The longer someone has type 2 diabetes, the higher their cardiovascular disease risk, and changes in red blood cells may help explain it, new research suggests.

The study found red blood cells from patients with long-term diabetes harmed blood vessel function, while no such effect was seen in those newly diagnosed.

After seven years of follow-up, the blood cells of people initially diagnosed had developed the same harmful properties.

Zhichao Zhou, associate professor at Karolinska Institutet and lead author, said: “What really stands out in our study is that it is not only the presence of type 2 diabetes that matters, but how long you have had the disease.

“It is only after several years that red blood cells develop a harmful effect on blood vessels.”

Researchers at Karolinska Institutet in Sweden studied animals and patients with type 2 diabetes.

They identified microRNA-210, a small RNA that helps regulate gene activity, as a possible early biomarker of cardiovascular risk.

When its levels were restored in red blood cells, blood vessel function improved.

Eftychia Kontidou, doctoral student and first author, said: “If we can identify which patients are at greatest risk before vascular damage has already occurred, we can also become better at preventing complications.”

The researchers are now investigating whether the biomarker can be used in larger population studies.

The UK has banned junk food adverts on TV before 9pm and online at all times to tackle childhood obesity.

The rules are expected to remove up to 7.2bn calories from children’s diets each year, reduce the number of children living with obesity by 20,000 and deliver around £2bn in health benefits over time.

Evidence shows advertising shapes what and when children eat, forming preferences from a young age and increasing the risk of obesity and related illnesses in later life.

Obesity and overweight are linked to at least 13 different types of cancer, as well as type 2 diabetes, heart disease and other conditions that affect healthy ageing.

At the start of primary school, 22.1 per cent of children in England are living with overweight or obesity, rising to 35.8 per cent by the time they leave. Children living with obesity are far more likely to live with obesity as adults.

Ashley Dalton, minister for health, said: “We promised to do everything we can to give every child the best and healthiest start in life.”

“By restricting adverts for junk food before 9pm and banning paid adverts online, we can remove excessive exposure to unhealthy foods – making the healthy choice the easy choice for parents and children.

“We’re moving the dial from having the NHS treat sickness, to preventing it so people can lead healthier lives and so it can be there for us when we need it.”

Colette Marshall, chief executive at Diabetes UK, said:

“With type 2 diabetes on the rise in young people, the need to improve children’s health in the UK has never been greater.

“Obesity is a major risk factor for type 2 diabetes, and the condition can lead to more severe consequences in young people – leaving them at risk of serious complications like kidney failure and heart disease.

“The long-awaited move to restrict junk food advertising – along with other measures such as mandatory healthy food sales reporting for businesses and the extension of the Soft Drinks Industry Levy – can help protect the health of our children, creating a future where conditions like type 2 diabetes can be prevented in young people.”

The measures form part of a broader government approach to prevention, including extending the Soft Drinks Industry Levy to cover more products such as sugary milk-based drinks, and a ban on the sale of high-caffeine energy drinks to under-16s.