High fat, low fat, no carb, more carb - when it comes to getting information on eating to manage high blood cholesterol, confusion reigns.
From recent trials that tested the impact of specific foods on blood cholesterol, it was found that eating more nuts, plant sterols (molecules found in plants), legumes and olive oil helps to lower blood cholesterol.
The bad news? Discretionary foods raise blood cholesterol, especially bad cholesterol (LDL). Eating less lowers it.
1. EAT LEGUMES
Legumes and pulses, including baked beans, kidney beans, chick- peas, lentils and split peas, can help lower cholesterol levels.
The results of 26 randomised control trials, which involved 1,037 people who had either normal or high cholesterol levels, were added together.
The data showed LDL cholesterol was reduced by 5 per cent in response to eating 130g of pulses per day. This is equivalent to one small can of baked beans.
Pulses are high in vegetable protein and fibre. They lower blood cholesterol in a number of ways.
The soluble and insoluble fibres help lower cholesterol absorption in the gut and promote the growth of beneficial gut bacteria in the large bowel.
Legumes and pulses take longer to digest, compared to processed foods. This means you tend to eat less when they are part of a meal.
2. EAT PLANT STEROLS AND MARGARINES
Plant sterols, or phytosterols, are chemically similar to blood cholesterol and are found in some plant foods, including nuts.
Plant sterols are concentrated from plant sources and added to some commonly-eaten foods such as margarines, spreads or milk.
Plant sterols compete with two other types of cholesterol for absorption in the gut - pre-made cholesterol, found in foods like prawns; and cholesterol, which is made in your liver.
This "competition" lowers the amount of cholesterol that ends up in your blood.
A review concluded that 2g of plant sterols a day leads to an 8 to 10 per cent reduction in LDL cholesterol. The type of fat the plant sterols are mixed with is important.
A meta-analysis of 32 random- ised control trials, involving about 2,100 people, found bigger reductions in total cholesterol (a mix of good and bad types) and LDL cholesterol when plant sterols were added to margarines or spreads derived from canola or rapeseed oil, rather than sunflower or soya bean oil.
3. EAT NUTS
Nuts are high in protein and fat, but the amounts of polyunsaturated, monounsaturated and saturated fat vary.
In a review of 25 trials, eating 67g of nuts a day led to a 5.1 per cent reduction in total cholesterol and 7.4 per cent for LDL.
People with higher LDL cholesterol or who were not overweight had a bigger improvement.
Do note that half a cup of nuts contains 400 calories, so you need to eat nuts instead of another food, or eat less each day but have it every day.
4. USE OLIVE OIL
Olive oil contains a high proportion of monounsaturated fat.
More than 80 per cent of its compounds are lost during the refining process, so less refined varieties, such as virgin olive oil, are a better choice.
A review of eight trials that involved 350 people consuming high phenolic olive oil found medium effects on lowering blood pressure and small effects on lowering oxidised LDL, with no significant effects on total or LDL cholesterol.
Another trial randomly selected more than 7,400 men and women at high risk of heart disease to follow three diets: the Mediterranean diet plus extra-virgin olive oil, or Mediterranean diet plus nuts, or a control diet (low fat).
About five years later, a follow-up showed that those in the olive oil and nut groups had a 30 per cent lower risk of heart attack, stroke or death from heart disease, compared to those on the control diet.
In a recent trial, 47 men and women substituted 4.5 per cent of their usual food intake of olive oil or butter for five weeks, and then crossed over to the other group for another five weeks.
Researchers found total cholesterol and LDL-cholesterol levels were significantly higher after consuming butter, compared to olive oil.
5. AVOID JUNK FOOD
In our study, we found people were able to make a number of small changes across a range of the foods that lower blood cholesterol levels.
But the biggest change people made was cutting back on energy- dense, nutrient-poor foods (junk foods) and eating a wider variety of healthy foods.
The benefits? They lost weight, and lowered their cholesterol and blood pressure.
A big study examined changes in diet-quality scores and heart disease risk in 29,000 men from the Health Professionals Follow-up Study and 51,000 women from the Nurses' Health Study (1986-2010).
After four years of follow-up, almost 11,000 people had a heart disease "event".
Those who had the biggest improvement in their diet-quality score had a 7 to 8 per cent lower risk.
When it comes to heart-disease risk factors, get your cholesterol and blood pressure checked the next time you see your doctor.
•This article was contributed by Clare Collins, a professor in nutrition and dietetics; Tracy Burrows, an associate professor of nutrition and dietetics; and Tracy Schumacher, a research associate, from the University of Newcastle in Australia.
•This article first appeared in The Conversation (http://theconversation.com), a website which carries analysis by academics and researchers.