1. Lipids

2. What Are Lipids and How Do They Differ in Structure?
Lipo means fatty, and lipids refers to a category of compounds that includes triglycerides (fats and oils), phospholipids, and sterols.
Lipids all contain carbon, oxygen, and hydrogen, and they are all hydrophobic (hydro = water, phobic = fearing), i.e. they don’t dissolve in water

3. Lipids Functions of lipids:
To store and provide energy in the human body
To insulate and protect the body
To make steroids, bile, and sex hormones
To transport fat-soluble nutrients in the blood
To contribute to the structure of cell membranes

4. Triglycerides
Triglycerides and phospholipids are built from a basic unit called a fatty acid.
The ratio of carbon and hydrogen to oxygen accounts for the higher number of kilocalories in fat (9 kilocalories per gram) than in carbohydrates and proteins (4 kilocalories per gram).

5. Triglycerides
The length of a fatty acid affects the way we digest, absorb, and metabolize fatty acids.
Foods with long-chain fatty acids tend to take longer to digest and absorb than those with short chains. There are also medium-chain fatty acids.
Short-chain fatty acids are more water soluble than those with more carbons.
The length of the chain also affects the way the body transports the fatty acids.

6. Triglycerides
The “saturation” of fatty acids refers to the presence or absence of a carbon-carbon double bond.
In saturated fatty acids, all carbons in the fatty acid are bound with hydrogen.
Fatty acids with carbons that have bound to each other are unsaturated fatty acids; they have one or more double bonds.
A monounsaturated fatty acid (MUFA) has one double bond (two carbons are paired to each other rather than to hydrogen).
Two or more double bonds are present in a polyunsaturated fatty acid (PUFA).

9. Triglycerides
Fatty acids are capable of becoming rancid. When this happens, a bitter, pungent smell or taste occurs
Because of less-stable double bonds, foods with unsaturated fatty acids will turn rancid faster than those with saturated fatty acids.
The chances of rancidity can be reduced in various ways by manufacturers, and by the consumer through limiting foods’ exposure to oxygen, heat, and light.
Hydrogenation—heating oil and exposing it to hydrogen gas—can extend the shelf life of some foods more solid at room temperature. It is less expensive and provides a “mouthfeel” like butter.

10. The location of the double bond dictates how a fatty acid is named.
The omega-3 fatty acids have the first double bond between the third and fourth carbons from the omega end.
The omega-6 fatty acids have the first double-bond between the sixth and seventh carbons from the omega end.
Linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid) are essential fatty acids—they must be obtained from foods

13. Phospholipids
Like triglycerides, phospholipids contain a glycerol backbone, but instead of three fatty acids, the glycerol is linked to two fatty acids, a phosphate group, and different nitrogen-containing compounds such as choline.
Phospholipids play a vital role in cell membrane structure, and serve as an emulsifier in food systems
Salad dressings use emulsifiers to keep the product stable in storage.
Lecithin is an example of a major phospholipid in the human body. It contains a choline group attached to the phosphate on the third carbon of the glycerol backbone.

14. How Are Lipids Digested, Absorbed, and Transported in the Body?
During digestion, fatty acids are removed from the glycerol backbone via hydrolysis and lipases (lipid-digesting enzymes) to form a combination of free fatty acids, glycerol, and monoglycerides

15. How Are Lipids Digested, Absorbed, and Transported in the Body?
Triglyceride digestion begins in the mouth and stomach.
The warmth of the body begins to melt the foods; chewing continues and food mixes with saliva
Lingual lipase (secreted from the glands located at the base of the tongue) begins to hydrolyze the fatty acids.

16. Small Intestinal Digestion of Fats
Most triglycerides are digested and absorbed in the small intestine.
When the triglyceride enters the duodenum, the hormone cholecystokinin (CCK) is secreted, which in turn stimulates the gallbladder to release bile through the bile duct into the duodenum.
The action of bile reduces the fat globules to smaller droplets that are packaged into phospholipid carriers, called micelles
The micelles are responsible for transporting the fat remnants into the intestinal walls for absorption.
Phospholipids and sterols are also emulsified by bile during digestion.
Phospholipids are hydrolyzed and absorbed.
Sterols are absorbed intact through the intestinal wall.

18. Chylomicrons Chylomicrons facilitate lipid absorption
Micelles transport digested fats and phospholipids from the lumen of the GI tract into the enterocyte.
There, large lipoproteins called chylomicrons are formed and released into lymph fluid in the vessels of the lymph system before entering the liver or the bloodstream.
These chylomicrons eventually enter the bloodstream when the lymph joins the blood through the thoracic duct. They then interact with the enzyme lipoprotein lipase (LPL), which separates the fatty acids so that they can be stored in the cells.

20. Lipoproteins
Lipoproteins transport lipids through the lymph and blood.
Very low-density lipoproteins (VLDLs) and low-density lipoproteins (LDLs) primarily transport triglycerides and cholesterol from the liver to the cells.
High-density lipoproteins (HDLs) pick up cholesterol from the body cells and return it to the liver to be used for the production of bile.
When a person has a checkup and blood is drawn, total cholesterol as well as blood lipoprotein content can be analyzed.
Higher levels of LDL and lower levels of HDL indicate a risk for heart disease.

21. What Are the Functions of Lipids in the Body?
Fatty acids are used for energy; one gram of fat contains 9 kcals.
The human body relies on fat cells (adipocytes) for storage of triglycerides.
The heart, liver, and resting muscles prefer fat as their fuel source.
Glycerol is the only part of the stored triglycerides that can be used for gluconeogenesis.

22. What Are the Functions of Lipids in the Body?
Dietary fat aids the absorption of lipid compounds.
Many essential nutrients, including the fat-soluble vitamins A, D, E, and K (as well as carotenoids, cholesterol, phospholipids, and other lipid compounds), require dietary fat in order to be absorbed in the body.

23. What Are the Functions of Lipids in the Body?
Triglycerides stored in adipose tissue insulate the body and protect vital organs.
The fat located under the skin functions as an insulator and a protector of the skeleton.
Stored triglycerides also act as a protective cushion against trauma for the bones and vital organs, including the brain, liver, kidneys, and spinal cord.

24. What Are the Functions of Lipids in the Body?
Essential fatty acids manufacture eicosanoids and maintain cell membranes.
Linoleic acid and alpha-linolenic acid are the two essential fatty acids; these are used as precursors for the production of other compounds in the body, such as arachidonic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)
Eicosanoids are hormone-like substances that help regulate the immune system, blood clotting, inflammation, and blood pressure.

25. What Are the Functions of Lipids in the Body?
The liver uses cholesterol to make hormones, bile, and Vitamin D.
Cholesterols serve as the starting material in the synthesis of steroid hormones including the sex hormones estrogen and testosterone, and the adrenal corticoids such as cortisol and aldosterone.
The liver uses cholesterol to manufacture bile, and a type of cholesterol in the skin is converted to a previtamin D by the ultraviolet rays of the sun.

26. What Are the Functions of Lipids in the Body?
Phospholipids and cholesterol make up cell membranes.
Phospholipids make up the phospholipid bilayer in cell membranes.
Cholesterol improves cell fluidity.

27. What Are the Recommendations for Daily Intake of Triglycerides and Cholesterol?
Dietary fat intake is based on a percentage of total kilocalories.
The current AMDR (Acceptable Macronutrient Distribution Range) recommendation is to limit fat intake to 20 to 35 percent of daily kilocalories.
For heart health, the recommendation is to consume no more than 10 percent of total kilocalories from saturated fats (and ideally less than 7 percent) and to limit trans fats to less than 1 percent.
Fat content is calculated in total fat grams. The recommended number varies based on daily energy needs.

28. What Are the Recommendations for Daily Intake of Triglycerides and Cholesterol?
Essential fatty acids have specific recommendations.
The Adequate Intake (AI) of alpha-linolenic acid per day for men and women is 1.6 and 1.1 grams, respectively.
The AI for linoleic acid is set much higher, at 17 grams per day for adult men and 12 grams per day for adult women.
Americans currently consume only about 0.1 to 0.2 grams of EPA and DHA in their daily diet.
Elevated blood triglycerides is known as hypertriglyceridemia.

29. What Are the Best, Worst, and Alternative Food Sources for Fat?
Foods that contain unsaturated fats are better for health than eating foods high in saturated fat, trans fat, and/or cholesterol.

30. What Are the Best, Worst, and Alternative Food Sources for Fat?
The best food sources are low in saturated fats.
Unsaturated fats are abundant in vegetable oils, such as soybean, corn, and canola oils, as well as in soybeans, walnuts, flaxseeds, and wheat germ.
Fish are generally good sources of omega-3 fatty acids, and all fish contain EPA and DHA, with fatty fish being especially rich sources
Foods high in saturated fats should be limited in the diet.
Most saturated fat comes from fatty animal foods, whole-milk dairy products, and the skin on poultry. Some vegetable oils (coconut, palm, and palm kernel oils) are also high in saturated fat.
The nutrition label of packaged foods can be used to compare the amount of total fat, the type of fat, and the calories from fat per serving of a food.

31. What Are the Best, Worst, and Alternative Food Sources for Fat?
Reduce foods that contain trans fat
The major food sources of trans fats are commercially prepared
Baked goods, snack items, margarine, shortenings, salad dressings, and fried potatoes.
Trans fats also occur in some dairy and meat products.
Despite the fact that the health effects of trans fats are now well known—
Research shows that trans fats raise LDL cholesterol levels and lower HDL cholesterol in the blood—these fats are still found in many foods.

32. What Are the Best, Worst, and Alternative Food Sources for Fat?
In 2013, the FDA proposed a ban on the use of partially hydrogenated oils in foods to reduce trans fat in the diets of Americans.
Food sources of cholesterol include animal food products such as meat, chicken, fish, shellfish, eggs, and dairy foods.
Food sources of plant sterols include phytosterols and stanols
Soybean oil, some fruit, vegetables, legumes, seeds, nuts, cereals, and other plants are examples of foods that contain plant sterols.

33. What Is Heart Disease and What Factors Increase Risk?
Cardiovascular disease (CVD) encompasses several disorders affecting the heart, its valves, heart rhythms, and infections.
Heart disease has been the number-one killer of adults in the U.S. since 1918.
One in three Americans dies of heart disease every 40 seconds.

34. Atherosclerosis
The development of heart disease = accumulation of fat and cholesterol along the walls of the arteries
Narrowed arteries and vessels reduce the amount of oxygen in the blood, and there is an increased likelihood that a blood clot can form, detach, and get caught in a vessel, blocking blood flow and leading to a heart attack.
If the blockage leads to the brain, the result can be a stroke.
The precise cause of the narrowed arteries (atherosclerosis) is unclear, but researchers currently believe an injury to the lining of the arteries forms the starting point for the disease.
Fats and cholesterol-laden substances form plaque, the arterial blocking substance.

35. Risk factors include age, gender, and some genetic predispositions.
Some groups have normal levels of LDL cholesterol in their blood but still develop heart disease
High blood levels of C-reactive protein (CRP), high levels of the amino acid homocysteine, the presence of Chlamydia pneumonia bacterium, and levels of Lp(a) lipoprotein.
Controllable risk factors include a high or low level of HDL cholesterol, chronic blood pressure (hypertension), diabetes, and smoking.

36. How Do You Decrease The Risk of Heart Disease?

37. Mediterranean Diet
What are the characteristics of a Mediterranean diet that can reduce the risk for heart disease by 30%?
What dietary recommendations would you give to someone who wants to reduce their risk for heart disease?
What methods can be used to increase intake of protein rich foods and healthy fats?