Debby asks: Are all fats bad for you?
Wynnie says: Fat plays an important part in your diet - and health - as a source of fuel. It provides essential fatty acids the body can not make itself, and helps to carry fat-soluble vitamins (A, D, K and E) into the bloodstream. It is also needed for nerve transmission and maintaining the integrity of cell membranes.
Yet eating too much fat can lead to weight gain and increase the chance of developing heart disease, strokes and some cancers. Dietary surveys in Hong Kong, United States and Britain show that many people eat much less fat than they did 10 years ago. But the reality is that we are still eating too much.
There are several different kinds of fats present in food - saturated, polyunsaturated, monounsaturated and trans fats. You may also have heard of omega 3, omega 6 fats and hydrogenated fats.
So does it matter what kinds of fats we eat? Although all types of fats provide the same amount of energy - 9 calories per fat gram - all fats are not made equal when it comes to health: some are far more harmful than others.
Two of the most harmful are saturated and trans fats. This is because they both raise 'bad' LDL cholesterol levels in the blood. High levels of 'bad' cholesterol increase our risk of heart disease and stroke.
Saturated fats come mainly from animal products, such as red meat and dairy products, although some oils such as coconut and palm oil are also rich in saturated fat. Saturated fats clog up our heart arteries as well as raise 'bad' cholesterol.
Trans fat are made when hydrogen is added to liquid oils to solidify them and lengthen the shelf life of foods. Trans fats are usually found in vegetable shortening, baked goods such as biscuits and crackers, packaged snacks such as popcorn, and many commercially fried foods such as French fries. Trans fats deliver a fatal double whammy - not only do they raise 'bad' cholesterol levels, but they also lower 'good' HDL cholesterol levels.
But not all fats are bad. Monounsaturated fats are the healthiest. They are found in olive and canola oils, as well as avocados. Polyunsaturated fats are found in oils including safflower, soy and sunflower. These fat help the body to get rid of 'bad' cholesterol, and also reduce the amount of cholesterol inside the artery walls.
Omega 3 fats are essential fats: they can not be produced by the body and so must come from your diet. Good sources of omega 3 include fatty fish, such as salmon, fresh tuna, pilchards and mackerel, flaxseeds, soy and walnuts. Getting enough omega 3 fats reduces the chance of heart disease and boosts the immune system, too.
Omega 6 fats - found in poultry, eggs, vegetable oils, margarine and baked foods - support skin health, lower blood cholesterol, and help make our blood 'sticky' so it clots.
It's important to get the right blend of omega 3 and 6 oils, otherwise they can cancel each other out. Experts recommend a ratio of one part omega 6 to four parts omega 3.
Wynnie Chan is a British-trained nutritionist. If you've got a question for her or would like to be featured in this column, e-mail firstname.lastname@example.org Topics: Chemistry Health Heart Disease