For many years the finger was pointed at fat for increasing the risk of obesity, heart disease, cancer and other diseases. Eating too much of certain types of fat can be harmful but we need to be mindful that some fats are essential for normal body function and good health. Many remain confused about the role of fat in the diet. Is it a friend or foe?
Why do we need dietary fat?
Fat is needed in the diet as an energy source. Gram for gram it provides more than twice as many calories as carbohydrates and proteins (fat provides 9 calories per gram while carbohydrates, including sugars, and proteins provide 4 cals per gram).
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| Fast food: A foe indeed |
Fat supplies essential fatty acids such as linoleic and linolenic acids in the diet, is needed for the regulation of cholesterol metabolism, prostaglandin production and for the supply and/or absorption of fat soluble vitamins (Vitamins, A,D, E and carotenoids).
Most of the fat in the body is stored as adipose tissue (fat cells) which store energy, insulate the body and cushion organs.
Fats and health – what
are the facts?
Many nutrition recommendations in the 1980s and onwards called for low fat diets. High fat diets were thought to contribute to obesity, heart disease and cancer. However, many scientists are now questioning simple messages about fat reduction especially given emerging research that the type of fat may be at least as important as the amount of fat.
One of the biggest changes in recent years is the report from the World Cancer Research Fund last year which, in contrast to previous reports, did not specifically include a recommendation on fat reduction.
Cancer: The World Cancer Research Fund (WCRF) and the American Institute for Cancer Research report on ‘Food, Nutrition, Physical Activity and the Prevention of Cancer’ (2007) reviewed all of the science on dietary fats and oils and cancer risk.
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| avocado constitute friendly fats |
The report concluded that " ... there is only limited evidence suggesting that diets relatively high in fats and oils (in total or any type) are in themselves a cause of cancer. This judgment contrasts with those of earlier reports which concluded from evidence then available that diets high in fats and oils might be a substantial cause of some cancers".
Overweight and Obesity: Body weight is determined by a complex interaction between genetic, metabolic, behavioural, environmental and cultural influences. In terms of dietary intakes, an increase in body weight occurs when we take in more calories than we expend. Fats, providing twice the calories of proteins or carbohydrates, may lead to weight gain if the excess calories are not balanced by physical activity. However, an excess intake of calories from any source can lead to weight gain.
Heart disease: Excess intakes of saturated and trans fats can increase blood cholesterol, a risk factor in the development of coronary heart disease (CHD). Trans fats can also lower high density lipoprotein levels.
Recommendations to reduce the risk of heart disease are to replace saturated fats with monounsaturated and polyunsaturated fats and to keep the intake of trans fatty acids as low as possible.
A healthy body weight is also important in preventing cardiovascular disease. In the past, low fat diets were the standard recommendation to prevent heart disease. However, new research suggest that higher fat diets with better palatability may provide better heart health benefits provided the right type of fat is eaten. A study comparing low fat (12% total fat) weight loss diets to those with a level of 35% monounsaturated fat but with equivalent calories reported that the diet high in monounsaturated fats lowered LDL cholesterol and oxidative susceptibility thereby lowering the risk of coronary heart disease.
Mediterranean populations eating traditional diets, with high intakes of monounsaturated fats, also appear to enjoy cardio-protective effects.
What are consumers saying?
Fat is a key concern for Asian consumers. The recent study on food labelling undertaken by the Asian Food Information Centre (2007) found that "fat content" was the most commonly searched for information on nutrition labels on foods in Shanghai. In Bangkok, fat content was the fourth most commonly sought piece of information.
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| Salmon constitute friendly fats |
The study also found high levels of confusion about the role of fats in the diets. Significant numbers of consumers associated fat only with calorie levels and many believed that the energy or calorie figure on food labels represented calories from fat alone.
Achieving a healthy balance
Eating too many fats of any kind can be harmful to health but excluding fats can cause a dietary imbalance. The body requires about 25g of fat a day to enable it to absorb fat soluble vitamins and beta carotene. Fats are also vital for the provision of essential fatty acids (omega 3 and omega 6 fatty acids) which the body cannot produce itself.
Here are some tips for making sure the diet is balanced.
- Replace trans (check food labels for TFA content) and saturated fats (animal fats such as butter, the fat on meat) with monounsaturated (olive, canola, avocado, nuts) and polyunsaturated (safflower, sunflower) fats.
- Try to eat oily fish (such as salmon, tuna, sardines and mackerel) at least twice a week. These fish are excellent sources of omega-3 fatty acids.
- Choose low fat dairy products and lean cuts of meat trimmed of fat. Remove the skin from poultry.
- Eat natural sources of fat such as nuts, seeds, grains, avocado and fatty fish to obtain extra nutrients and phytochemicals.
How much fat should you take daily?
Children 30-60g
Teenagers (active) 40-80g
Women 30-60g
Men (active) 40-80g
Heavy activity/athlete 80-120g
Trans Fatty Acids
Hydrogenation is a process which adds hydrogen molecules directly to unsaturated fatty acids such as those found in vegetable oil. Hydrogenated oils contribute unique properties to foods - they make margarines more spreadable and pastries flakier. Trans fatty acids also occur naturally in meat and dairy products.
The US National Academy of Sciences has concluded that trans fatty acids have a similar effect to saturated fats on blood cholesterol - they raise low-density lipoprotein (LDL) cholesterol. TFAs may also lower high-density lipoprotein (HDL) cholesterol. Intakes of trans fatty acids should therefore be kept as low as possible.
- Courtesy Food Facts Asia |
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