(NDT) Chapter 5: Lipids

What Are Lipids?

Diverse groups of molecules that are insoluble in water

• When referring to Fats: lipid content of diets and foods

1. Triglycerides

2. Phospholipids

3. Sterols

Triglycerides

A molecule consisting of a 3 carbon backbone with 3 fatty acid chains

• Classified by chain length, shape and level of saturation

• Long chain fatty acid is most common in our diet (>14)

• Saturated (no double bond, solid at room temp), unsaturated (mono or poly, double bond, liquid at room temp)

• Trans: Hydrogen on opposite sides, kinked shape

Foods rich in fat contain different types of fatty acids.

Essential Fatty Acids

Cannot be produced by the human body and therefore they are needed to be consumed in ones diet.

• Linoleic acid (omega-6 fatty acid) found in vegetable and nut oils

• Alpha Linoleic acid (omega-3 fatty acid) found in dark, green leafy vegetables, soybeans/oil,

flaxseeds/oil, walnuts/oil, canola oil

Omega-3 fatty acid

Fatty acid that reduces inflammatory responses, and blood clotting as well as decreasing the risk of heart disease.

• Found in fish and fish oil

• Eicosapentaenoic acid (EPA) + Docosahexaenoic acid (DPA)

• UL= 5g a day

• Omega 6 (proinflammatory)

Omega-6 fatty acid

Essential polyunsaturated fats that increase inflammatory responses, such as blood clotting

• Key sources include soybean, corn, safflower, and sunflower oils, along with walnuts, sunflower seeds, and almonds

Phospholipids

Contain a glycerol backbone and two fatty acid phosphates

• soluble in water and transports fat into the bloodstream

• manufactured in out bodies (not needed to be consumed)

• Lecithins combine with bile salts= BILE

Sterols: Cholesterol

Subclass of steroid lipids containing multi ring structure which naturally occur in cell membranes in animals, plants and fungi

• Already made in the body therefore consumption is not needed

• Naturally occur in animal products as well as plants (block absorption of dietary cholesterol)

• (e.g.,) Sex hormones, bile and vitamin D

Lipid Digestion: Oral Cavity

• Lingual lipase is secreted by tongue cells + saliva

• Little lipid digestion occurs

Lipid Digestion: Stomach

• Most fat arrives in tact

• Mixed and broken down in droplets

• Gastric lipase digests SOME triglycerides

Lipid Digestion: Small Intestine (Bile)

Majority lipid digestion and absorption will occur in small intestine

• Bile salts (hydrophobic and hydrophilic) break large lipid droplets into small ones

• Large fat droplets filled with triglycerides emulsified by bile

Lipid Digestion: Small intestine (Pancreatic lipase)

• Once it is emulsified the pancreatic lipase can access and break then into free fatty acids

Micelle

• Made of products of lipase digestion along with cholesterol esters

• Transports digestion products into intestinal enterocyte to be ABSORBED

Lipoprotein

Transports lipids into the bloodstream

• Chylomicron: produced in intestine to transport lipids from a meal

• Absorbed by enterocyte of the small intestine then travels through the lymphatic system

Absorption of fats

Chylomicrons are transferred from the lymphatic system to the bloodstream (thoracic duct)

• Short and medium chain fatty acids are easily absorbed

• enter directly into the circulatory system

Chylomicron

Highest in triglycerides

• Transports dietary fat into the body + body’s tissues

VLDL (Very low density lipoprotein)

Transports endogenous lipids, especially triglycerides to various tissues of the body.

LDL (Low density lipoprotein)

• High in cholesterol (transports cholest.)

HDL (High density lipoprotein)

Lowest in triglycerides and cholesterol, transports cholesterol from tissues back into the liver.

Various functions of Lipids

They function to serve energy storage, satiety, flavor, protection and maintaining cell functions)

Essential fatty acids

◦ Eicosanoids

◦ Cell membranes

◦ Needed for growth

Transport of Fat: Chylomicrons

How much fat do we need?

• AMDR (DRI): 25-35%

• Dietary guidelines: los in sat fats <10% and high is 10%>

Selecting healthful fats…

Beneficial fats

• Increase Omega 3’s: Eat more fish

• Sustainable fish, walnuts, chia seeds, pumpkin

  seeds, flaxseed

• Use olive or canola oil in place of butter or margarine

• Select low-fat or nonfat dairy products