Nutrition Chapter 3, Fat as a fuel for exercise

Triglycerides

- Are the largest part of the lipid mass consumed -Structure ----Glycerol + 3 fatty acids (HSL) -Functions ----Energy source and reserve ----Insulation and protection ----Carrier of fat-soluble compounds ----Metabolic properties -------Leptin, resistin, TNF-alpha

Essential fatty acids: Types of fatty acids: monounsaturated fatty acids part 2

-Contain one double bond between carbon atoms -typically liquid at room temperature -Found primarily in plant sources -Recommendations: 15 to 20% total caloric intake -Use of oleic acid (olive, canola, nut oil) in place of carbohydrates -Decreases triglycerides -Increases HDL cholesterol -Increases the total-to-HDL cholesterol ratio

Essential fatty acids: Polyunsaturated fatty acids part 2

-Contain two or more double bonds between carbon atoms -The healthiest of the fats -May help decrease cardiovascular disease risk when used as replacement for saturated fats or refined carbohydrates ----Essential polyunsaturated fatty acids

Essential fatty acids definition

-Humans cannot synthesize double bonds within the last nine carbons of the methyl end (n) of any fatty acid chain -Fatty acids with double bonds in those locations must therefore come from the diet—and are considered essential -Only two EFA are essential: --Omega-3 (α-linolenic acid) ----Reduce blood clotting, dilate blood vessels, reduce inflammation, impaired wound healing, and growth retardation --Omega-6 (linoleic acid) ----Large quantities might contribute inflammations, dermatitis and many skin problems -Need ~2 percent of calories as essential fatty acids ----Men: 17 g of linoleic acid & 1.6 g of alpha-linoleic acid ----Women: 12 g of linoleic acid & 1.1 g of alpha-linoleic acid

Essential fatty acids: Types of fatty acids: monounsaturated fatty acids

-Less hydrogen atoms and one double bond or point of unsaturation -Food sources ----Olives, avocados, and some nuts, like peanuts and almonds

Essential fatty acids: Polyunsaturated fatty acids

-More than one point of unsaturation or more than one double bond -Essential vs. Non-Essential fatty acid (EFA) (α and ϒ linoleic acids) -Food sources ----Most vegetable oils

Lipid digestion and absorption

-Mouth and stomach ----Minimal digestion of triglycerides -----Lingual lipase and gastric lipase -Small intestine ----Emulsified by phospholipids (bile salt) ----Digested by pancreatic lipase ----Absorbed into intestinal cells -----Formed into chylomicrons and moved into lymphatic system

Triglycerides in food

-Sources of omega-3 fatty acids ----Soybean, walnut, & flaxseed ----Salmon & tuna -Sources of omega-6 fatty acids ----Vegetable oils ----Nuts and seeds -Commercial Processing of Fats ----Hydrogenation

Phospholipids

-Structure ----Glycerol + 2 fatty acids + phosphate group with a N- containing component ----hydrophilic and hydrophobic -Functions ----Emulsifiers ----Lipid transport as part of lipoproteins ----Component of cell membranes -Food sources ----Egg yolks, liver, soybeans, peanuts.

Classes of lipids

-Triglyceride: Fatty acids -Phospholipids: Fatty acids -Sterols: Cholesterol

Sterols (cholesterol)

-fatlike substance found in all animal product -Functions ----Component of cell membranes ------Abundant in nerve and brain tissue ----Precursor to other substances ------Sterol hormones & Vitamin A, D, E, K -Synthesis ----Made in the liver ----2000 mg/day -Food sources ----Found ONLY in animal foods

The Daily Value suggests 65 grams of fat as acceptable within a 2,000 Kcalorie diet. If a serving of potato chips contains 10 grams of fat, what percentage of the Daily Value is that? How can you use this Daily Value to determine if you are meeting the estimated needs for fat?

10 grams of fat (from the potato chips) 65 grams of fat for the suggested DV = about 15 percent. By eating a serving of potato chips you have used 15 percent of your total fat suggested for the day. In choosing what else you will eat today, keep in mind that you have used 10 of the allowed 65 grams, so you have 55 grams, or 85 percent of your daily fat intake left.

What percent of energy comes from a serving of potato chips that contains 10 grams of fat and 150 total Kcalories?

10 grams of fat x 9 Kcalories per gram = 90 Kcalories from fat / 150 total Kcalories = .6 x 100 (to convert to a percent) = 60% of Kcalories comes from fat

HDL

= High Density Lipoprotein. They are made in the Liver and Small Intestine and secreted into the bloodstream. Their function is to pick up cholesterol from body cells and take it back to the liver = "reverse cholesterol transport" Potential to help reverse heart disease. Levels should be >35 mg.dl-1, high levels of HDL >60 negate one other risk factor.

LDL

= Low Density Lipoprotein. They are made in the liver as VLDL arise from VLDL once it has lost a lot of its TG's, and secreted into the bloodstream. They are rich in Cholesterol and their main function is to deliver cholesterol to all body cells. Optimal is <100 mg.dl-1

VLDL

= Very Low Density Lipoprotein. They are made in the liver from excess dietary carbohydrate and protein along with the Chylomicron remnant. It is secreted into the bloodstream. Their functions is to deliver TGs which is similar to Chylomicrons, but made by different tissues

Key Terms: Hydrogenation

A chemical reaction in which hydrogen atoms are added to a fat; it produces more saturated fatty acids and converts some unsaturated fatty acids

Key Terms: Monounsaturated fatty acid

A fatty acid in which the carbon chain contains one double bond

Key Terms: Polyunsaturated fatty acids

A fatty acid in which the carbon chain contains two or more double bonds.

If you eat a very high-fat, high-protein, low-carbohydrate diet, how does your body obtain the glucose fuel it needs for essential energy production?

A lack of available carbohydrate accelerates ketone body production. Ketone bodies become the important fuel source.

Key Terms: Cholesterol

A waxy lipid whose chemical structure contains multiple hydrocarbon rings

Key Terms: Omega-3 fatty acid

An essential fatty acid; alpha-linolenic acid is the major type. Alpha-linoleic acid is an essential omega-3 fatty acid that contains 18 carbon atoms and 3 carbon-carbon double bonds.

Key Terms: Omega-6 fatty acids

An essential fatty acid; linoleic acid is the primary type

Key Terms: Phospholipids

Are compounds that consist of a glycerol molecule bonded to two fatty acid molecules, and a phosphate group with a nitrogen-containing component. They have both water-soluble and fat-soluble regions, which make them good emulsifiers.

Key Terms: Essential fatty acids

Are fatty acids that the body needs but cannot synthesize and must obtain from the diet.

Lipoproteins

Are made by the small intestines in the fed state and absorbed into the lymph vessels, then moves into the blood. Their function is to deliver TG's to body cells to be used as fuel

Lipids in the body and diet: HDLs

Are scavenger lipoproteins, picking up excess cholesterol released by dying cells and arterial plaques. These plaques are created by LDL degrading over a long period of time. White blood cells that have embedded themselves in arterial walls damaged by smoking or diabetes have scavenger receptors, which bind to LDL and cause it to release its cholesterol. If HDL levels are low, there is an increased risk for atherosclerotic heart disease.

Lipids in the body and diet: Lipoprotein

Carriers transport lipids through the bloodstream. Chylomicrons are formed in the intestinal tract. They eventually reach the bloodstream. As they travel through the bloodstream, they gradually give up triglycerides to capillary walls. Lipoprotein lipase breaks them down. After 10 hours little is left of the chylomicron except cholesterol-rich remnants.

Key Terms: Subcutaneous fat

Fat stored under the skin

During a fast, when glycogen stores have been depleted, what does the body synthesize glucose from?

Fats (glycerol), amino acids, and non-CHO other sources such as lactate.

Describe why a high level of HDL has a protective effect against atherosclerotic heart disease. .

HDL picks up cholesterol released by dying cells and from cell membranes as they are renewed. HDL also picks up cholesterol from arterial plaques, reducing their accumulation. HDL hands off cholesterol to other lipoproteins, especially IDL, which return the cholesterol to the liver for recycling

Key Terms: Lipoprotein

Is a complex that transports lipids in the lymph and blood. It consists of a central core of triglycerides and cholesterol surrounded by a shell composed of proteins, cholesterol, and phospholipids. The various types differ in size, composition, and density. sterols — A category of lipids that includes cholesterol. They are hydrocarbons with several rings in their structures.

Key Terms: Glycerol

Is the backbone of mono-, di-, and triglycerides; alone, it is a thick, smooth liquid.

Function of Lipids?

Lipids provide -A readily available source of stored energy during times of caloric deprivation -Insulation, protection of vital organs and bones -Means for absorption of the fat-soluble vitamins ----Vitamins: A, D, E, and K -Are precursors to hormones -Cell membrane structure

Classes of lipoproteins (fats in diets)

Lipoproteins: Transport of fat soluble substances Chylomicron (small intestine): Deliver TG's to body cells to be used as fuel Very low density lipoproteins (VLDL): (liver) Deliver TGs to body cells Low Density Lipoprotein (LDL): a product of VLDL metabolism that serves as the primary transporter of cholesterol High Density Lipoprotein (HDL): involved in the reverse transport of cholesterol to the liver (Clearance of cholesterol from circulation)

Describe the role of omega-3 fatty acids in disease prevention

The Omega-3 fatty acids have the overall effect of dilating blood vessels, discouraging blood clotting, and reducing inflammation. Additional health benefits that have been associated with omega-3 fatty acids include the secondary prevention of chronic diseases and an association with inflammatory conditions, ulcerative colitis, cardiovascular disease, type 2 diabetes mellitus, renal disease, mental function, and growth and development.

The dietary guidelines

The dietary guidelines: The Daily Value on food labels recommends consuming 65 grams of fat based on a 2,000-kcal diet. To fulfill the need for omega-6 fatty acids, linoleic acid should provide 2 percent of our calories

Key Terms: Lipoprotein lipase

The major enzyme responsible for the breakdown of lipoproteins and triglycerides in the blood

Key Terms: Ketogenesis

The process in which excess acetyl CoA from fatty acid oxidation is converted into ketone bodies.

Key Terms: VLDL

The triglyceride-rich lipoproteins formed in the liver. They enter the bloodstream and are gradually acted upon by lipoprotein lipase, releasing triglyceride to body cells.

If your estimated energy needs are 2,000 Kcalories/day, and you overeat to 2,300 Kcalories, but 90 percent of your diet intake includes carbohydrate-rich, low-fat foods, what does your body do with the Kcalories it does not use for energy production, and can this result in body weight gain?

When the diet supplies an excess of energy (regardless of the macronutrient source), your cells make fatty acids and triglycerides. Glycerol and fatty acids are assembled into triglycerids on the endoplasmic reticulum. Although excess dietary carbohydrate is not readily converted to fat, it does shift the body's selection of fuel and encourages the accumulation of dietary fat in body fat stores, ultimately resulting in weight gain.

Synthesis of lipoproteins

look at notebook (slide 19)

Fat metabolism and Lipogenesis

look at notebook (slide 20)