by Joanne Gallo
August 4, 1999
Chances are, if you've been trying
to lose weight, build muscle, or increase your energy
levels, then you've been hearing about protein. This
essential nutrient has stolen the spotlight of the health
industry as the alleged key to vitality and a solid
With books like Protein Power (Bantam) and Dr. Atkins'
New Diet Revolution (Avon) firmly implanted on The New York
Times bestseller list, and protein bars and shakes growing
in popularity, more people than ever are seeking to tap into
the power of protein.
But before you go on an all-out protein-blitz, how can
you decide what's best for you?
The Purpose of Protein
No doubt about it, protein performs a variety of roles.
First and foremost, it is used to manufacture and repair all
of the body's cells and tissues, and forms muscles, skin,
bones and hair. Protein makes up the connective tissue that
forms the matrix of bones; keratin is a type of protein used
to make hair and nails.
It is essential to all metabolic processes; digestive
enzymes and metabolism-regulating hormones (such as insulin,
which influences blood sugar levels) are all made of
protein. This nutrient also intricately takes part in
transport functions: Without sufficient protein the body
cannot produce adequate hemoglobin, which carries nutrients
through the blood. Lipo-proteins are fat-carrying proteins
which transport cholesterol through the bloodstream.
Protein helps regulate fluid and electrolyte balance,
maintaining proper blood volume. Immunoglobulins and
antibodies that ward off diseases are also comprised of
Any protein that you eat that is not utilized for these
purposes is stored as fat, although some may be broken down,
converted to glucose and burned for energy. This can occur
during intensive workouts, or when the body runs out of
carbohydrates from the diet or glycogen from its muscle and
"Even though the body can depend on the fat it has
stored, it still uses muscle protein, unless it is fed
protein as food," explain Daniel Gastelu, MS, MFS, and Fred
Hatfield, PhD, in their book Dynamic Nutrition for Maximum
Performance (Avery). "When dietary circumstances cause the
body to use amino acids as a source of energy, it cannot
also use these amino acids for building muscle tissue or for
performing their other metabolic functions."
One can see why it is so important to eat a sufficient
amount of protein daily in food, shakes or bars. Without it,
bone tends to break down, the immune system can become
impaired, and muscle strength drops as the body uses up
muscle protein for energy.
Proteins are built of chains of amino acids, and 20
different kinds of these building blocks are necessary for
protein synthesis within the body. Eleven of them can be
manufactured by the body through a process called de novo
synthesis; these are referred to as non-essential amino
acids. The other nine, which must be obtained from the diet,
are known as essential amino acids. (Although some amino
acids are called "non-essential," in actuality they are
vital: The body needs all 20 amino acids to function
Some of the more familiar non-essential amino acids
include: n Carnitine helps remove fat from the bloodstream n
Arginine helps burn sugar Essential amino acids include: n
L-tryptophan, a precursor of the neurotransmitter serotonin,
helps create calm moods and sleep patterns n L-lysine,
required for the metabolism of fats n L-methionine a
component of SAM-e (a supplement intended to relieve
depression and arthritis, see p. 45)
The body forms and destroys protein from amino acids in a
constant cycle of synthesis and degradation. You must
consume protein regularly to replace the lost amino acids
that are oxidized when protein is broken down and used for
fuel. The amount of amino acids lost each day depends on
what you eat and how much exercise you do.
Athletes vs. Weekend Warriors
Protein intake in the general population is still adequate,
notes Gail Butterfield, PhD, RD, director of Sports
Nutrition at Stanford University Medical School. "But we're
learning that what is true for the general population may
not be true for the athletic population," she says. "With
heavy training there is greater protein degradation and you
need to increase your intake. Thus, protein requirements are
higher for athletes than regular people."
Also, if you diet or restrict your eating in any way, you
may also not be getting enough protein.
Certainly, if you work out, eating protein is important.
Providing four calories of energy per gram, protein keeps
blood sugar steady during exercise. After exercise, it helps
replenish and maintain stores of glycogen (stored muscle
fuel) and decreases the loss of amino acids, as recent
research has shown (J Appl Physiol 81 (5), Nov. 1996:
2095-2104). Lab studies in animals show that protein
consumed after you run, lift weights, bike, etc..., helps
stimulate muscle growth (Jrnl of Nut 127 , June 1997:
High-protein diets are frequently touted to promote
weight loss and increased energy. One of the most
influential: the so-called 40-30-30 formula, developed by
Barry Sears in his book The Zone: A Dietary Roadmap
(HarperCollins), which describes a diet whose calories are
40% carbohydrates, 30% protein and 30% fat. The rationale:
when you eat too many carbohydrates, your body uses these
starches for energy instead of burning body fat. A high
protein diet is supposed to keep your blood sugar balanced
and stimulate hormones that burn body fat instead of
carbohydrates for energy.
Other fitness experts such as Sherri Kwasnicki, IDEA
International Personal Trainer of the Year of 1998, say that
while protein is a necessary component of any diet, extreme
high-protein plans aren't necessary for recreational fitness
buffs. However, she notes that maintaining muscle mass is
the key to aging gracefully, and getting enough protein is
critical for that.
Many people today won't eat meat and dairy for ethical
reasons, or to avoid the antibiotics and other chemicals in
the raising of poultry and cattle. But that doesn't have to
prohibit adequate protein intake. All soybean products,
including tofu and soymilk, provide complete proteins, which
supply ample quantities of all the essential amino acids.
In the past vegetarians were told to combine particular
foods to make sure they consumed all the essential amino
acids at each meal. (For example, beans with either brown
rice, corn, nuts, seeds or wheat forms "complete" protein.)
Today, diet experts aren't so picky. Eating a variety of
plant-based foods throughout the day is just as effective as
combining them at one meal.
Vegans who avoid all animal products should eat two
servings at sometime during the day of plant-based protein
sources, such as tofu, soy products, legumes, seeds and
The newest sources of protein are bars and shakes, which are
growing steadily in popularity. Protein bars now constitute
about 12% of the so-called energy bar market, with sales
increasing about 38% per year. These bars generally provide
at least 20 grams of protein, including soy and whey protein
and calcium caseinate (milk protein). The benefits: bars
supply protein along with carbohydrates for energy; protein
powders, on the other hand, provide quickly digested, easily
absorbed amino acids.
Edmund Burke, PhD, author of Optimal Muscle Recovery
(Avery), suggests "If you need extra protein, you may
benefit from the convenience of a mixed carbohydrate-protein
supplement... choose a supplement that's healthy and low in
Amino acid supplements are also growing in popularity,
reported to build muscle and burn fat, or improve mood by
boosting brain neurotransmitters. The amino acids glutamine,
phenylalanine, tyrosine and 5-HTP (a form of tryptophan) are
all used to boost spirits and enhance brain function.
And if you still ponder the merits of those high protein
diets, do keep in mind that protein may be better at
controlling hunger than carbohydrates or fat since it
steadies blood sugar, so it may help you stick to a
reduced-calorie plan. But excess protein can't be stored as
protein in the body: It is either burned for energy or
converted to fat. And carbs are still the body's top energy
source, so forgoing too many can leave you tired and
Still, with so many vital functions-and a variety of
sources to choose from-you can't afford to not explore the
benefits of protein.