NTRN 201 | Ch. 5 - Lipids: Fats, Oils, Phospholipids, + Sterols

• LO 5.1 Describe the usefulness of lipids in the body and in food. • LO 5.2 Compare the physical and chemical properties and functions of the three categories of lipids. • LO 5.3 Describe the processes of digestion, absorption, and transportation of lipids in the body. • LO 5.4 Describe how fats are stored and used by the body. • LO 5.5 State the significance of blood lipoproteins and dietary fats to health. • LO 5.6 Summarize the functions of essential fatty acids. • LO 5.7 Outline the process of hydrogenation and its effects on health. • LO 5.8 Identify sources of fats among the food groups. • LO 5.9 Describe ways to reduce saturated fats in an average diet. • LO 5.10 Discuss both sides of the scientific debate about current lipid guidelines.

Lipids

a family of compounds that contain C, H, + O and don’t dissolve in water; includes triglycerides, phospholipids, + sterols

AMDR for fats

20-35% of total cal/day

triglycerides

the most common type of lipid in food + in the body

what’re the uses of fats in the body?

• energy fuel (provides 80-90% of resting body’s energy + energy to fuel muscles)

• energy stores

• emergency reserve

• padding (protects internal organs)

• insulation

• cell membranes

• raw materials (converted to hormones, bile, vitamin D, etc)

• signaling

what’re the uses of fats in food?

• nutrients (has essential fatty acids, fat-soluble vitamins, + other needed compounds)

• transport (carries fat-soluble vitamin A, D, E, K + phytochemicals)

• energy

• sensory appeal (contributes to aroma, flavor, + physical sensation)

• appetite stimulation

• texture (crisp + tender)

  • satiety (fullness)

basic structure of a fatty acid

long chains of carbon atoms linked together, surrounded by hydrogen atoms

how can carbon chains vary?

in number of carbons, extent of saturation w/ hydrogen, shape (straight or bent)

long-chain fatty acids

12+ carbons; in beef, pork, lamb, most plant oils

medium-chain fatty acids

6-10 carbons; coconut + palm oils

short-chain fatty acids

fewer than 6 carbons; 3% of fat in butter

saturated fatty acid

all bonds between carbons r single; filled w/ hydrogen

monosaturated fatty acid

one double bond is found in the chain; missing 2 hydrogens in the chain

polyunsaturated fatty acid

at least 2 double bonds in the chain; hydrogens missing at these double bonds

monosaturated fatty acid (trans double bond)

one double bond is found in the chain; the hydrogens are found on opposite sides of the carbon chain

saturated and trans fatty acids have ___ chains

straight

unsaturated cis fatty acids have a ___ chain

bent

unsaturated cis fatty acids

hydrogens found on same side of carbon chain; oils from nuts + seeds

hydrogenation

the process that adds hydrogen to carbon chain of unsaturated fats, making the chain more saturated, solid, + straight; creates trans fatty acids

what are the two systems of naming fatty acids based on?

the number of carbons + the location of double bonds

omega system

one of the naming systems for fatty acids where the first double bond closest to the methyl end occurs

delta system

one of the naming systems for fatty acids where the first double bond closest to the carboxyl end occurs

essential fatty acids (EFAs)

• cannot be made by the body

• alpha-linolenic acid (Omega 3) —> make EPA + DHA

• linoleic acid (Omega-6) —> make ARA

eicosanoids

prostaglandins, prostacyclins, thromboxanes, leukotrienes, lipoxins; made from the essential fatty acids

triglycerides

• 3 fatty acids attached to a glycerol backbone

  • fatty acids can be the same or different

esterification

the process of attaching fatty acids to glycerol; in the process, releasing 1 water molecule

hydrolysis

the reaction that releases fatty acids from glycerol called free fatty acids

diglyceride

triglyceride that lost a fatty acid

monoglyceride

triglyceride that lost 2 fatty acids

re-esterification

process of reattaching a fatty acid to glycerol

food sources of triglycerides (most food)

• animal + vegetable fat

• bakery items, snack foods, dairy desserts

• olive oil (monounsaturated fat)

foods w/ little or no fat

• fat-free milk + yogurt, breakfast cereal, + yeast breads

• fruits + vegetables (excepted coconuts + avocados)

functions of triglycerides

• essential for optimal health

• concentrated source of energy

• insulates + cushions organs

• helps transport nutrients

True or False: high intakes, especially of saturated + trans fat, + imbalances of essential fatty acids can cause health issues

True

Triglycerids provide _ kcals/g

9

True or False: Triglycerides are the main fuel source for all cells, especially the nervous system + red blood cells

False; It’s the main fuel source for all cells except nervous system and red blood cells. When at rest or during light activity, 30-70% of energy is supplied by triglycerides.

Excess calories from ___, ___, ___, and ___ can be converted

to triglycerides.

carbohydrates, fat, protein, and alcohol

Triglycerides are:

• ___ ___, delivering more energy

• Expandable to ____ their normal size

• Some ___ ___ ___ are essential, having too much or too little can pose

health risks

• Calorie dense

• 2 to 3 times

• body fat stores

Where can subcutaneous fat be found + what’s its function?

Just below the skin; keeps the body at a constant temperature

Visceral fat is found ___ ___

• Cushion ____

• Protects organs from ___

• around organs

• organs

• injury

Dietary fats:

• Carry fat-soluble vitamins to the ___ ___

• Aid in the ___ of these ___

• ___ ___ are transported in the ___ with dietary fats

• small intestine

• absorption, vitamins

• Fat-soluble vitamins, bloodstream

Essential Fatty Acid Functions

• Important structural components of cells

• Keep cell membranes fluid and flexible

DHA

Needed during fetal life and infancy for normal development of vision and the nervous system and throughout life for regulation of nerve transmission and communication

Eicosanoids

• have several ___ ___

• from ___, influence blood vessels to constrict and ___ blood pressure

• ___ eicosanoids dilate blood vessels and ___ blood pressure

• regulatory functions

• omega-6 fats; raise

• Omega-3; decrease

phospholipids

• has a structure like triglycerides, except 1 fatty acid is replaced w/ a phosphate molecule

  • allows it to function in watery solution

• Phosphate head is ___; fatty acid tail is ___.

• When placed in water, phosphate head will ___ water and fatty acid tail will ___ ___ from water

• hydrophilic, hydrophobic

• face; extend away

phospholipid functions

• cell membrane component

  • the double-layered outer covering of cell that corrals cells contents + regulates substance movement

• emulsifier

  • forms a shell around fat droplets + suspends them in a watery solution

  • essential for fat digestion + transportation

    • bile + lecithin

phospholipid functions in foods

emulsifier

• lecithin in egg yolks suspends fat in muffin batter

• phospholipids in egg yolks + mustard emulsify oil in vinegar to make mayonnaise

what’re the sources of phospholipids?

• synthesized by the body

  • in food (egg yolks, wheat germ, peanuts)

what can high doses of phospholipids cause?

gas, diarrhea, weight gain

sterols

carbons arranged in multi-ringed structures

cholesterol

a type of sterol used to make sex hormones, active form of vit D, adrenal hormones, bile, cell membranes, shell-covering chylomicrons

sources of sterols?

• foods of animal origin (meat, fish, poultry, eggs, dairy products)

• synthesized in the body

• plants (which also make stanols + sitostanols)

• ergostanol (active form of vit D)

• beta sitostanol (added to some margarine, can help reduce bile + cholesterol absorption)

• Digestion begins in the ___

  • __ __ : Active during infancy, minor role in adults

  • Continues in the ___, aided by ___ ___

  • Occurs mostly in the ___ ___; fat in this organ triggers release of ___, which causes release of bile from ___ and lipase and colipase from ___

• mouth

  • Lingual lipase

  • stomach; gastric lipase

  • small intestine; cholecystokinin; gallbladder; pancreas

Bile ___ fat

• Breaks down fat into ___

• Increases the ___ ___ of lipids and allows pancreatic lipase to ___ ___ triglycerides to free fatty acids and monoglycerides

emulsifies

• micelles

• surface area; break down

Lipid Transportation, Storage, and Usage

Lipoproteins (transport)

• Chylomicrons

Body fat storage (storage)

• Subcutaneous

• Dismantling of fat stores

• Complete fat breakdown requires carbohydrates

Ketosis occurs when there is insufficient carbohydrates (usage)

Absorption occurs by the ___ ___ of the absorptive cells

brush border

Carbon chain length determines which system fatty acids are absorbed by

Vascular system:

• ___-chain and ___-chain fatty acids

• Portal vein → Liver

Lymphatic system:

• ___-chain fatty acids

• Re-esterified into triglycerides

• Short, medium

• Long

Lipids are transported in blood as ____

lipoproteins

ex: chylomicrons, VLDL, LDL, HDL, intermediate-density lipoproteins

lipoproteins

• composed of a core of lipids

• covered with a shell of proteins, phospholipids, + cholesterol

chylomicron

primary component: triglyceride

• carries dietary fat from the small intestine to cells

very-low-density lipoproteins (VLDL)

primary component: triglyceride

• carries lipids both taken up + made by the liver to cells

low-density lipoproteins (LDL)

primary component: cholesterol

• carries cholesterol made by the liver + from other sources to cells

high-density lipoproteins (HDL)

primary component: protein

• helps remove cholesterol from cells + excrete cholesterol from the body in turn

chylomicrons

made up of dietary triglycerides reformed in absorptive cells that combine with either cholesterol, phospholipids, or protein

Apolipoprotein

• found in protein portion of shell

• turn on lipid transfer enzymes

• assist in binding lipoprotein to receptor

• assist enzymes

HDL (high-density lipoprotein)

• highest proportion of protein

• produced by liver and intestine

• roams bloodstream, picking up cholesterol from dying cells/other sources

• donates cholesterol to other lipoproteins for transport back to liver for excretion

• helps block oxidation of LDL

• slows development of cardiovascular disease

high polyunsaturated fat intake

can increase amount of cholesterol deposited in arteries and impair immune system

omega-3 fatty acid intake

can impair immune system, allow uncontrolled bleeding, cause hemorrhagic stroke

imbalances in omega-3 and omega-6 fatty acids

can worsen inflammatory diseases

oxidated fats

• contain peroxides and aldehydes that can damage cells

• double bonds of polyunsaturated fats are easily destroyed

• rancidity prevented by hydrogenation, airtight packages, antioxidants+other additives

diets high in trans fat

can raise blood cholesterol levels (inc risk of cardiovascular disease), lower HDL levels, increase inflammation

avoiding high fat intake

when eating out, avoid fried food, pastries, flaky bread products, cookies

sub at home with veggie oils, softer tub/squeeze margarine and applesauce/fruit purees

diets high in total fat

inc risk of obesity, cardiovascular disease, some cancers (colon, prostate, breast)

fat intake

there is no RDA (recommended dietary intake)

infant fat intake

adequate intake (AI) is 31 g/day for 0-6 months and 30 g/day for 6-12 month

fat intake for other age groups

based on acceptable macronutrient distribution range (AMDR) - % of tot cal

AMDR: 20-35% of total calories (sat fat, trans fat, chol as low as possible) – if fat >30%, extra shld b monounsaturated

cholesterol limited to 300 mg/day

fat intakes for those at risk of heart disease

american heart association recommends lower amts: fat no more than 20%, sat fat no more than 7%, chol no more than 200 mg/day

2025 DGA recommendation for fat

2020 and 2025 DGAs both recommend less than 10% of energy from sat fat

2025 mention butter and beef tallow as options for cooking w fats

2025 have proteins higher in sat fat placed prominently in inverted pyramid graphic

Mediterranean Diet

up to 40% cals from fat (most monounsaturated)

olive oil main fat, abundant fruit+veggie+whole grain+beans+nuts+seeds

minimally processed + seasonally fresh local foods

small amt of cheese + yogurt daily

low-moderate fish intake weekly

limit eggs/red meat

exercise

moderate wine intake

essential fatty acid reqs

2-4 tbsp daily

deficiency can cause: diarrhea, slowed growth, delayed healing, flaky/itcy skin

american fat intake

many north americans consume too much sat fat, too little mono/polyunsaturated, good amt of omega-6, too little omega-3

sat fat sources

dairy, beef, chicken, mayo, margarine

trans fat sources

margarine, baked goods

omega-3 sources

omega-3 from: cold-water fish, walnut, flaxseed, chia seed, canola/soybean/flaxseed oils

omega-6 sources

nuts and seeds, poultry fat, veggie oils and margarines made from veggie oils

hidden fats

not visible, found in: whole milk, cheese, pastries, cookies, cake, hot dog, cracker, fries, ice cream

reading nutr facts label helps

effects of processing of fats

hydrogenation, nutrient losses, trans fat health effects

hydrogenation

make fats resistant to oxidation (longer shelf life, not good for body)

hydrogenated oils have higher smoke point and easier to spread

nutrient losses

loss of unsaturated characteristics and health benefits

decrease in vit K activity

health effects of trans fats

raise LDL cholesterol, lower HDL cholesterol, inc inflammation, inc risk of heart disease + stroke

alt to hydrogenation

can use naturally stable fats (butter, lard, coconut oil), interesterified fats (alter structure without making trans fats), blends of oils, high-oleic oils ← all from chat so idk if we needa know ts

fat replacements

lowers fat in food by replacing with water, protein (dairy-lo), starch derivatives (nu-trim), fiber (avicel, stellar, oatrim), gums (salatrim (benefat))

us vs mediterranean diet fat intake

us: provide 35% of tot cals, 12% sat

med: abt 40% fat, low red meat, extra-virgin olive oil

lipid intake

20-35% total fat

less than 10% sat fat (5-6% for heart risks)

trans fat as low as possible

polyunsaturated fat: linoleic acid 5-10% of cals (17 g/day men, 12 women), linolenic acid 0.6-1.2% (1.6 g/day men, 1.1 women)

limit cholesterol

types of lipoproteins

chylomicron, VLDL (very low density), LDL (low density), HDL (high density)

LDL

larger, lighter, richer in chol

deliver chol to tissues

high levels = inflammation + heart disease

HDL

smaller, denser, packaged w more protein

scavenge excess chol and other lipids

high levels oppose heart disease and vice versa

food cholesterol impact on blood cholesterol

little effect

most sat/trans fats raise bad blood chol

high LDL = CVD risk

food lipids associated w raising LDL chol (sat and trans in excess amts)

CVD

cardiovascular disease is the major killer in NA, high fat diets (esp sat/trans) inc risk of CVD, symptoms develop over multiple yrs

start of CVD

initial: damaged blood vessel

causes: smoking, diabetes, hypertension, homocysteine, LDL, viral/bacterial infection, blood-vessel inflammation