Fats, oils, Triglycerides and cholesterol

Fats, oils, and waxes belong to the group of naturally occuring organic materials called lipids. Lipids are those constituents of plants or animals which are insoluble in water but soluble in other organic solvents.

Amongst the various foodstuffs, fats provide the body with maximum energy (9 kcal per gram), approximately twice that for an equal amount of protein or carbohydrates.

Lipids are concentrated sources of energy as well as structural components of cell membranes. Everybody needs a certain amount of dietary fat for normal body functions. When fats are digested, emulsified, and absorbed, they facilitate the intestinal absorption and transport of fat soluble vitamins A, D, E, and K. They are also used to cushion and protect the heart, kidneys and liver. In certain climates subcutaneous body fat helps to insulate the body from the cold and prevent heat loss through the skin. These functions can be met by a daily intake of 15 to 25 grams of fat.

Lipids enter the body through the mouth and pass to the stomach, but are little affected by its acidic environment. They are absorbed primarily in the small intestines, where they are emulsified by salts of the bile acids and are hydrolyzed to fatty acids and glycerol by various water-soluble enzymes (lipases). From the intestines, the hydrolyzed lipids enter the bloodstream and are transported to other organs, mainly the liver, for further metabolism. Ultimately the fatty acids may be degraded to carbon dioxide and water to furnish energy.

There are many types of fatty acids, but they can be grouped into three divisions – saturated fats, monounsaturated fats and polyunsaturated fats. Polyunsaturated fats consist of two classes, omega-3 and omega-6.

Saturated fats have a profound hypercholesterolemic (increase blood cholesterol levels) effect. They are found predominantly in animal products (butter, cheese and meat) but coconut oil and palm oil are common vegetable sources. Saturated fat raises blood cholesterol levels more than anything else in the diet, even more than dietary cholesterol.

Intake of monounsaturated fats in oils such as olive oil is thought to be preferable to consumption of polyunsaturated fats in oils such as corn oil because the monounsaturated fats apparently do not lower high-density-lipoprotein (HDL) cholesterol levels. Evidence for this belief is derived primarily from metabolic ward studies of relatively short duration. [Dreon, D.M., Vranizan, K.M., Krauss, R.M., Austin, M.A., and Wood, P.D., The effects of polyunsaturated fat vs monounsaturated fat on plasma lipoproteins, Journal Of The American Medical Association, 263:2462, 1990]

Unsaturated fats come primarily from vegetable oils (safflower, corn, soyabean, cottonseed, sesame, and sunflower oils), nuts and seeds, although fish is a good source of unsaturated fatty acids. Most of the essential fatty acids are found in unsaturated fat, so foods high in saturated fat and cholesterol (animal fat, dairy products and eggs) should be eaten sparingly.

Fats should make up only 10 to 25 percent of the calories (not weight) in your diet. There is an overwhelming consumption of fats in the average Western Diet, this has lead to a huge health problem among population groups with a diet high in animal fats (ice-cream, chocolates, fast foods and desserts). There are many diet related human disorders that are found almost exclusively in the Western World, Coronary Heart Disease (CHD) and cancer of the colon, are a few of the more severe.

This factsheet is for people who want to learn more about cholesterol levels and health. Cholesterol is a type of fat (lipid) made by the body. It is essential for good health and is found in every cell in the body. However, a high cholesterol level in the blood (hypercholesterolaemia) is associated with an increased risk of heart disease and stroke. Seven out of 10 people over 45 have high cholesterol.

Why is high cholesterol a problem?
The main risk associated with high cholesterol is cardiovascular disease (CVD). This includes diseases of the heart and blood vessels. High cholesterol causes blood vessels to become narrowed with fatty deposits called plaques. This can result in heart attacks, strokes and blood vessel problems. For more information see the separate Bupa health factsheets Angina, Heart attack and Stroke.

Types of cholesterol
Cholesterol is transported around the body in the blood attached to a protein. This combination of fat and protein is called a lipoprotein. Lipoproteins can be high density (HDL), low density (LDL) or very low density (VLDL), depending on how much protein there is in relation to fat.

LDL (low density lipoprotein)
Most of the body’s cholesterol is transported as LDL. This is made up of mostly fat and a small amount of protein. Too much LDL in the blood can cause cholesterol deposits to build up in the arteries, making it harder for the blood to flow through these blood vessels. High levels of LDL in the blood are associated with an increased risk of CVD. So LDL is sometimes referred to as " bad cholesterol".

HDL (high density lipoprotein)
A small amount of cholesterol is transported as HDL, which is mostly made up of protein and a small amount of fat.

HDL actually helps prevent cholesterol deposits building up in the arteries. Having low levels of HDL (compared with LDL) in the blood is associated with an increased risk of CVD. So HDL is sometimes referred to as "good cholesterol". Women tend to have a higher levels of HDL cholesterol than men.

If the total cholesterol (TC) level is too high, this is one risk factor for health problems. However, it’s important to consider the relative amounts of HDL and LDL. This is often referred to as the TC:HDL ratio. A high level of HDL and a low level of LDL (so a low TC:HDL ratio) is desirable.

Triglycerides
Triglycerides are a different type of fat, which mostly come from fats in your food. Energy that is eaten and not used immediately is converted into triglycerides and transported to fat cells for storage. This is an important source of stored energy.

Although most triglycerides are stored in fat tissue, low levels are also found in the blood. They are carried in the blood as very low density lipoproteins (VLDL).

A raised level of blood triglycerides together with high LDL can increase the risk of heart disease, particularly in people with diabetes.

There are several factors that may contribute to high blood cholesterol:

a diet that’s high in saturated fat and, less so, high in cholesterol (see How diet affects cholesterol below) lack of exercise may increase LDL ("bad") cholesterol and decrease HDL ("good") cholesterol family history – people are at a higher risk of high cholesterol if they have a direct male relative aged under 55 or a female relative aged under 65 affected by heart disease
being overweight, which may increase LDL ("bad") cholesterol and decrease HDL ("good") cholesterol
age and sex – cholesterol generally rises slightly with increasing age, and men are more likely to be affected than women
drinking more than the recommended amount of alcohol (ie more than three to four units per day for men and two to three units per day for women)
Rarely, high cholesterol can be caused by a condition that runs in the family called a lipid disorder (familial hypercholesterolaemia). About one in 500 people have this condition.

Other health conditions such as poorly controlled diabetes, certain kidney and liver diseases and an underactive thyroid gland may also cause cholesterol levels to rise. Some medicines such as beta-blockers, steroids or thiazides (a type of diuretic) may also affect blood lipid levels.

How diet affects blood cholesterol
Only a small amount of cholesterol comes directly from your diet – the majority is produced by your liver. However, if your diet is high in saturated fats and cholesterol this can cause your liver to produce more LDL ("bad") cholesterol. The amount that diet influences cholesterol levels varies from person to person.

Measuring cholesterol
The amount of cholesterol in your blood is measured in units called millimoles per litre of blood, usually shortened to "mmol/litre" or "mmol/l". America uses the units milligrams per decilitre of blood: "mg/dl" instead. Current UK guidelines state that it is desirable to have a total cholesterol level under 5mmol/l, and an LDL level under 3mmol/l.

In order to estimate your risk of getting CVD, the best indicator of risk is your TC:HDL ratio. A lower ratio is desirable, because this indicates that you have high levels of HDL.

Measuring cholesterol involves a simple blood test. Usually you will be asked not to eat for 12 hours before the test so that your food is completely digested and doesn’t affect the test. A blood sample may be taken either by using a needle and a syringe, or by using a finger prick. You can have this test at your GP surgery, at a hospital appointment, or as part of a health assessment examination.

Home-testing kits for cholesterol may not be very accurate. Also, cholesterol is just one of the risk factors for heart disease. It should ideally be measured under medical supervision so that other important issues, such as blood pressure, age and whether or not you smoke, are taken into account. Speak to your pharmacist about your result if you do choose a home testing kit.

Many people mistake cholesterol as fat. Cholesterol is not a fat, does not have any calories and it is not fattening. Still, that does not mean that it is good for our health. Cholesterol can be really harmful to our health, like anything else in excess for that matter. Of course, fat is also bad for our health

Fat and cholesterol are also known as lipids. Another name for fat is triglyceride. It has been proven that significant contributors to heart disease and high cholesterol are high cholesterol and triglyceride levels. Also, it has been scientifically proven that in order to prevent heart disease and prolong life, it is very important to lower cholesterol and triglyceride levels. This is applied to both men and women, old and young. Lowering cholesterol and triglyceride levels can help even people with established heart disease since this can slow the progression of their disease.

Lowering your cholesterol levels and fat levels is something that will show results in a very short time. The risk of heart disease is already reduced within six months of starting treatment for a high cholesterol level. Slowing or preventing the growth of atherosclerotic plaques in the arteries can also be achieved by lowering the serum cholesterol level. In time, some plaques may even get smaller.

A lower cholesterol level also helps the arteries of the heart dilate during times of stress to provide additional blood flow to the heart muscle. Finally, with the help of cholesterol lowering medications, you can stabilize the atherosclerotic plaque so that it does not rupture. The rupturing process is generally known to be responsible for heart attacks and strokes.
Knowing which fats raise LDL cholesterol and which ones don’t is the first step in lowering your risk of heart disease. In addition to the LDL produced naturally by your body, saturated fat, trans-fatty acids and dietary cholesterol can also raise blood cholesterol. Monounsaturated fats and polyunsaturated fats appear to not raise LDL cholesterol; some studies suggest they might even help lower LDL cholesterol slightly when eaten as part of a low-saturated and trans-fat diet.

The American Heart Association’s Nutrition Committee strongly advises these fat guidelines for healthy Americans over age 2:

Limit total fat intake to less than 25–35 percent of your total calories each day;
Limit saturated fat intake to less than 7 percent of total daily calories;
Limit trans fat intake to less than 1 percent of total daily calories;
The remaining fat should come from sources of monounsaturated and polyunsaturated fats such as nuts, seeds, fish and vegetable oils; and
Limit cholesterol intake to less than 300 mg per day, for most people. If you have coronary heart disease or your LDL cholesterol level is 100 mg/dL or greater, limit your cholesterol intake to less than 200 milligrams a day.
For example, a sedentary female who is 31–50 years old needs about 2,000 calories each day. Therefore, she should consume less than 16 g saturated fat, less than 2 g trans fat and between 50 and 70 grams of total fat each day (with most fats coming from sources of polyunsaturated and monounsaturated fats, such as fish, nuts, seeds and vegetable oils).

KEY RECOMMENDATIONS
Consume less than 10 percent of calories from saturated fatty acids and less than 300 mg/day of cholesterol, and keep trans fatty acid consumption as low as possible.
Keep total fat intake between 20 to 35 percent of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils.
When selecting and preparing meat, poultry, dry beans, and milk or milk products, make choices that are lean, low-fat, or fat-free.
Limit intake of fats and oils high in saturated and/or trans fatty acids, and choose products low in such fats and oils.
Key Recommendations for Specific Population Groups
Children and adolescents. Keep total fat intake between 30 to 35 percent of calories for children 2 to 3 years of age and between 25 to 35 percent of calories for children and adolescents 4 to 18 years of age, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils.
Trans fats are artificially hydrogenated oils used primarily to extend the shelf life of food. Extra hydrogen is pumped into polyunsaturated vegetable oils to saturate the carbon molecules in them. Margarine, butter substitutes and any food containing hydrogenated or partially-hydrogenated oils contain trans fats, even if they are not listed on the label. (The government allows products with less than 0.5% trans fat per serving to call themselves trans-fat-free. The problem is that most people eat more than one serving at a time.)

Trans fats have been the “secret” ingredient of a lot of low-fat “health foods,” even though they’ve been recognized by medicine as a health risk since the early 1970’s. Studies indicate that over 30,000 cardiovascular deaths per year could be avoided if we didn’t eat trans fats. Despite these risks, only the most health-conscious consumers currently avoid trans fats. Congress finally passed legislation requiring standout trans fat labeling on every food product by January 2006.

The dangers of trans fats are very real. The USDA can’t even determine a healthful limit because very small amounts appear to be harmful.

And trans fats are everywhere. A large serving of McDonald’s fries contains 6–7 grams of trans fat. A cup of Bisquick contains 4.5 grams. I once told my children that I would buy them any cookie in the store if they could find a brand that didn’t contain hydrogenated or partially hydrogenated oil. After scouring the store shelves — and believe me they looked — they couldn’t find a single one. Fortunately, this is no longer the case — many products in the aisles nowadays contain no trans fats.

(If you haven’t yet seen the movie “Supersize Me,” you really owe it to yourself and your family to rent it. Everyone will have a good laugh but at the same time see dramatic proof of how quickly fast food can de-rail your metabolism.)

High heat used in rendering oil from plants or cooking with such oils creates trans fatty acids, changing the chemical structure of healthy polyunsaturated fats into something very unhealthy. Our bodies don’t know what to do with this damaged fat. Some scientists believe that molecules of the oil actually break off in the digestive tract to become free radicals.

Likewise, when unsaturated oils are left out in the open air for extended periods of time, as they often are in deep fryers and many home kitchens, they oxidize and turn rancid, which also creates trans fats. So even though polyunsaturated oils have been touted as the healthy choice, you have to treat them carefully — and most food suppliers and restaurants don’t.

When I think of the confusion around fat, I think of Lucy. She’s an average health-conscious woman who reads a lot about nutrition. She’s watching her weight and cholesterol, so for breakfast she has EggBeaters and orange juice; lunch is salad out of a bag (which could be weeks old) with chopped deli ham (processed), topped with a low-fat dressing made from partially hydrogenated soybean oil; and dinner is usually a frozen diet entrée made from unpronounceable ingredients.

Where is the food in that menu? Moreover, where is the fat? In trying to “eat well” — that is, low-fat, low-cholesterol, low-carb — Lucy is actually starving her cells of the vital fats they need to function. Eventually her metabolism will shut down and she’ll be on that slippery slope toward accelerated aging and a lifetime of medication.

Our great-grandmothers ate a diet rich in animal fat for thousands of years out of necessity. It was all they had until polyunsaturated vegetable oils became available at the turn of the century — around the same time heart disease began to increase. Today, the majority of women get their daily fat from salad dressing, and these are often low-fat formulas loaded with unhealthy trans fats and sugar — usually the lower the fat the higher the sugar!

It’s interesting to note that Europeans still eat like we used to, with an emphasis on minimally processed fats, like animal fat and monounsaturated oils instead of polyunsaturated oils. Maybe that’s their weight-maintenance secret

CAUSES OF ABNORMAL BLOOD FATS:

1. POOR DIET

Diets high in unhealthy fats such as trans-fatty acids, found in margarines and hydrogenated vegetable oils. These can be found hidden in a number of over the counter products like cakes, biscuits, dips and the list goes on.

A high intake of fatty meats and full fat dairy products and deep fried foods can also elevate cholesterol levels. If the diet is high in sugar and refined carbohydrates, abnormally high levels of the fat triglyceride may develop. The combination of high triglycerides and low HDL cholesterol is the most powerful risk factor for cardiovascular disease.

2. LIVER DYSFUNCTION/FATTY LIVER

When the liver is not functioning to its optimum this can lead to abnormal cholesterol levels. This is because it is the liver, which manufactures HDL and LDL cholesterol. A healthy liver keeps cholesterol under control. A fatty liver condition may be associated with abnormal cholesterol levels.

3. BLOOD SUGAR ABNORMALITIES

You may have a chemical imbalance that may make you store fat-insulin.

4. HEREDITARY FACTORS

They produce a problem in the liver’s ability to regulate Cholesterol production.