People in the UK are being urged to eat less ham, bacon and cheese in order to reduce their salt intake and in turn their risk of having a heart attack or stroke.

Eating foods high in salt contributes to high blood pressure, which is the country’s biggest cause of avoidable death. Up to 4 million Britons may have undiagnosed high blood pressure, the charity Blood Pressure UK said.

The condition is a major concern to doctors because it has no obvious symptoms and often goes undetected unless someone gets a checkup or has a serious health setback such as a heart attack.

“It’s hard to believe a little bit of salt can have such an impact on our health, especially when it risks raising our blood pressure,” said Phil Pyatt, the charity’s chief executive. “Given this, we are urging all adults of all ages to check their blood pressure and take control of their health, along with simple improvements in diet and lifestyle such as eating less salt, more fruit and vegetables and doing more exercise.”

The NHS advises people to consume no more than 6g of salt a day. Average intake fell from more than 9g to about 8g in the 2000s but has remained largely unchanged since.

Treating high blood pressure, or hypertension, cost the NHS in England more than £2bn a year in 2014, the last time such figures were published.

In sobering news for bacon lovers, Blood Pressure UK said there was typically about 3g of salt in every 100g of the product. It singled out Morrison’s smoked streaky bacon which contains almost double that, at 5.6g.

“A two-rasher bacon bap with ketchup would make up a third of your daily salt limit,” it said. “And if you add an extra two rashers that’s half your recommended salt limit reached in just one meal.”

The charity said people should reduce their salt intake by not adding it to food at the dining table, avoiding using stock cubes, gravy and soy sauce and limiting intake of processed foods.

Its estimate of 4 million undiagnosed sufferers in the UK tallies with NHS England data and research published last year by the Office for National Statistics. It estimated that 32% of adults in England had high blood pressure, and that in 29% of these it had not been detected.

NHS England pointed to a new initiative it is launching shortly in which people will be offered a blood pressure check when having dental care or an eye test, to show how it is trying to detect undiagnosed hypertension. It said more than 1m checks had been provided by pharmacies over the last year.

It is estimated that 1.28 billion adults worldwide have hypertension, and in 80% of cases it is not well controlled.