Mmmmm…fat. The good, the bad, and the artery-clogging “Chapter 3: Lipids” Mmmmm…fat. The good, the bad, and the artery-clogging

Do You Ever… Think of fats as unhealthy foods that are best eliminated from the diet? Wonder about the differences between “good” and “bad” cholesterol? Choose fish for health’s sake without fully knowing why? Recognize invisible fats in your foods?

Let’s say… Your bill from a lab reads “Blood lipid profile: $250.” Your doctor tells you that your blood cholesterol is high. The doc also tells you to cut down on saturated fats. But what does it all mean?

Intro to the Lipids “The lipids in foods and in the human body fall into three classes.” Each of these are stored in different parts of the body, and found in different foods.

“About 95% are triglycerides.” “The rest are phospholipids and sterols.” (Cholesterol is the best known) Some of these names may sound familiar…we’ll discuss them in more detail later.

What are fat’s uses in the body? “Fat is the body’s chief storage for the energy from food eaten in excess of need.” Evolutionarily, if you didn’t know where your next meal was coming from, it made sense to store extra.

“Most cells store limited fat.” “Fat cells are specialized and can expand almost indefinitely.” So the more fat they store, the larger they grow.

These aren’t just sacks of fat, though! “Adipose (fat) tissue secretes hormones that regulate appetite and influence other body functions.” So these cells are, indeed, important to our health.

Why not just store energy in carbs? Glycogen (sugar storage) holds a great deal of water, so it is a bulky, heavy molecule. Fats pack tightly together, and store more energy in a small space.

What else does fat do? “Pads of fat surround and protect our vital organs.” This is why we are very durable and aren’t injured easily.

“Fat under the skin insulates us.” This protects us from both hot and cold, like a thermos. “It is also part of our cell membranes.”

“Fat is needed to absorb vitamins A, D, E, and K, which are fat-soluble.” This means that they only dissolve into fat. “Our bodies make molecules from essential fatty acids (part of fat).” So our fat is absolutely vital!

Usefulness of Fats in Food The energy density of fat makes it valuable in some situations. A hunter or hiker can carry fat calories easier than carb calories, because fat is lighter.

Fat is naturally appealing to us, because evolutionarily, we needed calories! Fat also adds tenderness to meats and baked goods. “Fat contributes to satiety, feeling full after a meal.” The fat triggers a physiological response that slows digestion and stops us from eating more.

Although fat in the stomach signals us to stop eating, The taste of fat tells us to keep eating, so it is possible to overeat easily.

A Closer Look At Fat “Fat usually refers to triglycerides.” “Made of three fatty acids and one glycerol molecule.”

Tissues all over the body can assemble or disassemble these triglycerides as needed. “Fatty acids differ in two ways:” “Chain length”

“and degree of saturation.” Saturated, unsaturated…more about that in a minute. Usually, triglycerides contain a mixture of different fatty acids.

“The shorter the chain, the softer and more liquid the fat.” So vegetable oils have shorter molecule chains; Beef fat has a longer chain of fatty acids. This does matter!

“Each species of animal makes different triglycerides.” This is governed by genetics. Fats in the diet can affect which triglycerides are made, because the fatty acids we eat are often incorporated into our triglycerides in the body. Remember, you are what you eat!

Saturated vs. Unsaturated Fatty Acids Saturation: whether or not a fatty acid chain is holding all of the hydrogen atoms it can hold.

“If every available bond is holding a hydrogen molecule, that chain is a saturated fatty acid.”

Sometimes, in the fats of plants and fish, this chain has a place where hydrogens are missing. “A chain with one missing hydrogen is monounsaturated.”

“A fat with two or more missing hydrogens is polyunsaturated.” All of this affects the point at which that fat melts.

“The more unsaturated, the more liquid it is at room temperature.” So since beef fat is solid, it has lots of saturated fat. Since chicken fat is softer, it has less saturated fat. A good way to tell if it is healthy!

The Catch Some liquid plant oils are still high in saturated fat. (coconut, palm) How do we tell? “Refrigerate oil: if it turns cloudy, it has more saturated fat.” One exception is olive oil: although only mono-, good for you!

Where the Fatty Acids are Found “fish, veggies: polyunsaturated” “some veggies (canola, olive): monounsaturated” “meat: most saturated” Beware: veggie fat can contain trans fat…dangerous! (More later)

What’s so great about olive oil? Rich in antioxidant phytochemicals Excellent replacement for butter and other animal fats

“Some Special Fats”

“Phospholipids (PPLs) and Sterols” “PPLs have two fatty acid chains instead of three, and a phosphorus molecule.” Why does this matter? “It is water- and also fat-soluble.” So it dissolves in both water and fat. Why do we care?....

“Manufacturers use PPLs as an emulsifier to blend fats and water.” One of the most common on labels: lecithin Used in mayo to blend vinegar and eggs

“Sterols are rings of carbon atoms with hydrogens and oxygens attached Cholesterol is the best known. Good cholesterol is vital to cell membrane structure; bad cholesterol clogs arteries.

What is the difference? “Low-density lipoproteins (LDL) are carriers of cholesterol to the tissues.” These are larger, lighter, and richer in cholesterol.

“High-density lipoproteins (HDL) carry cholesterol away from tissues, to the liver for disposal.” These are lighter, smaller, and contain more protein. So both contain the same cholesterol…what’s with the good and bad?

We’ve come to call them good and bad cholesterols, when cholesterol is cholesterol. The key is, “LDL carries lipids that trigger inflammation and contribute to heart disease.” “HDL proteins oppose inflammation and protect against heart attack.”

Therefore, elevated LDL in the blood warns of an increased heart attack risk; Elevated HDL points to a reduced risk. These numbers are SO important to health! So how do we change our numbers?

“LDL can be lowered by avoiding saturated fat and trans fat.” Happily, the national cholesterol level is dropping! But heart disease is still this country’s top killer. “We should choose a diet with less than 10% of calories from saturated fat.”

LDL Cholesterol Risks

How do we raise HDL? “Diet rarely raises HDL; regular exercise works better.” Although some foods, like olive oil, fiber, fish, and nuts can help. Remember HDL = Happy DL 

Coming soon… More about fat!