Nutrition midterm 2

Chapter 6

PROTEINS AND AMINO ACIDS

Source of dietary protein

• protein deficiency is rare in Canadacanada

• Canadianscanadians average protein intake was typically about 17% of total calories.

• milk and milk products are the most commonly consumed sources of protein, followed by meat

• Canada’s food guide encourages plant based proteins

Nutrients supplied by animal and plant foods

• animal products provide sources of protein, B vitamins and minerals such as iron, zinc, and calcium

• and animal products are low in fibre and can be high in fat

• plant sources of protein are also a good source of b vitamins, iron, zinc, fibre, calcium but less absorbable form

Amino Acids

• Amino acids are the building blocks of protein.

• Each amino acid contains a central carbon atom bou a hydrogen atom, an amino group, an acid group, a side chain.     Essential (indispensable) amino acids:

• Amino acids that cannot be synthesized by the human body in sufficient amounts to meet needs and therefore must be included in the diet.

• Nonessential dispensable) amino acids:

• Amino acids that can be synthesized by the human b sufficient amounts to meet needs.

Nitrogen makes amino acid different from other chemicals.

Essential Amino Acids:

• Histidine

• Isoleucine

• Leucine

• Lysine

• Methionine

• Phenylalanine

• Threonine

• Tryptophan

• Valine

Nonessential Amino Acids

• Alanine

• Arginine

• Asparagine

• Aspartic acid

• Cysteine

• Glutamic acid

• Glutamine

• Glycine

• Proline

• Serine

• Tyrosine

Transamination

When a nonessential amino acid is not available from the diet, it can be made in the body by the process of transamination.

Protein Structure

• Peptide bonds are chemical bonds that link amino acids together.

• Peptide bonds are formed between the acid group of one amino acid and the nitrogen group of the next amino acid.

• Dipeptide bonds are formed between two amino acids.

• Polypeptides are formed between many amino acids.

• A protein is made of one or more polypeptide chains folded into a three-dimensional shape.

Protein Shape Determines Function

• The final shape of a protein determines its function.

• Connective tissue proteins and collagen are elongated.

• Hemoglobin has a spherical shape.

• If the shape of a protein is altered, its function may be disrupted.

Protein Digestion and Absorption

1. In the mouth, chewing begins the mechanical breakdown of protein.

2. In the stomach, hydrochloric acid and the enzyme pepsin begin the chemicaldigestion of protein.

3. in the small intestine, protein-digesting enzymes secreted from the pancreas, along with those in the brush border, break down polypeptides into amino acids, dipeptides, and tripeptides.

4. A variety of transport proteins move the products of protein digestion into the mucosal cell. Some amino acids share the same transport system. In this figure, the larger number of purple. amino acids means that more purple than green ones cross the membrane into the cell.

5. Dipeptides and tripeptides can enter the mucosal cell. Once inside, they are broken down into single amino acids.

6. Amino acids pass from the mucosal cell into the blood and travel to the liver, which regulates the distribution of amino acids to the rest of the body.

7. Little dietary protein is lost in feces.

Protein Digestion and Food Allergies

• Food allergies are triggered when a protein from the diet is absorbed without being completely digested.

• Proteins from milk, eggs, nuts, wheat, soy, fish, and shellfish and peanuts are common causes of food allergies

• A rapid, severe allergic reaction is called anaphylaxis.

• People with Gl disease are prone to allergies because their damaged intestines allow for the absorption of whole proteins.

Amino Acid Pool:

all of the amino acids in the body tissues and fluids that are available for use by the body.

Protein turnover:

The continuous synthesis and breakdown of body proteins

Protein Synthesis l

1. In the nucleus, the blueprint, or code, for the protein is copied or transcribed from the DNA gene into a molecule of messenger RNA (mRNA)

2. The mRNA takes the genetic information from the nucleus to structures called ribosome in the cytosol, where proteins are made.

3. In the cytosol. transfer RNA reads the genetic code and delivers the needed amino acids to the ribosome to form a poly peptide.

Energy Production from Protein

Urea: a nitrogen obtaining waste product formed from the breakdown of amino acids that is excreted in the urine.

Urea Synthesis

1. Deamination: the removal of an amino group from an amino acid

2. production of ammonia

3. ammonia converted to urea

4. urea filtered through the kidneys

Protein functions

• Enzymes speed up metabolic reactions.

• Transport proteins move substances in and out of cells.

• Antibodies help the immune system in fighting off foreign bodies.

• Contractile proteins help the muscles to move.

• Hormones are chemical messengers, such as insulin and glucagon.

• Proteins help to regulate fluid and acid-base balance.

Protein Deficiency

• Protein-energy malnutrition (PEM) is a term that covers a range of protein deficiency conditions that may include only protein deficiency or protein deficiency plus energy deficiency.

• Kwashiorkor is a pure protein deficiency.

• Marasmus is an energy deficiency.

Protein Excess

• Elevated protein intakes over long periods of time can result in:

• Hydration and kidney function issues

Kidney stones

• Increased risk of heart disease and cancer

Proteins and Amino Acids that may cause Harm: Phenylketonuria

• PKU is an inherited condition, attributed to a defective gene, in which the body cannot metabolize pheny

• Aspartame contains phenylalanine.

Labelling for Allergies

• Health Canada has identified the following food allergens: peanuts, tree nuts, sesame seeds, milk, eggs, fish (including crustaceans and shellfish), soy, wheat, and sulphites.

• These products are responsible for 90% of reported adverse reactions to food.

• Food manufacturers are required to clearly state if a product contains any of the priority food allergens.

• 3 ways allergens can appear on a food label: listed in the ingredients list, identified in a parenthetical statement, with use of the word “contains”

Determining Protein Requirements

To determine protein requirements

• determine body weight- configure it to kilograms (divide pounds by 2.2)

• Determine the grams of protein required per day. Multiply weight in kilograms by the grams of protein per kilogram recommended for the specific genre and age.

ex. a 23 year old women weighing 68kg would require 0.8.g/kg/day x 68k = 54.4 grams of protein a day

Calculating Protein Requirements

• Following the recommendations of Canada's Food Guide will result in a diet that includes both animal and plant sources of protein.

• A 250 mL serving of milk will provide 8g of protein.

• Serving of beans 7 to 10 g of protein.

• 75 g serving of meat 14 to 20g of protein.

• Serving of grains or vegetables 1 to 3 g of protein.

Considering Protein Quality

Protein quality:

A measure of how efficiently a protein in the diet can be used to make body proteins.

Complete dietary protein:

Protein that provides essential amino acids in the proportions needed to support protein synthesis.

Incomplete dietary protein:

Protein that is deficient in one or more essential amino acids relative to body needs.

CHAPTER 8

WATER SOLUBLE VITAMINS

Vitamins are organic compounds needed to promote growth and health maintenance.

Water-soluble vitamins include the B vitamins and vitamin C.

• Fat-soluble vitamins include A, D, E and K.

• B vitamins were originally thought to be one chemical substance but are actually many different substances. That is the reason for B, B2, B12, etc.

WATER SOLUBLE VITAMINS

B vitamins

Thiamin

Riboflavin

Niacin

Biotin

Pantothenic acid

Vitamin B6

Folate

Vitamin B12

Vitamin C

Fortified and Enriched Foods

• Fortification: process of adding nutrients to foods generally not found in the food (e.g., adding calcium to orange juice).

• Enrichment: adding nutrients back to foods that have lost nutrients due to processing (e.g., adding B vitamins to white rice).

Fortification

• Health Canada regulates which foods must be fortified and which nutrients should be added.

• Examples:

table salt with iodine milk with Vitamin D

grains with thiamine, riboflavin, niacin, iron, and folic acid

Approximately 40% of Canadian adults use vitamin and mineral supplements

Vitamin in the Digestive Tract

1. In the mouth, chewing breaks food into small particles, helping to release vitamins.

2. In the stomach, digestion of food releases vitamins. Some niacin is absorbed here.

3. The gallbladder releases bile, which emulsifies fat and helps absorb fat-soluble vitamins.

4. The pancreas secretes digestive enzymes that aid in the release of vitamins from food.

5. In the small intestine, fat-soluble vitamins are incorporated into micelles and then absorbed by simple diffusion. Once they are inside the mucosal cells, fat-soluble vitamins are packaged in chylomicrons, which enter the lymph hefore nassina into the blood.

6. Water soluble vitamins are absorbed from the small intestine directly into the blood

7. In the large intestine, bacteria synthesize small amounts of vitamins, some of which are absorbed

Bioavailability of Vitamins

• Vitamins must be absorbed by the body in order to perform their functions.

• Approximately 40-90% of vitamins are absorbed in the small intestine.

• Fat-soluble vitamins require fat in the diet to be absorbec

• Water-soluble vitamins may require transport molecules or specific molecules in the Gl tract.

• Some vitamins are absorbed in inactive provitamin or vitamin precursor forms that must be converted into active forms by the body.

Understanding Vitamin Functions

1. The vitamin combines with a chemical group to form the functional coenzyme (active vitamin).

2. The functional coenzyme combines with the incomplete enzyme to form the active enzyme.

3. The active enzyme binds to one or more molecules and accelerates the chemical reaction to form one or more new molecules.

4. The new molecules are released, and the enzyme and coenzyme (vitamin) can be reused or separated.

• Thiamin was the first B vitamin to be identified and is also called B1.

• Thiamin is widely available in foods, especially in enriched grains, whole grains, legumes, nuts, and seeds.

• Thiamin assists in energy production, carbohydrate metabolism, the production of ribose, and the health of the nervous system.

• Dairy products are a good source of riboflavin.

• Plant sources of riboflavin include mushrooms, broccoli, asparagus, whole grains, and green, leafy vegetables.

• Animal sources include red meat, poultry, and fish.

• Riboflavin is easily destroyed by heat and exposure to light.

• Riboflavin is an important component in the citric acid cycle and for assisting the body with the absorption of other vitamins.

• Niacin is added to enriched flours in North America.

• A niacin deficiency disease is pellagra.

• Niacin can be synthesized in the body from the essential amino acid tryptophan if the diet is adequate in tryptophan.

Niacin plays an important role in the production of energy and in general metabolism.

• Two forms of niacin are nicotinic acid and nicotinamide.

• Niacin toxicity from overuse of niacin supplements can result in elevated blood pressure, cardiac arrhythmia, nausea, vomiting, elevated blood sugar levels, and impaired liver function.

Biotin in the diet

• Liver, egg yolks, yogurt, nuts

• Coenzyme involved in adding COOH group to other molecules (e.g., citric acid cycle, glucose synthesis).

Pantothenic Acid

• Abundant in meat, eggs, whole grains, legumes

• Part of coenzyme A

• Part of the acyl carrier protein for cholesterol and fatty acid synthesis

Vitamin B6 (1 of 2)

• Vitamin Bo is also called pyridoxine and comprises a group of compounds including pyridoxal, pyridoxine, and pyridoxamine.

• All three forms can be converted into pyridoxal phosphate, which is required for many enzyme reactions in the body.

• Vitamin Be deficiency may result in anemia due to impaired hemoglobin synthesis and neurotransmitter issues.

Folate or Folic Acid

• Folate coenzymes are needed for DNA synthesis and the metabolism of some amino acids.

• Low folate intake in early pregnancy is associated with an increased risk of neural tube defects.

• Low folate intake has been associated with an increased risk of heart disease related to the metabolism of the amino acid homocysteine.

• Neural tube defects have decreased by 50% in Canada since food fortification.

• Newfoundland rates have dropped by 80%.

• Alberta and Quebec have found a reduction in the number of congenital heart defects.

• Ontario reported a reduction in neuroblastoma.

• Some studies have shown an increase in colon cancer since folate fortification began in 1998.

• This maybe the result of folate stimulating DNA synthesis and promoting growth of pre-existing cancerous cells.

• When considering food fortification it is important to consider that what may benefit one segment of the population may harm another segment.

Vitamin B12 (2 of 2)

• Pernicious anemia: form of anemia unresponsive to iron supplementation.

• Vitamin B,2 is necessary for the proper absorption of iron in the body.

• Excessive intake of folic acid can mask B12 deficiencies.

• Vitamin B12 is most readily absorbed from animal products.

• Vegan diets need to be supplemented with readily-absorbable forms of B12.

Vitamin C

• Vitamin C is also known as ascorbic acid or ascorbate.

• Vitamin C in foods can be destroyed by oxygen, light, and heat, as well as contact with copper or iron cookware.

Vitamin C functions as an antioxidant in the body, helps maintain the immune system, is important in the production of collagen, and aids in iron absorption.

Chapter 9

the fat soluble vitamins

• vitamins A, D, E and K are fat soluble vitamins

• fat soluble vitamins require bile and dietary for absorption. Unlike water soluble vitamins.

• once absorbed, they are transported with fats through the lymphatic system in chylomicron before entering the blood.

• U like water salable vitamins that can be peed out, fat soluble are stored in body fat which is not easily excreted. This increases the risk of toxicity with high intakes.

VITAMIN A

• found preformed from animals products or supplements, or in precursor, from plant foods in the diet.

• Vitamin A plays a key role in night vision.

• Preformed vitamin A compounds are known at retinoids.

• Plants contain precursors to vitamin A known as carotenoids

• A derivative of retinoids acid is used topically to treat certain skin conditions.

Vitamin in the Diet

• Carrots have a large amount of vitamin A in 1/2 c of carrots

• Beef liver always has a lot of vitamin a because it is stored in the liver in animals

Vitamin A and the Visual Cycle

see slide 13

Vitamin A Gene Expression

see slide 14

Vitamin A Deficiency and Toxicity

• Vitamin A deficiency is a threat to the health. sight, and lives of millions of children around the world.

• Can be caused by insufficient intake of Vitamin A, fat, protein, or zinc.

• Preformed vitamin A can be toxic if taken in high amounts.

• Medications made vitamin A like detox A , accutane, can cause serious side effects.

Vitamin A Deficiency and Toxicity

see slide 20

VITAMIN D

• known as sunshine vitamin. Can be produced in the skin by exposure by uv light.

• only a few foods are a natural source of vitamin d ex. liver, fatty fish, fish oils, egg yolks.

• Can be toxic at high levels, so there are strict limitations on what foods that can be vitamin d fortified

• important for bone health, normal functioning of the parathyroid gland, and regulation of the immune system.

Vitamin D Synthesis

see slide 28

Vitamin D deficiency and toxicity

• When vitamin D is deficient calcium cannot be absorbed efficiently and there can be improper bone mineralization and abnormalities in bone structure.

• In children, vitamin D deficiency can result in rickets and in adults osteomalacia

• over supplementation of vitamin D can result in high blood and urine calcium concentrations, depositing of calcium in blood vessels and kidneys, cardiovascular damage, and possibly death.

VITAMIN E ( tocopherol)

• Has antioxidant properties

• Aloha-tocopherol: the form of vitamin E absorbed by the human body.

• Vitamin E absorption depends on normal fat absorption.

• Once absorbed, vitamin E is incorporated into chylomicrons ( same with other vitamins)

• Vitamin E deficiency in newborns might result in hemolytic anemia.

VITAMIN K

named for koagukation, the danish word for coagulation

• found in several forms, including phylloquinone and menaquinone.

• A normal blood coagulation is the major symptoms of vitamin K

• Vitamin K deficiency is very rare in healthy adult population

• when babies are born they don’t have any vitamin k so they will give a shot of vitamin k in the foot

• Kiwis have the most vitamin k but we make most of our vitamin k in our body

Role of Vitamin K in Blood Clotting

see slide 49

CHAPTER 13

NUTRITION AND PHYSICAL ACTIVITY

• The cardiorespiratory system includes the circulatory and respiratory systems, delivering oxygen and nutrients to the cells.

• Hypertrophy: an increase in the size of a muscle or organ.

• Atrophy: wasting or decrease in the size of a muscle or other tissue caused by lack of use.

Exercise, the Heart, and the Muscles (1 of 2)

• Regular aerobic exercise strengthens the heart muscle, increases stroke volume, decreases the resting heart rate.

Resting heart rate can be measured by counting the number of pulses per minute while at rest.

• Aerobic capacity: The body's maximum ability to generate

ATP by aerobic metabolism during exercise. Also called VO2

Exercise, the Heart, and the Muscles (2 of 2)

• Hypertrophy: when stress or overload during exercise causes muscles to adapt by increasing in size and strength.

• When muscles are not used, they atrophy, becoming smaller and weaker.

• Exercise builds and maintains muscles. People who are fit have a greater proportion of lean body tissue than those who are not fit.

HEALTH BENEFITS OF EXERCISE

• In addition to increased flexibility and the ability to easily perform daily activities, benefits of regular exercise include:

perform daily activities, benefits of regular € include:

Weight management

Cardiovascular health

Diabetes prevention or management

Bone and joint health

Possible reduction of cancer risk

Psychological health

Fuelling Exercise (1 of 2)

• Aerobic metabolism: metabolism in the presence of oxygen.

Glucose, fatty acids, and amino acids are completely broken down to form CO2 and H2O and to produce ATP

Fuelling Exercise (2 of 2)

• Anaerobic metabolism: metabolism in the absence of oxygen.

• Each molecule of glucose produces two molecules of ATP.

Glucose is metabolized in this way when oxygen cannot be supplied quickly enough to the tissues to support aerobic metabolism.

Also called anaerobic glycolysis.

Relationship of Exercise to Intake

• In an athlete's diet, the source of dietary energy can be as important as the amount of energy.

Vitamins and minerals requiring special attention from athletes:

B vitamins

Antioxidant vitamins (e.g., vitamins C and E)

Iron

Calcium

• the general proportion of energy for athletes and healthy individuals should be:

45-65% total energy from carbohydrates

20-35% from fat

10-35% from protein