NUTR 3381: Quiz 4 Lipids

Feasting

excess energy stored as triglycerides in adipose tissue.

Fasting

triglycerides broken down into fatty acids used for energy (ATP).

What are phytosterols and phytostanols?  

Plant sterols that lower LDL by competing with cholesterol for absorption. Found in soybean oil, fruits, vegetables, legumes, sesame seeds, nuts, and cereals.

How does smoking affect heart disease risk?

Smoke damages artery walls and accelerates atherosclerosis. Smokers are THREE TIMES more likely to have a heart attack than nonsmokers.

How does exercise affect cholesterol levels?

Raises HDLs, lowers LDLs, and reduces high blood pressure and insulin resistance. Aim for 30+ minutes of moderate exercise daily.

What is the Mediterranean diet and why is it heart-healthy?          

A dietary pattern based on fruits, vegetables, legumes, and olive oil that limits meats and sweets. Associated with low rates of heart disease.

What dietary factors INCREASE heart disease risk?             

High sodium, saturated fat, trans fat, high red meat intake, excess sugar, excess alcohol, excess calories.

What dietary factors DECREASE heart disease risk?           

High soluble fiber, unsaturated fats, B-vitamins, antioxidants, fish, nuts, whole grains, fruits, vegetables, moderate alcohol, Mediterranean-style eating.

What HDL level is considered low (a risk factor)?  

Less than 40 mg/dL

What total cholesterol level is considered desirable?         

Less than 200 mg/dL

What total cholesterol level is considered high?    

240 mg/dL or above

What LDL level is considered optimal?         

Less than 100 mg/dL

What LDL level is considered very high?      

190 mg/dL or above

What HDL level is considered desirable?    

Greater than 60 mg/dL

Describe the 6 steps of atherosclerosis leading to a heart attack.

1. Normal artery. 2. Damaged artery (LDL + white blood cells enter). 3. Plaque formation (foam cells form). 4. Plaque enlargement. 5. Plaque rupture + blood clots. 6. Heart attack (blocked artery, dead heart muscle).

What are controllable risk factors for heart disease?

Obesity, diabetes, high blood pressure, blood lipid levels, smoking, lack of exercise, and poor diet.

What are non-controllable risk factors for heart disease?

Gender (men at greater risk earlier), genetics/family history, and age (men >45, women >55).

What is atherosclerosis?        

The process by which fat and cholesterol accumulate in the arteries, causing them to narrow, impeding blood flow and decreasing oxygen delivery to the heart.

What are the effects of too little fat in the diet?       

Reduced absorption of fat-soluble nutrients, slowed growth, and impaired function of skin, eyes, liver, and other organs.

What are the effects of too much fat in the diet?   

Increases total calorie intake, contributes to excess body fat storage, and can increase risk for chronic disease.

What is cardiovascular disease (CVD)?        

A group of disorders affecting the vascular system, including the heart. Heart disease is the #1 cause of death of U.S. adults.

What does 'fat free' mean on a label?            

Contains less than 0.5g of fat per serving.

What does 'low fat' mean on a label?

Contains 3g or less of fat per serving.

What does 'reduced fat' mean on a label? 

Contains at least 25% less fat per serving than the regular product.

What fat types must be listed on a nutrition label?

Saturated fat and trans fat must be listed. Cholesterol is NOT included in the Total Fat number.

What is the %DV rule for fat on food labels?

5% DV or less = LOW; 20% DV or more = HIGH

Name dietary sources of cholesterol.

Beef, pork, poultry, fish, egg yolks, and dairy. Plant foods and oils are considered cholesterol-free.

Name dietary sources of saturated fat.

Animal: fatty cuts of meat, poultry skin, whole-milk dairy. Plant: coconut, palm, and palm kernel oils.

Name dietary sources of Omega-3 fatty acids.

Flaxseeds and flaxseed oil, walnuts, fish oil, canola oil, and fatty fish.

Name dietary sources of Omega-6 fatty acids.

Corn oil, safflower oil, soybean oil, nuts, fats from fish, meats, and eggs.

What is the average American fat intake?

~33% of total calories, but the TYPE of fat is out of balance.

What is the AI for Alpha-linolenic acid (Omega-3)?

Women: 1.1 grams/day; Men: 1.6 grams/day

What is the AI for Linoleic acid (Omega-6)?

Women: 12 grams/day; Men: 17 grams/day

What is the recommendation for trans fat?

Limit to less than 1% of total calories.

What is the recommendation for saturated fat?

Less than 10% of total calories

What are lipids?

A class of molecules that do not dissolve in water (hydrophobic). They clump together in water and are made of carbon, hydrogen, and oxygen; some also contain phosphorus.

What are the 3 main types of lipids?                

Triglycerides, Phospholipids, and Sterols

Why are lipids described as hydrophobic?

Because they repel water and clump together when placed in water rather than dissolving.

What are triglycerides?            

The most common type of lipid found in food and the body. They make up 95% of lipids in food and are stored as adipose tissue for energy.

What is the structure of a triglyceride?          

One glycerol backbone + three fatty acids. When combined, they release 3 water molecules.

Why are high triglyceride levels in the blood dangerous? 

High blood triglyceride levels are a risk factor for heart disease.

What are fatty acids?                 

The building blocks for triglycerides and phospholipids. They consist of a carbon chain with a methyl (omega) end and an acid group.

What are the two main types of fatty acids?               

Saturated and Unsaturated fatty acids.

What defines a saturated fatty acid?               

It is fully saturated with hydrogen atoms and contains only single bonds between carbons. It is solid at room temperature (e.g., fat on a steak).

What defines an unsaturated fatty acid?     

It contains one or more carbon-carbon double bonds. It is liquid at room temperature (e.g., vegetable oils).

What is a monounsaturated fatty acid (MUFA)?      

A fatty acid with ONE double bond along the carbon chain. Example: Oleic acid.

What is a polyunsaturated fatty acid (PUFA)?           

A fatty acid with TWO or more double bonds along the carbon chain.

What are the two essential fatty acids the body cannot make?    

1. Linoleic acid (Omega-6) and 2. Alpha-linolenic acid (Omega-3)

How are omega fatty acids named?                 

They are named for the location of the FIRST double bond on the carbon chain from the methyl/omega end.

What are the three categories of fatty acid chain length?

Short-chain, medium-chain, and long-chain. Lengths range from 4 to 24 carbons. Shorter fatty acids are more liquid and water-soluble.

What are the two shapes of unsaturated fatty acids?          

Cis form (hydrogens on the SAME side of the double bond — creates a bend) and Trans form (hydrogens on OPPOSITE sides — straighter chain).

How are trans fatty acids created?  

During the process of HYDROGENATION — adding hydrogen to unsaturated fats to make them more solid.

Why do trans fatty acids behave like saturated fats?            

Because their hydrogens are on opposite sides of the double bond, making the carbon chain straighter (similar shape to saturated fatty acids).

What is rancidity?       

The spoiling of fats through oxidation. Foods with unsaturated fats go rancid faster because double bonds are less stable than single bonds.

What is the structure of a phospholipid?    

Glycerol backbone + phosphate group + choline + TWO fatty acids. It has a hydrophilic polar head and a hydrophobic nonpolar tail.

What is lecithin?           

The most common phospholipid (also called phosphatidylcholine). Made in the liver (nonessential), is a major component of cell membranes, and acts as an emulsifier.

What is an emulsifier?              

A substance that helps two liquids (like oil and water) mix together. Lecithin acts as an emulsifier.

What are sterols?        

Lipids made of four connecting rings of carbon and hydrogen. They do NOT contain glycerol or fatty acids and do NOT provide energy.

What are plant sterols called?            

Phytosterols and phytostanols. They help form plant cell membranes.

What does the body use cholesterol to make?        

Cell membranes, myelin, Vitamin D, bile acids, and hormones (cortisol, testosterone, estrogen).

How many calories per gram do fats provide?          

9 calories per gram (more than carbs and protein, which provide 4 cal/g each).

What are adipocytes?               

Fat cells. They store 60 times more energy than liver and muscle glycogen combined.

What organs preferentially use fat for energy at rest?          

The heart, liver, and resting muscles — to spare glucose for the brain.

How does fat protect the body physically?

Subcutaneous fat insulates the body and maintains body temperature. Fat also protects bones and vital organs from trauma.

Which essential nutrients require dietary fat for absorption?         

Fat-soluble vitamins (A, D, E, K), carotenoids, cholesterol, and phospholipids

How do phospholipids and cholesterol function in cell membranes?     

Phospholipids form the phospholipid bilayer; cholesterol is a structural component that maintains membrane integrity.

Where does MOST triglyceride digestion take place?          

In the SMALL INTESTINE (by pancreatic lipase).

What are the three sites of fat digestion and their enzymes?          

1. Mouth: lingual lipase — fats become tiny droplets. 2. Stomach: gastric lipase — 30% of triglycerides become diglycerides and fatty acids. 3. Small intestine: pancreatic lipase — becomes glycerol, monoglycerides, and free fatty acids.

What is the role of bile in fat digestion?        

Bile acid emulsifies large fat droplets into smaller ones, allowing pancreatic lipase to digest them more easily.

What is a micelle?      

A lipid complex formed in the small intestine that transports lipids across the small intestinal wall (enterocyte).

What happens to undigested lipids in the large intestine?                

They bind with fiber and are eliminated in feces. Normally, very little fat is lost this way.

What is a chylomicron?           

A lipoprotein formed in intestinal cells that transports absorbed dietary lipids through the lymphatic system to the bloodstream.

What is the structure of a chylomicron?      

Triglycerides (90%), plus phospholipids, cholesterol, and protein on the outer shell.

How are medium- and short-chain fatty acids absorbed differently?      

They are absorbed DIRECTLY into portal blood circulation, bypassing the lymphatic system, unlike long-chain fatty acids which go through chylomicrons.

What are the 4 major lipoproteins? 

Chylomicron, VLDL (very-low-density), LDL (low-density), and HDL (high-density).

What does VLDL do?

Produced by the liver to transport triglycerides to cells. Lipoprotein lipase catalyzes fatty acid uptake, transforming VLDL into LDL.

What does LDL do and why is it 'bad'?           

LDL carries cholesterol FROM the liver TO tissues. LDL not taken up degrades over time, releasing cholesterol that may adhere to blood vessel walls — hence 'Lousy' cholesterol.

What does HDL do and why is it 'good'?       

HDL carries cholesterol FROM cells BACK to the liver for reuse or elimination. High HDL is associated with reduced heart disease risk — hence 'Healthy' cholesterol.

What lipoprotein has the highest % of triglycerides?            

Chylomicron (~90% triglycerides).

What lipoprotein has the highest % of cholesterol?              

LDL (~50% cholesterol)

What lipoprotein has the highest % of protein?       

HDL (~50% protein).

What is the AMDR for total fat intake?            

20–35% of daily calories.