Lipids are fats.

Fats are greasy substances that are not soluble in water but are soluble in other substances

• Provide a more concentrated source of E than carbohydrates but have 2x calorie content of carbohydrate

• Composed of Carbon, hydrogen and little oxygen

Fat-rich foods are more expensive than carbohydrate-rich foods.

Adipose tissue —> Another name for fatty tissue

Functions

Fats are essential for functioning and structure of body tissues

Fats are a necessary part of cell membranes.

Fat stored in body tissues provides energy when one cannot eat —> during illness and after abdominal surgery

Adipose tissue protects organs and bones from injury

• Serves as protective padding and support

Body fat also serves as insulation from cold.

Fats provide a feeling of satiety (feeling of satisfaction; fullness)

Food Sources

Present in both animal and plant foods.

Animal Foods

• Provide the richest sources of fats —> Red meats

• Includes fat-milk, cream, butter, cheeses made with cream, egg yolks (egg white contains no fat —> made up with protein and water) and fatty fishes

• Saturated fat from animal foods raises serum cholesterol

  • Contributes to heart disease

Plant Foods

• Also contains the richest sources of fat —> cooking oils made from olives or many other ingredients

  • Soybeans, margarine, salad dressing, nuts, seeds, avocados, coconut and coca butter or mayonnaise —> Other sources of rich fat

• DO NOT raise cholesterol levels

  • Heart Healthy —> Very good!!!

Visible and Invisible Fats in Food

This depends on their food sources

Visible fats —> fats in foods that are purchased and used as fats

• Such as butter, margarine, and cooking oils

Invisible fats —> fats that are not immediately noticeable

• Such as whole milk, cheese, fried foods, avocados and nuts

• Makes it difficult for clients on limited-fat digest to regulate their fat intake

Classification

95% of the lipids in the body are triglycerides in the body cells and circulate in the blood

Triglycerides

• Composed of 2 fatty acids attached to a framework of glycerol

  • derived from a water-soluble carbohydrate

  • Glycerol —> A component of fat

Fatty Acids

• organic compounds of carbon atoms which hydrogen atoms are attached

• Classified as essential or nonessential

• Essential fatty acids (EFA)

  • Necessary fats that humans cannot synthesize

  • Obtained through diet

  • Derived from linoleic acid and linolenic acid

    • Both are fatty acids that are essential but cannot be synthesized by the body

  • 2 families of EFA’s —> omega-3 and omega-6

  • Omega-9 —> necessary but nonessential because body can manufacture a modest amount when EFA’s are there.

Saturated Fats

Fats whose carbon atoms contain all of the hydrogen atoms they can

Animals foods have more saturated fats than unsaturated

• Ex: Ice cream, cream, meat, egg yolks, whole milks

Plant foods generally contain more polyunsaturated fatty acids than saturated fatty acids.

• Exceptions from the above rule - Chocolates, coconut, palm oil and palm kernel oils

  • These contain substantial amounts of saturated fatty acids

Foods containing a high proportion of saturated fats are usually solid at room temp

Monounsaturated Fats

Fats that are neither saturated nor polyunsaturated

Ex: olive oil, peanut oil, canola oil, avocados and cashew nuts

Monounsaturated fats lower the amount of bad cholesterol (low density lipoprotein) in the blood but only when they replace saturated fat’s in one’s diet

They have no effect on good cholesterol (high density lipoproteins)

Polyunsaturated Fats

Fats whose carbon atoms contain only limited amount of hydrogen

• Ex: cooking oils made from sunflower, safflower or sesame seeds or from corn or soybeans; soft margarines whose major ingredient is liquid vegetable oil; and fish

Omega-3 fatty acids —> Lower the risk of heart disease

• Found in fish oils —> An increased intake of fatty fish is recommended

Omega-6 (Linoleic acid) has a cholesterol lowering effect

• The use of supplements of either of there fatty acids isn’t recommended

Foods containing high proportions of polyunsaturated fats are usually soft/oily

Trans-Fatty Acids (TFAs)

Produced by adding hydrogen atoms to a liquid fat, making it solid

Major source of TFAs in the diet is baked foods and foods eaten in restaurants

TFAs raise LDLs (bad cholesterol) but decrease HDLs (good cholesterol)

Eating trans fats can increase your risk of devloping heart disease and stroke

• Also associated with a higher risk of developing type 2 diabetes

Hydrogenated Fats

These are polyunsaturated vegetable oils to which hydrogen has been added commercially to make them solid at room temp

• Called hydrogenation —> The combining of fat with hydrogen, thereby making it a saturated fat and solid at room temp

Cholesterol

A fat-like substance that is part of body cells, is synthesized in the liver and available in animal foods

Does NOT exist in plant foods

• Found in egg yolk, fatty meats, shellfish, butter, cream,cheese, whole milk and organ meats.

Cholesterol is though to be a contributing factor in heart disease because of hypercholesterolemia.

• Hypercholesterolemia —> Unusually high levels of cholesterol in the blood also know as high serum cholesterol

Atherosclerosis —> A cardiovascular disease in which plaque forms on the inside of artery walls, reducing the space for blood flow

• If blood can’t flow —> a heart attack occurs

• If it is near the brain —> A stroke occurs

• Plaque —> Fatty deposit on the interior of artery walls

Digestion and Absorption

Chemical digestion of fats occurs mainly in the small intestine.

Not digested in the mouth

In the small intestine, bile turns the fats into like a mixture, then the enzyme reduces them to fatty acids and glycerol which the body absorbs.

Lipoproteins

Main component of blood —> Fats

Lipoproteins —> carriers of fat in the blood

Classified based on their mobility + density

• Chylomicrons —> The largest lipoprotein; transport the lipids after digestion into the body

  • Lightest in weight

  • composed of 80-90% of triglycerides

• Very low density lipoproteins (VLDLs) —> lipoproteins made by the liver to transport lipids throughout the body

  • Composed of 55-65% of triglycerides

  • pick up cholesterol from other lipoproteins in the blood as they lose triglycerides

• Low density lipoproteins (LDLs) —> carry blood cholesterol to the cells

  • has 45% cholesterol with few triglycerides

  • carry most of the blood cholesterol

• High density lipoproteins (HDL) —> lipoproteins that carry cholesterol from cells to the liver

Metabolism and Elimination

Liver control fat metabolism

• Occurs in the cells where fatty acids are broken down to carbon dioxide and water —> releasing E

  • Used or removed from the body by the circulatory, respiratory, and excretory systems

Fats and the Consumer

Lecithin

Fatty substance classified as a phosholipid.

Found in both plant + animal foods —> synthesize in the liver

Used commercially to make food products smooth

Fat Alternatives

Olestra is an example of this —> made from sugar and fatty acids

• Contains no calories but causes cramps and diarrhea.

• Should be used in moderation

Simplesse is made from either egg white or milk proteins

• Used only in cold foods such as ice creams

Oatrim is carbohydrate-based and derived from oat fiber

• heat-stable and can be used in baking but not in frying

Dietary Requirements

Deficiency symptoms do occur when fats provide less than 10% of the total daily calorie requirement

• Eczema can develop

• Weight loss can occur when diets are seriously deficient in fats

Excessive fat in the diet lead to obesity or heart disease, cancers of the colon, breast, uterus, and prostate