Cholesterol and Fat
This section aims to provide some information on cholesterol and the various types of fats in our bodies and our diets. Where possible we will include the best (or worst) food sources for each.
The first section deals with cholesterol. If you want to jump past that to ther other topics please use these quick links:
What is cholesterol anyway?
Cholesterol is a fat found in the cell membranes and transported in our blood. Cholesterol is also required for ensuring vitamins A, D, E and K are available in our bodies. Various hormones including cortisol, adrenaline, progesterone and testosterone depend on cholesterol in their manufacture within the body.
It has been become a household “truth” that having high levels of cholesterol in your body and bloodstream is bad for you, leading to increased risk of suffering a heart attack. In the next few paragraphs we hope to update that general view so that you can adapt your food choices to the most up to date thinking on cholesterol.
Until fairly recently, measuring the amount of cholesterol in the body has involved your medical practitioner taking a blood sample, sending it off for analysis and then giving you a simple cholesterol score (actually a measure of mmol/litre):
Scores between about 3.6 and 5.0 were considered to be the desirable level corresponding to lower risk for heart disease,
between 5.2 and 6.2 was interpreted as borderline high risk,
while anything over 6.2 would put you in the high risk category
Increased levels of cholesterol lead to problems as they contribute to the “furring up” or “hardening” of arteries and blood vessels. As this becomes progressively worse over time it can lead to heart attacks, strokes and other damage to the circulatory system.
Prescription medication is available which can help to maintain a lower level of cholesterol in the blood.
Good and bad cholesterol
Recently more emphasis has been placed on the relative levels of two substances closely associated with transport of cholesterol within the body. Low density lipoprotein or LDL is often referred to as “bad” cholesterol. LDL is involved is delivering cholesterol from the liver to the various cells in the body which need it. Consequently this type is the most common in our blood, usually accounting for around 70% of our total.
Then there is high density lipoprotein or HDL, hailed as “good” cholesterol. HDL has the job of transporting unused cholesterol back to the liver for reprocessing and disposal.
Normally the LDL and HDL work together in a balanced system. If, however, the amount of active “bad” LDL gets too large then too much cholesterol is made available in our bloodstream and the excess can be included in deposits on our artery walls.
HDL has the ability to carry off excess cholesterol including stripping it away from these deposits thus combating the harmful effect of raised “bad” LDL cholesterol levels.
So not only is the total amount of cholesterol important but the amount of HDL compared to LDL is very important. Damage to arteries can and does occur in people with low overall cholesterol levels if their proportion of HDL is too small.
The UK Government recommendation is currently that you should have a total blood cholesterol level of less than 5.0 mmol/litre and an LDL cholesterol level of under 3.0 mmol/litre.
How can I influence my cholesterol levels?
Most of our cholesterol is made in our liver. We can also source cholesterol directly from our food. But if we consume increased amounts of cholesterol our livers normally respond by making less in order to maintain correct levels. It seems that our genetic make-up has a very strong influence in this. People who have parents and close relatives who suffer from high cholesterol levels tend to have higher levels themselves.
Typically around just 20% of our body’s cholesterol comes from the naturally occurring cholesterol in our food. Cholesterol is found to some degree in all food containing animal fats, including common foods like cheese, cream, eggs, beef, pork and poultry. Until fairly recently anyone who wanted to regulate their cholesterol levels was encouraged to restrict these foods in their daily diet.
That advice still remains in place but it has become clear that the biggest dietary influence by far is the effect from saturated fats and trans fats. Having these in our diets significantly increases the amount of LDL “bad” cholesterol and, in the case of trans fatty acids, may even reduce the amount of HDL “good” cholesterol.
If you wish to improve control of cholesterol levels the first step should be to remove trans fats from your dietary intake as much as you can, to zero if possible. Trans fats offer no known nutritional benefit to the body over and above their calories – which could be obtained from a wide range of far more nutritious sources. You can read more about trans fats, including typical foods containing them, towards the bottom of this page.
Saturated fats should also be restricted in the diet. Vegetarians have a head start here if they can cut down on products made with palm oil. Others will come across saturated fats in the animal based foods particularly meat and dairy products.
Unless you have been advised otherwise by a medical practitioner, the good news is that eggs and egg yolks in particular, once the villain of raised cholesterol levels, can now be included in the diet. Some studies have shown that no impact on blood cholesterol was seen even on a diet which included one egg per day. Eggs offer a good source of several key nutrients, although they do also provide saturated fat.
And oily fish such as fresh tuna, mackerel, and salmon provide a great source of the omega-3 fatty acids which help to boost “good” HDL levels. One or two portions per week can form part of a varied and healthy diet.
Fat in the diet
Including fat in your diet is fundamentally important. Many normal body functions rely on it. Some vitamins and other nutrients are consumed along with the fat. The key for ensuring your daily diet is healthy and well-balanced is to include fat in the correct amount using the best mix of the various fat types.
So how much is enough?
Well the World Health Organisation suggests that no more than 30% of our calorie intake comes from fat. The UK Government is a little more generous by setting a maximum figure at 33% of daily calorie intake. In either case, since all fats have a high energy density of 9 kcal per gram, the actual volume of fat in the diet should be relatively low at around 95g per day for an average man and 70g per day for an average woman.
[Editor’s note; 33% of 2,000 kcal = 667 which, divided by 9 = 74g which is then rounded down]
The good, the bad and the downright ugly fats in the diet
The good fats are the unsaturated fats. These are split down into monounsaturated fats and polyunsaturated fats. The latter encompasses the omega-3 and omega-6 families of fats.
Monounsaturated fats can be found in our diets in olive oil, rapeseed oil (often the main constituent in the vegetable oils bought in the supermarket), nuts such as almonds, walnuts, cashews, peanuts and peanut butter, seeds like sunflower and sesame seeds and in avocados.
When used in place of saturated fats these monounsaturated fats help to lower the levels of potentially harmful LDL in the blood without lowering the “good” HDL.
Many of the seed and nut oils can be easily damaged by heating them. For that reason it is best to always use olive oil for frying or baking foods.
Polyunsaturated fats should form around a third of our total fat consumption. The main sources are nuts, seeds and seed oils like sunflower and sesame. Margarines made from sunflower oil also provide a common food containing polyunsaturated fat.
Two essential fats which fall within the polyunsaturated fats are found in the omega-3 and omega-6 families. The omega-3 fatty acids are needed only in small amounts in the development and function of the brain and retina. Oily fish provide the best source for many people with salmon, fresh tuna (not tinned as the processing degrades the omega-3 fats), mackerel, sardines and pilchards being the most popular. Vegetarian sources are linseed (flax) oil, cereals and fat spreads. Availability of functional foods such as bread, eggs and milk fortified with omega-3 may help boost the intake.
The omega-6 fats are more common being found in olive and sunflower oils plus various fruits, nuts and seeds and in cereal products.
Having too many omega-6 fatty acids may cut down the amount of omega-3 fats which the body can absorb as they both make use of similar processes in the body.
...the bad...
The bad fats are the saturated fats. They come from animal products such a meat and dairy foods. Butter, lard, most margarines and spreads, and many cakes, biscuits, pastries and desserts contain high amounts of saturated fats and should be limited in a healthy diet.
Saturated fats in the diet raise the level of “bad” LDL cholesterol and increase the risk of cardiovascular disease and strokes.
Saturated fats are not thought to be essential for our health and should be cut down to a minimum. Their use is very widespread and removing them from the diet completely would be difficult so the UK Government recommend that they contribute no more than 10% of our caloric intake.
Copyright 2007, President and Fellows of Harvard College
...and the ugly...
The downright ugly are the trans fats. Some trans fats, or trans fatty acids, do occur naturally in food. But the large majority that find their way into our food started life as vegetable fats which have been factory processed to make them easier and more cost effective to use in manufacturers’ food products.
Increasing the amount of trans fats that form part of your diet dramatically increases the risk of coronary heart disease. In the United States the Harvard School of Public Health, along with several other key health promoting bodies, have applied pressure to successive administrations for action to reduce the use of trans fats. They forced a change in labelling laws for prepared and packaged foods such that trans fats must be declared on food labels since January 2006. This, coupled with the adverse publicity, has cause a major and welcome decline in the use of trans fats as an ingredient in products sold in the USA. The city of New York went one step further in 2007 and banned their use completely in the city's restaurants and fast food outlets.
As yet there is no requirement in Europe to declare trans fats on the food labelling. You may be able to deduce it from comparing the total fat with the figures for saturated and unsaturated fats. But you may have better success from spotting trans fats from the product’s list of ingredients. They will be described as hydrogenated fats and partially hydrogenated fats. Hydrogenation is the name of the process which creates trans fatty acids.
If trans fats are so bad why do manufacturers continue to use them in common products?
Well they bring some advantages to the production process. Using trans fats means using a hard or semi-solid fat instead of a liquid fat. This can make processing and achieving particular textures easier. Trans fats can also extend the useful life of both ingredients and finished products, allowing less wastage and more profit for the food manufacturers and retailers.
You will find trans fats in many food products. If you are serious about adopting a healthier diet then most of them will already be on your “avoid” list; biscuits, cakes, buns, pastries, pies, desserts and puddings. However, other may surprise you; cereal bars, ice cream, crackers and some low fat spreads and margarines.
The most recent health advice from independent experts is to reduce the consumption of trans fats in yur diet to zero if possible or as close to that as you can.
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