Eating a lot of heavily processed foods is linked to a risk of earlier death, according to a study.

A team in France worked with more than 44,000 people in a study running from 2009 called NutriNet-Santé. They looked at how much of their diet – and calories – was made up of “ultra-processed” foods – those made in factories with industrial ingredients and additives, such as dried ready meals, cakes and biscuits.

Over seven years of follow-up, there were 602 deaths, of which 219 were from cancer and 34 from cardiovascular disease. The research, published in the journal Jama Internal Medicine, found that deaths were more likely to occur in those who ate more ultra-processed food.

The link was clear even after taking into account the greater likelihood of deprivation, smoking, obesity and lower educational background among those who ate ultra-processed food, the researchers say.

Ultra-processed foods tend to be high in sugar, salt and saturated fat. France consumes less of such packaged foods and ready meals than many other countries, at around 14% of the diet. More than half the UK diet is ultra-processed food, the Guardian revealed last year.

Other scientists were unsure whether the study proved a link between ultra-processed food and an early death, but agreed it was more evidence that a junk food diet was bad for health.

“The case against highly processed foods is mounting up, with this study adding importantly to a growing body of evidence on the health harms of ultra-processed foods,” said Prof Nita Forouhi, of the MRC Epidemiology Unit at the University of Cambridge. She said more evidence was needed, “yet we would ignore these findings at public health’s peril”.

“A vital takeaway message is that consumption of highly processed foods reflects social inequalities – they are consumed disproportionately more by individuals with lower incomes or education levels, or those living alone,” Forouhi said.

“Such foods are attractive because they tend to be cheaper, are highly palatable due to high sugar, salt and saturated fat content, are widely available, highly marketed, ready to eat, and their use-by dates are lengthy, so they last longer. More needs to be done to address these inequalities.”

Other scientists said it was difficult to draw firm conclusions from the study, partly because the “ultra-processed” foods category was so large, ranging from packet soups to chocolate bars.

“This is a large, carefully conducted prospective study of healthy middle-aged and older French people, in which a statistically significant association between death from any cause and a relatively higher consumption of ‘ultra-processed foods’ has been identified,” said Dr Ian Johnson, nutrition researcher and Emeritus Fellow at the Quadram Institute Bioscience.

“To put things into perspective, although the risk of dying over the seven-year period of investigation was about 15% higher among those consuming more of these foods, the background risk across the whole group was low.”