You think your fat intake is under control. You rarely eat foods high in cholesterol such as eggs, shrimp and organ meats. You have learned to read labels and you are aware of foods that are high in fat. You have switched from butter to soft margarine, whole milk to one per cent. What more can you do?
When talking about fats and heart disease, your doctor tells you the major culprit in heart disease is cholesterol and the types of fat you eat affect the cholesterol in your blood. You then learn there is 'good' cholesterol (high density lipoprotein or HDL) and 'bad' cholesterol(low-density lipoprotein or LDL). These are affected differently by different dietary fats. At this point in the cholesterol discussion, you may well be confused.
And there is more. The fact is not all the fat you eat is obvious. Some fats come from unexpected sources such as commercial baked goods that often are made with palm or coconut oil. To help clarify the relationship between dietary fats and cholesterol control, here is a look at fats in your body.
A useful place to start in understanding fats in your body is an explanation of cholesterol. Cholesterol is a soft, waxy substance found in the lipids (fats) in the bloodstream and in the body's cells. It is needed to form cell membranes and some important hormones and helps in digestion. Only when the level is too high does it become a risk factor for heart disease.
Cholesterol comes from two sources. It is produced in your body, mostly in the liver, and it is
found in foods that come from animals such as meat, poultry, fish, seafood and dairy products. Foods that come from plants, such as fruits, vegetables, grains, nuts and seeds, do not contain cholesterol.
Fats are composed of strands of carbon atoms linked together. Each carbon has some hydrogen atoms attached. Saturated fats carry all the hydrogen atoms they can hold and there are no openings for more hydrogen atoms. Unsaturated fats contain fewer hydrogen atoms attached to carbon. Polyunsaturated fats are missing two or more hydrogen atoms. Monounsaturated fats are missing one hydrogen atom. These differences affect the properties of a fat.
Saturated fats: Saturated fats are usually solid at room temperature and come primarily from animal sources, such as butter, meat and lard. Three vegetable oils - coconut, palm and
palm kernel oil - are also high in saturated fat content. Saturated fats accelerate the liver's production of the bad LDL cholesterol. That is why you want to avoid saturated fats for cholesterol control.
Polyunsaturated fats: These unsaturated fats help lower your body's production of LDL cholesterol, but may also lower the HDL, or the 'good' cholesterol. Polyunsaturated fats are usually liquid at room temperature and include corn oil, safflower oil and sunflower oil.
Monounsaturated fats: These are also unsaturated fats and are found in vegetable oils such as canola, olive and peanut oil. Mono unsaturates are the preferred choice among fats because they help decrease the LDL 'bad' cholesterol and have no negative affect on HDL cholesterol.
Trans fats: You may also be familiar with the term 'trans fats.' These fats are the by-product of a food manufacturing process called hydrogenation that is used to extend the shelf life of many foods. In trans-fats, the manufacturing process changes the alignment of hydrogen atoms. These fats push the liver's production of cholesterol into high gear. Like saturated fat, trans fats raise the bad LDL cholesterol and lower the good HDL cholesterol, making it even worse than saturated fat!
In 1999, Canadians actually had higher per capita consumption of trans fats than Americans. The key source of trans fats is partially hydrogenated vegetable oil that is used in the production of many of the fast foods we eat: crackers, baked goods, doughnuts, pastries and snack foods such as cheesies and chips. As well, partially hydrogenated fat is used in fast food restaurants for frying foods.
Triglycerides: These are another type of fat found in the human bloodstream. The role of triglycerides in heart disease is less clear than LDL cholesterol but a high level of triglycerides is an indication that you need to pay attention to your diet and to other risk factors for cardiovascular disease.
If a label lists hydrogenated vegetable oil, you should assume that trans fats are present. There is also a group of scientists lobbying the government to discourage the wide-spread use of partially hydrogenated fat by our food industry.
What happens in the body? When there is too much LDL in the blood, it can build up along the walls of the arteries. The substance formed is called plaque, and over time, it gradually blocks the arteries. This condition is known as atherosclerosis. If the plaque causes a blood clot to form, the flow of blood to the heart muscle can be blocked, causing a heart attack. A blockage of the blood flow to the brain can cause a stroke.
Research suggests that HDL carries cholesterol away from the arteries and back to the liver where it is passed from the body. It may be that HDL removes excess cholesterol from the plaque on the artery walls, thus slowing its growth. This is the positive effect from HDL.
Fish, especially salmon, trout and mackerel contain a large amount of omega-3 fatty acids that help to decrease blood clotting and may decrease the risk of a heart attack.
Fibre is something that we as Canadians just do not get enough. Fibre, especially soluble fibre found in oatbran, oatmeal, rice, barley, lentils, vegetables, fruits and psyllium-containing cereals, can help reduce your LDL.
Soy products such as soybeans, tofu and miso contain soluble fibres that may help reduce LDL. Flaxseeds are also high in soluble fibres and omega-3 fatty acids. Try adding these healthy seeds to breads and other baking you do.
Ask your family doctor if you should have your blood fats checked. These are the accepted healthy blood levels of cholesterol and triglycerides:
To lower your risk for heart disease:
LDL cholesterol is called the 'bad' cholesterol because it builds up on the artery walls. HDL cholesterol is called the 'good' cholesterol because it gathers up the excess cholesterol in the blood and carries it back to the liver to be excreted by the body.
TC (total cholesterol) is the sum of HDL, LDL cholesterol and VLDL (mainly triglyceride). Although a low TC is considered good news, your HDL must be higher than 0.9 mmol/L to be considered healthy.
Go easy on cholesterol boosting fats and keep your life active to stay healthy. Every time you reduce your LDL blood cholesterol level by one per cent that means a two to three per cent decline in the risk of a heart attack. Every change you make counts!
For more information about cholesterol, fat and heart health, contact your local Heart and Stroke Foundation office. For specific dietary advice, ask your family doctor for a referral to a dietitian.