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 and lentils.
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
-mee-no
a
-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 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 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 about 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 70-pound (or 32-kilogram) kid should have about 35
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
35 grams of protein in a day:
- 2 tablespoons (15 milliliters) peanut butter (7 grams
protein)
- 1 cup (240 milliliters) low-fat milk (8 grams protein)
- 1 ounce (30 grams) or two domino-size pieces of cheddar
cheese (7 grams protein)
- 1.5 ounces (90 grams) chicken breast (10.5 grams
protein)
- 1/2 cup (80 grams) broccoli (2 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:
Mary L. Gavin, MD
Date reviewed: February 2008
Originally reviewed by:
Jessica Donze Black, RD, CDE, MPH
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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