Dietary fat has a bad reputation. The human diet has contained rather a lot of fat for a long time. Lard, dripping and butter were once common place in kitchens, mothers would bake cookies, cakes, pies and flans on an almost daily basis for their families. Then the western world was suddenly gripped by rising reports of heart disease in the 1970’s and fat was blamed. But was that fair?
In recent years there has been a fat revival. Some nutritionists have said that fat is the key to good health. Many people who suffer from diabetes have adopted a “primal diet” which involves eating large amounts of saturated fat, protein and little else. Also, some oils are good for health, but how do these fit in with our diets? The most recent research has found that fat can fight tooth decay – under some specific circumstances. On the one hand many people now say that more fat is good, while on the other hand doctors and health professionals are still saying that it is very unhealthy. Should we be eating it?
Fat is a vital part of our diet. The body needs fats and oils. However, excessive dietary fat does raise cholesterol levels and this can lead to heart disease and stroke. A healthy and balanced diet provides all the fat we need, some lean proteins such as chicken, fish and eggs, contain fat. Nuts, seeds and olive oils are also good sources of fat and oils, as are some fruits such as avocado and coconuts (coconuts can be classified as a fruit or a nut, but when we talk about the fruit we refer to the fleshy part).
Saturated Fat
Saturated fat (proper name is actually saturated fatty acid) is the fat that is most dangerous to health. It causes the bad cholesterol levels to rise (the LDL – low density lipoproteins) and this leads to a build up of plaque on the lining of the arteries. As the plaque accumulates over time the arteries can become blocked which can lead to heart attacks and strokes.
Consumption of saturated fat has been falling since 1970. In 1970 total fat intake in the UK was around 121 g per day, and this represented around 19.3% of total energy from diet. By the year 2000 consumption had fallen to around 74 g per day, which is around 15% of total dietary energy. However, the latest recommendations are that only 11% of total energy comes from the consumption of saturated fatty acids.
There are several types of saturated fat: Stearic acid, palmitic acid, butyric acid, myristic acid and lauric acid. Stearic acid and palmitic acid are the two most common saturate fats found in diet.
Stearic acid is found in many animal and vegetable fats and oils. Palmitic acid is found in palm oil, meats, cheeses, butter and dairy products. Overall, saturated fat is commonly found in animal fats, such as butter, beef fat, lard and some synthetic fats such as hard margarine. Red meat (burgers, steaks, meat pies) is a major contributor, as are cookies, cakes, pies and flans, all of which are made with butter.
Saturated fat is generally present in most convenience foods, ready meals and junk food. It is used to give flavor and is needed to bind flour for pasties, pies and other baked foods.
There has been a lot of research over the years examining the relationship between the consumption of saturated fat and the development of coronary heart disease. Some studies have found that there is only an insignificant connection. For example, Andrew Mente (2009) said that “insufficient evidence of association is present for intake of … saturated and polyunsaturated fatty acids …”.
Also, a research paper by Patty W Siri-Tarino (and others, 2010) concluded that “there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD.”
However, overall research has shown that a 30% reduction in the intake of saturated fats over a 6 month period results in a 14% reduction in heart attack, stroke and unplanned heart surgery (The Cochrane Library, 2011). It is important to note that individual studies can give unexpected results, so a piece of research should not be viewed in isolation from other epidemiological studies and research.
As for the nutritionists and personal trainers who are currently advocating high saturated fat diets, the best advice is to be careful and use your common sense. There is no need to consume a diet high in saturated fat for the purposes of weight loss or fitness, so why adopt these “primal” diets that suggest it is all healthy? The world’s best athletes consume well balanced diets with most of their energy from carbohydrates, not fats.
Too Much of a Good Thing
Just to emphasise this point, then next time you read advice telling you that saturated fat is healthy and that it is vital to many bodily functions, remember that you can have too much of a good thing. Yes, saturated fat is needed by the human body. But we do not need a lot of it, and too much will raise risk of heart disease.
It is possible that some of the people who advocate a high fat diet are also exercising so much that they are burning off excess energy and clearing the cholesterol plaque from their arteries. This is all very well for them. But it is not good advice to attempt to mimic what somebody else is doing, and certainly not a good idea to adopt the diet of somebody who is exercising for 3 hours a day when you are only doing 1 hour a week.
Trans Fats and Hydrogenated Vegetable Oil
Trans fats are the other really unhealthy fat. They raise cholesterol levels in the blood just like saturated fats. Trans fats should not provide any more than 2% of your total energy, which is about 5 g per day. Fortunately many food manufacturer have reduced the trans fat content of their food.
Cholesterol
Cholesterol is not actually all bad. You may know that saturated fat causes increased cholesterol levels, which in turn causes heart disease and other problems. However, cholesterol is vital to good health.
Cholesterol is required for the formation of all human cell membranes. It is also required for the formation of bile salts, which are needed to allow the absorption of fats from the digestive system into the blood. Finally, various hormones, some steroids and vitamin D all need cholesterol to function.
“variations in dietary intake of cholesterol do not, for most individuals, have much effect on blood cholesterol levels” Audrey Brown, 2011.
This means that eggs can be a healthy part of a balanced diet. In the past nutritionists advised against eating eggs because of their high cholesterol content, however, they are actually very healthy. As well as containing a lot of protein, they contain all the essential amino acids required by humans and also many vitamins, healthy fats and oils. Only 27% of the fat in an egg is saturated too, which means that 73% of the fat is good fat. Egg yolks contain most of the fat and cholesterol, the egg white is almost pure protein.
However, people with diabetes should keep all saturated fat and dietary cholesterol to a minimum as they are at higher risk of developing coronary heart disease.
Unsaturated Fats
Unsaturated fats are the healthy fats which can help to combat rising blood cholesterol levels. These include mono-unsaturated fatty acids, polyunsaturated fatty acids (PUFA) and omega-3 fatty acids. These are found in many seeds, fish, nuts and soy beans. Olive oil is about 75% monounsaturated fat, and cashes and beef fat also contain monounsaturated fat.
Essential Fatty Acids
Fats are made up of fatty acids, and while our bodies can synthesise most of the fatty acids we need, some must be obtained from the diet. These are called essential fatty acids. There are two essential fatty acids, linoleic acid and linolenic acid. Linoleic acid is found in some meats, eggs, nuts and many oils. Linolenic acid is found in dark green leafy vegetables, as well as nuts and the oils derived from them, and also a little is found in poultry meat. These fats are polyunsaturated.
Both of these essential fatty acids are vital for the healthy function of the nervous system and also for fat metabolism. They are also vital for the formation of cell membranes and help with the control of blood pressure, blood clotting, inflammation and maintenance of body temperature.
Does Eating Fat Make You Fat?
Yes and no. While it is a myth that eating fat causes immediate weight gain (fat accumulation), fat is very high in energy and a diet that is high in fat is generally more calorific than one that is mostly plant based.
For instance, an average meat pie, that has saturated fat within the meat and the pastry, has around 220 Calories in a 100g serving. By contrast, 100g of mixed salad leaves contains around 17 Calories.
A 100g serving porridge (oats without the milk) contains around 360 Calories. More calories, and slower release energy, so you stay full for longer, and they are better for your health.
How To Eat Healthy Fat
All you need to ensure is that you eat a well balanced and healthy diet. Healthy fats are present in a wide range of foods, so if you consume fish, poultry, dairy, lean red meat, eggs, seafood, vegetables, nuts, seeds and olive oil, you will be taking in healthy fats. A simple diet will provide all the fat you need. Avoiding fast food, convenience foods and baked foods (cookies, cakes, pies, pastries) will help limit the bad fats.
References and Resources
“Studying Human Nutrition” by Audrey Brown. 2011. The Open University. ISBN B000WB9KYO
“Fat: the facts” NHS Choices.
“Reduced or modified dietary fat for preventing cardiovascular disease” by Hooper L, Summerbell CD, Thompson R, Sills D, Roberts FG, Moore H, Smith GD. July 2011. The Cochrane Library (7): CD002137.
“Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease” by Patty W Siri-Tarino, Qi Sun, Frank B Hu, and Ronald M Krauss. 2010. American Journal of Clinical Nutrition.
“Nutrition and healthy eating: Dietary fats: Know which types to choose” Mayo Clinic.
“Dietary Fats” Medicine Plus