Not only is a low-fat diet unappealing, our bodies need a certain amount of fat to work properly. Still, too much of the wrong kind can do harm, increasing blood cholesterol levels and the risk of heart disease. The wrong kind of fat makes ’bad’ cholesterol levels rise while ’good’ levels fall (see sidebar). The risk of clogged arteries, high blood pressure, heart attack and stroke increases.
Does a high-fat diet cause weight gain? No matter what we eat, extra pounds result from taking in more calories than we can burn. The problem with dietary fat is that it is very high in calories - more than double per gram compared to carbohydrate or protein.
Extra fat calories really add up, especially those from high-fat foods like fatty meat, cream sauces and snack foods. Eating out is also tricky, as it is hard to be certain about exactly what fats a meal might contain. These types of foods often have more of the ‘bad’ fats in them, increasing the risk of disease.
Some fats increase the risk for disease, while others lower it. The key is to use good rather than bad fats. Avoid overdoing any food to keep your weight within a healthy range.
Good fats can improve blood cholesterol levels and may even lower the risks of other diseases, especially when used instead of bad fats.
Unsaturated fats come from plant sources, such as vegetable oils, nuts, and seeds, and from fish. There are two types of unsaturated fats.
Bad fats make blood cholesterol levels worse, and may increase risk of other diseases.
Saturated fat occurs naturally in nearly all fatty foods, but mostly in higher fat meat and dairy products, poultry skin, and tropical oils like palm kernel and coconut. Since these fats can raise both good and bad cholesterol in the blood, it is important to limit them.
A ‘low cholesterol diet’ was once recommended to improve blood cholesterol levels. We now know that this does not improve blood cholesterol for the majority of the population. Saturated and trans fats, not dietary cholesterol, are the major contributors to elevated blood cholesterol in most people.
Most trans fat in the diet is industrially produced. Hydrogenation is the process of heating vegetable oil in the presence of hydrogen. Oils become more stable and are solid at room temperature. Margarine and shortening are made from vegetable oil in this way. Food processors use trans fat to extend the shelf life of foods. Many restaurants use it to keep oil stable for deep-frying. In liquid form, vegetable oils are healthy. Once hydrogenated, they are similar to and worse for us than saturated fats.
Most trans fat in the diet comes from harder margarines, snack and instant foods, as well as commercially fried foods and bakery products made with shortening, margarine or partially hydrogenated oil. The trans fat content of these foods can be as high as 45 per cent.
Trans fat increases bad (LDL) cholesterol more than saturated fat. Unlike saturated fat, it also tends to reduce good (HDL) cholesterol. Trans fat also increases blood levels of triglycerides, another blood fat that in high levels is linked to higher risk of heart disease and stroke.
In some foods such as dairy products, beef, goat and lamb, trans fat occurs naturally in low levels (two to six per cent of the fat). These fats are produced in the animal by the normal action of bacteria in the gut. To date, there is no evidence that this kind causes the same health risks as manufactured trans fats do.
Since nobody knows how much trans fat is too much, limit it as much as possible. (In some U.S. cities, the use of trans fats by restaurants have been restricted.) A large study found that even one gram of trans fat per day could increase the risk of heart disease by 20 per cent. What worries some scientists is that Canadians are eating high levels of trans fats on a daily basis – between eight and 39 grams a day. Furthermore, Canadian breast milk contains some of the highest levels of trans fats in the world because women are consuming high levels of trans fat – primarily from baked and prepared foods.
Canada recently became the first country in the world requiring food labels to list the amount of trans fat, along with saturated fat, in a food. These two fats are most linked to heart disease. Cholesterol is also listed on the label, although it is less of a risk.
Unfortunately, at this time, restaurants are not required to do trans fat labelling. Baby foods are not labeled yet either. However, many manufacturers and restaurants have already taken steps to reduce or remove trans fats from their products.
Currently, Health Canada is developing recommendations and strategies to reduce trans fat in Canadian food to the lowest possible levels.
All vegetable oils combine varying amounts of saturated, monounsaturated and polyunsaturated fats. In other words, there is no such thing as an oil that has no saturated fat, or one containing only polyunsaturated or monounsaturated fat. The difference in oils lies in the proportions that each contains of the three basic types of fat.
Generally, we tend to eat enough polyunsaturated omega-6 fats, such as soy oil, particularly if we buy prepared foods like spaghetti sauce and salad dressings. At home, balance out your fat intake by using oils higher in monounsaturates and omega-3 fats. Canola and olive oil are two good choices. Too many omega-6 fats may keep the omega-3 fats from doing their job.
Some misleading information about canola oil has appeared on the Internet. Contrary to what is being said, canola oil is not harmful to health. Clinical studies done over the past 20 years on thousands of healthy volunteers have shown that canola oil, used as part of a balanced diet, helps lower the risk of heart disease. Canola oil is very low in saturated fat and has a very high level of monounsaturated fat. It is also the best source of omega-3 fats of all popular oils, so it is a healthy choice.
Another point of confusion is that some good fats become unhealthy once heated. This is more of an issue in restaurants when oil is heated at high temperatures for long periods of time, as with deep-frying. As well, oil that is reused or allowed to burn breaks down and has low nutritional value.
Most unsaturated oils can withstand the high temperatures needed for a stir fry or baking. At home, the key is to use small amounts of the good fats and avoid overcooking.
Keep in mind that any oil is 100 per cent fat, with a whopping 120 calories per tablespoon. Curbing the total amount of fat in the diet is a good idea. Particularly try to avoid deep-fried foods as they are higher in fat and calories.
Have you decided which spread is better? It depends, because either could be part of your diet. If you choose a margarine low in saturated and trans fat, then you are making a good choice. Soft tub margarine with ‘non-hydrogenated’ on the label is the best choice. However, if nothing but butter will do, use it in small amounts where taste matters. Use healthier oils the rest of the time. Remember, it is what you do most of the time that counts.