KNES 337 - Unit 18 Fats and Cholesterol

lipid classes

triglycerides, phospholipids, sterols

triglycerides

glycerol + 3 fatty acids, 98% of our dietary fat intake and the majority of body fat stores 

• Used by cells for energy and for tissue maintenance

• Fatty acids in fats determine the type of triglyceride - major ones are saturated or unsaturated 

saturated fatty acids

every carbon saturated with hydrogens, usually solid

• Animals fats, butter, lard, coconut oil, palm kernel oil

unsaturated fatty acids

double bonds, kinks in the chain, usually liquid

monounsaturated

 = 1 double bond 

omega 9 fatty acids

• olive oil, avocados, peanuts, almonds, canola oil

  • Good for your health, eat more! Good for heart 

  • Canola oil better for high temperature cooking than olive oil 

monounsaturated!

polyunsaturated

= multiple double bonds

omega 3 fatty acids (alpha-linolenic acid)

• fish, shellfish, also flaxseed, soybean, walnut, rapeseed oils

  • Good for us, we don’t normally eat enough 

• short chain and long chain forms

polyunsaturated!

short chain omega 3

walnuts, flaxseed, chia seeds, canola oil, navy beans

long chain omega 3

fish, salmon, trout, sardines, oysters, tuna

high amounts in brain and other nervous system tissue, good for the heart

EPA (eicosapentaenoic acid) & DHA (docosahexaenoic acid)

• Reduce heart disease risk

• Reduce tendency for blood to clot (therefore strokes, which are blood clots in the brain)

• High consumers can have impaired blood clotting

• Risk for uncontrolled bleeding and hemorrhagic stroke - if very high consumption of omega-3 (daily fish consumption) → blood thinning, might bleed out faster in an injury

• Recommend fish 2x per week - most Canadians don’t meet this 

omega 6 fatty acids (alpha-linoleic acid)

• corn oil, safflower oil, sunflower oil

  • Do not overconsume, be cautious

  • Too much omega 6 can trigger inflammation 

  • Found in a lot of packaged foods, don’t use them at home

polyunsaturated!

phospholipids

lipid bilayer (cell membranes)

sterols

e.g. cholesterol, vitamin D

is there a food that’s 100% saturated or unsaturated?

no, there’s always a ratio

foods classified based on what type the majority fat is

coconut oil and butter

mostly saturated fat

olive oil and canola oil

mostly monounsaturated fat

safflower oil and sunflower oil

mostly polyunsaturated fats (omega 6)

low density lipoprotein (LDL)

bad cholesterol

high density lipoprotein (HDL)

good cholesterol

healthier fats

lower LDL and raise HDL

monounsaturated fats, polyunsaturated fats

essential fats

both polyunsaturated - omega-6 fatty acids, omega-3 fatty acids

DHA

• a structural component of the brain and is found in high amounts in the retina, promotes intellectual and visual development during last 3 months of pregnancy and during infancy, added to many infant formulas 

  • Very strong research on benefits - most formulas have DHA as a standard ingredient 

  • Breastfeeding - mom needs to consume DHA for baby to have a good amount of DHA, moms should eat fish

ratio of omega 6 to omega 3

• Optimum is 4 omega-6 to 1 omega-3 (4:1)

• Canadian’s ratio is more like > 9:1 (overconsuming omega-6)

  • Can lead to inflammation 

  • Need to increase intake of n-3 fatty acids 

less healthy fats

• Elevate LDL cholesterol levels - trans fats, saturated fats

• Less healthy fats are usually solid at room temperature - meat, “block” margarine, lard, also coconut oil 

invention of modified fat

• Unsaturated fats are unstable - they turn rancid with time, oxygen, and heat due to double bonds (smell bad and taste bad)

• Solid fats last longer than oils during frying - therefore, solution was hydrogenation

hydrogenation

• adding hydrogen to liquid unsaturated fats (oils) makes them more saturated and solid 

  • Improve shelf life, cooking properties, and taste

cons of hydrogenation

• Two drawbacks:

  • Hydrogenated vegetable oils have more saturated fat

    • Corn oil contains 6%

    • Corn margarine has 17%

  • Hydrogenation changes structure of the unsaturated fatty acids

    • Converts some fats into trans fats (the worst for heart disease)

trans fatty acids

partially hydrogenated vegetable oils, raise blood cholesterol more than any other type of fat and promote inflammation

• Increase LDL and lower HDL (worse than saturated fats)

  • Saturated fats increase LDL, neutral effect on HDL

• Not made by body and limited amount naturally in beef and dairy 

• Increase the risk of heart disease, stroke, sudden death from heart disease, and type 2 diabetes (2 g/day)

  • Hawkin’s cheezies - 2 g of trans fats in one bag 🙁 I actually like those sometimes

common food sources of trans fats

• Margarine, shortening, peanut butter

• Deep-fried fast foods

• Salad dressing, mayonnaise

• Cookies, cakes, crackers, doughnuts

• Fried snacks and chips

• Health Canada (2017) announced its notice to prohibit Partially Hydrogenated Oils in food in Canada - no foods can contain these after September 2020

  • Fully hydrogenated can still be used - no trans fats, mostly saturated 

• Rancid oils not good - don’t eat it, oxidized 

cholesterol

• Only found in animal products

• Tasteless, odorless, clear liquid 

• Plants do not contain cholesterol because they can’t produce it and don’t need it 

• Blood cholesterol reflects two sources - the liver (2/3) and the diet (1/3)

• not an essential nutrient - liver produces it, found in every cell in your body

• more modest effect on LDL

• building block for estrogen, vitamin D, testosterone

• major component of nerves and the brain

• cannot be used for energy (o kcal/gram)

functions of cholesterol

for bile, vitamin D, testosterone, estrogen production

food sources of cholesterol

eggs (egg yolk) 29%, meats 36%, milk and milk products 15%, fats 5%, other foods 15%

recommended cholesterol intake

• 300 mg/day of cholesterol (an egg is 213 mg)

  • Most comes from the liver of course (two-thirds)