Tinned tomatoes can be high in sodium - one of the main causes of high blood pressure.

The average can of chopped tomatoes in the US contains about 132mg of sodium per 100g, according to the US Department of Agriculture.

There are just 5mg of sodium in 100g of fresh tomatoes, it added.

Canned foods can often use sodium as a preservative, or flavouring.

“As a rule, tomato products are problematic for people with hypertension,” said medical website Healthline.

“Canned tomato sauces, pasta sauces, and tomato juices are all high-sodium culprits.

“A half-cup serving of classic marinara sauce can have more than 450mg of sodium. A cup of tomato juice comes in at 650mg.

“You can often find low-sodium or reduced-sodium versions of all of these. For people looking to keep their blood pressure down, these alternative options are a smart choice.”

Adding more salt to the diet reduces the amount of water that’s filtered out of the blood by the kidneys, according to Blood Pressure UK.

This results in higher blood pressure, as the extra fluid puts strain on the blood vessels.

To counteract the rise in blood pressure, arteries build up their walls to become stronger and thicker. But, this only makes the space inside the arteries smaller, and raises blood pressure further.

Continued high blood pressure could block up arteries, or make them burst. Blood won’t be delivered to the heart, and it could lead to a heart attack.

About a third of adults have high blood pressure in the UK. The condition is the third biggest risk factor for all diseases, after smoking and poor diet.

About 75,000 people died in the UK form high blood pressure, in 2015.

Meanwhile, heart health could be improved by eating a handful of nuts a day, it was revealed.

Nuts could also reduce the risk of developing cancer, diabetes, early death, and respiratory diseases.