Except for some brief maligning during the 1980s low-fat craze, protein has always been a dietary star. The most popular diets of the past ten years—Zone, Atkins, and South Beach—all emphasize limiting simple carbohydrates like white flour and sugar in favor of a higher-than-average dose of protein. Even among non-dieters, protein is a dietary given, and yet many don’t know exactly why it’s so essential to their health.

Here’s an easy way to understand it: When you eat protein in any form—whether it’s from tofu, chicken, lentils, or dairy—your body breaks it down into its component amino acids, which function as our bodies’ building blocks. Our cells combine amino acids to make everything from bones to muscles to skin, enzymes, hormones, and blood.

It’s important to eat protein everyday because our bodies can’t store it like they can store fat and carbohydrates. We use it or lose it. To keep from upping your overall fat intake (saturated fat in particular), you want to make sure that protein comes from lean sources.

Plant proteins are some of the leanest around. (To learn about sources for plant-based protein read Understanding Complete Plant Proteins.) The majority of Americans, however, get most of their protein from animal sources: meat, fish, poultry, eggs, and dairy, and that’s what we’ll focus on here.

Animal protein can be part of a healthy diet. The trick is to realize that animal proteins come packaged with other nutrients, including, in many cases, saturated fats. For example, a nicely marbled 6-ounce rib-eye steak boasts 38 grams of protein, but it’s chock full of fat, too—44 grams worth.

In contrast, consider the ubiquitous skinless chicken breast. It has practically no saturated fat, but a 6-ounce portion has over 40 grams of protein.

Between those two extremes you have a whole range of healthy choices, including:

• Low-fat Dairy Choose from the incredible array of reduced-fat milk, yogurt, cheddar, cottage cheese, ricotta, cream cheese, ice cream—you name the dairy product, there’s probably some low-fat variation.
• Eggs The American Heart Association says that healthy adults can safely eat one whole egg a day. Of course, for an even leaner option you can eat more fat-free egg whites.
• Poultry Both turkey breast and chicken breast give you lots of protein without the saturated fat. Watch out for ground turkey or ground chicken, though. Both are sometimes made with fattier dark meat and skin, so be sure to check the label.
• Fish Most fish are recommended as a source of lean protein, which may be confusing to those of us familiar with the rich, somewhat fatty quality of salmon or mackerel. Yet with 39 grams of protein and 13 grams of fat in a 7-ounce serving, these “fatty” fish qualify as lean sources of protein. Their fat contains omega-3 fatty acids, which have been associated with decreased risk of heart disease, decreased risk of depression, and even improved memory. Leaner fish, like mahi mahi, sole, or snapper, are also great. Given concerns about mercury and other contaminants, however, the American Heart Association recommends eating two servings of seafood per week.

Find the protein amounts of a wide range of foods in our Protein Sources Chart.