Most of us will be aware of the link between cholesterol and heart disease but are perhaps less familiar with why.
Its role in the development of heart disease has been extensively researched, best summarised by a meta-analysis published inin 2007 involving 900,000 people from 61 studies.
The results concluded that even a small reduction in the overall cholesterol, especially the less favourable type, LDL, can significantly reduce the risk of death from cardiovascular disease.
The Irish Heart Foundation reports that almost 9,000 people died of cardiovascular disease in 2019, making it the second biggest killer, while a 2007 study reported that 82% of adults over the age of 45 had raised cholesterol.
Cholesterol is far from the only factor in developing heart disease, but these stark figures make it easier to understand why we need to know a little more about cholesterol, and how what we eat can help keep levels in check.
The first thing to understand about cholesterol, a waxy substance made by the liver, is that it is vital to human health. It plays an integral role in the structure of cells, helps make bile, is required for the production of a variety of hormones including oestrogen and testosterone and is closely involved in vitamin D production in the skin.
Cholesterol is transported from the liver in the blood wrapped in a coating of a substance called lipoprotein. There are several different types of lipoproteins, but the two main ones are low-density lipoprotein (LDL) and high-density lipoprotein (HDL).
Although we need both, LDL is often thought of as ‘bad’ while is HDL considered ‘good’ and despite the oversimplification, it's mostly true.
They have contrasting roles in that LDL delivers cholesterol and HDL collects any excess to be taken back to the liver for recycling or excretion.
When deliveries and collections are matched, everyone is happy. But if deliveries increase, then the surplus can accumulate and damage the innermost layer of arteries, also contributing to blockages.
This underlines the importance of not just the overall levels of cholesterol, but the ratio between the two, as the more HDL, the better.
There are several ways we can help manage cholesterol levels. These include stopping smoking as its effects reduce HDL while making LDL stickier and more likely to accumulate in arteries.
Alcohol intake should be limited as it too can influence liver function making it less effective at removing cholesterol from the blood.
Obesity is implicated and we know that losing weight will have a positive outcome on total cholesterol levels as well as reducing LDL.
Physical activity plays a role in managing cholesterol as exercise can raise HDL while reducing LDL.
Including specific foods in the diet can also have a positive effect on cholesterol, starting with fibre. Among its many roles, fibre helps bulk up and soften the stool, encouraging easier transit through the digestive system which in turn facilitates the removal of cholesterol inhibiting reabsorption.
The Irish Heart Foundation says 80% of adults don’t reach the optimum intake of fibre, 25-35g a day, but increasing fibre intake is really quite achievable.
Fibre is found in many foods such as wholegrains, fruits, vegetables, nuts, seeds, and legumes. Nuts are especially rich in fibre. There’s as much as 4g fibre in 30g of almonds a day, and a little less in hazelnuts, walnuts and pecans.
Another easy way to start increasing fibre intake is to move from five- to seven-a-day servings of fruits and vegetables. For example, there’s 5g of fibre in a whole orange, 4.5g in an apple and the same in a medium-sized avocado.
When it comes to vegetables, a heaped tablespoon of cooked spinach offers 1g, two spears of broccoli 2g and 2.5g in eight cooked Brussels sprouts. A medium-sized carrot contains 1.4g, while half a can of cannellini beans has 9g.
Fruit and vegetables are also sources of water and, as inadequate hydration can encourage increased cholesterol production, the more you eat these foods the better, along with 1.5l of fluids a day.
Oats are especially beneficial as they are a good source of beta-glucan, a specific type of fibre that is highly efficient at binding to excess cholesterol.
Research from 2016 showed that 3.5g of beta-glucan daily improved that all-important ratio between LDL and HDL, reducing only LDL.
Beta-glucan content of oats is between 2 and 8% of the dry weight, so a 50g serving of porridge will provide anywhere between 1 and 4g — an oatcake has 1g.
Beta-glucan is also found in barley, albeit not quite at the same level as oats, but 40g barley flakes and 75g cooked pearl barley both offer around 2g each.
You may not think of fats as having a positive influence on cholesterol levels, but the right fats in the diet can help increase HDL.
There are many types of dietary fats but broadly speaking, they could be categorised as either saturated or unsaturated. When a fat is saturated its structure is less flexible than an unsaturated fat and has different effects on human health.
Like cholesterol, saturated fats have benefits, although we don’t need much of it, not least because excess is implicated in raised cholesterol, and the advice for women is to have no more than 25g daily, 30g for men.
Saturated and unsaturated fats are found together, but the former is higher in animal fats, dairy products, coconut oil and cream, biscuits, and pies.
To give you an idea of how much saturated fat is in familiar foods, there’s 6g per 100g in Greek yogurt, 3.5g in a single burger and 2g in a chocolate digestive.
Another type of fat, transfats, are also implicated in raising LDL, and are found in processed and many takeaway foods too. The general advice is to limit transfats to no more than 1% of the daily calorie intake.
For an adult on 2,000 calories a day this equates to 2g, a figure easily exceeded when you think that a takeaway kebab contains over 5g transfats.
Unsaturated fats can raise HDL and we can find them in virgin olive and rapeseed oil. They also contain vitamin E and phenolic acid, both of which may offer some protection against the damage LDL can cause to the lining of arteries.
Aim for at least two tablespoons, or around 25ml, of unheated olive or rapeseed oil a day.
Putting all these dietary elements together can help make noticeable improvements to overall cholesterol levels as well as improving the ratio between HDL and LDL. They are generally easy to adopt and should show positive results within a few months.