What Are Proteins?

Copyright © 2010 Pearson Education, Inc.

What Are Proteins?

• Proteins: large, complex molecules found in cells of all living things• Dictated by genetic material (DNA)

• Contain carbon, hydrogen, oxygen, nitrogen

• Made from 20 different amino acids

The Building Blocks of Proteins


Amino Acids

• Nine essential amino acids• Cannot be produced in sufficient quantities to meet

physiological needs

• Must be obtained from food

• Nonessential amino acids• Can be synthesized in sufficient quantities



Protein in the Diet

• For protein synthesis, all essential amino acids must be available to the cell

• Limiting amino acid • Essential amino acid that is missing or in the

smallest supply

• Slows down or halts protein synthesis

• Inadequate energy consumption • Limits protein synthesis


Protein in the Diet

• Incomplete protein (low quality): insufficient essential amino acids • Does not support growth and health

• Complete protein (high quality): sufficient amounts of all nine essential amino acids• Derived from animal and soy protein


Protein in the Diet

• Mutual supplementation: combine two or more incomplete protein sources to make a complete protein

• Complementary proteins: two or more foods are combined to supply all nine essential amino acids for a complete protein


Functions of Proteins

• Cell growth, repair, maintenance

• Enzymes and hormones

• Fluid and electrolyte balance

• Acid−base balance

• Immune system

• Energy source

• Nutrient transport and storage


Protein Adequacy

• Nitrogen balance determines protein needs• Positive nitrogen balance

• Negative nitrogen balance

• In nitrogen balance

Nitrogen Balance


RDA for Protein

• RDA = 0.8 g per kg body weight per day

• Recommended percentage of energy is 10−35% of total energy intake

• Protein needs are higher during growth and development (children, adolescents, and pregnant/lactating women)


Too Much Protein Can Be Harmful

• High cholesterol and heart disease• Animal-protein-rich diets are associated with high

blood cholesterol levels (saturated fat)

• Contribution to bone loss• High-protein diets increase calcium excretion and

possibly lead to bone loss


Too Much Protein Can Be Harmful

• Kidney disease• High protein intakes are associated with an

increased risk among susceptible individuals• People with diabetes have higher rates of kidney

disease and may benefit from a lower-protein diet • Maximum of 2 g of protein per kilogram body

weight each day is safe for healthy people

Fat Synthesis from Excess Protein


Protein Sources

• Meats

• Milk-based products

• Soy products

• Legumes

• Whole grains

• Nuts

• Quorn


Vegetarian Diets

• Vegetarianism: restricting the diet to foods of plant origin

• People chose vegetarianism for:• Health benefits

• Ecological reasons

• Religious reasons

• Ethical reasons

• Concerns over food safety


Health Benefits of Vegetarianism

• Lower fat and total energy intake

• Lower blood pressure

• Reduced risk of heart disease

• Fewer digestive problems

• Reduced risk of some cancers

• Reduced risk of kidney disease, kidney stones, and gallstones


Challenges of Vegetarian Diets

• Can be low in some nutrients

• Associated with disordered eating

• Varied and adequate diet planning

• Soy and complementary proteins

• Vegetarian Food Guide Pyramid

• Special attention to vitamins D, B12, and riboflavin (B2); minerals zinc and iron


Protein-Energy Malnutrition

• Protein-energy malnutrition: caused by inadequate protein and energy intake

• Common forms:• Marasmus

• Kwashiorkor


Marasmus

• Grossly inadequate energy and nutrient intake• Consequences of marasmus:

• Wasting and weakening of muscles (heart)• Stunted brain development and learning• Depressed metabolism• Stunted physical growth• Deterioration of the intestinal lining (anemia)• Severely weakened immune system• Fluid and electrolyte imbalances


Kwashiorkor

• Disease resulting from low protein intake

• Kwashiorkor symptoms include:• Some weight loss and muscle wasting

• Retarded growth and development

• Edema resulting in distention of the belly

• Fatty degeneration of the liver

• Loss of appetite, sadness, irritability, apathy

• Skin problems and hair loss


Genetic Disorders

• Numerous disorders are caused by defective DNA

• Genetic disorders include:• Phenylketonuria

• Sickle cell anemia

• Cystic fibrosis


Hormones that are protein or have protein component


Short polypeptides and small proteins

• Hypothalamus

• Pituitary gland

• Parathyroid glad

• Pancreas (discussed in relation to carbohydrates)


Major Endocrine Organs: Pituitary (Hypophysis)

• Pituitary gland – two-lobed organ that secretes nine major hormones

• Neurohypophysis – posterior lobe (neural tissue) and the infundibulum

• Receives, stores, and releases hormones from the hypothalamus

• Adenohypophysis – anterior lobe, made up of glandular tissue

• Synthesizes and secretes a number of hormones


Pituitary-Hypothalamic Relationships: Posterior Lobe

• Is a down growth of hypothalamic neural tissue• Has a neural connection with the hypothalamus

(hypothalamic-hypophyseal tract)• Nuclei of the hypothalamus synthesize oxytocin and

antidiuretic hormone (ADH)• These hormones are transported to the posterior pituitary

• Stores antidiuretic hormone (ADH) and oxytocin• ADH and oxytocin are released in response to nerve

impulses• Both use PIP-calcium second-messenger mechanism at

their targets



Neurohypophysis hormones

Hormone Target Effect

Antidiuretic hormone (ADH)

Arginine vasopresin (AVP)

Kidneys Reabsorption of water,

elevation of blood volume and pressure (vasoconstriction)

Oxytocin (OT) Uterus, mammary glands (female)

Ductus deferens and prostate gland (male)

Labor contractions, milk ejection

Contractions of ductus deferens and prostate gland

Hormones that are produced in the hypothalamus and stored in the neurohypophysis


Oxytocin

• Stimulates uterine contractions during childbirth by mobilizing Ca2+ through a PIP2-Ca2+ second-messenger system

• Also triggers milk ejection in women producing milk

• Plays a role in sexual arousal and orgasm in males and females


Antidiuretic Hormone (ADH)

• Hypothalamic osmoreceptors respond to changes in the solute concentration of the blood

• What can cause changes in blood concentration?• Body fluids – water

• Electrolytes – in the ECF – mainly sodium


Water

• Water• Essential for life• Amount needed varies with gender, age, body size,

health status, physical activity level, environment• Sources of drinking water: carbonated, mineral,

distilled, purified, tap, bottled

ABC Video Bottled Water


Body Fluids

• Body fluid is the liquid portion of cells and tissues

• Characterized by its ability to move freely and changeably, adapting to the shape of the container that holds it

• About 50−70% of healthy adult body weight

• Intra cellular fluid (ICF) and Intracellular fluid (ECF)


Body Fluids

• Fluid composition of tissue varies by:• Tissue type: lean tissues have higher fluid content

than fat tissues

• Gender: males have more lean tissue and therefore more body fluid than females

• Age: decrease in body water results partly from loss of lean tissue as people age


Sodium functions

• Major positively charged electrolyte in the extracellular fluid

• Blood pressure and acid−base balance

• Nerve impulse transmission

• Muscle contraction and relaxation

• Assists in glucose absorption from the small intestine


Sodium intake

• AI: 1,500 mg, most recommend < 2,300 mg/day

• Processed foods are high in sodium

• High blood pressure more common from high-sodium diets

• Excessive intake may increase urinary calcium excretion in some people, which in turn may increase the risk for bone loss


Too much sodium

• What if you consume too much sodium?• Hypernatremia is an abnormally high blood sodium

concentration

• Patients with congestive heart failure or kidney disease cannot effectively excrete sodium

• Causes high blood volume, edema (swelling), and high blood pressure


Not enough Sodium

• What if you don’t consume enough sodium?• Hyponatremia is an abnormally low blood sodium

level

• From prolonged sweating, vomiting, diarrhea

• Symptoms: headaches, dizziness, fatigue, nausea, vomiting, and muscle cramps

• If untreated: seizures, coma, and death


Functions of Electrolytes

• Electrolytes help regulate fluid balance

• Cell membranes are permeable to water, but not freely permeable to electrolytes

• Water moves by osmosis to areas where the concentration of solute is high (low water concentration)

• This action provides a means to control movement of water into and out of the cells


Water and fluid balance

• What happens if we drink too much water?• Becoming overhydrated is rare• Dilution of blood sodium concentration

• What happens if we don’t drink enough water?• Dehydration• Leading cause of death around the world

Water Balance


Fluid Balance

• Thirst mechanism (hypothalamus) prompts us to drink when it is stimulated by

• Increased concentration of salt and other dissolved substances in the blood

• A reduction in blood volume and blood pressure, such as during profuse sweating, vomiting, diarrhea, or low fluid intake

• Dry mouth and throat from reduced saliva

• ADH signals the kidneys to retain water


Fluid Balance – gain fluids

• Body gains fluids• Water enters the body through beverages

• Some foods have very high water content

• Water from metabolic reactions contributes 10−14% of daily water need


Fluid Balance – fluid loss

• Sensible water loss• Kidneys excrete water as urine

• Sweat during exercise or in hot environment

• Insensible water loss• Skin (not sweating) or lungs during exhalation

• Significant loss• Illness, injury, exercise, high altitude, pregnancy,

breastfeeding, diuretics


Antidiuretic Hormone (ADH) – works when body lacks water or high in sodium

• If solute concentration is high

• Osmoreceptors depolarize and transmit impulses to hypothalamic neurons

• ADH is synthesized and released, inhibiting urine formation

• We will talk about this hormone in details with the urinary system


The anterior lobe

• Is an out pocketing of the oral mucosa from epithelial tissue

• There is no direct neural contact with the hypothalamus• Hormone production is regulated by the

hypothalamus

• Regulatory factors from the hypothalamus arrive

directly to the adenohypophysis through the

hypophyseal portal system


• Portal system - a system of blood vessels that begins and ends in capillaries. The blood, after passing through one capillary bed, is passing through a second capillary network.

• All blood entering the portal system will reach the target cells before returning to the general circulation

Hypophyseal portal system


Pituitary-Hypothalamic Relationships: anterior Lobe• The hypophyseal portal system,

consisting of:

• The primary capillary plexus in the infundibulum

• The hypophyseal portal veins

• The secondary capillary plexus


Activity of the Adenohypophysis is regulated by the hypothalamus

• The hypothalamus sends a chemical stimulus to the anterior pituitary

• Releasing hormones stimulate the synthesis and release of hormones

• Inhibiting hormones shut off the synthesis and release of hormones

• The hormones of the anterior pituitary (7) are called tropic/trophic hormones because they “turn on” other glands or organs


Anterior Pituitary Hormones

• All are proteins

• TSH, ACTH, FSH, and LH are all tropic hormones (regulate the secretory action of other endocrine glands)


Tropic Hormones of Hypothalamus and Anterior Pituitary


Anterior pituitary hormonesRegion

Hormone Target Effect Hypothalamic regulatory hormone

Follicle-stimulating hormone (FSH)

Follicle cells of the ovaries, sustentacular cells of testes

Secretion of estrogen, follicle development, stimulation of sperm maturation

Gonadotropin-releasing hormone (GnRH)

Luteinizing-Hormone (LH)

Follicle cells of ovary

Interstitial cell of testes

Ovulation, formation of corpus luteum, secretion of progesterone

Secretion of testosterone


Prolactin (PRL)

Mammary glands Production of milk Prolactin-releasing factor (PRF)

Prolactin-Inhibiting hormone (PIH)Growth hormone (GH)

All cells Growth, protein synthesis, lipid mobilization and catabolism

Growth-hormone- releasing hormone (GH-RH)

Growth-hormone-inhibiting hormone (GH-IH)














Prolactin (PRL)



















Prolactin (PRL)







Normal Growth in Humans

• Growth is a continuous process that varies in rate, and depends on four factors

1. Growth hormone and several other hormones (for example – hormones that control calcium and glucose)

2. An adequate diet

3. Absence of chronic stress

4. Genetic potential for growth


Growth Hormone (GH) or somatotropin

• GH is an anabolic (tissue-building) hormone• Stimulate most body cells to increase in size and

divide by increasing protein synthesis

• Major target tissues are bone, cartilage and skeletal muscle

• GH release is regulated by• Growth hormone–releasing hormone (GHRH)

• Growth hormone–inhibiting hormone (GHIH) (somatostatin


Effects of Growth Hormone

• Growth Hormone has several distinct cellular effects• Increases plasma glucose

• Increases bone and muscle growth

• Stimulates protein synthesis

• Stimulates liver to secrete IGFs

• IGFs stimulate cartilage growth


Growth Hormone (GH) or somatotropin• The stimulation of growth by GH involves 2

mechanisms:

• The primary one is indirect and more understood:

• GH influence the liver, skeletal muscle, bone, and cartilage to release insulin-like growth factors (IGF)/somatomedins

• The IGF binds to specific receptors on cells and increase the uptake of amino acids and their incorporation into new proteins


Growth Hormone (GH) or somatotropin• Direct effects

• In ET and CT stimulate cell division and differentiation (the subsequent cell growth is mediated by IGF)

• In adipose tissue GH stimulates the breakdown of stored triglycerides by adipocytes and the release of fatty acids to the blood. That promotes the use of fatty acid for energy instead of the use of glucose (glucose-sparing effect)

• What other hormone has glucose-sparing effect?

• cortisol


SomatostatinGHRH

GH

Hypothalamus

Liver andother tissues

Insulin-likegrowth factors

Anteriorpituitary

Circadian rhythmStress and cortisol

Fasting

Bone andtissue growth

Cartilagegrowth

Bloodglucose

Growth Hormone Control Pathway

Figure 23-13


Tissue Growth Requires not only GH and IGF

• GH and IGFs required for protein and cell division

• Thyroid hormone plays permissive role

• Insulin supports tissue growth (how?)

• adequate diet


Anterior pituitary hormones

Region Hormone Target Effect Hypothalamic regulatory hormone

Thyroid-stimulating hormone (TSH/ thyrotropin)

Thyroid gland Secretion of thyroid hormones (T3, T4)

Thyrotropin-releasing hormone (TRH)

Adrenocorticotropic hormone (ACTH)

Adrenal cortex (zona fasciculate)

Secretion of glucocorticoids (cortisole, corticosterone)

Corticotrophin-releasing hormone (CRH)


Thyroid-Stimulating Hormone (Thyrotropin)

• Produced by thyrotrophs of the anterior pituitary• Stimulates the normal development and secretory

activity of the thyroid• Regulation of TSH release

• Stimulated by thyrotropin-releasing hormone (TRH)

• Inhibited by rising blood levels of thyroid hormones that act on the pituitary and hypothalamus

• We will talk about it more in relation to thyroid


Anterior pituitary hormones

Region Hormone Target Effect Hypothalamic regulatory hormone

Thyroid-stimulating hormone (TSH/ thyrotropin)

Thyroid gland Secretion of thyroid hormones (T3, T4)

Thyrotropin-releasing hormone (TRH)

Adrenocorticotropic hormone (ACTH)

Adrenal cortex (zona fasciculate)

Secretion of glucocorticoids (cortisole, corticosterone)

Corticotrophin-releasing hormone (CRH)


Adrenocorticotropic Hormone (Corticotropin)

• Secreted by corticotrophs of the anterior pituitary• Stimulates the adrenal cortex to release

corticosteroids• Regulation of ACTH release

• Triggered by hypothalamic corticotropin-releasing hormone (CRH) in a daily rhythm

• Internal and external factors such as fever, hypoglycemia, and stressors can alter the release of CRH


Adrenal gland - the target organ for the ACTH• Adrenal cortex secrete glucocorticoids in response to ACTH

(Cortisol, hydrocortisone and small amounts of corticosterone)

• Glucocorticoids often called the body’s stress hormones

• While adrenaline is responsible for rapid metabolic responses the glucocorticoids are responsible for long-term stress:

• Accelerate the rates of glucose synthesis

• Promotes lipolysis to supply energy

• Clucocorticoids also have anti-inflammatory effect – inhibit the activities of WBC


Immunesystem Liver

Functionsuppressed

Gluco-neogenesis

Proteincatabolism

Muscle Adiposetissue

Lipolysis

CRH

ACTH

Cortisol

Hypothalamus

Anteriorpituitary

Adrenalcortex

Circadianrhythm

Stress

long

-loop

neg

ativ

e fe

edba

ck

Pathway For the Control of Cortisol Secretion

Figure 23-3


Protein hormones that control calcium

• Thyroid gland – calcitonin

• Parathyroid gland - PTH


Parathyroid Glands

• Tiny glands embedded in the posterior aspect of the thyroid

• Contain oxyphil cells (function unknown) and chief cells that secrete parathyroid hormone (PTH) or parathormone

• PTH—most important hormone in Ca2+ homeostasis


• PTH release increases Ca2+ in the blood as it:• Stimulates osteoclasts to digest bone matrix

• Enhances the reabsorption of Ca2+ and the secretion of phosphate by the kidneys

• Increases absorption of Ca2+ by intestinal mucosal

• Rising Ca2+ in the blood inhibits PTH release

• The antagonist is the Calcitonin secreted by the thyroid gland

Effects of Parathyroid Hormone


PTH Control of Calcium Balance

Figure 23-20

PlasmaCa2+

Vitamin D

Endogenousprecursors

Diet(fortified milk, fish

oil, egg yolks)

Liver

25-hydroxycholecalciferol(25(OH)D3)

Calcitriol(1,25-dihydroxycholecalciferol)

Bone,distal nephron, and intestine

Kidney

PlasmaCa2+

Parathyroidhormone

Sunlighton skin


The thyroid gland on the anterior side of the neck. The thyroid gland has a right lobe and a left lobe connected by a narrow isthmus

http://webanatomy.net/histology/endocrine_histology.htm

Thyroid Gland


• A peptide hormone produced by the parafollicular, or C cells

• Lowers blood calcium levels

• Antagonist to parathyroid hormone (PTH)

Calcitonin


• Calcitonin targets the skeleton, where it:• Inhibits osteoclast activity (and thus bone

resorption) and release of calcium from the bone matrix

• Stimulates calcium uptake and incorporation into the bone matrix

• Regulated by a humoral (calcium ion concentration in the blood) negative feedback mechanism

Calcitonin


Calcium Balance in the Body

• Total body calcium = intake output

• Total body calcium is divided into three pools• Extracellular calcium (0.1% of total)

• Intracellular calcium (0.9% of total)

• Calcium in bone matrix (99% of total)

• Ca2+ ions in the extracellular fluid move freely in and out of plasma

• Extracellular fluid calcium is carefully regulated


Calcium

• Calcium absorption • Is enhanced in an acid environment

• Requires 1,25-dihydroxyvitamin D

Calcium Metabolism


Functions of Calcium

• Provides structure for bones and teeth

• Assists with acid−base balance

• Transmission of nerve impulses

• Assists in muscle contraction

• Maintains healthy blood pressure

• Initiates blood clotting

• Regulates hormones and enzymes



Calcium Intake

• Adequate Intake (AI) varies with age and gender: 1,000 mg to 1,300 mg/day

• Upper Limit (UL): 2,500 mg

• Bioavailability: body’s ability to absorb and utilize calcium depends on• Individual’s age and calcium need

• Dietary calcium and vitamin D

• Binding factors (phytates, oxalates) in foods


Sources of Calcium

• Excellent sources include milk products • Skim milk, low-fat cheese, nonfat yogurt

• Other good sources include • Green leafy vegetables (kale, collard greens,

broccoli, and cabbage are low in oxalates)

• Fortified foods (orange juice, soy milk)

• Fish with edible bones (sardines, salmon)


Excess Dietary Calcium

• Excess dietary calcium is excreted in feces

• Mineral imbalances from supplements

• Hypercalcemia (high blood calcium)• Cause: cancer or parathyroid hormone (PTH)

overproduction

• Symptoms: fatigue, appetite loss, constipation, mental confusion, calcium deposits in soft tissues


Calcium Deficiency

• Osteoporosis from long-term calcium deficiency

• Hypocalcemia (low blood calcium) • Causes: kidney disease, vitamin D deficiency, or

diseases that inhibit the production of PTH

• Symptoms: muscle spasms and convulsions


• Thyroid hormone – major metabolic hormone

• Consists of two related iodine-containing compounds

• T4 – thyroxine; has two tyrosine molecules plus four bound iodine atoms

• T3 – triiodothyronine; has two tyrosines with three bound iodine atoms

Thyroid Hormone


Synthesis of Thyroid Hormone

• Thyroglobulin is synthesized by the follicular cells and released into the lumen

• Iodides (I–) are actively taken into the cell by membrane carrier proteins

• The iodide ions diffuse to the apical surface of the cells (these cells are facing towards…?), oxidized to iodine (I2) by the enzyme thyroid peroxidase and released to the colloid.

• Iodine attaches to tyrosine in the thyrogobulin, forming T1 (monoiodotyrosine, or MIT), and T2 (diiodotyrosine, or DIT)


Synthesis of Thyroid Hormone

• Iodinated tyrosines link together to form T3 and T4

• Coupling reaction

MIT + DIT T3 / triiodothyronine

DIT + DIT T4 / thyroxin (tetraiodothyronine)

• The colloid is then endocytosed and combined with a lysosome, where T3 (10%) and T4 (90%) are cleaved and diffuse into the bloodstream

• 75% of the T4 and 70% of the T3 are transported attached to thyroid-binding protein (TBGs) and the rest to a special albumin


Thyroid Hormones are Made from Iodine and Tyrosine

Figure 23-8


Thyroid Hormone and target cells

• Thyroid hormones influence almost every cell of the body

• Inside the cells they bind to receptors in one of 3 locations:

• In the cytoplasm – storage of thyroid hormones to be released if the intracellular levels decrease

• On the mitochondria surface – increase rate of ATP production

• In the nucleus – activate genes that control the synthesis of enzymes that involve with energy production and utilization (for example increase of production of sodium-potassim ATPase that uses ATP)


Other effects of Thyroid Hormone

• TH is also concerned with:• Activate genes that code for enzymes that are

involved in glycolysis (Glucose oxidation)• Increasing metabolic rate of the cells• Increase heat production (calorigenic effect)

• Although the major thyroid hormone that is being produced is the T4 (90%) T3 is the one responsible for the TH effects

• Enzymes in the kidneys, liver and other tissues convert T4 to T3

Copyright © 2010 Pearson Education, Inc. Figure 16.7

Hypothalamus

Anterior pituitary

Thyroid gland

Thyroidhormones

TSH

TRH

Target cellsStimulatesInhibits


TSH

T4, T3

T4 T3

Hypothalamus

Anteriorpituitary

Thyroidgland

Systemicmetabolic

effects

Stimulus

Integrating center

Efferent pathway

Effector

Systemic response

TRH

Tonic release

KEY

Negative feedback

Thyroid Hormone Control Pathway

Figure 23-11


Adrenal Medulla

• Secrete epinephrine and norepinephrine

• Epinephrine is the more potent stimulator of the heart and metabolic activities

• Norepinephrine is more influential on peripheral vasoconstriction and blood pressure


Epinephrine and Norepinephrine• increase in the rate and strength of the heartbeat resulting in increased

blood pressure;

• Increase skeletal muscle strength and endurance by increasing glucose breakdown

• Increases availability of fatty acids from adipose tissue

• Induce blood shunted from the skin and viscera to the skeletal muscles, coronary arteries, liver, and brain;

• Cause rise in blood sugar;

• Trigger bronchi to dilate to assists in pulmonary ventilation;

• pupils dilate;

• Reduce clotting time of the blood;

• increased ACTH secretion from the anterior lobe of the pituitary.

• All of these effects prepare the body to take immediate action


What Are Lipids?

• Three types of lipids are found in foods and in body cells and tissues:• Triglycerides

• Phospholipids

• Sterols


Triglycerides

• Triglycerides (triacylglycerides) contain:• Three fatty acid molecules

• One glycerol molecule


Triglycerides

• Fatty acids are classified by: • Carbon chain length

• Saturation level

• Shape


Triglycerides: Chain Length

• Short-, medium-, or long-chain fatty acids

• Carbons can be numbered• Carboxyl end (COOH): -carbon (alpha—first)

• Methyl end (CH3): Ω-carbon (omega—last)

• Determines method of lipid digestion, absorption, metabolism, and use


Triglycerides: Saturation

• Saturated fatty acids have hydrogen atoms surrounding every carbon in the chain

• Monounsaturated fatty acids lack one hydrogen atom (one double bond)

• Polyunsaturated fatty acids have more than one double bond


Triglycerides: Shape

• Determined by the saturation of the carbon chains

• Saturated fatty acids pack tightly together and are solid at room temperature• Animal fats, butter, and lard are high in saturated

fatty acids


Triglycerides: Shape

• Unsaturated fatty acids do not stack together well and are more liquid at room temperature

• Hydrogen atoms at the unsaturated part can be arranged in different positions:• Cis: same side of the carbon chain

• Trans: opposite sides of the chain


Triglycerides

• Hydrogenation: hydrogen atoms are added to unsaturated fatty acids

• Make oils more solid and more saturated

• Create trans fatty acids

• Reduce oxidation; resist rancidity

• Increase risk of cardiovascular disease


Triglycerides

• Essential fatty acids: cannot be made by the body and must be obtained from food

• Linoleic acid (omega-6 fatty acid)• Found in vegetable and nut oils

• Alpha-linolenic acid (omega-3 fatty acid)• Found in vegetables, soy, flaxseeds, walnuts


Triglycerides

• Omega-3 fatty acids found in fish and fish oil• Eicosapentaenoic acid (EPA)

• Docosahexaenoic acid (DHA)

• Reduce risk of heart disease• Stimulate prostaglandins and thromboxanes that

reduce inflammatory responses

• Reduce blood clotting and plasma triglycerides


Phospholipids

• Phospholipids contain• Glycerol backbone, two fatty acids, phosphate

• Soluble in water

• Transport fat in the bloodstream

• Manufactured in our bodies (not required)


Sterols

• Sterols contain multiple rings of carbon atoms

• Plant sterols appear to block the absorption of dietary cholesterol

• Cholesterol is made in our bodies and therefore is not necessary in the diet• Sex hormones, vitamin D, bile


The Roles of Fat

• 9 kcal per gram

• Major fuel at rest

• Endurance exercise

• Stored energy

• Essential fatty acids

• Fat-soluble vitamins

• Regulates cell function

• Maintains membrane

• Protects the body

• Provides flavors and textures of foods

• Helps us feel satiated


How Much Fat?

• Acceptable Macronutrient Distribution Range (AMDR) for fat: 20−35% of calories

• Minimize saturated and trans fatty acid intake to lower risk of heart disease

• Active people may need more energy from carbohydrates and can reduce their fat intake to 20−25% of total calories


How Much Fat?

• Dietary Reference Intakes (DRIs) set for essential fatty acids• Linoleic acid: AMDR of 5−10% of energy

• Alpha-linolenic acid: 0.6−1.2% of energy

• 5:1 to 10:1 ratio of linolenic:alpha-linolenic acid

• Saturated fat: less than 7% of energy• Trans fats: reduced to the absolute minimum


Food Sources of Fat

• Visible fats• Fats we add to foods

• Butter, cream, mayonnaise, salad dressings

• Invisible fats• Fats hidden within foods

• Occur naturally or added during processing

• Baked goods, dairy, meats, fast foods


Food Sources of Fat

• Beneficial fats• Omega-3 fatty acids may be low in diets• Fish, walnuts, soy, canola, flaxseed

• Switching to more healthful fats without increasing total fat intake• Use olive or canola oil in place of butter or

margarine• Select low-fat or nonfat dairy products


Food Sources of Fat

• Fat replacers• Used to lower fat content of foods

• Found in chips, cakes, cookies

• May cause GI side effects in large amounts

• Example: olestra (Olean)

Fats in Food

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What Are Proteins?