Nutrition Ch 6
Lipid Consumption Patterns
1987 to 1988 > approx. 54 lbs/year/person 2007 to 2008 > 63 lbs/year/person Fat contributes ~34% of the average American's daily caloric intake.
Embolus Formation
A thrombus that breaks away and travels through the blood is an embolus. If an embolus lodges in the heart, it can cause a heart attack (myocardial infarction). If an embolus lodges in the brain and deprives brain cells of oxygen and nutrients, a stroke results.
Dietary Lipid Recommendations
Acceptable Macronutrient Distribution Range> 20 to 35% of total calories American Heart Association: < 10% of calories from saturated fats < 300 mg cholesterol daily trans fatty acid intake as low as possible < 30% total kcal from fat
Using Triglycerides for Energy
Adipose cells can break down triglycerides into fatty acid and glycerol molecules before releasing them into blood stream. Liver can convert glycerol to glucose—another energy source. Triglycerides provide 9 kcal/g (carbohydrate & protein provide 4 kcal/g)
Adipose Tissue
Adipose cells store triglycerides as fat droplets.
Enterohepatic Circulation
After bile salts are used to aid lipid digestion, the salts are absorbed in the ileum and return to liver for the production of new bile.
Lipid (Lipoprotein) Profile
Blood test that determines total cholesterol, HDL & LDL cholesterol, and triglyceride levels
Cardiovascular Disease (CVD)
CVD: diseases of the heart and blood vessels Most common forms of CVD are: Heart disease ("coronary artery disease") Stroke 1 in 3 adult Americans have some form of CVD Responsible for ~30% of deaths in the U.S. in 2009
Phospholipids
Chemically similar to a triglyceride, 1 fatty acid is replaced by a compound containing phosphorus and nitrogen groups
Cholesterol
Cholesterol is a sterol, a compound that is more complex than most other lipids.
Hypertension
Chronic condition characterized by abnormally high blood pressure levels May cause hardened arteries to tear or burst
Triglycerides
Composed of 3 fatty acids attached to a glycerol "backbone" *~ 95% of lipids in the body and foods is in the form of triglycerides.
Arteriosclerosis
Condition that results from atherosclerosis Characterized by loss of arterial flexibility Commonly referred to as "hardening of the arteries" Contributes to hypertension
Atherosclerosis
disease in which lipid-containing plaques build up inside arteries Plaque forms in an artery when something irritates the lining of the artery wall. •Plaque narrows arteries, interfering with circulation. •Plaque may also result in the formation of a fixed clot •a thrombus
(T/F) Increasing your intake of trans fats can reduce your risk of heart disease
False
(T/F) On average, Americans consume 60% of their calories from fat
False
(T/F) To lose weight, use regular, stick margarine instead of butter because it has 25% fewer kilocalories per teaspoon
False
Saturation
Fatty acids also vary by saturation
High-density Lipoproteins
HDL commonly called "good" cholesterol (low risk of CVD) Transports cholesterol away from tissues and to the liver where it can be eliminated
Precursors of prostaglandins
Hormone-like substances formed from EPA, DHA, and arachidonic acid
Lipids in Your Body
In the duodenum, pancreatic lipase digests triglycerides, forming primarily: Monoglycerides Free fatty acids
Low-density Lipoproteins
LDL commonly called "bad" cholesterol Conveys cholesterol to tissues May become oxidized LDL and contribute to atherosclerotic plaque
Partial hydrogenation
Not all double bonds are hydrogenated Natural cis double bonds convert to the unhealthy trans form
Emulsifiers
Phospholipids act as emulsifiers, because they have hydrophobic and hydrophilic regions. Hydrophobic region Attracts lipids and avoids water Hydrophilic region Attracts water and avoids lipids
Hydrogenation
Process that adds hydrogen atoms to liquid vegetable oils
Lipoproteins
Protein molecules which transport lipids in the blood Play major role in atherosclerosis development Carry different types of lipids and can influence plaque formation differently
Function of Fats
Providing and storing energy Maintaining cell membranes Producing certain hormones Insulating the body against temperature extremes Cushioning internal organs Absorbing fat-soluble vitamins and phytochemicals
Modifiable Risk Factors
Smoking Hypertension* Diabetes* Excess body fat* Elevated blood cholesterol (LDL)* Physical inactivity *influenced by diet
Omega-6
Sources: Animal fats and vegetable oils Actions: Increases inflammation and blood clotting (?) May also reduce risk of heart disease
Omega-3
Sources: Fatty fish, canola oil, walnuts, and flaxseed Actions: Reduces inflammation, blood clotting, and blood pressure May reduce risk of heart disease
Hormone-like substances formed from EPA, DHA, and arachidonic acid
Stimulate uterine contractions Regulate blood pressure Promote immune system response
Summary of Lipid Digestion and Absorption
Stomach — minor fat digestion occurs Liver — produces bile that helps emulsify fat Pancreas — secretes lipase into small intestine Small intestine — main site for lipid digestion and absorption Anus — less than 5% of undigested fat is excreted in feces
Functions of Cholesterol
The body uses cholesterol to make various substances, including Vitamin D Steroid hormones Estrogen/progesterone Testosterone Bile
Desirable levels
Total Cholesterol < 200 mg/dl LDL Cholesterol < 100 mg/dl HDL Cholesterol above 40-60 mg/dl* Triglycerides < 150 mg/dl * 40-60 for men, 50-60 for women
Lipid Classes
Triglycerides Phospholipids Cholesterol
(T/F) Egg yolks are a rich source of cholesterol
True
(T/F) Taking too many fish oil supplements may be harmful to health
True
Trans Fats
Unsaturated fats with at least 1 trans double bond rather than the more common cis double bond High amounts of trans fats in diet increase heart disease risk by raising blood cholesterol levels (increase LDL) FDA requires amount of trans fat displayed on Nutrition Facts panel
Alpha-linolenic acid
a polyunsaturated essential fatty acid; part of the omega-3 fatty acid family
Linoleic acid
an essential polyunsaturated fatty acid of the omega-6 family
Fatty Acids
chains of carbon atoms bonded to hydrogen atoms •Short chain fatty acids — 2 to 4 carbons •Medium chain fatty acids — 6 to 12 carbons •Long chain fatty acids — 14 to 24 carbons
Lipids
insoluble in water less dense than water
Bile
made in the liver and stored in the gallbladder Bile contains bile salts that aid in lipid digestion. *Without bile, lipids clump together in large fat globules.
Lecithin
main phospholipid in foods, such as egg yolks, liver, wheat germ, peanut butter, and soy
Unsaturated
one or more carbon atoms within the chain lack 2 hydrogen atoms, and as a result, the molecule has 1 or more double bonds.
C-reactive Protein
• High-sensitivity C-reactive protein (hs-CRP) •Protein produced primarily by liver in response to inflammation •Marker for CVD and hypertension A "marker" is an early physiological warning sign that can be measured.
