Too much cholesterol in the blood causes fatty deposits to gradually build up in blood vessels. This makes it harder for blood to flow through, which increases the risk of heart attack or stroke.

Regular exercise and a healthy diet may help reduce cholesterol levels, but if your cholesterol is particularly high there are extra measures you can take, like taking cholesterol-lowering medications or eating cholesterol-lowering foods.

Getting on the sterols

More and more products that claim to help lower your cholesterol are showing up on supermarket shelves. Where previously this added benefit was offered by spreads alone, you can now get yoghurts and milks that do the same job, with cholesterol-lowering breakfast cereals on the horizon. And there's good evidence that they do what they say.

These products have been enriched with plant sterols (also known as phytosterols), which have a similar chemical structure to cholesterol. When eaten, they're thought to compete with and block the absorption of cholesterol from the intestine, ultimately reducing the amount of cholesterol that ends up in your blood.

Eating 2–3 g per day of plant sterols in the form of enriched spread, yoghurt, milk or a combination of these products can help lower your cholesterol.

These products can have an impact on your cholesterol levels in a matter of weeks. But as with cholesterol-lowering medication, you need to have them daily for the benefits to last, so the costs can quickly add up.

Who can they benefit?

People at risk of heart disease and in particular those who have high blood cholesterol levels (total cholesterol of 5.5mmol/L or more) can benefit from eating products enriched with plant sterols. Research shows that if you lower your blood cholesterol levels, you lower your risk of heart disease and stroke. Some research suggests that a reduction in LDL cholesterol levels by about 10% could reduce the risk of heart disease by 20–25% – although a benefit this great is most likely in someone with risk factors (a family history of heart disease, high blood pressure, being overweight or a smoker, for example) as well as high blood cholesterol.

Choosing the right mix to lower your cholesterol

Products enriched with plant sterols can work together with cholesterol-lowering drugs such as statins, as well as cholesterol-lowering diets, to lower blood cholesterol levels even further, but they're not meant to replace your medication. And if you're taking cholesterol-lowering medication, check with your doctor first before eating foods enriched with plant sterols.

People with familial hypercholesterolaemia (an inherited genetic condition that results in high blood LDL cholesterol levels from birth) or diabetes may also benefit from eating these products. However, recent research has suggested that people with metabolic syndrome (also known as Syndrome X) may not. People with a very rare, inherited metabolic disease called sitosterolaemia shouldn't eat these products.

Are they safe?

Foods enriched with plant sterols are generally recognised as being safe to eat, although they haven't been tested specifically for pregnant women. However, there's rarely any need for pregnant or breastfeeding women or young children – unless under medical advice – to be concerned about lowering cholesterol.

There's one small caveat: plant sterols have been shown to lower blood levels of the antioxidants beta-carotene and lycopene. So if you're regularly eating products enriched with plant sterols, also eat additional fruit and vegetables – orange-coloured ones in particular – to help compensate for any loss.

Costs per serving (spreads vs alternatives)

Overall, spreads are the cheapest and yoghurts the most expensive way to get an equivalent amount of plant sterols (0.8g).

Eating about six teaspoons (three serves) of spread may seem at odds with the usual message to cut down on fat for a healthy heart.

However, the Heart Foundation recommends you replace saturated fats (such as those found in butter and dairy blends) with healthier polyunsaturated and monounsaturated fats, which sterol-enriched products have in abundance – and you have the benefits of plant sterols to help lower your blood cholesterol levels further.

Past CHOICE testing has shown spreads to deliver the appropriate daily serving to help lower your cholesterol at under 17c. Alternatives such as yoghurts and milk with sterol are more expensive with milk costing you around 70 cents a serve while yoghurt can cost up to $2 a serve.

But if cost isn't such a concern and you don't normally use spreads, but do pour milk on your cereal and eat a tub of yoghurt every day, you might as well buy the more expensive sterol-enriched milk and yoghurt that you'll be sure to eat enough of.

How much do you need?

Most of us eat about 200 to 400mg of plant sterols daily – vegetarians often eat more – via plant-based foods that contain them naturally, including vegetable oils, nuts, seeds, legumes, bread and cereals. But the amount recommended to get a significant cholesterol-lowering benefit is much more – 2 to 3g per day – and that's where products enriched with plant sterols can really make a difference.

Research suggests that eating 2 to 3g of plant sterols daily can lower your LDL (bad) cholesterol levels by 10% on average. Eating more than this amount is unlikely to hurt you, but it's unlikely to lower your cholesterol any further. Less than this amount will simply have a lesser result.

In order to get the recommended 2 to 3g of plant sterols a day, you need to eat about three standard serves of sterol-enriched products. This could be three cups of milk or two serves of spread and a tub of yoghurt or any other combination of sterol-enriched products – it's the quantity not the type of product that matters.

Sterols aren't a get out of jail free card

Even though sterol-enriched products are effective at helping to control cholesterol levels, high blood cholesterol needs to be managed under medical supervision. To reduce your overall risk of heart disease it's still vital that you eat a healthy diet that's low in saturated fat and high in fruit, vegetables and whole grains, and that you stop smoking and increase your activity. If your blood cholesterol levels are normal, there's little advantage to eating these products – they'll just cost you more money.