It seems like nearly everyone I see in my practice lately avoids fats. When recalling their daily diet to me, they proudly point out all the low fat and fat-free foods they eat. This is all very well, but I am not too impressed. The reason is that fat is essential for good health. With the growing controversy in the media recently regarding cholesterol and statin drugs, it is time to set the record straight about the benefits of fats.
So why do we need fats in the diet?
Fats are important for healthy brain function (60% of brain is composed of fat), for hormone production, for absorption of certain nutrients and for healthy cell function. Certain fats also carry the ‘fat soluble’ vitamins (vitamin A, D, E & K), so a low fat diet often creates vitamin deficiencies. Fat in a meal will slow down the absorption of other foods such as sugars and increases satiety – a fact often overlooked. Most fat-free products contain additional sugars and flavours to make up for the absence of fat. This in turn adds calories to the product and can lead to weight gain despite its fat-free label. Many people report being hungry again soon after eating fat free products which may cause them to eat more. Indeed, the increasing incidence of obesity and diabetes is linked to carbohydrate intake, not fat intake.
So fats are essential in the diet but all fats are not equal when it comes to health. Let’s look at different fats and see which ones are good for us and which ones are not so good. Firstly you need to know that fats are categorised according to their chemical structure. In reality, all fats are made up of different types of fatty acids, however the dominant fat is the one they are grouped under. The more ‘saturated’ a fat, the more stable it is, whereas the ‘polyunsaturated’ fats have inherent instability in the structure and can easily be denatured with cooking and processing.
- Saturated Fats – saturated fats are found mostly in animal foods (eg. butter), but also in coconut and palm oils. While these fats have been demonised in recent years, saturated fats make up 50% of every cell membrane in the body, contain important vitamins and are required for a host of body functions including healthy immunity. These fats are also very stable for cooking.
- Monounsaturated Fats – well known one is olive oil, but many people are surprised to learn that lard (pig fat) is also a monounsaturated fat. Monounsaturates are healthy fats that are also quite stable for cooking.
- Polyunsaturated Fats – this large group of fats have a chemical structure that makes it vulnerable to oxidation and damage. Polyunsaturates include the wonderful omega 3 fats (eg. Fish oil) linked to healthy hearts and smart brains. While many of these oils have health benefits, they should never be heated in cooking as they form free radicals.
- Trans Fats – these are not generally found in nature and are formed when polyunsaturated fats are hydrogenated. Hydrogenation is used to convert liquid vegetable oils into margarines or other solid fats and in the process changes its shape making it a very unstable free radical. Trans fats can damage healthy cells in the body and have been linked to cardiovascular disease and cancer. You should void margarines and all commercial foods containing margarines or hydrogenated fats (check labels). See my article on butter versus margarine for more info.
- Cholesterol – around 80% of the cholesterol in our blood is made by our liver. Cholesterol is essential for hormone production, bone health, brain function, digestion and other cell functions. Avoiding cholesterol in the diet will only have a modest effect on blood levels of cholesterol. While many people are scared of cholesterol and its theoretical link to heart disease, it is much more complex than merely looking at cholesterol levels in the blood. Eg. The proteins lipoprotein (a) and homocysteine are also involved in atherosclerosis and lifestyle factors such as smoking and stress are linked to heart disease. For more information about cholesterol see Cholesterol & Health website.
So don’t assume that a fat free diet is healthy as healthy fats are essential for many aspects of body function. If you are worried about weight gain, cut back on the carbs before you cut back on the fats!