Protein is the major functional and
structural component of all body cells; all enzymes, membrane carriers,
blood transport molecules, intercellular matrices, hair, fingernails,
serum albmin, collagen are proteins. In addition, the constituent
amino acids of protein act as precursors of many coenzymes, hormones,
nucleic acids, and other molecules essential for life. An adequate
supply of dietary protein is essential to maintain cellular integrity
Protein is a macronutrient made up of two types of amino acids.
Amino acids are the building blocks for new protein to build new
tissue and repair old tissue. Non-essential amino acids are synthesized
by a healthy body from the foods that we eat each day. Essential
amino acids must be obtained daily from our diet.
For more information on protein,
Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids,
Cholesterol, Protein, and Amino Acids, 2002, Chapter 10, pages
465-608, Food and Nutrition Board (FNB), Institute of Medicine (IOM).
Also see my Carbohydrates and Fats
Protein deficiency signs?
Sufficient protein must be ingested to maintain body cellular and
organ functions. Sufficient carbohydrates must also be consumed
to meet energy needs, otherwise the carbon skeletons of amino acids
in protein will be used for energy purposes. In addition, amino
acids in the right balance must be present in the ingested protein
otherwise protein utilization will be affected. Protein-energy malnutrition
is quite common in both children and adults and is associated with
disease. Protein deficiency has an adverse affect on all body organs
and has been shown to have harmful effects on the brain, immune
system, digestion, and kidney function. Protein malnutrition can
be detected by low levels of albumin and transferrin in the blood.
Common physical signs associated with protein deficiency are:
- Skin becomes thinner and appears dull
- Hair changes color, stops growing, or falls out
- Increased secretions from the mouth, nose, and eyes
- Edema of the hands and feet
- Muscle and/or menstrual cramps
- Low tolerance for exercise
- Cold hands and feet
- Bleeding gums
If you suspect you have a protein deficiency, contact your doctor
or healthcare professional immediately.
Non-essential amino acids
- Alanine (synthesized from pyruvic acid)
- Arginine (synthesized from glutamic acid)
- Asparagine (synthesized from aspartic acid)
- Aspartic Acid (synthesized from oxaloacetic acid)
- Glutamic Acid (synthesized from oxoglutaric acid)
- Glutamine (synthesized from glutamic acid)
- Glycine (synthesized from serine and threonine)
- Proline (synthesized from glutamic acid)
- Serine (synthesized from glucose)
- Tryosine (synthesized from phenylalanine)
Essential amino acids
Protein in our diets can come from animal and plant sources. Most
animal sources (meat, poultry, fish, eggs, milk, cheese, and yogurt)
provide complete protein, meaning that
they contain all the essential amino acids. Protein from plants,
legumes, grains, nuts, seeds, and vegetables don't contain all the
essential amino acids but different sources are deficient in different
amino acids; so eating different sources can supply all the essential
amino acids. The digestive system, via enzymes, breaks all proteins
down into their constituent amino acids so that they can enter the
bloodstream. Your body needs protein, it cannot survive on just
carbohydrates. Like carbohydrates, one gram of protein provides
4 calories of energy. There is some evidence that the source of
protein may be important and that animal protein can cause problems,
much protein may cause reduced kidney function and The
Effect of Dietary Protein Intake on Kidney Function in Women with
Normal or Mildly Abnormal Kidneys which are based on the research
Impact of Protein Intake on Renal Function Decline in Women with
Normal Renal Function or Mild Renal Insufficiency, E.L. Knight,
M.J. Stampfer, S.E. Hankinson, D. Spiegelman, and G.C. Curhan, Annals
of Internal Medicine, 18 March 2003, Volume 138, Number 6,
Tissue protein can also be broken down into amino acids and used
for energy if there are not enough fats and carbohydrates in the
diet. This can result in loss of muscle mass.
How much protein does my body need?
The amount of protein needed by your body depends on your activity
level with a minimum of 0.36g/lb (0.8g/kg)
and a maximum of 0.91g/lb (2.0g/kg)
of body weight. The recommended maximum percentage of protein in
our diet is 30% of total calories.
How much protein is converted to glucose?
It is generally believed that about 55% of protein is converted
to glucose within 3-4 hours of being eaten and that fat has little
effect on blood glucose levels. However, according to recent studies,
very little protein or fat is converted to glucose. In addition,
protein does not slow down the absorption or glucose response of
a carbohydrate-dense meal. Fat delays the peak but not the total
glucose response. So increasing the amount of protein and fat in
our diet looks like a viable means of controlling postprandial glucose
responses; however, this doesn't mean that a high-fat or high-protein
diet is warranted.
The same studies alluded to above also indicate that, over the
long term, high-fat and high-protein diets may induce insulin resistance!
Another study indicates that monounsaturated fatty acids (found
mostly in vegetable and nut oils such as olive, peanut, and canola)
can improve insulin resistance (when calories from fat are less
than 37% of total calories). See Protein
Controversies in Diabetes, Marion J Franz, Diabetes Spectrum,
Vol. 13, No. 3, 2000, pages 132-141; Effect
of Protein Ingestion on the Glucose Appearance Rate in People with
Type 2 Diabetes, MC Gannon, JA Nuttall, G Damberg, V Gupta,
FQ Nuttall, The Journal of Clinical Endocrinology & Metabolism,
Vol. 86, March 2001, pages 1040-1047; and Substituting
dietary saturated for monounsaturated fat impairs insulin sensitivity
in healthy men and women: The KANWU study, B Vessby, M Uusitupa,
et al, Diabetologia, Vol. 44, Issue 3, 2001, pages 312-319.
I think there may be a connection with the effect of high levels
of protein and possible calcium depletion (for example, see Dietary
protein intake and urinary excretion of calcium: a cross- sectional
study in a healthy Japanese population, R Itoh, N Nishiyama
and Y Suyama, AJCN, Vol 67, 438-444, 1998; and Dietary
protein and phosphorus do not affect calcium absorption, Robert
P Heaney, AJCN, Vol. 72, No. 3, 758-761, September 2000).
I also find myself asking about the use of calcium in bones and
the production of red blood cells by bone marrow. Overall, it would
seem prudent to take a calcium supplement and limit
protein intake to 0.4g/lb of body weight with a
maximum of 100g/day.
In addition, it would also seem prudent to
limit fat intake to a maximum of 30% of total calories with less
than 10% saturated fat with the rest made of monounsaturated
and polyunsaturated fats. Essential fatty acids (polyunsaturated
fats) also improve protein and amino acid utilization, so a balanced
EFA supplement seems warranted, I take 1 tbsp/day of Udo's
Choice Ultimate Oil Blend (1tbsp=15mL: 135cals/ 14.5g fat/ 0.2g
protein/ 0g carb).
Diabetes may deplete Glutathione
(GSH) levels and a low GSH level may even be a contributing factor
to the onset of diabetes, ongoing difficulty in controlling
glucose levels, and in the development of diabetic
protein stimulates GSH synthesis and enhances the body's immune
system and there is some evidence that it also reduces hypertension,
the leading causes of heart disease and stroke. It seems prudent
to supplement our diet with about 30g/day
of whey protein; I currently use and recommend GNC Pro Performance
Elite Series Whey ISO Burst, Banana Berry Burst or French
Vanilla, sucralose sweetened (45g: 160cal, 0.5g fat, 40g
protein, 1.5g carb).
Whey is a high quality complete
protein, second only to eggs, that contains all the essential amino
acids required by the body. Typical whey protein quality measure
values: PDCAAS=1.0; Amino Acid Score=1.14; PER=3.2; BV=100.
Whey protein is obtained from
milk. Milk consists of 87% water and 13% solids; it contains two
primary proteins (which make up 27% of the milk solids) casein (80%
of milk protein) and whey (20% of milk protein). When cheese is
produced, liquid whey separates from the casein (curd). The whey
protein is then separated from the liquid whey and purified to various
protein concentrations. To ensure maximum assimulation, use only
products based on Whey Protein Isolate or Hydrolyzed
Whey Protein Isolate which both have >90% protein, 0.5-1.0%
lactose, and 0.5-1.0% fat.
For more information on whey protein, see the Whey