Lipids and Nutrition Flashcards

Lipids are a broad class of hydrophobic compounds comprising Triglycerides (fats and oils), Phospholipids, and Sterols.
Fats are solid at room temperature, while oils are liquid.
Functions include energy storage, cell membrane maintenance, hormone synthesis, regulation of BP and inflammation, and absorption of fat-soluble vitamins.
Energy Density: provides $9\,kcal/g$ .

Triglycerides are the primary lipid class and main food storage form, composed of a glycerol backbone and 3 fatty acids.
Fatty acids vary by chain length and saturation, featuring a Carboxyl end (alpha carbon) and a Methyl end (omega carbon).
Saturated Fatty Acid (SFAs): Max hydrogen atoms, no double bonds, straight chain, solid at room temperature. Sources include animal fats and tropical oils (palm and coconut oil).
Monounsaturated Fatty Acid (MUFA): Contains 1 double bond (e.g., Oleic Acid); typically liquid at room temperature.
Polyunsaturated Fatty Acid (PUFA): Contains 2 or more double bonds (e.g., linoleic and linolenic acid).

Essential Fatty Acids must be obtained through the diet: - Omega-6 (Linoleic Acid): Precursor to arachidonic acid; found in sunflower and pumpkin seeds. - Omega-3 (Linolenic Acid): Converted to EPA and DHA; found in fish oils, flaxseeds, and walnuts. Recommended: 2 servings of fish/week.
Hydrogenation: Adds hydrogen to unsaturated fatty acids to increase shelf-life, creating saturated and trans fatty acids.
Trans Fatty Acids: Straighter chain (trans configuration); increases LDL ("bad" cholesterol), decreases HDL ("good" cholesterol), and raises Cardiovascular Disease (CVD) risk.

Sterols: Include cholesterol (liver-produced), Vitamin D, and sex hormones. Dietary cholesterol is only found in animal products.
Dietary Cholesterol Recommendation: $200-300\,mg/day$ .
Phospholipids: Soluble in water; act as emulsifiers to transport fats in the blood.
Lecithin (Phosphatidylcholine): A phospholipid found in egg yolks and liver containing choline, which is used to produce acetylcholine.
Emulsifiers: Substances that mix fat and water to create an emulsion.

Adipose tissue: Stores lipid droplets; provides $60\%$ of the body's energy needs during rest.
Fat serves as the primary fuel during rest and low-intensity or long-duration endurance exercise after glycogen depletion.
Acceptable Macronutrient Distribution Range (AMDR): $20-35\%$ of total calories.
Saturated Fat: Should be <10\% of total calories.
Athlete Recommendation: $20-25\%$ of total calories from fat.

Fats are insoluble, making digestion complex; minimal activity occurs in the mouth and stomach due to the watery environment.
Most digestion occurs in the small intestine, where bile emulsifies fats into smaller droplets to increase surface area for enzymes.
Pancreatic enzymes (lipase) break triglycerides ( $TGs$ ) into monoglycerides and free fatty acids.
Micelles, formed from fatty acids, monoglycerides, and bile salts, transport fats through intestinal fluid to the intestinal lining.
Inside enterocytes, fat components are reassembled into $TGs$ and packaged with proteins into chylomicrons ( $CM$ ).
Chylomicrons enter the lymphatic system, initially bypassing the liver, to transport dietary fat to tissues via the bloodstream.

Lipoprotein lipase ( $LDL$ ) is primarily located on the surfaces of cells lining capillaries in muscle and adipose tissue.
$LPL$ breaks down $TGs$ in chylomicrons into fatty acids and glycerol for energy use or storage.
Between $10-12\,hrs$ after a meal, chylomicrons are reduced to small cholesterol-rich remnants picked up by the liver.
The liver produces Very Low-Density Lipoprotein ( $VLDL$ ), which carries a high proportion of lipids in the bloodstream.
As $VLDL$ loses $TGs$ to tissues, it becomes Low-Density Lipoprotein ( $LDL$ ).

$VLDL$ : Transports $TGs$ for energy or storage; high levels increase cardiovascular disease ( $CVD$ ) risk.
$LDL$ ("bad cholesterol"): Delivers cholesterol to cells; buildup causes atherosclerosis; high levels increase $CVD$ risk, while the transcript notes "Low $LDL$ cholesterol" is linked to higher disease risk.
$HDL$ ("good cholesterol"): Collects excess cholesterol from cells and returns it to the liver; high $LDL$ is noted as a lower risk of $CVD$ in this context.
Oxidized $LDL$ : Damage from free radicals makes $LDL$ more harmful, contributing to arterial plaque formation; risk factors include smoking, excessive alcohol, and high intake of refined carbs.

High intake of saturated and trans fats raises blood $LDL$ cholesterol.
Replacing saturated and trans fats with monounsaturated fats reduces $CVD$ risk.
Omega-3 Fatty Acids ( $EPA$ + $DHA$ ) protect the heart by lowering blood $TGs$ and blood pressure ( $BP$ ), preventing clots, and protecting against irregular heartbeats.