Fats, more accurately known as lipids, form a diverse group of essential compounds that include both fats and oils. Found throughout the body, these lipids play a crucial role in maintaining overall health by supporting cell structure, energy storage, and hormone regulation. Understanding the different types of lipids—like triglycerides, cholesterol, and lipoproteins such as LDL, HDL, and VLDL—is key to managing heart health and well-being. In this guide, we’ll dive deep into the world of lipids, explaining how each type impacts your body and the steps you can take to maintain optimal levels.
The Chemist’s View of Fats
“Your blood triglycerides are fine.” If a doctor says this, the patient may be reassured. Most of us are aware nowadays that there is a close relationship between the fats in the blood and the health of the heart. A closer look at the fats will lay the foundation for an understanding of this relationship. Read More
When we speak of fats, we are usually speaking of triglycerides. Almost all the lipids in the diet (95 percent) are triglycerides. The other two classes of dietary lipids are the phospholipids (lecithin is one) and the sterols (among them, cholesterol) . Because the triglycerides predominate in the diet, the following section focuses on them. Read More
1. Triglycerides
Triglycerides come in many sizes and several varieties, but they all share a common structure; all have a “backbone’ of glycerol to which three fatty acids are attached. All glycerol molecules are alike, but the fatty acids may vary in two ways: length and degree of saturation.
Fatty acid chains may contain no double bonds; they are loaded with all hydrogen atoms they carry (that is, be saturated fat) or contain one or more double bonds; some hydrogens are removed (that is, be mono- or polyunsaturated fat). In humans, the majority are saturated or monounsaturated.
The distinction between these kinds of fats is of interest, because people threatened with heart trouble may be told to reduce their intake of saturated fats and to increase their intake of monounsaturated and polyunsaturated fats. (Cutting out butter and using soft margarines or vegetable oils instead is one way to do this.)
Saturated fats have high melting point and are solid at room or body temperature. Polyunsaturated and monounsaturated fats have low melting point and are liquid at room or body temperature. Read More
Importance of Fatty Acids
Fatty acids play essential roles in energy production, cell structure, and hormone synthesis. Alterations in fatty acid metabolism are associated with obesity and diabetes.
2. Cholesterol
Cholesterol is found in the bloodstream and in all cells of the body. It is an essential component of cell membranes and is necessary for various biological functions, including the production of hormones, vitamin D, and bile acids that aid in digestion. Read More
Cholesterol is needed metabolically but is not an essential nutrient, our diet contains little amount of cholesterol. Your liver is manufacturing it. The raw materials that the liver uses to make cholesterol can all be taken from glucose or saturated fatty acids. (Another way of saying the same thing is that cholesterol can be made from either carbohydrate or fat.) The carbohydrates that are used to make cholesterol are the excess carbohydrates that we eat but don’t burn them through physical activity—the importance of regular activity. After manufacture, cholesterol either leaves the liver or is transformed into related compounds like the hormones. The cholesterol that leaves the liver has three possible destinations:
- It may be made into bile and move into the intestine, and some may then be excreted in the feces.
- It may be deposited in body tissues.
- It may wind up accumulating in arteries and causing artery disease.
How Cholesterol is Excreted
Liver uses some of cholesterol to make bile salts, which are released into the intestine to help in fat digestion. After doing their job, some of them reenter the body with absorbed products of fat digestion and is taken into the liver. The cholesterol is thus recycled- back to the liver, once again into the bile salts.
Once out in the intestine, however, some of the bile salts can be trapped by certain kinds of dietary fibers, which carry them out of the body with the feces– the importance of taking fibres in diet. The excretion of bile salts reduces the total amount of cholesterol remaining in the body.
How Cholesterol is Deposited in the Body
Some cholesterol leaves the liver packaged with other lipids for transport to the body tissues. ‘These packages are the lipoproteins, which are vehicles for transportof cholesterol.
The blood carries them through all the body’s arteries, and any tissue can extract lipids from them.
More than nine-tenths of all the body’s cholesterol is located in the cells, where it performs vital structural and metabolic functions. To pass into the cells, lipids must first cross the artery walls and it is in connection with the artery walls that they may be implicated in artery disease(atherosclerosis).
The Lipoproteins
There are several types of lipoproteins that carry cholesterol, including:
- Low-Density Lipoprotein (LDL): Often referred to as “bad” cholesterol, LDL carries cholesterol from the liver to cells throughout the body. High levels of LDL cholesterol are associated with an increased risk of cardiovascular disease because LDL can deposit cholesterol in the walls of arteries, leading to the formation of plaques that can narrow and block blood vessels.
- High-Density Lipoprotein (HDL): Known as “good” cholesterol, HDL helps remove cholesterol from the bloodstream by transporting it back to the liver, where it can be excreted from the body. High levels of HDL cholesterol are associated with a reduced risk of cardiovascular disease because HDL helps prevent the buildup of plaque in arteries.
- Very Low-Density Lipoprotein (VLDL): VLDL is similar to LDL but contains more triglycerides. VLDL carries triglycerides and cholesterol from the liver to cells throughout the body.
The Fats in Food
It seems more than likely that dietary fat (triglycerides) and possibly cholesterol are among the contributing factors in heart and artery disease.Cholesterol accumulates in arteries, and is manufactured largely from fragments derived from saturated fat. Thus, limiting your consumption of fat will do no harm and it may do some good. And on the assumption that some of the body’s cholesterol may come from diet, it may make sense to limit your cholesterol intake as well. The simple recommendation is to avoid excess fats, saturated fats and cholesterol to avoid heart troubles and certain kinds of cancer. Read More
Those who wish to reduce and alter their dietary fat intakes need to know where the fats are found in the food. There are three lists, the milk list, the meat listand the fat list – include foods that contain appreciable amounts of fat:
- Items on the milk list contain protein, carbohydrate, and fat. Skim milk as milk, and of low-fat and whole milk as milk with added fats.
- Items on the meat list contain protein and fat (legumes contain carbohydrate as well). A person studying the meat list may be surprised to know how much kcalories are in meat. An ounce of lean meat supplies 28 kcalories from its protein and 27 kcalories from its fat.
An ounce of high-fat meat supplies the same number of kcalories- -28-from protein, but 72 kcalories from fat.
Two tablespoons of peanut butter, also with 28 kcalories from protein, supply 140 kcalories from fat! Thus, meat, which is often thought of as a protein food, actually. contains more fat energy than protein energy, and. excess consumption of meat often accounts for the. excess weight meat eaters tend to gain.
- To focus on the members of the fat list for a moment, everyone knows that butter, margarine, and oil belong there, but it can be a surprise to discover that bacon, olives, and avocados are also on the list. These foods are listed together because the amount of lipid they contain makes them essentially contributors of pure fat.
Saturated Fat and Cholesterol In Foods
Milk Fats
The fat in milk is mostly saturated fat. The cholesterol content is 25 milligrams per cup of whole milk or 7 milligrams per cup of skim milk. Thus choosing skim in place of whole milk reduces your intakes of both saturated fat and cholesterol. Interestingly, milk has mostly saturated fats, still liquid at room temperature. This property is due to nature of fatty acids ie the short chains of fatty acids in milk.
Plant Based Fats
Coconut oil, palm oil, palm kernel oil are also saturated fats but like milk they contain medium and short chain fatty acids and are soft or liquid at room temperature.
Fats in Meat and Eggs
The fats in meats and eggs are mostly saturated; those in poultry and fish have a better balance between saturated and polyunsaturated fats. As for cholesterol, the foods that contain the highest amounts are such organ meats as liver and kidneys and such shellfish as lobster, oysters, and shrimp. Lower but still detectable levels of cholesterol are contained in beef, ham, lamb, veal, and pork, followed by poultry and fish.
As a general rule, a meat-eater wishing to reduce both saturated fat and cholesterol intake could accomplish these objectives by eating less meat and more poultry and fish (except shellfish). A vegetarian who uses animal products could shift to skim milk and low-fat cheeses, and could limit butter and egg intake. Pure vegetarians eat a diet very low in fat and consume no cholesterol, because plant foods do not contain it.
Eggs contain about 240 milligrams of cholesterol each, all of it in the yolk. For a person trying to adhere strictly to a low cholesterol diet, the use of eggs has to be curtailed. For most people trying to lower blood cholesterol, however, it is not as effective to limit cholesterol intake as to limit saturated fat intake. Evidence on the blood cholesterol-raising effect of eggs has been contradictory. Some experiments have seemed to show that subjects could eat several eggs a day for days at a time without their blood cholesterol’s changing. Others have seemed to show that blood levels would rise if enough eggs were eaten.
In any case, eggs are an inexpensive, high quality protein source, and should probably not be eliminated from most people’s diets, only cut back.
The degree of saturation of a fat determines how hard it is at a given temperature. Thus, you can tell one fat is more saturated than another if it is harder say, at room temperature. Chicken fat, for example, is softer than pork fat, which is softer than beef tallow. Of the three , beef tallow is the most saturated and chicken fat the least saturated.
Polyunsaturated fats melt more readily. Generally speaking, vegetable and fish oils are rich in polyunsaturated, whereas the hard fats–animal fats–are more saturated.
According to U.S Dietary Goals, a low cholesterol diet might allow only 300mg of cholesterol a day or less.
Unsaturated Fats in Foods
Monounsaturated Fats
Sources of these fats are; olive oil, canola oil, peanut oil.
Polyunsaturated Fats
Sunflower oil, corn oil, safflower oil, fish oil. Read More
Hidden Fats in Foods
The fat in some foods is visible: butter on bread, mayonnaise in potato salad, and marbling in raw meat. In many foods, however, fat is hidden, as is the fat in whole milk, cheese, pastries, cookies, cake, hot dogs, crackers, french fries, and ice cream. Nutrition Facts labels can help you learn more about the quantity of fat in the foods you eat.
By: Dr. Maisam Raza, Follow
