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Eating bananas ‘is more effective at reducing blood pressure’ than cutting down on salt

Two women holding up peeled bananas
Two women holding up peeled bananas

Eating bananas is more effective at lowering blood pressure than reducing salt intake, a study has found.

Scientists discovered that consuming an extra gram of potassium, which is the equivalent of two medium-sized bananas, a cup of spinach or a large sweet potato, per day could be a simple way for someone to tackle high blood pressure.

In the UK, 90 per cent of adults do not eat the recommended 3.5 grams of potassium each day, while the average adult consumes 8.4 grams of salt, which is 40 per cent more than the recommended maximum intake of six grams per day.

Experts from The George Institute of Global Health at Imperial College London analysed data from its Salt Substitute and Stroke Study, which spent five years monitoring 20,995 people in China who had either suffered strokes or were aged over 60 with high blood pressure.

While half of the participants continued to use normal table salt while cooking and on their meals, the other half were given a “salt substitute” in which a quarter of the salt, known chemically as sodium chloride, was replaced with potassium chloride.

The research found that those who consumed the potassium-enriched salt had lower blood pressure levels, as well as a reduced chance of stroke and heart disease.

The new analysis, published in the Journal of Human Hypertension on Wednesday, revealed that up to 80 per cent of the reduction in blood pressure was because of the increase in potassium, rather than a lowering of salt intake.

It is the first study to directly compare the benefits of the two and used the “gold standard” measure of sodium and potassium in participants’ urine to establish how much had been consumed.

The research revealed that a gram increase in daily potassium intake lowered systolic blood pressure levels - the higher of the two figures from a blood pressure reading - by two millimetres of mercury (mm Hg) on average.

During the five-year study, 3,000 people suffered a stroke, but researchers found that those taking potassium-enriched salt were 14 per cent less likely to suffer from one.

On further analysis, they found that the benefits to blood pressure from increasing potassium consumption equated to around 10 per cent of the reduced risk of a stroke, while the reduction in salt intake equated to around four per cent.

Salt substitute ‘addresses both problems’

Dr Polly Huang, the lead author of the paper from The George Institute, said: “High levels of sodium intake and low levels of potassium intake are widespread, and both are linked to high blood pressure and greater risk of stroke, heart disease and premature death.

“Using a salt substitute where part of the sodium chloride is replaced with potassium chloride addresses both problems at once.”

She said the research highlighted how important potassium intake could be to controlling blood pressure.

“The findings in this study may be particularly pronounced because people started at low levels of potassium consumption, but there are probably billions of people around the world with similar consumption levels,” Dr Huang added.

International experts are now calling for an overhaul of official advice on high blood pressure to include refences to increasing potassium intake.

A global collaboration of researchers from the US, Australia, Japan, South Africa and India have called for potassium to be added to international health guidelines, with just Chinese and European guidelines currently suggesting it as an effective way to reduce blood pressure.

Potassium is found in a variety of foods, including leafy greens, legumes and nuts, but the quantities are often reduced when food is processed.

Too much potassium can lead to hyperkalemia, in which excess levels in the blood can affect the function of the heart.

However, the condition is very rare and would require someone to eat hundreds of bananas in one sitting, according to experts.

‘Cost-effective and practical’

About a third of adults in England have high blood pressure, which is defined as when an individual has a reading of 140mm Hg or above.

As many as five million people are thought to be living with it undiagnosed, according to the British Heart Foundation.

It is a leading risk factor for developing heart disease or suffering from a stroke.

About 34,000 Britons die each year from a stroke, which is the leading cause of disability, and more than 100,000 hospital admissions a year are attributed to heart attacks.

Dr Elisa Pineda, a research fellow at Imperial College, said high blood pressure was the biggest risk factor for premature death after smoking and poor diet.

“A balanced diet, low in salt and high in potassium, can help prevent high blood pressure, stroke, and cardiovascular disease,” she said.

“In the UK, efforts to decrease sodium intake have shown limited progress. Potassium-enriched salt substitutes emerge as a cost-effective and practical opportunity to mitigate the population’s risk of high blood pressure.”