Princess Poly and the Polyunsaturated Fats
Princess Poly eats only polyunsaturated fats. These are liquid at room temperature.
Now, will you help me feed the Polynesian family? Which ones would you feed to King Satch? Which ones to Queen Mama Mono and which ones to Princess Poly? Which ones do you want to use less of?
I hope you enjoyed hearing about the Polynesian family I met on the cruise. I hope they helped you understand what is meant by the different kinds of fat. Think of Princess Poly and the fat you eat. Try to eat more of the polyunsaturated and less of the saturated kind of fat. Most of all, try to get no more than about 30 percent of your calories each day from fat. Try to get most of your calories from complex carbohydrates. Reading labels can help you keep track of the amount and kind of fat you eat.
Monoglycerides, Diglycerides and Triglycerides
A pure fat is made up of fatty acids and glycerol molecules. Let's think of glycerol as the backbone of a pure fat skeleton. The glycerol might be thought of as the torso or backbone part of a fat. To this backbone, there may be one, two or three appendages attached, like our arms and legs are appendages attached to our backbone or torso. A pure fat has up to three appendages attached to its torso. The appendages in fat are called fatty acids; ours are called arms and legs. The name of the fat refers to how many fatty acids are attached. If one fatty acid is attached, the fat is called monoglyceride, if two are attached, it's called diglyceride and if three are attached, triglycerides. Most fats and oils are triglycerides or are made of a glycerol backbone with fatty acids attached.
Fatty acids vary in two ways: the degree of saturation and the length of the carbon chain. The position of unsaturation along the chain is important chemically and nutritionally. Nutritionally, the position of unsaturation may determine the point of breakup of the chain in metabolism and how well the body can handle the remaining fragments.
Degree of saturation - Saturated, Polyunsaturated and Monounsaturated Fatty Acids
The variety in fats comes from the kinds of fatty acids that are linked to the glycerol or backbone of a pure fat. Are all three fatty acids alike? Are all three different? Are they all saturated, monounsaturated or polyunsaturated? All fats and oils contain a mixture of saturated and unsaturated fatty acids; however, the fatty acid in the greatest proportion determines how they are named.
Saturated fatty acid - If all of the carbons are filled with hydrogen or saturated with hydrogen like a sponge is saturated with water, there will just be single bonds between each of the carbons. There will not be any double bonds. This is a saturated fatty acid. Animal fats are generally high in saturated fats.
Monounsaturated fatty acid - If a fatty acid has one double bond, it is monounsaturated. Olive and canola oils are called monounsaturated oils. They have a lot of fatty acids that are monounsaturated.
Polyunsaturated fatty acid - If a fatty acid has two or more double bonds, it is polyunsaturated. Corn, soybean, safflower and other vegetable oils are good sources of polyunsaturated fatty acids. They are called polyunsaturated oils. Vegetable oils seem to reduce the risk of heart and artery disease.
Essential Fatty Acids - Linoleic acid, linolenic acid and arachidonic acid are called essential fatty acids. Sources of essential fatty acids are canola oil, soybean oil, corn oil and others. One tablespoon of corn oil daily provides an adult all the needed essential fatty acids.
Of the three types of polyunsaturated fatty acids essential for nutrition, linoleic acid becomes very important. It is more abundant in foods than the other two and must come from food we eat because it can't be formed by the human body. We get linoleic acid from many grain oils, seed oils and nuts -- especially walnuts, peanuts, poultry and coconuts. Whenever we eat fat or vegetable oils, we are getting linoleic acid. Linoleic acid is also referred to as omega-6 fatty acid.
Linolenic acid also must come from the food we eat since the body doesn't make it. Good sources of linolenic (omega-3) fatty acids include fatty fish such as salmon, tuna, sardines, canola and soybean oil. We need to eat some of these each week. Arachidonic acid is an omega-6 fatty acid, but the body can make this if linoleic acid is supplied in the diet.
The essential fatty acids that include linolenic acid (omega-3), linoleic acid and arachidonic fatty acid (omega-6 fatty acids) form parts of our body structure, have a role in our immune system and vision, help form cell membranes and produce hormone-like compounds that are important regulators of vital body functions such as blood pressure, childbirth, blood clotting immune responses, inflammatory responses and stomach secretions. The essential fatty acids are important for us to include in our diet to maintain good health.
Length of fatty acid's carbon chain
A fatty acid is made up of a chain of carbons, similar to King Satch's necklace. Carbons can have hydrogen attached to them. These necklaces come in three main sizes: short chain, long chain or extra-long chain. Fatty acids that have a short chain have up to 12 carbons in its chain. Fatty acids that have a long chain have up to 18 carbons. Other fatty acids have an extra-long chain of carbons. They have 20 or carbons.
The carbon chains of fatty acids are attached to the glycerol or backbone of a pure fat. Each carbon in the necklace of carbon chains has a specific number or count. The count begins at the end of the carbon necklace that is attached or hooked to the glycerol or backbone. Where the double bonds are placed on the carbon necklace determines the name and is referred to as omega-3, for example. If the double bonds located near the glycerol end first appear at the third carbon, it is called an omega-3 fatty acid. Where the double bonds are placed on the carbon string can make a big difference in how the body metabolizes or used it, as we will see later.
Omega-3 fatty acids in our diets tend to reduce blood clotting that in some people may lead to a heart attack. Linolenic acid is the major omega-3 fatty acid in food. Decreasing the tendency for blood to clot reduces the risk of heart attacks. We get omega-3 fatty acid only from food. Good sources of linolenic (omega-3) fatty acids include fatty fish such as salmon, tuna and sardines and canola and soybean oil. We need to eat some of these sources each week. Linoleic acid is an omega-6 fatty acid. If the double bonds near the glycerol first appear at the sixth carbon, it is an omega-6 fatty acid. We get omega-6 fatty acid only from food. Linoleic acid is the most common fatty acid and is of the most dietary importance.
Most vegetable oils are predominately linoleic acid. We get linoleic fatty acid from corn, soybean, cottonseed, sunflower and safflower plant oils. We need about 1 tablespoon of polyunsaturated vegetable oil (plant oil) per day. When linoleic acid is fed as 25 percent or more of the fat, it lowers blood cholesterol in adults under certain dietary conditions. Oleic acid is an omega-9 fatty acid. Our bodies produce double bonds after the ninth or higher carbons; therefore, we don't have to depend on our diet for this fatty acid.
Cis and Trans Fatty Acids
Monounsaturated and polyunsaturated fatty acids can exist in two forms called cis and trans. Plant fatty acids are in the cis form. A few trans fatty acids are in milk because the bacteria in a cow's stomachs rearrange the fatty acids from the cis form into the trans form. Margarine and shortenings have the highest concentrations of trans fatty acids. Many studies show that trans fatty acids are not linked to significantly increased risk for any disease, especially heart disease and cancer, probably because we eat so little of these. Margarine, a major source of trans fatty acids in our food, has been used increasingly for the last 30 years while blood cholesterol levels and heart disease rate have declined. Trans fatty acids are metabolized like saturated fatty acids in that some forms of trans fatty acids raise blood cholesterol levels when consumed in amounts about four times our average intake. For people who eat a large number of commercially prepared foods and fast food, this is of concern. Trans fatty acids also do not function in the body as essential fatty acids.
There are two main concerns we have regarding trans fatty acids. One is that they are not identified on the food label. Therefore, many consumers are unaware that they are in that food product. Since trans fatty acids tend to behave as saturated fats, labeling trans fatty acids as monounsaturated fats leaves consumers unaware of the true contribution of trans fatty acids to the diet. Second, there is a potential for a high intake by some people. As fast-food restaurants have switched from beef fat (tallow) to vegetable shortenings, the trans fatty acid content of some of their various food products has increased.
We can avoid getting a high intake of trans fatty acids if we:
1. Use little or no stick margarine or shortening.
2. Substitute stick margarine or shortening with softer, tub margarine and vegetable oils.
3. Minimize consumption of deep-fat fried food in restaurants such as French fries, fried pies, potato skins and any deep-fat fried meat, fish or poultry at fast-food restaurants.
The fully saturated fatty acids are solid at room temperature.
Digestion of Fat
We get fat and cholesterol from two sources - from the food we eat and from our liver. About 95% of all fat in the body and in food are triglycerides. Natural fats in meats, grains and nuts are made up mostly of triglycerides. Processed fats, such as hydrogenated commercially hardened shortenings, may contain up to 20 percent of monoglycerides and diglycerides.
Triglycerides are made up of two parts - the glycerol backbone with three fatty acids attached to it. During digestion, most of the fatty acids break away from the triglycerides molecule. These fatty acids then reach the small intestine. When the fatty acids reach the small intestine, they are absorbed by passing through the cell membranes in the small intestine.
Once foods are broken down into nutrients through digestion and are absorbed through the small intestine, the nutrients are carried to various parts of our body through our blood stream. A problem with fat is that fat can't dissolve in our blood. So, something has to happen to the fat in order that it can be carried in our blood to all parts of our body. This process is called emulsification. Breaking down the fats in foods into tiny oil droplets by emulsification, intestinal mixing and the warming action of the body greatly increases their surface areas and improves the process of digestion.
The gallbladder and liver play important roles in emulsifying dietary fats. The liver produces lecithin, a phospholipid, and bile acids which are sterols. Phospholipid and bile acids are secreted into the small intestine by way of the gallbladder to emulsify dietary fats. These are the body's main emulsifiers. Lecithin (less-uh-thin) is a group of phospholipids containing two fatty acids, a phosphate group and a base. The membrane of cells is made up mostly of two layers of phospholipids, arranged along the length of the cell. It creates a shell around the cell. A cell membrane is made up of other things in addition to phospholipids such as protein, cholesterol and other types of molecules. Cholesterol is a necessary component of cell membranes.
Phospholipids also function as emulsifiers. Emulsifiers are compounds that allow fat to break into small droplets. When they do this, emulsifiers have the ability to suspend fat in water. Because of the emulsifiers, fat can now be suspended in water. Thus, emulsifiers help fat overcome the problem of not being able to dissolve in water.
When the fat is emulsified, it's like giving fat a float that will let the fat float along in the bloodstream throughout our body. Let's pretend that the fat will become cold during it's long trip while traveling in the blood, so during emulsification, fat is wrapped in a coat for warmth. This coat is not called a fur coat; rather, it is called a lipoprotein. Fats leaving the intestine where it is then absorbed in the blood travel in large lipoprotein coats called chylomicrons. The chylomicron structure makes it possible for fat to float in blood.
The other source of fat and cholesterol is our liver. Liver makes both cholesterol and triglycerides. The fat made by the liver also has to be emulsified in order to be carried through the blood. The structure liver makes to emulsify fat is called a very-low density lipoprotein (VLDL). It has lipid or fat in the center with a combination of protein, cholesterol and phospholipid shell coating, similar to the chylomicron structure formed in the small intestine. The VLDL lipoprotein consists of 55-65% triglycerides, 10-15% cholesterol, 15-20% phospholipid and 5-10% protein. It contains the greatest amount by far of triglycerides and the least amount of cholesterol as its other forms. Fat is less dense than water.
Lipoproteins
Both cholesterol and triglycerides are carried through the bloodstream in large molecules called lipoproteins. There are three types of cholesterol-carrying lipoproteins: very-low-density lipoprotein ((VLDL-C), low-density lipoprotein (LDL), and high-density lipoprotein (HDL). Cholesterol in blood can be identified as either VLDL-cholesterol, LDL-cholesterol or HDL-cholesterol, depending on which lipoprotein carries it. High levels of LDL-cholesterol in blood are a primary cause of heart attacks. LDL can be found in the wall of heart arteries. The HDL's are heart healthy; they help remove cholesterol from tissues. Generally, people have a lot more LDL-cholesterol in their blood than HDL-cholesterol.
Elevated lipoprotein may form a role in the formation of blood clots. A lipoprotein concentration greater than 30 mg/dL may double the risk of coronary heart disease. Niacin and estrogen-replacement may help lower the concentration of lipoprotein. Keeping the LDL-C under control may help control lipoprotein. A person who has an elevated lipoprotein level may also increase the risk of death or complications regarding bypass surgery or angioplasty. Our lipoprotein level is determined more by heredity.
Very Low Density Lipoprotein (VLDL)
When the liver makes cholesterol or triglycerides, it is faced with the same problem that the small intestine is faced with - fat doesn't dissolve in water. Since fat is carried by way of the blood stream, it has to be treated with a coating of protein, cholesterol and phospholipid in order that it will float in the blood to various parts of the body. Thus, the liver also coats lipid with a protein, cholesterol, and phospholipid shell, just as the small intestine does for chylomicrons. The liver's version of a chylomicron is a very low density lipoprotein (VLDL). They carry the fat through the blood to body cells. The VLDL is made of 55-65% triglycerides, 10-15% cholesterol, 15-20% phospholipid, and 5-10% protein. With the weight of so much fat, their coat is heavy, so to speak. Similarly to chylomicrons, when the VLDLs leave the liver, the enzyme lipoprotein lipase breaks down the triglycerides in the VLDLs. The VLDL has most of its triglycerides removed upon leaving the liver. With less triglycerides in the VLDL, it becomes more dense because lipids are not as dense as water. Since it becomes more dense than the VLDL, it then becomes an intermediate density lipoprotein, because of the lipid it has lost. About two thirds of this intermediate density lipoprotein goes back into the liver and the rest is converted to low-density lipoproteins (LDLs).
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