Vegetarian food combinations that give you complete protein, for example, include rice and beans or peanut butter and bread.  Eggs are also a good source of complete protein.  People who don’t eat eggs or dairy products need to be particularly careful to get all the essential amino acids they need.

Another group that may not get enough protein is older adults.  A recent NIH study of men and women in their 70s found that those who ate the least protein lost significantly more muscle than those who ate the most protein.  Maintaining muscle is particularly important as you age.  Older adults who lose muscle in their legs and hips are more likely to fall and have injuries like broken hips.  Those who don’t maintain strong muscles as they age might also have trouble doing basic things like getting up from a chair, walking up stairs or taking a stroll through the park.

For most Americans, however, there’s little benefit to eating more protein than they already do.  In long-term studies of high-protein diets, researchers have found that most differences in weight loss can be explained by the amount of calories people eat rather than their protein intake.  High-protein diets may make some people feel fuller, but that effect has been hard for researchers to tease out, because many high-protein diets are also high in fat.

There are questions about the benefits of protein supplements as well.  Advertisements for protein powders and shakes say their products have essential amino acids that the body can’t make.  “That is true,” Hubbard says, “but if you’re eating a varied diet, particularly animal protein, there is skimpy, if any, data that it’s better to eat protein in supplement form than in food.”

In special cases, these products can prove useful.  For elderly people who can’t eat enough protein or patients with diseases that leave them malnourished, a protein supplement can be one way to help get enough protein.  But be sure to talk to a doctor or nutritionist before trying this.

Is it possible to eat too much protein?  Hubbard says, “There is insufficient data to say that a person can eat too much protein.”  He says there is evidence to suggest that people with certain diseases and conditions should limit their intake.  For people with kidney disease, for instance, a reduced-protein diet may help delay the progression towards kidney failure.

If you’re like most Americans, though, you don’t need to worry about eating enough protein.  Recent weight loss, muscle fatigue or a drop in muscle strength may be signs you’re not eating enough protein.  But they may be signs of other problems as well.  If you have any of these symptoms, you need to see your health care provider to pinpoint their cause.