Protein

You probably know you need to eat protein, but what is it? Many foods contain protein (say: pro-teen),
but the best sources are beef, poultry, fish, eggs, dairy products,
nuts, seeds, and legumes like black beans. Protein builds up,
maintains, and replaces the tissues in your body. (Not the tissues you
blow your nose in! We mean the stuff your body's made up of.) Your muscles, your organs, and your immune system are made up mostly of protein.

Your body uses the protein you eat to make lots of specialized
protein molecules that have specific jobs. For instance, your body uses
protein to make hemoglobin (say: hee-muh-glow-bin), the part of red blood cells that carries oxygen to every part of your body. Other proteins are used to build cardiac muscle. What's that? Your heart!
In fact, whether you're running or just hanging out, protein is doing
important work like moving your legs, moving your lungs, and protecting
you from disease.

All About Amino Acids



When you eat foods that contain protein, the digestive juices in your stomach and intestine go to work. They break down the protein in food into basic units, called amino acids (say uh-me-no ah-sids).
The amino acids then can be reused to make the proteins your body needs
to maintain muscles, bones, blood, and body organs.

Proteins are sometimes described as long necklaces with differently
shaped beads. Each bead is a small molecule called an amino acid. These
amino acids can join together to make thousands of different proteins.
Scientists have found many different amino acids in protein, but 22 of
them are very important to human health.

Of those 22 amino acids, your body can make 13 of them without you
ever thinking about it. Your body can't make the other nine amino
acids, but you can get them by eating protein-rich foods. They are
called essential amino acids because it's essential that you get them from the foods you eat.

Different Kinds of Protein



Protein from animal sources, such as meat and milk, is called
complete, because it contains all nine of the essential amino acids.
Most vegetable protein is considered incomplete because it lacks one or
more of the essential amino acids. This can be a concern for someone
who doesn't eat meat or milk products. But people who eat a vegetarian
diet can still get all their essential amino acids by eating a wide
variety of protein-rich vegetable foods.

For instance, you can't get all the amino acids you need from
peanuts alone, but if you have peanuts or peanut butter on whole-grain
bread you're set. Likewise, red beans won't give you everything you
need, but red beans and rice will do the trick. The good news is that
you don't have to eat all the essential amino acids in every meal. As
long as you have a variety of protein sources throughout the day, your
body will grab what it needs from each meal.

How Much Is Enough?



You can figure out how much protein you need if you know how much
you weigh. Each day, kids need to eat about 0.5 grams of protein for
every pound (0.5 kilograms) they weigh. That's a gram for every 2
pounds (1 kilogram) you weigh. Your protein needs will grow as you get
bigger, but then they will level off when you reach adult size. Adults,
for instance, need 60 grams per day.

To figure out your protein needs, multiply your weight in pounds times 0.5 or you can just take your weight
and divide by 2. For instance, a 56-pound (or 25-kilogram) kid should
have about 28 grams of protein every day. If you only know your weight
in kilograms, you need about 1 gram of protein each day for every
kilogram you weigh.

You can look at a food label to find out how many protein grams are
in a serving. But if you're eating a balanced diet, you don't need to
keep track of it. It's pretty easy to get enough protein. Here's an
example of how a kid might get about 30 grams of protein in a day:

• 1 tablespoon (15 milliliters) peanut butter (4 grams protein)
  
• 1 cup (240 milliliters) low-fat milk (8 grams protein)
  
• 1 ounce (30 grams) or 2 domino-size pieces of cheddar cheese (7 grams protein)
  
• 1.5 ounces (90 grams) chicken breast (10.5 grams protein)
  

Of course, you can choose your own favorite combination of protein-rich foods - now that you're a pro at protein!

Reviewed by: Jessica R. Donze, RD, MPH
Date reviewed: March 2004