Fats and oils

Good fats, bad fat

Fats are one of the three macronutrients that nourish the body. They are esters of three fatty acid chains bonded to an alcohol known as glycerol. Fats are also known as triglycerides and they consist of long chains of carbon atoms. In the carbon chains of the fatty acids, there are either single bonds (-C-C-C-) or a combination of single and double bonds (-C-C=C-C). Fats that have only single bonds and are said to be saturated and this kind is found mostly in animal fats. The ones that have one or more double bonds are unsaturated fats found commonly in plants and fish. When there is only one double bond, the fatty acid is known as monounsaturated fatty acid. Where there is more than one double bond, it is referred to as polyunsaturated fatty acid.

The double bond of the unsaturated fat can be broken into two and each half of the bond made to take up a hydrogen atom. When this happens, all the bonds become single and the fat is said to be saturated. This is achieved by heating liquid vegetable oil to very high temperatures and pumping hydrogen atoms into it. The heat breaks the double bonds and hydrogen atoms pumped in get attached to the single bonds created. This process is known as hydrogenation.

The saturated fat thus produced, known as trans fat and like all single bonded saturated fats, is solid at room temperature. Not only that, it has an extended shelf life, which is the intention of the manufacturer in the first place. However, saturated fats are dangerous to the consumer.

Types of fats

From the above description, four types of fats can be identified and they are; Monounsaturated fats, Polyunsaturated fats, Trans fat, Saturated fat. Unsaturated (good) fat.

Unsaturated fats are either monounsaturated or polyunsaturated. The monounsaturated have only one double bond in the fatty acid chain, while the polyunsaturated has more than one double bond.

Sources of good fat - monounsaturated: Almonds, hazelnuts, macadamia nuts, peanuts, pecans, cashew nuts, avocados and olives.

Polyunsaturated fats: Walnuts (roasted), pumpkin seeds, sesame seeds, flaxseed, sunflower seed. Polyunsaturated fats are predominantly found in fresh water fatty fish such as salmon, tuna, herring, sardines, mackerel and trout.

Omega 3 is the best-known example of a polyunsaturated fat. There are three types that have been extensively studied which also play important roles in the health of humans.

1. Eicosapentaenoic acid – EPA

2. Docosahexaenoic acid – DHA

These two are commonly found in cold water fatty fish as listed above. Oysters also have some omega 3. Plant sources particularly rich in omega 3 are flaxseed, Brussels sprouts, walnut, spinach and parsley.

3. Alpha-linolenic acid – ALA is the third type of omega 3 fatty acid. Common sources of ALA are flaxseed, walnut and canola oil. Alpha-linolenic acid is also converted to EPA and DHA in the body, but slowly.

Health benefits of omega 3 fatty acid

There is a lot of evidence to support the finding that polyunsaturated fats lower the risk of coronary heart disease CHD. Coronary heart disease is as a result of occlusion of the arteries that supply blood to the heart by plaques. These plaques cut off the blood supply to the heart giving rise to heart attack. Omega 3 and 6 reduce the risk of heart attack by preventing plaque build up on the wall of the arteries. These fatty acids increase the blood level of HDL good cholesterol and reduce LDL bad cholesterol and triglycerides. It is this bad cholesterol that is implicated in the formation of plaques on the arteries.

Polyunsaturated fats also reduce blood clot formation and reduce the blood pressure. It is believed that there effect on blood lipid level, inflammatory response and endothelial function further help to reduce the risk of heart disease. In the same vein, they reduce the risk of stroke. Furthermore, these long chain polyunsaturated fats exhibit some glycaemic control over the blood insulin level thereby regulating blood sugar level. They may be useful in the management of type 2 diabetes.

The brain has been found to be particularly rich in these fatty acids and there is sufficient evidence to show that they support cognitive function and behaviour. In fact it is recommended that pregnant women should increase their dietary intake and supplementation throughout pregnancy and lactation. This helps in the neurological development and cognitive function of the baby.