein consumption may be important; the traditional protein-heavy dinner might need to give way to a more even intake throughout the day, starting at breakfast.
“Although the RDA for protein is substantively the same for all adults, older adults tend to consume less protein than younger adults, primarily due to reduced energy needs,” according to Paul F. Jacques, DSc, director of Tufts’ HNRCA Nutritional Epidemiology Program. “Approximately one-third of adults over 50 years of age fail to meet the RDA for protein, and an estimated 10% of older women fail to meet even the lower Estimated Average Requirement for protein.”
The RDA for protein is 46 grams for women and 56 grams for men, while the Daily Value percentage used on nutrition labels is based on 50 grams. But experts say those general numbers should be adjusted for body weight: Sedentary adults should aim for 0.36 grams of protein per pound, so an individual weighing 150 pounds would need about 54 grams of daily protein. Endurance runners and strength training athletes need slightly more protein in their diets.
In a report on “Protein and Healthy Aging” published earlier this year in the American Journal of Clinical Nutrition, however, Jacques and colleagues noted that aging adults might need more than the current RDA for protein. Multiple experts have argued that older adults actually should aim for 0.45 grams to 0.68 grams of protein per pound of body weight. For a 150-pound person, that translates to 67.5 to 102 grams of protein daily—substantially more than the 50-gram DV used in the Nutrition Facts panel.
What would that much extra protein look like? To get an additional 35 grams of protein per day, for example, you’d need to eat about four ounces of chicken breast (171 calories), more than four ounces of lean beef (257 calories), or more than a cup and a half of soybeans (406 calories). For a sedentary adult to add that much protein without gaining weight from the accompanying calories could be a challenge. Even if you’re only aiming to meet or modestly exceed the RDA, you’ll need to be smart about substituting high-protein, lower-calorie foods for less-healthy choices in your diet.
TIMING IS KEY: But Jacques and colleagues suggest that when you eat your daily protein may be as important as how much you consume: “Meeting a protein threshold of approximately 25 to 30 grams per meal represents a promising yet relatively unexplored dietary strategy to help maintain muscle mass and function in older adults.” In one recent seven-day trial, they note, muscle protein synthesis was 25% higher when the same quantity of protein was evenly distributed across breakfast, lunch and dinner, compared with the typical pattern that skews toward a protein-heavy dinner.
Breakfast, Jacques adds, may provide the greatest opportunity to more evenly distribute the day’s protein. A typical bowl of cereal and glass of OJ might add up to only about 10 grams of protein, even if all the milk in the bowl is consumed. Adding six ounces of Greek yogurt (17 grams of protein) would put the morning’s protein intake into the optimal range.
Smart snacking can also add protein at times other than dinner. One study found that older adults who snack consume about 6 grams more protein daily than their nonsnacking peers. That’s no excuse to gobble potato chips, however, which have only 1.8 grams of protein per ounce. An ounce of unsalted mixed nuts—about a handful—is a better snacking choice at 4.4 grams of protein. Or a stick of string cheese has 5-8 grams of protein.
QUALITY COUNTS: The quality of the protein you consume also counts. Jacques and colleagues cite research showing that protein quality affects protein digestion, absorption, and whole-body and muscle metabolic processes in older adults.
When scientists talk about “protein quality,” they don’t mean how good the protein dish in your favorite restaurant tastes. For nutritional benefits, protein quality depends on the digestibility of the protein source and its amino-acid contents. Unless you want a crash course in biochemistry, the most important thing to remember about protein quality is whether a food delivers all nine “essential” amino acids—the building blocks of protein—that the body can’t make itself (see box). Foods that meet this requirement are called “complete” proteins.
You don’t have to obtain all the essential amino acids at a single meal; it’s the balance over a whole day that matters. The importance of “complete” proteins, however, is why people often eat rice with beans—together, they deliver all the essential amino acids. So do peanut butter plus whole-grain bread. Some foods, including meat, poultry and fish, eggs, dairy products, soybeans and quinoa, are complete proteins needing no nutritional partners. Grains (with the notable exception of quinoa) are usually not an adequate source of the amino acids lysine and isoleucine, and thus are not complete proteins by themselves.
MUSCLE MASS MATTERS: Why should older adults in particular pay extra attention to protein? Sarcopenia, the gradual loss of lean muscle mass that can occur with aging, affects 15% of people older than age 65, and 50% of people older than age 80. Skeletal muscles reach peak mass by the third decade of life, and with each subsequent decade muscle fibers decrease in size and number. This process speeds up in the later years of life; by age 80, up to 30% of muscle bulk may be lost.
“Low muscle mass is a cause of poor muscle strength,” says Martha Savaria Morris, PhD, an adjunct scientist with Tufts’ HNRCA Nutritional Epidemiology Program. “One risk is the inability to carry out activities of daily living and, consequently, a lack of independence. Another risk is falls, which often result in serious injury among older adults.”
The Health, Aging and Body Composition Study, published in 2008, compared dietary protein intake with lean muscle mass in 2,066 men and women, ages 70 to 79. Over three years, participants consuming the highest amount of protein (an average 91 grams daily) lost 40% less lean muscle mass than those in the bottom one-fifth of protein intake (average 57 grams a day). Researchers concluded, “Dietary protein may be a modifiable risk factor for sarcopenia in older adults and should be studied further.”
A new study published in the Journal of Nutrition followed up on that theory. Shivani Sahni, PhD, of Hebrew SeniorLife Institute for Aging Research, and colleagues looked at data on more than 2,600 men and women from the Framingham Offspring Cohort, average age 59. Participants had their lean leg mass and the strength of their quadriceps (the large muscle on the front of the thigh) measured and recorded their protein intake.
Overall, participants averaged 76 grams of protein daily for women and 80 grams for men—above the RDA, a little above typical US intake for women (62 to 66 grams) and a little below the US average for men (88 to 92 grams). Lean leg mass was higher in those at the highest level of total protein consumption and animal protein consumption. Total protein intake in the highest group averaged 93.4 grams daily for women and 101.1 grams for men.
Quadriceps strength was higher in participants with the highest intake of plant protein. Researchers speculated that plant protein may help preserve muscle strength in older adults due to the alkaline properties of the plants. It’s also possible, however, that plant protein intake is actually a marker for an overall healthy diet, high in fruits and vegetables.
WISE WORKOUTS: Combining adequate protein intake with exercise can also help prevent muscle loss with aging. A Tufts study published in the British Journal of Nutrition reported that to get the most out of exercise, participants had to also be consuming enough protein. (See the July 2014 newsletter.) In fact, people who did muscle-strengthening exercises without protein intake of at least 70 grams daily actually had lower muscle mass.
In the study, Jacques and Morris looked at the combination of protein intake and physical activity in 2,425 people over age 50 during a four-year period. They studied measures of skeletal muscle mass, protein intake, and exercise patterns in both obese and non-obese subjects.
“Muscle mass won’t maintain itself without your help,” Morris emphasizes. “Exercise as vigorously as your body, your doctor and your physical therapist will allow. Begin at mild levels and work up to moderate and vigorous activities. Make sure your diet includes an adequate amount of high-quality protein.”
FULL AND HEALTHY: Getting enough protein might have other benefits beyond your muscles. Another study, published in March in the Journal of Nutrition, looked at the effects of protein intake on 24,000 US adults using data from a national nutrition survey. Participants who consumed the most protein were found to have the lowest body mass index (BMI) and waist circumference. That could be because protein is thought to promote satiety; feeling “full” could cause people to eat less of other, high-calorie foods.
The researchers, led by Stefan Pasiakos, PhD, of the US Army Research Institute of Environmental Medicine, also reported that people eating the most protein had higher levels of the good HDL cholesterol. They concluded, “Our findings strongly suggest that consuming protein well above the RDA is safe and may be considered a valid nutritional strategy to improve cardiometabolic health.”
STROKE-RISK SURPRISE: Could those benefits include reduced risk of stroke? That’s the surprising possibility raised by a Chinese study recently published in the journal Neurology. Researchers reviewed seven previous studies totaling more than 250,000 participants followed for an average 14 years, adjusting for other stroke risk factors and nutrients consumed. They found that people who consumed the most protein were 20% less likely to suffer a stroke than those with the lowest intake. Each higher intake level of 20 grams a day of protein was associated with a 26% lower risk of stroke; such a “dose-response” relationship strengthens the findings, though the study was not designed to prove cause and effect.
Importantly, however, the apparent benefit of protein intake did not include red meat, which previous studies have linked to increased stroke risk and which was omitted from the meta-analysis. Some evidence showed that other forms of animal protein, such as fish and poultry, were more strongly associated with risk reduction than plant protein. The data on vegetable consumption, however, was not sufficient to definitively show a difference. The association could be due to some other factor, such as fat intake.
But other studies have found no link between protein consumption and stroke risk. And it could be that people who consumed more protein also ate less of other foods that increase stroke risk. In the OmniHeart Trial, for example, people who ate more protein and fewer carbohydrates had better numbers for blood pressure, LDL cholesterol and triglycerides.
CALORIES AND CAUTIONS: Are there any downsides of consuming more protein? Of course, you need to be careful that you aren’t simply adding calories when you incorporate more protein in your diet. That’s why it’s smart to substitute lower-calorie sources of protein for less healthy choices, such as refined carbohydrates or sugary desserts. (Keep in mind that each gram of protein contains four calories.) And boosting your protein intake with a big, juicy ribeye steak will also add a heaping helping of saturated fat.
Some experts have worried that a high-protein diet might be bad for bone health, leading to excretion of calcium. But the Iowa Women’s Health Study found just the opposite: Women who consumed higher amounts of protein had a lower risk of hip fracture. Protein also appears to increase calcium absorption in the intestines and enhance bone formation.
People with chronic kidney disease should avoid high-protein diets, which may further damage kidney function. Diets high in protein may also increase the risk of kidney stones even in those with otherwise healthy kidneys.
Patients with gout should consult their physician about protein intake. Many protein sources, including red meat, poultry and fish, contain purines, which the body breaks down to form uric acid, the cause of the painful swelling in gout.
Overall, however, a review of the pros and cons of protein published in May in Advances in Nutrition concluded, “The consumption of a high-protein diet appears to be more advantageous than deleterious.”