There
has been a resurgence of diets emphasizing increased protein intake to
promote weight loss or to improve health, so the topic of protein and
its role in a healthy diet is worth reviewing.
What is protein and why is it important?
Protein contains nitrogen and provides amino acids that are essential
for building body proteins. Protein is used to build muscle and
maintain/repair lean tissue, including muscle and body organs.
There are nine essential amino acids:
histidine (essential for children), isoleucine, leucine, lysine,
methionine, phenylalanine, threonine, tryptophan, and valine. These
amino acids must be supplied by food; the body cannot make them. There
are also 12 nonessential amino acids, which are important, but called
nonessential because the body can make them from the essential amino
acids.
Proteins come from plant and animal sources.
Animal proteins more closely match the amino acid composition of human
proteins, however people who do not consume animal foods can get all
of the protein needs from plant sources, (they just need a larger
amount of plant protein versus animal protein to fulfill the body’s
requirement for protein).
According to the Food and Nutrition Board of
the National Research Council (who establish dietary recommendations
for the population), the body’s need for protein is met when protein
intake is at .8 grams of protein per kilogram of body weight. (Divide
your body weight in pounds by 2.2 to get the equivalent in kilogram
weight). This meets the needs of about 90% of the population of
adults. For men, this translates to about 63 grams of protein per day,
and for women, it is about 50 grams of protein per day.
Protein
for Athletes and others
Protein needs increase for growing
children, nursing mothers, severally injured or seriously ill
people, and athletes. Athletes, in particular, pay special
attention to their protein intake and often supplement with
protein powders. For muscle building, about 1.6 grams of
protein per kilogram of body weight is recommended. If you
consider that you'll be eating more food to gain muscle mass and cover
your increased energy needs, you can probably get enough protein just
through food (follow your eating guidelines in your plan for weight
gain). Any additional
protein above the body’s needs is either used for energy or
converted to body fat. A typical diet should contain between
15-20% of calories as protein. What athletes and others
expending great amounts of physical energy need are additional
calories, (in the proper balance of fat, protein, and
carbohydrate, not just protein).
So, if we already get enough protein, why
are high protein diets (like the atkins
diet -which is both high fat and
high protein) so popular right now? In the past few
years, there has been a swing towards hatred of carbohydrates, and
carbohydrates are being blamed for the obesity problem. The option on
low-carbohydrate diets is to increase fat and/or protein in the diet
to make up for a low-carbohydrate intake. What’s wrong with this is
that high protein, high fat diets severely limit sources of
carbohydrates that provide essential vitamins, minerals and other
protective factors against serious diseases such as cancer, heart
disease, and high blood pressure. And, at very low levels of
carbohydrate intake, the body produces ketones, which is a potentially
dangerous condition. Beside the dangers of a low carbohydrate intake,
a high protein intake produces waste products containing nitrogen that
require a lot of water to flush out of the body. Excess protein taxes
the liver and kidneys, and does nothing to increase muscle mass
because the excess that is not used for energy is converted to fat.
The fact is, the body needs all of the
nutrients that supply energy: fats, proteins, and carbohydrates.
Each have a unique purpose and are essential in the right amounts, and
taxing to the body in the wrong amounts. Too much of any of these
nutrients will lead to an increase in body fat.
