Protein, an essential nutrient, frequently has been touted as a cure-all: Use it to boost your energy, build strength, lose weight or enhance your athletic performance, the ads say. But most adults in the United States already get more than enough protein, and the benefits of eating even more aren’t especially clear.

The jury is out on how worried we all should be about our protein intake, and more than 400 clinical trials are underway studying the effects of dietary protein. While researchers continue their work, Consumer Reports combed through the previous studies to help you learn whether you’re getting enough and suggest the easiest way to get your daily dose.

How much should I eat?

Protein is the main building block of most of our cells. While the Centers for Disease Control and Prevention and nutritional agencies recommend that 10 percent to 35 percent of your calories come from protein, that message offers more confusion than clarity.

Here’s a good basic target for adults up to age 65: A 120-pound person should aim for at least 48 grams of protein daily; a 180-pound person should aim for at least 72 grams of protein daily.

Protein intake for adults older than 65 is slightly higher. Also important for seniors is to eat protein throughout the day to reduce the loss of muscle mass.

What are the best sources?

Protein is found in everything from meat to seeds, but what’s noteworthy is how many essential amino acids each source provides. There are amino acids that must be obtained through our diet because our bodies can’t make them. That’s important because those nutrients play a pivotal role in metabolism, bolstering your health and creating critical new protein molecules.

Complete proteins are animal-based (meat, poultry, fish, milk, eggs and cheese) and provide all essential amino acids. But don’t use that as a reason to binge at the butcher shop. Several studies have reported that red meat can increase the risk of cardiovascular disease as well as certain cancers and Type 2 diabetes.

Incomplete proteins are plant-based (legumes, grains, nuts, seeds and vegetables), and each is low in one or more of the essential acids, so vegetarians need to vary their sources. For example, eating rice and beans together should provide a complete mix of the amino acids. Studies show that these pairings don’t need to occur within meals but rather over a 24-hour span.

Any combination of corn-, rice-, wheat- or soy-based proteins will provide the acids you need. Of this group, soy comes closest to being a complete protein.

Can too much protein be harmful?

A high-protein diet can worsen kidney function in people with kidney disease. Think that warning doesn’t apply to you? The vast majority of people with kidney disease don’t know they have it because the damage occurs so slowly. Cleveland Clinic researchers speculate that one in five overweight adults has at least a mild form of kidney disease.

And when they analyzed the habits of more than 10,000 overweight adults in a 2012 study, they found that many had tried high-protein diets in an attempt to lose weight, putting their kidneys at risk. Excessive protein intake over the long term might also cause calcium to be excreted from bones, increasing the risk of osteoporosis and fractures.

There are also inherent dangers in taking protein supplements, which have soared in use. The Food and Drug Administration doesn’t test these supplements for safety before they reach the market, which means they are a potential source of such dangerous substances as amphetamines and steroids. And a 2010 Consumer Reports investigation found that some protein shakes, if consumed frequently, could expose people to potentially toxic levels of arsenic, cadmium and lead.

What happens if I don’t get enough?

If you’re a senior, take note: It’s especially important that you focus on getting your daily protein fix. An international group of researchers recently concluded that keeping your protein consumption high will help you recover more quickly from illness. Specifically, it could help offset aches and pains associated with age-related inflammatory conditions, according to their study, published in the Journal of the American Medical Directors Association.

What’s more, a lack of protein in anyone’s diet could increase the chances of gaining weight. When protein consumption is low, people tend to instinctively turn to unhealthful foods to raise their protein level. “People will overeat calories to get adequate protein,” says George Bray, chief of the division of clinical obesity and metabolism at the Pennington Biomedical Research Center at Louisiana State University.

“And to make matters worse, when people don’t get enough protein, research suggests that they store more fat.”

Copyright 2013. Consumers Union of United States Inc.

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