Introduction to foods to lower cholesterol
In this article we will look at the foods to lower cholesterol. High cholesterol is a condition many of us suffer with and can contribute to cardiovascular problems. Cardiovascular problems are especially common in diabetes and therefore medical teams are even more keen to keep cholesterol levels in target.
High cholesterol is a result of lifestyle, genetics and medical background. Unfortunately, we cannot do much about genetics but we can control our lifestyle. Diet and lifestyle plays a huge part in our overall health and this is no different to your cholesterol levels. The same is true for your diabetes control. Though it’s not always easy to control blood glucose levels, for most people, it is a variable we can exert influence over. This is true for most types of diabetes.
Normally it is recommended to keep cholesterol levels below 5mmol/L. However, in diabetes we aim a bit lower. You should aim to keep your cholesterol at 4mmol/l or below. This is because of the cardiovascular risks associated with higher than average glucose levels.
Risk is the currency we deal with in health care. Not everyone with high cholesterol will encounter cardiovascular problems but it increases the risk of them occurring. As you accumulate more risk factors, the chances of something happening, like cardiovascular problems, are increased. Diabetes is one risk factor for cardiovascular complications. Smoking is another huge risk factor for cardiovascular problems. You can probably work out by the way this is going that having high cholesterol is another risk factor for cardiovascular problems. Controlling as many risk factors as possible is important and will help lower your risk.
Therefore, cholesterol is just one part of a large puzzle to keeping you healthy. However, if you ignore some pieces, you will never complete the puzzle. So let’s look at one piece of the puzzle and examine the foods to lower cholesterol.
What is cholesterol?
Cholesterol is a type of fat produced in your liver that is needed in your body. It has lots of different jobs and therefore not all cholesterol is bad cholesterol.
For example, cholesterol is part of your body’s cells outer layers or membranes. It also helps you to produce hormones and vitamins, such as vitamin D, which helps you build strong bones, teeth and keeps muscles healthy. Lastly, cholesterol helps you to make bile which helps you to digest fats that you eat.
Different types of cholesterol
If you watched the video above you’re now in the know about the different types of cholesterol. For those of you that didn’t, let me break it down for you.
Cholesterol is a type of fat. Fat does not like water and therefore struggles getting around your body in the blood because blood is 70% water. Think of a glass of water with oil poured into it. The oil tends to sit on top of the water. This is because fat hates water and doesn’t like to mix with it. Substances that do not like water are called hydrophobic.
This causes a problem for the body. We eat a lot of fat in our diets and the liver produces cholesterol to do the jobs mentioned above. It does this using chylomicrons and lipoproteins. Chylomicrons transport fat to the liver after a meal but it is the lipoproteins we’re interested in here.
Lipoproteins are used to package both triglycerides (another type of fat used for energy) and cholesterol around the body. Lipoproteins are kind of like little buses dropping off and picking up cholesterol and triglycerides as they circulate around the body.
The reason lipoproteins do not encounter this same problem as fat is because they are made of protein (the clues in the name) and protein is not hydrophobic. In fact, protein likes water and so can travel around the blood quite easily. Substances that like water are called hydrophilic.
VLDL, LDL, HDL Cholesterol
You may be more familiar with these types of cholesterol but as I explain them some light bulbs may start to go off in your head.
VLDL and LDL cholesterol
When cholesterol or lipoproteins are released from the liver they are released as very low density lipoproteins (VLDL). They are very low density because these molecules have a high fat content and fat is very low density. Protein on the other hand is high density.
A good analogy to picture this might be likening fat to a life jacket and protein to the person wearing it. If you remove the life jacket, the person will start to sink unless they start swimming. The person sinks because their body is denser than the water. The life jacket makes the person float because air is less dense than water.
As fat is dropped off to the cells of the body by the lipoproteins the fat to protein ratio in the lipoprotein starts to shift in favour of protein. Therefore, the lipoprotein becomes more dense. Returning to our life jacket example, it’s like air being let out of the life jacket.
As cholesterol and triglycerides are dropped off to their destinations the lipoproteins shift from very low density to just low density or LDL (low density lipoprotein). You getting it yet? So VLDL is released from the liver and is full of triglycerides and cholesterol. Gradually this is released making the VLDL become LDL cholesterol. This is because less fat in the lipoprotein makes it more dense.
Damage to the blood vessels
Too much VLDL and LDL circulating in the blood essentially means there is too much fat circulating around your body. These excess lipoproteins can get stuck in and damage the blood vessels. This is why your diabetes team will be on at you to lower your cholesterol if it is high.
In fact, anyone over 40 with diabetes should be taking a statin regardless of their cholesterol levels. This is because statins block the production of too much VLDL and LDL and has proven benefits.
High density lipoproteins (HDL cholesterol) on the other hand have a low fat content and high protein content. These scoop up the remaining cholesterol and triglyceride in the body and whisk it back to the liver to be recycled. Therefore, HDL cholesterol lowers total cholesterol levels.
We use VLDL, LDL or HDL interchangeably with cholesterol when speaking about cholesterol. Though you can now see this isn’t exactly true.
Foods to lower cholesterol
One of the best ways to lower cholesterol is diet and exercise. There is an abundance of research demonstrating how these 2 factors can help improve health markers like cholesterol. Foods to lower cholesterol come in many forms and each exerts a slightly different effect. Lets look at them individually.
Monounsaturated and polyunsaturated fats
Most research looking into mono and polyunsaturated fats actually looks at the bigger picture of whether eating these foods lowers the number of cardiovascular events.
A large Cochrane review in 2015 pulled together the findings from many studies looking at a combined 59,000 people. Specifically, this was looking at the effect of reducing saturated fat in your diet and how this impacts your risk of developing cardiovascular disease (CVD).
Reducing saturated fat in the diet reduced the chances of having a cardiovascular problem such as a heart attack but it did not lower the risk of dying from one.
Replacing saturated fat with polyunsaturated fat seemed to exert the most benefit and reduced the likelihood of a cardiovascular event by as much as 17%. Polyunsaturated fat foods include things like oily fish, nuts, seeds, sunflower oil, soybean oil and safflower oil. These give us our omega 3 and 6, which are our essential fatty acids, and can only be obtained in our diet because our body’s cannot make them.
There also appeared to be a link between a reduction in total cardiovascular events with a reduction in the total cholesterol in the blood and saturated fat intake.
Unfortunately, there was only one study in the Cochrane review that looked at monounsaturated fats (e.g. avocados, olive oil, rapeseed oil) and therefore no conclusions could be drawn.
Upon further research it is clear for every article showing the benefits of adding monounsaturated fat in the diet there is another one showing no benefit with regard to cardiovascular disease and cholesterol. What does seem clear though is how they approach the study makes a big difference. If just adding a food high in monounsaturated fat into the diet, there is little benefit. If monounsaturated fat replaces existing elements in the diet like saturated fat, the benefit is more clear and it has a cholesterol lowering effect.
More research is required to draw definitive conclusions but as it stand there is likely a benefit.
Foods high in monounsaturated and polyunsaturated fats
- Oily fish
- Olive oil
- Rapeseed oil
- Safflower oil
- Sunflower oil
- Soybean oil
Dietary fibre are the non glycaemic component of carbohydrate. In other words, they do not contribute to rises in blood glucose levels. There are three main classes of fibre; non starch polysaccharides (NSP), resistant starch (RS) and resistant oligosaccharides.
NSP is basically made from cellulose, which is the main component of a plant cell wall. Examples of NSP include hemicellulose, pectins, gums and mucilages. They also include fructans and galactans. NSP are all different. Viscous solutions of NSP help reduce the speed of absorbing food into the small intestine and help lower blood glucose and lipid levels (such as cholesterol). These are also known as soluble fibre.
Examples of soluble fibre
Insoluble NSP are quite resistant to fermentation in the bowel and so make their way to the colon where they bind with water and add bulk. These are also known as insoluble fibre.
Examples of insoluble fibre
- wholegrain bread
- Wholewheat/grain or brown pasta
- Wholegrain or brown Rice
- Beans also
- Potatoes with skin
In reality, foods high in fibre tend to have a combination of both soluble and insoluble fibre and we therefore categorise them according to the one they have the most of.
Fibre helps to create the beneficial good bacteria in the bowel which is attracting more attention for its beneficial effects. New evidence is showing how good bacteria in the gut contributes to metabolism helping to break down fats and lower blood glucose levels. Good bacteria also helps to lower cholesterol levels and therefore eating foods that promote good bacteria development can help us reach our goal of lowering cholesterol.
Research looking at fibre and Cardiovascular disease (CVD)
An interesting literature review published in the very impactful journal, the Lancet (here), showed some interesting insights into eating fibre. They combined the data from 185 studies looking at 4635 adults and found a 15-30% decrease in CVD death, the numbers of stroke and heart disease, type 2 diabetes and colorectal cancers in people who ate the most fibre.
The studies the article analysed also showed people achieved significantly lower body weight, blood pressure and cholesterol when they ate more fibre. Interestingly, the benefit seems linked to the amount of fibre you eat. So in other words, the more fibre you eat, the more benefit you gain. In this study the amount of fibre eaten for these health benefits was between 25-29g. This is pretty consistent with the UK fibre intake guidelines where it is recommended to eat 30g of fibre per day.
Plant sterols and stanols
The easiest way to think of plant sterols and stanols is as plant cholesterol. They do exist in the diet but are mainly included in the foods we have listed thus far. In this instance we are referring to specific products designed specifically for lowering cholesterol.
Plant sterols and stanols have received quite a bit of research into them and it seems quite clear they do help lower cholesterol.
The Cochrane database and an article in the British journal of nutrition both analysed several studies and confirmed there is a cholesterol lowering effect. The last big review I can find on the subject both came in 2014 but individual studies looking into this have been published since. Although, these are in less impactful journals. Therefore, I primarily looked at the highest impact journals where they’ve pulled lots of research together to make their conclusions.
The British Dietetic Association also says an intake of 1.5-2.4g per day can lower cholesterol by 7-10% and an intake of 2.5-3.0g per day by 10-12.5%. To ensure you get the benefit, most studies suggest aiming for around 3g per day but no additional benefit is usually seen by taking more than this.
Examples of plant sterols and stanols
- Yogurt drinks – many brands including supermarket own
- Flora pro
Vegetarian diets vs Omnivorous diet
Another interesting systematic review of the available evidence in 2015 performed by the American Heart Association (here) found vegetarian and vegan diets might be cholesterol lowering. This is something that has been repeatedly found elsewhere.
They looked at over 2000 studies. However, this was whittled down to 11 as these were the only ones that met the entry criteria. This does not mean these 11 studies were perfect. When it comes to studying nutrition, few studies are. However, they found vegetarian and plant based diets significantly reduced blood lipids including cholesterol when compared with meat eaters.
There could be many reasons for this but the most obvious one is adopting a vegetarian diet likely means you eat more fruit and vegetables. With the void left in the diet by removing meat, often beans, pulses and lentils are added to help fulfil peoples protein requirements from plant sources.
It’s also an ongoing topic of debate about the role of saturated fat in raising cholesterol and how moving to a lower saturated fat diet can help lower cholesterol. I’ve blogged about this previously here.
Vegetarian diets by definition need to choose lower fat or better types of fat in their diet as in reality the vast majority of saturated fat in our diet comes from animal sources. Animal protein replacements such as Quorn, Tofu and soya are much lower in fat than their meat equivalents. Furthermore, if someone hasn’t gone full vegetarian and follows a pescatarian diet allowing fish, some of the animal saturated fat is replaced by mono and polyunsaturated fats instead and we’ve seen the benefit of this above.
The Mediterranean diet
A lot of research looks at the mediterranean diet as one of the best lifestyle choices to help lower the chances of developing cardiovascular problems. Cholesterol is one of the risk factors for determining if you might develop CVD problems.
Looking at the Mediterranean diet is a good way of looking at foods that might help lower the risk of cholesterol and CVD because we don’t just eat foods in isolation.
Definitions of a Mediterranean diet vary widely and can be a problem when comparing research studies. Generally speaking a Mediterranean diet includes a high amount of monounsaturated fats such as olive oil, nuts, seeds and fish. The Mediterranean diet includes lots of fruits, vegetables and legumes. It is quite high in whole grains and cereals and doesn’t include a great deal of meat but does include a fair amount of fish and modest amounts of dairy. However, the combinations and distributions of each nutrient used in practice vary widely and so it is impossible to specifically say what is the one and only Mediterranean diet.
There remains some doubt about the beneficial effect of the Mediterranean diet on lowering overall CVD risk. A review of the literature published by the Cochrane library in 2019 (here) found no conclusive evidence that a Mediterranean diet prevented the occurrence of CVD. The review pulled together all the best articles written on the subject in recent years and compared the findings. The risk of having a stroke or getting heart disease was less if following the Mediterranean diet but no certain conclusions could be made. There is still some discrepancy between what each study found and therefore more research is necessary.
These findings can likely be explained by the differences in how the studies are designed. Sometimes studies are too short in duration or use an insufficient dietary composition. In fact, there are many reasons why discrepancies might exist and why it then becomes difficult to study nutrition. When looking at enough individual studies it looks like there is some benefit of following a Mediterranean diet but due to the various methods used to study the reduction in CVD it’s impossible to reach a definitive conclusion to date.
Hopefully you have a good understanding of the foods to lower cholesterol. High cholesterol and cardiovascular complications are a tricky area to assess. Often patients do not only have high cholesterol. Alongside high cholesterol the person may also be overweight, inactive or have a number of other problems.
Eating lots of fruits, vegetables, beans, pulses, lentils, legumes, fish, oils and some wholegrains looks like a good way to remain in good health. Adding in plant sterols and stanols can also be a good way to lower cholesterol levels and so might be an option to consider.
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