Articles

Nutrition 101: Protein

By Steve Baldwin, MS, RD
February 2008

In a field of study that is often confusing, protein might be the most commonly misunderstood piece of the nutrition puzzle. So let’s start by getting a couple of protein myths out of the way:

Myth #1: Eating protein makes your muscles bigger. If that were true, the typical American would look like Mr. Olympia. On average, we eat about double the amount of protein our bodies need. Eating protein doesn’t make your muscles big – for that, you need to do resistance (weight training) exercises.

Myth #2: High protein diets are a weight loss panacea. This one has made dietitians cringe (and authors rich) for nearly 40 years. The truth is that weight loss occurs when an individual takes in fewer calories than they use, regardless of protein intake. Protein is more satiating than carbohydrates and provides fewer calories per gram than fat, but it’s not the be-all-end-all answer that some diet books would have you believe.

So then, what exactly does protein do, and what foods offer the best source?

Proteins are the structural units (or building blocks) that make up our body tissues. They are used to form muscles, organs, hormones, enzymes, and the immune system. Your heart is made of protein-rich muscle; other types of proteins make hemoglobin, the red blood cell that transports oxygen to every part of the body. Still others are used to form white blood cells that protect our bodies from infection.

When we eat food that contains proteins, the body’s digestive system breaks them down into amino acids, which are easily absorbed. The body can then reform the amino acids to build whatever protein-based tissues it needs.

Of the 22 amino acids we know are important for health, our bodies can manufacture 13 of them. The other nine are considered “essential”, meaning we must get them from an outside source: food. Some foods contain all nine essential amino acids – we call these foods “complete proteins”. Other foods lack one or more of the essential amino acids and are therefore known as “incomplete proteins”.

Proteins in food can be divided into two categories, based on their source: animal and plant. In general, animal sources of protein are “complete” and plant proteins are “incomplete”. Animal foods, like beef, fish, poultry, and milk, are complete; most plant proteins are not, with a few exceptions. Soy beans (and therefore soy products like tofu) provide complete protein. Quinoa (pronounced keen-wah) is the rare grain whose protein is complete.

Other plant sources of protein include nuts, seeds, legumes, and lentils. Although the protein in these individual foods is considered incomplete, people who follow a vegetarian diet can get all the amino acids they need by eating a variety of plant protein foods.

For instance, red beans alone won’t provide all the amino acids you need, but combine them with rice and you have a complete protein. Peanut butter on whole grain bread is another example. Neither peanuts nor whole grain bread alone counts as complete, but put them together and…voila! You’ve got a delicious, nutritious, complete protein.

The proteins in peanut butter and whole grain bread are said to be complementary – that is, they each fill in each other’s amino acid gap, providing the specific amino acid that their partner lacks.

Nuts, including peanuts, almonds, walnuts, and pistachios, are especially nutritious. Along with protein, they offer a healthy dose fiber and unsaturated fats, which help keep us feeling full for longer periods of time. Replacing a serving of meat with a handful of heart-healthy nuts a few times each week can not only assist in weight loss, it’s virtually guaranteed to add a delicious crunch to your weekly intake.

Selecting various proteins from animal and plant sources each week is a healthy habit. That way, you’ll get the nutrients you need to keep your body running smoothly. Now that you’re a protein pro, that shouldn’t be a problem.