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You may have heard of plant sterols – they are often added to margarines and dairy products with the claim they will support heart health, by lowering our levels of cholesterol.
We always take an evidence-based approach and in this article we’ll look at plant sterols and examine the science behind their effects on your cardiovascular system.
With 160,000 people dying each year in the UK from heart and circulatory disease and heart disease being the most common cause of death in Europe amongst the under 65’s (1), the scientific community is searching for measures to combat this disease.
One such discovery is plant extracts, called plant sterols, which are able to lower cholesterol levels.
What are plant sterols?
You might also see plant sterols referred to as phytosterols.
This simply means they’re comprised of a type of fat (sterol) which is found in the cell membranes of plants (phyto).
They belong to a family of molecules related to cholesterol.
As far as the plant goes, they help the cell membrane to allow certain substances to pass into the cell.
Phytosterols are contained in many plant foods such as nuts and seeds, fruit & vegetables, and legumes.
Our hunter-gatherer ancestors would have eaten a lot of phytosterols.
In comparison, nowadays we obtain most of our plant sterols from vegetable oils, especially corn and rapeseed oils, which are often added to processed foods.
They’re also found in cereal grains which are typically high in an average nutritional intake.
The British Heart Foundation estimates the average person consumes around 160-400mg plant sterols per day.
Plant sterols lower LDL cholesterol
Science shows us clearly that phytosterols are able to lower cholesterol levels.
Plant sterols are believed to interfere with the absorption of cholesterol in the gut.
Studies have shown eating 2g plant sterols per day can reduce LDL cholesterol by roughly 10% (2).
LDL cholesterol is nicknamed ‘bad cholesterol’ as it can be deposited in blood vessel walls and result in a build-up of plaque in the arteries.
Over time, this will narrow and stiffen the arteries, which is correlated with a risk of heart attack and strokes.
Cholesterol doesn’t dissolve in our blood so it needs to be transported by lipoproteins.
These can be high or low density, so whether cholesterol is classed as LDL (low density lipoprotein) or HDL (high density lipoprotein) depends on which type of lipoprotein it’s attached to.
High and low density basically refers to the size of the lipoprotein.
HDL cholesterol is the so called ‘good cholesterol’.
This is the type which is being carried away from our cells and blood vessels to the liver to be excreted.
Plant sterols do not increase HDL cholesterol, nor do they have any effect on the level of triglycerides in the blood, which are fats connected with increased risk of coronary artery disease.
Cholesterol in foods
Although cholesterol is contained in some foods, such as eggs and shellfish, we also manufacture it in our bodies, which could be seen as indicative that it’s actually beneficial to us.
When we eat food containing cholesterol, our body compensates by reducing the amount we produce.
Although some people have a genetic propensity to manufacture high levels of cholesterol, for most of us only about a quarter of the cholesterol in the body actually originates from food.
Cholesterol is useful
Although high cholesterol levels are associated with heart disease, cause and effect has not been established.
Typically cholesterol has traditionally been painted as a villain when in fact it’s crucial for a number of our body’s functions.
Cholesterol is a component of the membranes of our cells, helping to keep them flexible.
A flexible cell membrane is important to allow the correct substances in and out of the cell.
Cholesterol is also needed to manufacture some of our hormones, as well as vitamin D, and it’s used to make bile to help us digest fat.
Low cholesterol levels may lead to problems such as depression and anxiety.
Cholesterol and cardiovascular disease
Although elevated LDL cholesterol and cardiovascular health are linked, simply lowering our levels may not be the answer.
Some studies have discovered people with high intakes of plant sterols not only didn’t have significantly lower heart disease, but in certain circumstances higher blood levels of phytosterols were connected with an elevated risk of cardiovascular disease or a second heart attack.
In animals, one study noted arterial plaques actually increased after supplementation with plant sterols (3).
The reasons for these adverse effects are not yet clear.
It could be plant sterols are replacing cholesterol in cell membranes, and adversely affecting their function in some way.
Or it could be the elevated blood levels of plant sterols are not causing the adverse effects at all and they are the result of something completely different, such as alterations in the gut bacteria, which we’ll look at later.
Some experts worry plant sterols may reduce the absorption of certain fat-soluble vitamins.
Although analyses of studies have not shown a reduction in the levels of vitamins A and D, plant sterols have been linked with a reduction in beta carotene levels, as well as lower levels of antioxidants, such as lycopene and lutein (4).
The role of inflammation
Instead of simply concentrating on the levels of LDL cholesterol, some experts believe heart disease may be linked more closely with how much of it has been damaged by free radicals – this is known as oxidised LDL cholesterol.
Research suggests high levels of oxidised cholesterol are linked with elevated inflammation, which causes lesions in blood vessel walls.
Science has recently begun to recognise the crucial role of inflammation in many chronic diseases.
In other words, LDL cholesterol is a risk factor which represents a symptom of the problem rather than the cause.
Driving down cholesterol, in that case, would not be the entire solution.
One study found consumption of plant sterols altered the composition of the microbiome, resulting in more inflammatory molecules being produced.
Concurrently, subjects gained a significant amount of weight after consuming plant sterols (5).
It may be that sufficient dietary fibre would protect against this effect, although further research is needed.
The microbiome is crucial for cardiovascular health. Certain strains of beneficial gut bacteria, such as Lactobacillus plantarum, have been found to successfully decrease levels of oxidised LDL cholesterol.
Everything in moderation
It is highly likely plant sterols in the amounts contained in natural plant foods are completely safe.
However, when they are consumed in large amounts, such as in refined vegetable oils and fortified foods, it appears the situation is far from straightforward.
You will still see products fortified with plant sterols marketed as being heart healthy, however some health bodies like NICE discourage the use of phytosterols for the prevention of heart disease.
We certainly don’t want our levels of LDL cholesterol climbing too high, because the more we have, the more likely it is to oxidise, because it’s a small, dense molecule.
Therefore, a balanced intake of plant sterols may be useful alongside other measures to support heart health, particularly for people whose genetics predispose them to producing high levels of cholesterol.
Takeaway
Research to discover the link between cholesterol and heart disease is still ongoing.
Rather than concentrating solely on cholesterol, it’s important to recognise the role of our overall food choices and lifestyle in cardiovascular health.
A Personalised Health practitioner will work with you to assess your individual heart disease risk and may recommend appropriate functional tests.
Practitioners recognise the importance of the influence of environment on genetic predispositions, along with the role of the liver in excreting cholesterol, the microbiome in controlling inflammation and antioxidants in regulating the levels of oxidised LDL cholesterol.
Because everyone is different, your personal journey to optimum heart health will be unique to you.
We’re dedicated to providing you with both insightful information and evidence-based content, all orientated towards the Personalised Health approach.
We would love to know your thoughts.
Have you tried plant sterols?
Did you find them useful?
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