What are triglycerides?

What are triglycerides?

Ninety-five percent of the fats in foods are triglycerides, compounds that contain one molecule of glycerin and three (tri) molecules of fatty acids. Triglycerides are also the most common fats in your body. You use them to

• Build adipose (fatty tissue)
• Build cholesterol
• Fuel your energy

For the moment, just take my word for the fact that triglycerides are made of one unit of glycerol and three fatty acids. Glycerol is a small, water-soluble carbohydrate that carries fats through blood; fatty acids are chains of carbon atoms with hydrogen atoms attached. You get some triglycerides from food. You also manufacture them in your liver using carbohydrates, alcohol, and some of the cholesterol in food. Either way, high levels of triglycerides are a risk factor for heart disease because, like cholesterol, triglycerides — which travel in lipoproteins — can rough up the lining of your arteries, which enables floating particles to get stuck and begin to build plaque that can clog the artery, leading to a heart attack.

Fats exist in foods—and are usually stored in the body—as Triglycerides. Recent research relating levels of triglycerides in the blood stream to heart attacks in human presents a sometime confusing picture but amounting level evidence suggests that, along with other indicators, triglyceride levels can be used to predict heart attack risk, especially in women and diabetics.

Although the exact mechanisms are not fully known, elevated triglycerides allow increased blood clot formation and may slow the natural deterioration of clots once formed.

Fat molecules are generally made up of four parts:

• A molecule of glycerol.
• three molecules of fatty acids.

Each fatty acid consists of a hydrocarbon chain with a carboxyl group at one end. The glycerol molecule has three hydroxyl groups, each able to interact with the carboxyl group of a fatty acid. Removal of a water molecule at each of the three positions forms a triglyceride.

The three fatty acids in a single fat molecule may be all alike or they may be different. They may contain as few as four carbon atoms or as many as 24. Because fatty acids are synthesized from fragments containing two carbon atoms, the number of carbon atoms in the chain is almost always an even number. In animal fats, 16-carbon,for example, palmitic acid and 18-carbon, for example, stearic acid fatty acids are the most common.

Some fatty acids comprising a given triglyceride have one or more double bonds between their carbon atoms. They are then said to be unsaturated because they can hold more hydrogen atoms than they do.

Mono-unsaturated fats have a single double bond in their fatty acids while polyunsaturated fats, such as trilinolein, have two or more. Additionally, there are trans-fats, which are only partially hydrogenated having fewer double bonds in a trans (as opposed to the usual cis) chemical configuration, and also omega-3 fats, which have at least one double bond, three carbon atoms in from the end of the fatty acid molecule. Linolenic acid is an example and fish oils are generally a rich source of omega-3 fatty acids.

Double bonds are rigid and those in natural fats introduce a kink into the molecule. This prevents the fatty acids from packing close together and as a result, unsaturated fats have a lower melting point than saturated fats. Because most of them are liquid at room temperature, they are called oils. Corn oil, canola oil, cottonseed oil, peanut oil, and olive oil are common examples. As this list suggests, plant fats tend to be unsaturated while fats from such animals as cattle tend to be saturated.

Ingested fats provide the precursors from which fat as well as cholesterol and various phospholipids are created(synthesized). In humans, fat provides the concentrated form of energy. The energy content of fat (9kcal/gram) is more than twice as great as carbohydrates and proteins (4 kcal/gram).Humans can synthesize fat from carbohydrates. However, there are two essential fatty acids that cannot be synthesized this way and must be incorporated into the diet. These are linoleic acid (an omega-6 fat, with the end most double bond 6 carbons from the methyl end) and alphalinolenic acid (an omega-3 fat, with the endmost double bond 3 carbons from the methyl end).

Many studies have examined the relationship between fat in the diet and cardiovascular disease. There is still no consensus, but the evidence seems to indicate that a diet high in fat is harmful and that mono- and poly-unsaturated fats are less harmful than saturated fats, with the exception of trans unsaturated fats which, according to some, are more harmful than saturated fats. It is also been suggested that ingestion of omega-3 unsaturated fats may be protective for the human body

KEY TERMS

Polyunsaturated fat

—A fat missing two or more hydrogen atoms from the maximum number of hydrogen atoms that can be bonded to each carbon in the carbon chain of the compound. These fats can remain liquid at room temperatures.

Saturated fats

—Fats containing the maximum number of hydrogen atoms that can be bonded to each carbon in the carbon chain of the compound.

Triglycerides

—A molecule containing three fatty acids chemically bonded to a glycol molecule..

How high is high?

Clearly, you want to keep your triglycerides in the normal range, which means watching what you eat. But here’s an interesting fact: A diet that’s very low in fat and very high in carbohydrate foods, such as veggies, fruits, and grains — the quintessential “good heart” diet — may actually raise your triglycerides rather than lower them. To lower your triglycerides, the AHA recommends eating a reasonable amount of polyunsaturated fats.

Where cholesterol comes from?

Yes, you get some cholesterol from food, but the curious fact is that most of the cholesterol in your blood and body tissues is produced right in your very own liver. Your liver uses the proteins, fats, and carbohydrates in food to manufacture and churn out about 1 gram (1,000 milligrams) of cholesterol a day.

How cholesterol travels around your body?

Whether your cholesterol comes from food or your liver, it travels through your bloodstream in particles called lipoproteins, a name derived from lipos (the Greek word for “fat”) and protos (Greek for “first” or “most important”). The fatty substances in lipoproteins include cholesterol and triglycerides, the most common fatty substance in the human body The proteins that combine with fats to produce lipoproteins are called apolipoproteins, often abbreviated as apo. Lipoproteins develop through five distinct phases as they mature into the particles that carry cholesterol around your body:

• Phase 1: Chylomicrons
•  Phase 2: Very low-density lipoproteins (VLDLs)
•  Phase 3: Intermediate-density lipoproteins (IDLs)
•  Phase 4: Low-density lipoproteins (LDLs)
•  Phase 5: High-density lipoproteins (HDLs)

How does a chylomicron become a VLDL, then an IDL, then an LDL, and finally, maybe, an HDL? The following roadmap marks the route

How triglycerides are formed?

A lipoprotein is born as a chylomicron, a particle that your intestinal cells assemble from the proteins and fats you eat. Chylomicrons are very, very low-density particles.

Why are some lipoproteins called low-density and others high-density?

The term density refers to a lipoprotein’s weight.

• Protein weighs more than fat.
• Lipoproteins containing proportionately less protein than fat are low density lipoproteins, also known as LDLs. LDLs are the “bad” particles that carry cholesterol into your arteries.
• Lipoproteins containing proportionately more protein than fat are high density lipoproteins, also known as HDLs. HDLs are the “good” particles that ferry cholesterol out of your body.

Now, back to chylomicrons. These lipoproteins start out with very little protein and a lot of light and fluffy fat and cholesterol. But as they flow through your bloodstream from your intestines on their way to your liver (your body’s lipoprotein factory), the chylomicrons release their fats, known a triglycerides, into your blood.

Fat as a Nutrient

Fat is an essential nutrient, because our bodies require small amounts of several fatty acids from foods (the so-called essential fatty acids) to build cell membranes and to make several indispensable hormones, namely, the steroid hormones testosterone, progesterone, and estrogen, and the hormone-like prostaglandins. Dietary fats also permit one group of vitamins, the fat-soluble vitamins (A, D, E, and K), to be absorbed from foods during the process of digestion. Fats help these vitamins to be transported through the blood to their destinations. The fat in our bodies also provides protective insulation and shock absorption for vital organs.

As a macronutrient, fat is a source of energy (calories). The fat in food supplies about 9 calories per gram, more than twice the number of calories as the same amount of protein or carbohydrate. As a result, high-fat foods are considered “calorie-dense” energy sources.

Any dietary fat that is not used by the body for energy is stored in fat cells (adipocytes), the constituents of fat (adipose) tissue The Dietary Guidelines for Americans recommend that no more than 30 percent of our calories should come from fat, and only a third of that should be saturated fat.

Dietary fats, or triglycerides, are the fats in foods. They are molecules made of fatty acids (chain-like molecules of carbon, hydrogen, and oxygen) linked in groups of three to a backbone called glycerol. When we eat foods that contain fat, the fatty acids are separated from their glycerol backbone during the process of digestion.

Fatty acids are either saturated or unsaturated, terms that refer to the relative number of hydrogen atoms attached to a carbon chain. Fat in the foods that we eat is made up of mixtures of fatty acids—some fats may be mostly unsaturated, whereas others are mostly saturated Monounsaturated fatty acids are fatty acids that lack one pair of hydrogen atoms on their carbon chain.

Foods rich in monounsaturated fatty acids include canola, nut, and olive oils; they are liquid at room temperature. A diet that provides the primary source of fat as monounsaturated fat (frequently in the form of olive oil) and includes only small amounts of animal products has been linked to a lower risk of coronary artery disease. This type of diet is commonly eaten by people who live in the region surrounding the Mediterranean Sea. Polyunsaturated fatty acids lack two or more pairs of hydrogen atoms on their carbon chain. Safflower, sunflower, sesame, corn, and soybean oil are among the sources of polyunsaturated fats (which are also liquid at room temperature). The essential fatty acids, linoleic and linolenic acid, are polyunsaturated fats.

Like monounsaturated fats, polyunsaturated fats lower blood cholesterol levels and are an acceptable substitute for saturated fats in the diet. Saturated fatty acids, or saturated fats, consist of fatty acids that are “saturated” with hydrogen. These fats are found primarily in foods of animal origin—meat, poultry, dairy products, and eggs—and in coconut, palm, and palm kernel oil (often called “tropical oils”). Foods that are high in saturated fats are firm at room temperature. Because a high intake of saturated fats increases your risk of coronary artery disease, nutrition experts recommend that less than 10 percent of your calories should come from saturated fats.Omega-3 fatty acids are a class of polyunsaturated fatty acids found in fish (tuna, mackerel, and salmon, in particular)and some plant oils such as canola (rapeseed) oil. These fatty acids have made the news because of the observation that people who frequently eat fish appear to be at lower risk for coronary artery disease.

Omega-3 fatty acids also seem to play a role in your ability to fight infection. Hydrogenated fats are the result of a process in which unsaturated fats are treated to make them solid and more stable at room temperature. The hydrogenation process, which involves the addition of hydrogen atoms, actually results in a saturated fat. Trans-fatty acids are created by hydrogenation. An increase in consumption of these fats is a concern because they have been associated with an increased risk of coronary artery disease. Hydrogenated fat is a common ingredient in stick and tub margarine, commercial baked goods, snack foods, and other processed foods. Cholesterol is a waxy, fat-like substance that is a necessary constituent of cell membranes and serves as a precursor for bile acids (essential for digestion), vitamin D, and an important group of hormones (the steroid hormones). Our livers can make virtually all of the cholesterol needed for these essential functions. Dietary cholesterol is found only in foods of animal origin, that is, meat, poultry, milk, butter, cheese, and eggs.

Foods of plant origin, that is, fruits, vegetables, nuts, seeds, legumes, grains, and the oils derived from them, do not contain cholesterol. Eggs are the food most often associated with cholesterol, because the average large egg contains about 210 milligrams of cholesterol (only in the yolk), and the recommended daily cholesterol intake is 300 mg or less. However, for most people, meat contributes a higher proportion of cholesterol to the diet than do eggs, because cholesterol is found in both the lean and fat portions of meat. Shellfish have acquired an undeserved reputation for being high in cholesterol. Their cholesterol and total fat contents are actually comparatively low