In the 1980s “low fat” was the big buzzword used for packaged foods and weight-loss diets. After that came “low carb.” Now it’s “high protein.” Actually, this trend started a few years ago and may have partly evolved from earlier low-carb diets (such as Atkins, the Zone, and South Beach), which were relatively high in protein. Walk down the supermarket aisle and you’ll now see labels boasting about the protein either naturally in the foods or, increasingly, added to them—on everything from breakfast cereals, granola bars, cookies, and other baked goods to frozen entrees, shakes, chips, milks, and ice cream.
Why protein? It used to be that only bodybuilders and athletes focused on getting extra protein, in their quest for bigger muscles and enhanced performance. But today people trying to lose weight or trying to preserve or regain muscle as they age are largely the target audience. Beyond that, “high protein” sells because many consumers now perceive it to mean “healthy,” which is ironic because of the long-time concerns that consuming too much protein, especially animal protein, can cause kidney problems and other adverse effects. Indeed, many experts are now worried about the glut of protein-fortified foods, including junk foods. Dietary crazes almost always have unintended consequences.
Putting protein into context
It’s hard to generalize about the potential health benefits and risks of high protein intake because the foods and diets vary so much; the proteins in them also vary in their amino acid composition. Thus, while it makes sense for researchers to try to tease apart the effects of nutrients like protein, it can be misleading to base dietary advice on nutrients in isolation. Where nutrients come from and what compounds accompany them make a big difference, which is why dietary guidelines increasingly focus on foods and dietary patterns instead.
Lump together all protein sources—meat, dairy, fish, legumes, and now protein-fortified foods—and it’s no wonder that researchers don’t find clear, consistent health effects. Even though animal protein is more strongly associated with health risks than vegetable protein, animal protein itself comes from a disparate group of foods. Thus, when you get your protein from dairy products or fish, for instance, it may have different effects than protein from red meat—either because of its amino acid profiles or because of other substances that accompany it in these foods. In sum, it’s the food and overall diet, not necessarily the protein, that matter most.
What about diets rich in the protein-fortified foods Americans are now eating? We’re in uncharted territory, since little research has been done on such foods and eating patterns.
Note: As with much food and nutrition research, many (if not most) studies and researchers finding benefits from higher protein intake have been funded at least in part by industry groups representing high-protein foods such as dairy, beef, pork, soy, and eggs.
9 pressing protein questions
Keeping all of the above facts in mind, here are answers to some questions about protein.
Are we consuming too little protein?
Most Americans get more than enough protein from their diet. The recommended dietary allowance (RDA) for adults is a modest 0.8 grams of protein a day for each kilogram (2.2 pounds) of body weight. That works out to 47 grams of protein for a 130-pound person and 67 grams for a 185-pound person. Many Americans get twice the RDA without trying. On average, protein provides about 15 percent of daily calories in the U.S., which is 75 grams for a 2,000-calorie daily diet.
People over 65 are often exceptions, however—an estimated 40 percent of them don’t consume the RDA for protein. And the shortfall increases with advancing age. Sometimes it’s because older people simply eat less or have trouble chewing protein sources such as meat. On top of that, they need more protein than younger people to help counter age-related muscle loss (due to increased muscle breakdown and reduced muscle synthesis), which contributes to impaired mobility and frailty.
The RDA is based mostly on studies focusing on protein balance in younger adults, not on maintaining muscle in later decades. Thus, in recent years several panels of experts have recommended that the RDA be increased to 1.0 to 1.2 grams per kilogram (or even higher), particularly for older people. However, many older people have impaired kidney function, which can be worsened by high protein intake.
Do vegetarians have trouble getting enough protein?
Though they usually consume less protein than meat eaters, vegetarians can easily meet their needs if they eat a varied diet — especially if they eat dairy and eggs. This is true even though most protein from plant foods is “incomplete.” Beans are top sources of protein, but grains, nuts, seeds, and even vegetables all provide some. Meat substitutes, typically made from soy or wheat gluten, are often high in protein (sometimes as high as their meat counterparts), though products vary greatly, so read labels.
Essential Facts About Protein
Protein is not a single, simple substance but a multitude of chemical combinations, the basic units of which are amino acids.
What role does protein play in maintaining muscle?
First off, the key to preserving or gaining muscle is to stay physically active and, in particular, do strength training, which encourages muscle synthesis from protein. If you are sedentary, don’t expect any amount of protein by itself to keep muscles strong. Still, consuming adequate protein is crucial for muscle synthesis, particularly at older ages. In fact, most observational studies, including one from the Women’s Health Initiative in 2013, have linked higher dietary protein intake to reduced age-related muscle loss and better physical function. But short-term clinical trials using supplemental protein have had inconsistent results, with some finding that strength training plus extra protein builds no more muscle than strength training alone, especially in people who have adequate initial protein intake.
Do athletes and people who exercise a lot need extra protein?
If you exercise regularly you may need a little more protein than the RDA, but you’re probably getting more than enough from your normal diet. Even weightlifters and endurance athletes generally get enough protein, simply because their higher-calorie diets supply it. Athletes on low-calorie diets and vegans may need to make more of an effort. Keep in mind that it’s proper training that builds muscle and improves athletic performance, not extra protein.
Will eating more protein help with weight control?
Most (but not all) research has found that adding protein to calorie-restricted diets can help increase weight loss modestly, at least in the short term. The diets studied typically derived 20 to 30 percent of daily calories from protein (which translates into much more than the RDA). Consuming extra protein tends to make people feel fuller and less hungry, compared with lower-protein diets. Increased protein also slightly boosts thermogenesis—heat produced by the body after eating—which means that a few extra calories are burned. But most studies finding such benefits lasted less than three months, and the benefits may not be sustained. In fact, longer studies have produced mixed results, possibly because most people don’t stick to the higher-protein regimens (or indeed any dietary intervention) over time.
Whether or not protein helps with weight control, if you are on a calorie-restricted diet, it’s important to maintain or increase your protein intake to help prevent the loss of muscle mass and bone that generally occurs with weight loss. In other words, cut carbs and fat, not protein. Keep in mind that if protein helps preserve muscle while dieting, that could reduce weight loss somewhat—but in this case, that’s a healthy thing.
Does it matter when you eat protein?
Some research suggests that the timing of protein intake can make a difference for maintaining muscle and weight control, though there’s debate about the optimal schedule. A few short-term studies have found that dividing protein intake among three daily meals—typically 25 to 30 grams of protein per meal in the studies—may be best for muscle metabolism as well as weight control. For most people, that would mean shifting more protein to breakfast and lunch, away from dinner. Consuming more than 30 grams in a single meal does not appear to further enhance muscle synthesis, since the body can’t store it for later use and just turns excess dietary protein into fat.
A growing body of research has found that another way to help increase muscle protein synthesis is to consume some protein right after strength training. This doesn’t call for protein supplements—a cup of milk or yogurt after a workout may be enough.
Do high-protein diets affect blood pressure?
Some evidence suggests they help lower it. In an observational study in the American Journal of Hypertension in 2014, researchers analyzed data from the Framingham Heart Study and found that people with the highest protein intake (averaging 100 grams a day) were 40 percent less likely to develop high blood pressure than those with the lowest intake. And in a Dutch study in the American Journal of Clinical Nutrition in 2012, people with moderately elevated blood pressure saw improvements when they took supplemental protein. The well-known DASH eating plan, designed to help control blood pressure, is relatively high in protein, mostly from beans, dairy, fish, and chicken.
Your Checklist: Protein in Food
How much protein do you eat? Probably more than you think. Here's a chart of good food sources.
Do high-protein diets cause kidney disease?
Research has found that such diets are not associated with increased risk of developing chronic kidney disease (CKD) in people with healthy kidneys. But high protein intake can worsen it in the one-in-nine adults who have CKD, since filtering out waste products from protein metabolism puts an extra burden on the kidneys. Animal protein, especially red meat, appears to be most harmful. Most people with CKD don’t know they have it, and millions more have milder kidney impairment. That’s why if you eat a lot of protein regularly, you should talk with a health care provider, who may want to test your kidney function with a simple lab test, especially if you are over 60 or obese or have diabetes, high blood pressure, heart disease, or a family history of CKD.
Does higher protein intake increase the risk of bone loss?
This concern has been allayed by research in recent years. You need adequate protein to build and maintain bones. While it’s true that consuming lots of protein, especially animal protein, increases calcium loss from bones, it also boosts calcium uptake into bones, so there’s usually no net loss. In a study in the American Journal of Clinical Nutrition in 2010, higher intakes of protein, whether from animal or plant sources, did not have adverse effects on bone health in premenopausal women. An earlier systematic review, which included 61 studies focusing on adults of all ages, found that increasing protein intake had a small beneficial effect on bone density.
Regardless of its effect on bone density, adequate protein intake may help prevent fractures in older people by helping to maintain muscles and thus reducing falls, a major cause of fractures.
Most Americans needn’t worry about protein. Still, many older people fall short and should make sure they get adequate amounts. As for weight loss, higher-protein diets are certainly no panacea, but they may help some people at least a little, especially if they divide the protein fairly evenly among meals.
If you do decide to increase your protein intake, check with your health care provider about your kidney health. The key is not to go overboard and to choose lean protein sources or those rich in healthy fats (such as fish, nuts, and soy) to replace starchy or sugary foods. Even if you aren’t trying to lose weight or build muscle, that’s a healthy way to eat. Don’t fall for claims made for protein-fortified foods, which are often highly processed and of questionable nutritional value. Stick with whole foods. Protein supplements are generally unnecessary, but if you’re older and lack appetite, high-protein “nutritional drinks” such as Ensure or Boost are an option.
If you want to figure out how much protein you’re eating, fill out the food questionnaire on the USDA’s website.