hnsc 1210 unit 5 - fats, oils, phospholipids, and sterols

how to fats play an important role in health?

• provide us with energy stores

• insulating our bodies from extreme temperature

fats importance in food

• providing texture and taste properties

lipids

• organic compounds soluble in organic solvent but not water

• term fat is more familiar than lipids

what is fat to the body

• body’s chief storage space for excess food energy

• helps us survive times of famine

• fat cells expand to indefinitely store excess energy

• provides us with large amount of energy to perform much of the body’s work

fat tissue

• does more than store fat

• secretes hormones that help regulate appetite and influences other body function’s

fat serves many other important factors in our body:

• pads the vital internal organs, acting as shock absorbers

• insulates the body from temperature extremes

• is part of cell membranes

• can be converted to other compounds (hormones, bile, vitamin D) as needed

fats in food serve important functions

• provides essential nutrients (e.g essential fatty acids, fat soluble vitamins)

• provides concentrated source of energy & raw materials for making needed products

• provide tastes, smell, and a tender texture to foods

• stimulates appetite and contribute to feelings of fullness

the usefulness of fats

Recommendations for dietary fats

• DRI: 20-35% from dietary fats

• <10% energy from saturated fats

• lowering saturated and trans fat intake helps to reduce blood cholesterol and thus heart disease

• unsaturated fat reduced blood clotting

polyunsaturated fatty acids - DRI

• 5-10% energy from linoleic acid (omega-6)

• 0.6-1.2% energy from linolenic acid (omega-3)

cholesterol

• DRI: minimize intake within context of healthy diet

• only about 1/3 populations respond to lowering dietary cholesterol intake: limit eggs, shellfish, liver, etc. but these are nutritious foods

classification of lipids

1. triglycerides

2. phospholipids

3. sterols

triglycerides

• when people speak of fat, they are usually talking about triglycerides.

• major form of lipid found in the body and in food

• made of 3 fatty acids and a glycerol backbone

triglycerides formation

• most fatty acids are incorporated intro triglycerides, very few are found free in the body or in foods

• glycerol is an organic compound 3-carbons long

• each species makes its own characteristic types of triglycerides

• fats in the diet can affect the type of triglycerides made because dietary fats are incorporated into triglycerides in the body

the fatty acids are classified by

a. chain length

• short:< 10 carbons

• medium:12-14 carbons

• long:> 16 carbons

• Shorter chain fatty acids tend to be softer and melt more readily at room temperature.

b. degree of saturation (double bonds, C=C)

three types of fatty acids

• fatty acids can also be classified by degree os saturation

• saturation refers to the number of hydrogen atoms a fatty acids chain is holding

• the more hydrogen atoms attached, the more saturated the fatty acid is

unsaturated

• no hydrogen attached

• double bond occurs

• especially in fatty acids of plants and fish

saturated fatty acid

• no points of unsaturated

• tend to be solid at room temp.

• animal fats (e.g butter, lard), tropical oils (e.g coconut oil, palm oil)

monounsaturated fatty acid (MUFA)

• 1 point of unsaturation

• vegetable oils (e.g canola oil, olive oil)

polyunsaturated fatty acids (PUFA)

• 2 or more points of unsaturation

• tends to be liquid oils at room temperature

• vegetable oil and fish oil

fatty acid composition of common foods

degree of saturation affects what in foods

• temperature at which fat melts

• more unsaturated the fat, the more liquid it tends to be at room temperature

• animal fats are generally the most saturated and the hardest

researchers report benefit from replacing saturated and trans fat with mono and or poly unsaturated fats

• saturated fats can increase your ‘bad’ blood cholesterol levels (LDL)

• trans fat can increase your ‘bad cholesterol level (LDL) an decreased ‘good’ blood cholesterol (HDL), may increase risk or heart disease

effects of processing on unsaturated fats - margarines - A. hydrogenation

• process where hydrogen is added to unsaturated fatty acids, to make a ore solid fat. e.g turning vegetable oil into hard margarine

process of hydrogenation

• hydrogen attaches at the points of unsaturation (double bond) and the fatty acid becomes saturated (no longer has a double bond). makes fatty acid more solid at room temperature and increases shelf life

point of unsaturation are more vulnerable to oxidation

• which is when oxygen mixes with fat, causing it to go rancid or taste “off”

• store cooking oil in tight sealed containers

• therefore, hydrogenated fats are more resistant to oxidation (as it no longer has points of unsaturation). more resistant to breakdown from high cooking temperatures and will have a longer shelf life

• hydrogenated fats also have a higher smoking point and are more suitable for frying

when the hydrogen is added, some of the unsaturated fatty acids become…

• more saturated and the oils hardens and becomes easier to spread

• once hydrogenated the unsaturated fats lose their health benefits

problems with hydrogenation

• affects not only the fatty acids in fat but the vitamins as well (ex. decrease vitamin K in body)

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when unsaturated fatty acids are hydrogenated

• some change shape instead of becoming saturated

• creates unusually shaped unsaturated fatty acids look like saturated fatty acids

• fatty acids referred to as trans fatty acids

• consuming trans fats poses a risk to heart health and arteries by raising levels of bad cholesterol, and lowering levels of good cholesterol

• also produced inflammation

• DRI recommends consuming little trans fats as possible

health canada 2018

• banned the use of partially hydrogenated oils in foods sold in candida, which as significantly reduced trans fats intake

b. blending different oils to produce “soft margarine”

• can make margins to avoid creating trans fatty acids through a process of blending oils together.

• creates soft, non-hydrogenated margarine (e.g Becel)

• this product will not remain solid at room temp., however as the fats in this product are unsaturated

classification of lipids

• phospholipids

• sterols

phospholipids

• Glycerol backbone + 2 fatty acids + phosphorus containing molecule

• Water and fat soluble

• Can serve as emulsifier

• Examples - Lecithin is a phospholipid found in egg yolk. In mayonnaise, the lecithin blends the vinegar with the oil and keeps it from separating. Lecithin has no special health promoting abilities

• the phosphorus molecule ales the phospholipid soluble in water

lectin supplements

• available on the market that claim to lower blood cholesterol values, but these claims are not substantiated.

• We can make all the lecithin our body needs (i.e., it is not essential).

emsulsifer

• mixes with fat and water; allows fat to stay dispersed in water

cell membrane structures

• phospholipids play a key role

sterols

• large molecules consisting of interconnecting rings of carbon atoms, with side chain of carbon, hydrogen, and oxygen

• cholesterol is an example of a sterol. cholesterol is important in the structure of cell membranes, therefore is part of every cell ad is necessary for optimal body function

whats good about cholesterol?

Cholesterol is necessary to make:

1. Bile – important for fat digestion

2. Vitamin D

3. Sex hormones, e.g., estrogen, testosterone

4. Stress hormones, e.g., epinephrine

whats bad about cholesterol

• forms major part of the plaques that narrow the arteries in antherosclerosis, an underlying cause of heart attacks and strokes

• cholesterol is made by the body so is therefore, not essential

lipid digestion & absorption - in the stomach

• fat separated from the water chyme and floats on top of it.

• fat does not mix with watery stomach contents, little fat digestion occurs in stomach

lipid digestion & absorption - in the small intestine

• bile works to emulsify the fat with water digestive fluids because one end attracts and hold fats, while the other end is attracted to and held by water

• by the time fat enters SI, gallbladder already squirted stored bile. bile them emulsifies and suspends the fat particles so that fat-digesting enzymes from the pancreas can split them into smaller particles for absorption

process of lipid digestion and absorption

1. mouth and stomach: little fat digestion

2. small intestine: digestive enzymes break down fat, bile emulsifies fat. enzymes cleave triglycerides into free fatty acids, glycerol, and monoglycerides

3. intestinal lining: parts absorbed. glycerol and short-chain fatty acid directly enters blood stream

4. 4. cells of intestinal lining: convert large lipid fragments (mono) and long-chain fatty acids back into triglycerides and combine with protein forming chylomicrons that travel in lymph

5. large intestine: small amount of cholesterol trapped in fibre and exits with poop

if gall bladder was removed

• liver stops producing bile

• bile continuously released into SI in small amounts

• system can only handle small amounts of fat at a time

once intestinal contents are emulsified

• fat spitting enzymes work on triglycerides to free fatty acids from glycerol backbone

• free fatty acids, glycerol, monoglycerides cling together in balls surrounded by bile.

• bile helps move fat across the watery layer of mucus coats the absorption lining

at the lining of the digestive tract

• small lipid particles enter directly into the capillary network and travel unassisted to the liver.

• large lipid molecules are re-formed into triglycerides in the intestinal cells and are packaged together with proteins and phospholipids to form chylomicrons, which can safely travel in the watery blood.

lipid transport - lipoproteins serve to move lipids in blood and lymph

1. chylomicrons

2. very low density lipoprotein (VLDL)

3. low density lipoprotein (LDL)

4. high density lipoprotein (HDL)

LDL are larger, lighter, and richer in cholesterol while HDL are smaller, denser and packaged with more protein

chylomicrons

• clusters formed when dietary lipids combine with carrier proteins in the cells of the intestinal tract. They transport dietary fat through the water body fluids to the liver and other tissues.

very low density lipoprotein (VLDL)

• transport triglycerides and other lipids from the

  liver to various tissues in the body for use.

low density lipoprotein (LDL)

• transport cholesterol and other lipids from the liver to other tissues (muscle, fat). LDL are made from VLDL after they have donated most of their triglycerides to body cells.

high density lipoprotein (HDL)

• are critical in the process of carrying cholesterol away from body cells to the liver for disposal.

lipid metabolism

When the body starts to run out of fuel from food, it turns to body stores

• Fatty acids are used for energy by many organs: typical fuel mix at rest is 50/50 carbohydrate/lipid for liver and muscle

• Any time fat is broken down for energy, carbohydrate must be available

• Otherwise ketones develop (products of incomplete fat breakdown) and build up in blood and urine

blood cholesterol & cardiovascular disease

• High LDL levels increases risk for heart disease.

• High HDL levels are associated with a low risk.

major risk factors for heart disease

• High LDL cholesterol

• Low HDL cholesterol

• High blood pressure (hypertension)

• Diabetes

• Obesity

• Physical inactivity

• Smoking

• A diet high in saturated and trans fats, and low in vegetables, fruits and whole grains.

cholesterol

• important sterol in the structure of brain and nerve cells

• part of every cell & necessary for functioning body

• 75-80% of our blood cholesterol is synthesized de novo (in the body)

• though that sat fat trigger the body to produce cholesterol and trans fat may also play a role

limiting cholesterol-containing foods

• does not pose risk for increased levels of blood cholesterol (in most people)

• body adapts to slow it’s own cholesterol synthesis when diet provide greater amounts

• some people have genetic tendency towards high blood cholesterol and must limit foods that are high in fat (sat and trans)

• may require medicine to reduce the de novo synthesis of cholestrol

• food cholesterol has less of an impact on blood cholesterol than most people think

dietary cholesterol

• plays lesser role than sat and trans fat in cardiovascular disease

• ~60% exhibit little increase in blood cholesterol with high cholesterol diet

• plays smaller but still significant contribution to blood cholesterol values

• many foods higher in dietary cholesterol are also nutritious foods (I.e eggs, meat, cheese, animal derived foods) - don’t want to completely eliminate from diet

• therefore moderation, not elimination is key

atherosclerosis

• most common form of heart disease

• Characterized by plaque development along artery walls

• Starts with accumulation of soft fatty streaks, especially at points where the arteries branch.

• Soft fatty streaks gradually enlarge and harden to form plaque

• Damage the artery walls by narrowing the passage through them and making them inelastic.

plaques

mounds of lipids materials mixed with smooth muscle cells and calcium

saturated fatty acids and cvd risk

• replacing saturated fat with unsaturated fat reduced CVD risk. the reverse is also true: increasing saturated fat intakes increases the risk

atherosclerosis develops through a complex inflammatory response to tissue damage

• White blood cells (macrophages) are sent to the site of damage

• LDL particles become trapped in blood vessel walls

• Free radicals oxidize the LDL

• Macrophages engulf oxidized LDL and become foam cells (filled with lipid) – these foam cells become a source of oxidation

• Muscle cells in artery walls proliferate to try to heal damage

• Muscle cells combine with foam cells

• Fibrous plaques form (scar tissue)

problems associated with atherosclerosis

• narrowing of arteries causes increase in pressure from blood flow

• arteries become hardened and narrow by plaques - increased blood pressure

• hypertension and atherosclerosis work together to worsen cardiovascular disease

• artery walls hardened and narrow face stressed by high internal pressure

• heart beat raise the blood pressure

• fail to let blood flow freely through the kidneys (which control blood pressure)

• kidneys sense low bp and react through low bp

atherosclerosis begins in early life

• many people have well developed plaques by age 30

• diet plays a role in reducing the risk of for plaque development

• an atherogenic diet (high internal pressure heart sat fat, trans fat, cholesterol) increases LDL cholesterol whereas a well chosen diet ( low internal pressure heart fat and high in antioxidant nutrients) can lower CVD risk

increase HDL

• maintain a healthy body weight

• engage in regular physical activity

• quit smoking

lower ldl

• maintain a healthy body weight

• increase intake of soluble fibre

• reduce intake of saturated and trans fat

food fat, sat fat, & calories

essential fatty acids (EFA)

• fatty acids the body CANNOT make itself, must get from foods

• 2 types:

1. Linoleic acid (e.g omega-6 fatty acids)

2. Linolenic acid (e.g omega-3 fatty acids)

• EFAs can be used by body to make eicosanoids

eicosanoids

• biologically active compounds that regulate body functions

how do eicosanoids act somewhat like hormones

• they effect muscle relaxation and contraction, blood vessel dilation & constriction, blood clot formation, blood lipid regulation, and immune response to injury & infection

EFAs have many functions

• provide raw material for eicosanoids

• serve as structural and function parts of cell membranes

• contribute lipids to the brain and nerves

• promote normal health growth and vision

• assist in gene regulation

• maintain outer structures of the skin thus protecting against water loss

• help regulate genetic activities affecting metabolism

• support immune cell function

• research is showing EFAs benefit to improving cognitive abilities in infants

omega-6 (n-6) fatty acids

• Omega-6 fatty acids get their name because of a double carbon bond 6 carbons from the end of its chain. Linoleic acid is an example of an omega-6 fatty acid.

• DRI recommendation: 5-10% energy from n-6 fatty acids

• Sources: vegetable oils, seeds, nuts, whole grain products

food sources of omega-6 and omega-3 fatty acids

omega-3 (n-3) fatty acids

• Omega-3 fatty acids get their name because of a double carbon bond 3 carbons from the end of its chain. Linolenic acid is an example of an omega-3 fatty acid.

• DRI recommendation: 0.6-1.2% energy from n-3 fatty acids

• Sources: flaxseed, flaxseed oil, canola oil, fish (especially deep sea fish)

• research has shown that higher intake of omega-3 FA’s can often improve the health of the heart

three main types of omega-3 fatty acids

1. ALA (alphalinolenic acid) – from plant sources

2. EPA (eicosapentaenoic acid)– from fish sources

3. DHA (docosahexaenoic acid) – from fish sources

when given linolenic acid, te body can make other omega-3 FA’s

• two specific omega-3 FA’s are receiving great interest from research -EPA and DHA

• body only makes limited amounts of omega-3

• found abundantly in oils of certain fish (deep sea, fatty fish like salmon, char, mackerel, herring, cod, etc.)

recommended to eat fish

• high fat diets, had such low rates of heart disease

• high marine based diet with abundance of fish and an abundance of these heart healthy fatty acids

• EPA/DHA content tend to be higher in grilled, baked or broiled fish

• fish used for frying in a fast food setting and in frozen products (ex. fish stick), tend to be species with lower DHA/EPA content

problem with supplements

• it is preferred to get your EPA/DHA from food rather than supplements at this point

• studies show greater benefit from the DHA/EPA in foods

• fish oil supplements may raise LDL cholesterol levels in some individuals, and high intakes of omega-3’s (>3g/day) can increase bleeding time, interfere with wound healing and suppress immune function

• supplements also lack other nutrients that fish provides (protein and minerals such as iodine, selenium)

fish oil supplements

• may be made by skin and livers of fish, increasing contamination from pesticides, industrial contaminants and heavy minerals such as mercury

• unless pill is refined to eliminate these, contaminants will become further concentrated in the pill

• important to chose reputable brand

• naturally contain high levels of two of the most potentially toxic vitamins, A&D, although many supplements companies remove these vitamins from their supplements

• little is known about long-term effects of fish oil supplements

potential benefits of EPA/DHA

• Heart disease (supported by most studies)

• Mental health and cognition

• Cancer (research promising, but need further evidence)

potential health benefits of fish oils

consumer’s guide: weighing seafood’s risks and benefits

• need to know more about mercury in heart disease

• people with pre-existing heart disease should choose fish species that have low mercury level to support their fish intake

• fish that are more heavily contaminated tend to be larger fish that prey on smaller fish because the mercury builds up in their system

fish heavily contained with mercury

• Shark

• Swordfish

• King mackerel

• Fresh tuna steak (Albacore)

• Tilefish

fish/seafood lower in mercury

• Shrimp

• Canned light tuna - Canned albacore (“white”) tuna contains more mercury than light tuna

• Salmon

• Pollock

• Catfish

fish recommendations

consume a variety of fish

• minimize exposure to any particular toxin that may accumulate in a particular fish species

pregnant women and children

• most sensitive to the side effects of mercury

• safely benefit from safer fish varieties within recommended limits

recommended weekly fish consumption

• general population - 150g per week (eqv. to 1 cup)

• specified women - 150g per week

• children 5-11 years - 125 g per week

• children 1-4 75g per week

fats in the diet

• small changes in our food choices can drastically reduce our intake of dietary fat

fats in the diet: ways to reduce saturated fat intake

• watch how much fat you add to food (e.g salad dressing, mayo, butter/margarine, etc.)

tips for dining our at restaurant

• Watch the amount of sauces, salad dressings, oils and margarine that you add to food. Ask for sauces and salad dressings on the side at restaurants

• Choose grilled, broiled, baked, stir-fried or poached foods instead of deep fried or fried foods.

• Many restaurants have half portions of their meals. Choose these for portion control, or ask that the server only bring out half of the meal, and package up the other half for you to take home.

• Share with a friend or family member. You do not have to give up all your favourite foods. Control portion size by sharing a higher fat entrée or high calorie dessert.

• Avoid empty calorie beverages. Choose water or diet soft drinks instead of juice, regular soft drinks or iced tea.

artificial fats

• Zero-energy fat replacers that are chemically synthesized to mimic the sensory and cooking qualities of naturally occurring fats, but are totally or partially resistant to digestion.

• some products contain artificial fats while others use conventional ingredients in unconventional ways, or alter preparation methods to reduce fat and calories

alter preparation methods to reduce fat & calories

• adding water or whip air into foods

• adding non-fat milk to creamy foods

• using lean products instead of high fat

• baking rather than fry foods.

• common food ingredients such as fibre, sugar/carbs, and proteins can take the place of fats - even tho provide calories, provide far less calories

to gain FDA consent to use fat replacers

• proven that little energy is contributed

• non-toxic

• doesn’t build p in body tissues

• doesn’t rob the body of essential nutrients

controversy 5: is butter really back? the lipid guidelines debate

Several problems can accompany low-fat diets:

• It can be difficult to maintain such a diet

• Such diets are not necessarily low-calorie diets (many people with heart disease are overweight and need to reduce body weight)

• Diets high in carbohydrates (especially refined sugars) but low in fiber, may cause blood triglycerides to rise - unknown effects on heart health

• Taken to an extreme, a low-fat diet may exclude nutritious foods that provide the essential fatty acids, phytochemicals, vitamins, and minerals. For example, fatty fish, nuts, seeds, vegetable oils contain beneficial fats, but are higher fat foods

seven countries study of healthy people

evidence around the world has led researches to question whether ow-fat diets are the best way to promote health

To summarize some of the results found

• Death rates from heart disease were strongly associated with diets high in saturated fats

• Death rates from heart disease were only weakly associated with diets high in total fat

• Finland & the Greek island of Crete were the two countries with the highest fat intake

o Finland had the highest rate of death from heart disease

o Crete had the lowest rate of death from heart disease

Relative to Finland, people in Crete had a diet

• High in olive oil

• Low in saturated fat (Less than 10% of calories)

findings indicate that it isn’t total fat intake to blame for higher rates of heart disease, rather the type of fat consumed

dietary guidelines

• Health Canada and the Dietary Guidelines 2015 concluded that research supports that saturated fat is of public health concern

the debate

Some experts argue that saturated fat may not be as great of a risk because:

• lack of biological mechanism

• influence of a person's genetic inheritance on handling of fatty acids

• differing actions of saturate fatty acids

non-hydrogenated margarine

• unsaturated fat - more heart healthy choice

• non-hydrogenated margarines containing sterols or stanol esters (plant sterols) - reduction in cholesterol when used on daily bases

• sterol esters act like a drug in the body and may have undesirable effects

• some people cannot clear sterols esters from their blood and high blood concentrations may be linked to early signs of heart disease

• may lower blood concentrations of carotenoids such as lycopene

butter

• contains vaccenic acid - converted to conjugated linoleic acid (CLA) in the body

• animals studies shown CLA to inhibit cancers, lower cholesterol, improve diabetes, improve immune function, potentially lower body fat

• other studied have shown no effect or even negative effects so research on humans has been limited

hard stick margarine/ vegetable shortening

• som contain large amounts of trans fat - up to 40% by weight

• some brand reformulating their products to remove trans fat

non-hydrogenated margarine or butter?

• taste

• same calories and fat per serving

• moderation is important

• moderate intake of butter in healthy people ha negligible effects on health.

• hard stick margarine and vegetables shortening contain rand fats should be avoided

research on dietary fats effect disease risk continues, eating pattern that is associated wth lower chronic disease risk