CHAPTER 6 – PROTEIN
Chapter 6 – PROTEIN
Amino Acids are the building blocks of protein.
• Essential Amino Acids (9): The ones that must be supplied by your diet (the body cannot make)
• Non-essential Amino Acids: The ones the body can synthesize as long as all of the essential amino acids are supplied in the diet in proper ratios
|Essential Amino Acids |Nonessential Amino Acids |
|Histidine |Alanine |
|Isoleucine |Arginine |
|Leucine |Asparagine |
|Lysine |Aspartic Acid |
|Methionine |Cyteine |
|Phenylalanine |Glutamic Acid |
|Threonine |Glutamine |
|Tryptophan |Glycine |
|Valine |Proline |
| |Serine |
| |Tyrosine |
Dipeptide: A chain of two amino acids
Tripeptide: Three amino acids linked together
Polypeptide: Many (ten or more) amino acids linked together
DIGESTION AND ABSORPTION OF PROTEIN:
Digestion starts in the stomach with the help of hydrochloric acid
HCL
Pepsinogen →→→→→→→→→→ Pepsin
(inactive enzyme) (active enzyme)
In the small intestines, proteases from the pancreas hydrolyze the polypeptides into smaller peptide chains and individual amino acids for absorption.
FUNCTIONS OF PROTEIN:
1. Growth, maintenance and repair of body tissue
2. Protein is important for the immune system
3. Antibodies: act against viruses, bacteria, etc.
4. Enzymes (some proteins act as enzymes)
5. Helps regulate fluid and electrolyte balance
6. Helps regulate acid-base balance
7. Hormones (some hormones are proteins, and some proteins act as hormones)
8. Transport Protein (carries nutrients throughout the body)
9. Energy (if not enough calories or carbohydrates are available). Protein can be used for energy (converted to glucose) during fasting or extreme exercise.
Nitrogen Balance: occurs when the body maintains the same amount of protein in the tissues from day to day
• Positive nitrogen balance (Anabolism) – Tissue building. Ex: Growing children, pregnant women
• Negative nitrogen balance (Catabolism) –Tissue breakdown. Ex: starvation, trauma, burns, etc.
TYPES OF FOOD PROTEIN
• Complete Protein (High Quality Proteins)
• contains all of the essential amino acids in sufficient quantity, and are easily digestible
• Food Sources:
• Incomplete Proteins (Complementary Proteins)
• missing 1 or more of the essential amino acids
• can combine incomplete proteins to obtain all of the essential AA's
• variety of foods is important!
• Food Sources:
PROTEIN ENERGY MALNUTRITION (PEM)
• The most widespread form of malnutrition worldwide
• children die each day worldwide, most from PEM and infectious diseases
Marasmus (Severe deprivation of food over a long time)
• Occurs from inadequate calories AND protein
• Most commonly occurs in children months
• Impairs brain development and learning ability
• muscles and heart weaken
• body temperature drops below normal
• digestion and absorption fails (GI tract lining deteriorates)
• growth ceases
• immune system weakens, leading to infections
• diarrhea occurs (from dysentery)
Kwashiorkor (Sudden and recent deprivation of food)
• starts between months and years
• limbs and face become swollen with edema
• fatty liver occurs (causes characteristic large belly)
• hair loses its color
• skin becomes patchy and scary, sores won't heal
Infections combined with malnutrition are responsible for 2/3 of the deaths of young children in developing countries.
PROTEIN EXCESS (more than 35% of calories)
• Foods rich in animal protein also tend to be high in saturated fat and increase risk of heart disease
• High protein foods tend to be high in fat that may contribute to obesity
• Possible link between high meat diets and cancer
• Too much protein can promote calcium excretion and contribute to osteoporosis
• Too much protein can increase the risk for kidney damage and kidney stones
HAZARDS OF HIGH PROTEIN (LOW CARBOHYDRATE) DIETS:
• High protein, low carbohydrate diets may trigger ketosis, which can lead to dehydration, gout, hypotension, electrolyte imbalance, and possibly kidney and liver damage
• Tend to be deficient in nutrients like folate, vitamin C, fiber, and phytochemicals, which can increase risk for certain types of cancers
• Most high-protein, low-carbohydrate diets are also high fat diets.
• Part of the weight loss is water and lean muscle mass. Most people will regain water weight, and some of the lean body mass lost is replaced with fat. Loss of lean muscle mass reduces the metabolic rate, which will increase the probability of future weight gain.
PROTEIN RECOMMENDATIONS:
• RDA: ______grams / kg per day
• Protein should be 10-35% of total calories
Estimate Your Protein needs:
Weight ( lbs) ÷ 2.2 = (weight in kg)
Weight ( kg) x .8 = minimum grams of protein per day
PROTEIN AND AMINO ACID SUPPLEMENTATION:
You MUST exercise the muscle to build muscle!
Protein supplements are NOT needed by healthy people.
Taking single amino acid supplements can be harmful to the body. Too much of one can cause
a deficiency of others (they compete for absorption).
VEGETARIAN DIETS:
BENEFITS:
• Easier to maintain a healthy body weight
• Tend to have lower rates of hypertension
• Lower rates of heart disease
• Tend to have lower cholesterol
• Lower rates of cancer
DISADVANTAGES:
• More likely to have protein deficiency
• More likely to have nutrient deficiencies (iron, vitamin B12, calcium, etc.)
• More likely to lack omega-3 fatty acids
• Vegan diets are generally not recommended for young children
Consuming a variety of foods is important for vegetarians!
Vegans: Vegetarians who exclude ALL animal products from their diet.
Lactovegetarians: People who include products in their diet, but do not eat meat, seafood, or eggs.
Lacto-ovo-vegetarians: People who include milk products and eggs in their diet, but do not eat any type of meat or seafood products.
Macrobiotic Diets: Diets that are limited to only a few grains and vegetables.
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