FATS AND YOUR HEALTH

In recent years, scientific studies, public and regulatory policy activity and media coverage have focused extensively on the benefits of eating a low fat diet. However, in some cases, people have taken this advice to the extreme by adopting a diet that is far too low in fat or, worse yet, a diet that has no fat at all. Dietary fat is essential for digestion, absorption and transport of fat-soluble vitamins (vitamin A, D, E and K) and other vital fat soluble substances like carotenoids (yellow pigments in fruits and vegetables which are good for sight) and lycopenes (red pigments in fruits and vegetables which helps body defense system).

Fat in the body is categorized as either essential or storage. Essential fat, which is necessary for normal physiologic functioning, is stored in small amounts in the bone marrow, heart, lung, liver, spleen, kidneys, muscles and some parts of the nervous system. In men about 3% of body fats is considered essential but in women the figure raises to 12%.The higher percentage of essential fat in women is due to sex-specific body fat in the breast, pelvic regions and thighs. The storage fat, which is easily expanded, occurs under the skin and around internal organs to protect them from trauma. The range of total body fat (essential and storage) associated with optimum health is 8% to 24% in males and 21% to 35% in females, in relation total body mass. Sportsmen and women may have far less fat than an average person.

Types of dietary fat
Fats are categorized based on their degree of saturation. The higher the saturation, the more solid they are at room temperature. The unsaturated fats are usually liquid at room temperature. All naturally occurring fats are mixtures of polyunsaturated fats (PUFAs eg. Omega 3 and omega 6), saturated fats (SFAs) and monounsaturated fats (MFAs), although one type predominates in most foods. For example olive, soybean, groundnut and sunflower oils have saturated fats of 15%,15%,19% and 12%; monounsaturates of 76%,23%,48% and 16% and polyunsaturates of 10%,62%,33% and 72% respectively. These values indicate that olive and groundnut oils are rich in monounsaturates where as soybean and sunflower oils are rich in polyunsaturated fats.

Saturated fats- rich foods from animal sources include beef, goat meat, lamb, pork, poultry fat, butter, cream, milk, cheeses and other dairy products made from whole milk. All of these foods also contain dietary cholesterol. Foods from plants that contain saturated fat include coconut, coconut oil, palm oil and palm kernel oil (often called tropical oils), and cocoa butter. Polyunsaturated and monounsaturated fats are the two unsaturated fats. They're found mainly in many fish, nuts, seeds and oils from plants. Some examples of foods that contain these fats include salmon, trout, herring, avocados, walnuts and liquid vegetable oils such as soybean, corn, safflower, canola, olive and sunflower. There is no cholesterol in vegetable based oil. Your body needs cholesterol but in reasonable amounts.

Another group of fat is transfats, which are made by adding hydrogen to vegetable oil to create semi-solid fats, such as shortening (e.g. lard, used for making pastry) and margarine, which help food retain flavour and texture over a long shelf life. Clinical studies have shown that excess intake of trans fats instead of natural oils tend to increase the risk of heart disease by increasing LDL, or “bad” cholesterol, and decreasing HDL, the “good” kind. Trans-fatty acids (TFA) are still found in many processed foods, including crackers, cookies, and fried and baked goods. They cannot be eliminated from the diet completely, since small amounts are found in various animal products such as beef, pork, lamb and the butterfat in butter and milk.

Saturated fats are known to increase both 'good' and 'bad' cholesterol whereas PUFAs decrease both. Therefore a judicious mix of SFAs, MFAs and PUFAs has been recommended for good health. It is more prudent to ensure that most fats in your food are from plant and animal sources that are rich in unsaturated fats than the saturated ones.

Recommended Amounts
Medical nutrition experts recommend that fat make up no more than 35 percent of your daily calories. This is equivalent to eating no more than 70 grams (about one small local tomato puree tinful) of fat daily and trans fat should be less than 2 grams a day (see food labels). Keep in mind, however, that this is an upper limit and that most of these fats should come from monounsaturated and polyunsaturated sources, such as fish, nuts, seeds and vegetable oils.

Dietary cholesterol is strictly linked with foods of animal origin as all of them contain cholesterol since cholesterol is an essential constituent of animal cells. Medical nutrition experts recommend that we restrict dietary cholesterol intake to less than or equal to 300 milligrams a day ( mg/day). However, if you have coronary heart disease or your LDL or 'bad' cholesterol level is too high (above100 mg/dL) limit your cholesterol intake to less than 200 milligrams a day (mg/day). The recommended daily intake for meat, poultry, fish and alternatives should be 3-4 servings, which is equivalent to 6-7 match box (small) sizes of fish or meat or poultry or combined proportions of these a day and about three whole eggs a week. You can take more eggs but be mindful of your other sources of cholesterol.

One egg contains about 213 mg of cholesterol and 100g (about 4 match box –small sizes) of chicken or beef or mutton contains about 70 mg of cholesterol. A similar weight of organ meat- liver and kidney has 150mg of cholesterol. About 100g of brains - mostly obtained from eating sheep, goat and cattle heads carries 2000 mg of cholesterol. Therefore eating the recommended amount of meat or chicken presents no problem but excessive intake of organ meats, eggs and goat or cattle head can elevate blood cholesterol levels. It is advisable to limit intake of fatty portions of meats and if possible trim off visible fat before or after cooking. You can roast, broil, grill, steam or boil these foods instead of frying.

Monounsaturated and polyunsaturated fats have few adverse effects on blood cholesterol levels, but you still need to consume all fats in moderation. Eating large amounts of any fat adds excess calories which can result in excess weight gain.

The writer is a dietician, [email protected]