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Several months ago, I was having lunch with a couple of friends and one of them teased me about what I was eating (this
was in my Zone days and I had a large spinach salad with hardboiled egg, cheese, and turkey.) A second friend jumped to my
defense saying overall it was a healthy meal, but maybe I could have included a protein... I was stunned. An intelligent,
well-educated law student can't properly identify a protein in a salad? What are they teaching in health classes these days,
eh?
So in my dear friend's name... here's how to properly identify a protein:
The food that we eat is made up of three macronutrients: protein, carbohydrates and fat.
Twenty percent of the human body is composed of proteins (4). Proteins are composed of strings of 20
different amino acids (carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus and iron), of which nine cannot be produced
by the body and therefore need to be supplied by food. Protein is the stuff that bones, organs, tendons, ligaments, muscle,
cartilage, hair, nails, teeth, and skin is made of. In addition, proteins serve as enzymes that facilitate chemical reactions
within the body; as antibodies found in red blood cells that help fight infections; as hemoglobin that transports oxygen in
the blood; as hormones that regulate growth, insulin release, etc.
Proteins composed of the nine essential amino acids are called complete proteins, and these include most animal
sources: meat, fish, dairy, eggs (gelatin is the only incomplete source of animal protein) (2). Vegetable protein sources
include grains, legumes, nuts and seeds, but as these do not contain all nine essential amino acids, they are considered to
be incomplete proteins.
The combining two complementary proteins, or incomplete proteins who once paired up make up for the amino acids that
each one is lacking, is called mutual supplementation. A classic example is rice and beans.
Scientists rate protein quality by assigning a protein digestibility-corrected amino acid score (PDCAAS).
According this scale, egg whites, ground beef, milk protein (casein) and tuna have a PSCAAS of 100%; soybean protein has 94%;
garbanzos have 69%; kidney beans have 68%; peas have 67%; rolled oats have 57%; lentils have 52%; whole wheat has 40% and
when protein (gluten) has 25%. (5)
The Recommended Dietary Allowance (RDA) for adults is 0.8 grams per kilogram of body weight per day. The World Health
Organization recommends no less than 10% and no more than 15% of total calories from protein. (5). For more on protein
intake, see Protein Phobia.
"Give me a word, any word, and I'll show you how the root of that word is Greek..."
The word "protein" was coined in 1850 by a Dutch chemist. The word is derived from the Greek
proteios, meaning "of prime importance."
Carbohydrates are compounds of carbon, hydrogen and oxygen, hence the name which means "carbon and water."
The most basic chains of these three elements are sugars, also called simple carbohydrates, and they include the
sugars found in fruit, honey, table sugar, etc. More complex carbohydrates are called starches and fiber are
found in vegetables, legumes, grains, breads, pastas, etc. Complex carbohydrates, or polysaccharides, are made up of long
chains of sugar units (the most basic sugar unit is a molecule of six carbon atoms and one hydrogen atom.)
Carbohydrates (especially glucose) are produced by plants from sunlight in a process called photosynthesis. The
main function of carbs is to provide the body with a source of energy and becuase glucose is produced through photosynthesis,
carbohydrates are almost exclusively found in plant sources. The only animal-derived source of significant carbs is milk.
(5)
Simple carbs, or sugars, are divided into two groups: monosaccharides (single sugars) and disaccharides
(double sugars.) The monosaccharides are glucose (dextrose), fructose and galacose. Glucose, sometimes called
blood sugar, is the source of quick energy for both plant and animal tissues. Fructose is the sugar found in fruits, honey
and table sugar. Galactose does not occur free in nature but it is freed during the digestion of milk. (5)
The three disaccharides, lactose, maltose, and sucrose all contain glucose. Lactose, or milk sugar,
is made of glucose and galactose. Maltose, or malt sugar, is made of two glucose units. It is present during the breakdown
of starches, including during the germination of seeds, fermentation and digestion of starch. Sucrose is made of fructose
and glucose and makes up table sugar.
When thousands of glucose units appear strung together in a plant source, the carbohydrate present is called starch.
Glucose stored in long, conplicated strands in animal tissues is called glycogen or animal starch.
Chains of sugars that form leaves, stems and seeds, are known as fibers. Most fibers, including cellulose,
hemicellulose, pectin, gums, mucilages and lignins, pass through the body mostly undigested but provide the
body with valuable roughage which helps in digestion and the elimination of waste. Fibers help the body feel full becuase
they swell as they absorb water, and they help prevent constipation and hemmorrhoids. (5)
Fibers are divided into two groups, insoluble and soluble fibers. Insoluble fibers do not dissolve
in water and they include the though structures of fruits, vegetables and grains like celery strings and corn
kernel membranes. Soluble fibers do dissolve in water and can give foods gummy or gel-like charcteristics. For example,
pectin, derived from citrus fruits and apples, is often used to thicken jelly. (5)
According to popular low-carb diets, carbohydrates are the root of al evil because they increase insulin levels
in the blood, which can that lead to diabetes, heart disease and obesity. However, these diets forget that not all carbs are
created equal. Foods can be ranked according to their impact on glucose levels and this ranking is called the
Glycemic Index. On the index, researches have assigned glucose as 100, and foods with a GI above 100 turn into blood
sugar faster than table sugar does. The higher the food's GI, the greater its impact on glucose levels. The body's response
to elevated glucose levels is to release insulin from the pancreas, and this can lead to insulin resistance which has
been linked to adult-onset diabetes and obesity. (6)
Foods that have a rating of 50 or less are considered low-glycemic foods and they include green vegetables, soy,
lentils, sweet potatoes, whole grain breads and many fruits. High glycemic foods include instant rice, white bread, puffed
rice, dates and russet potatoes. (9)
For more information regarding the GI, check out the following sites: University of Sydney's Glycemic Index, the Glycemic Index by Rick Mendosa.
Contrary to popular belief, fats are not completely evil. Fats provide the body with a source of energy
and insulation, and certain fat-soluble vitamins (A, D, E and K) can't be circulated or absorbed without the presence of fat.
The main structure of most dietary fats are triglycerides or more simply, a chain of carbon called glycerol and three fatty
acids. Triglycerides are grouped in to three categories:
Monounsaturated fats are fats with one double carbon bond in the fatty acid molecule (c=c).
Studies suggest that these fats, found in olive peanut, sesame seed and canola oils, and avocados, may help
to lower blood cholesterol.
Polyunsaturated fats are fats with several double carbon bonds in the fatty acid molecule (c=c=c). Sources
of these fats include corn, cotton seed, safflower, sunflower, soybean oils and mayonaise. Omega-3 fatty acids in cold-water
fish is also a polyunsaturated fat.
Saturated fats are fats with single carbon bonds (c-c-c), and these "bad" fats can raise blood cholesterol.
Sources of saturated fat include animal products like meat and dairy as well as tropic oils (coconut, palm and palm kernel
oils).
And then there are trans-fatty acids which do not occur naturally but are created when unsaturated fats are hydrogenized,
or in other words when a liquid fat is processed into a semi-solid or solid fat (think margarine). Trans-fatty acids are as
harmful as saturated fats.
The other two categories of fats, or lipids, are phospholipids and sterols. Phospholipids, including
lecithin, are similar to triglycerides except they have a phosphorus-containing acid in stead of one of the fatty
acids. Lecithin is a component of cell membrances and is produced by the liver. It is also found in many foods. Sterols have
a similar structure to cholesterol.
Some fatty acids cannot be produced by the body but play a very significant role in a healthy body. These essential
fatty acids include Omega-3 and Omega-6 fatty acids. EFAs are the building blocks of eicosanoids,
or hormone-like substances that control blood clot formation, blood pressure, inflamation and immune responsses, among others.
(5)
Omega-3 fatty acids include alpha-linolenic acid (found in flax, hemp and walnuts), eicosapentaenoic acid (EPA) and docosahexaenoic
acid (DHA). EPA and DHA are found in cold-water fish like salmon, tuna, sardine. These fatty acids help protect the body from
heart attacks, stroke, cancer and rheumatoid arthritis.(8)
Gamma linolenic acid (GLA) is an omega-6 fatty acid found in evening primrose oil, black currant oil, and borage
oil. GLA is an effective anti-inflammatory agent, and it helps the growth of skin, hair, and nails. It can also be effective
for PMS.(9) Other good sources of omega-6 include vegetable oils, seeds, nuts and whole-grain products. (5).
For more information about EFAs, see the American Heart Association's New Guidelines Focus on Fish, Fish Oil, Omega-3 Acids and Udo Erasmus' FAQ.
Coming Soon: Vitamins & Minerals
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