Unhealthy diets are responsible for 11m preventable deaths globally per year, more even than smoking tobacco, according to a major study.

But the biggest problem is not the junk we eat but the nutritious food we don’t eat, say researchers, calling for a global shift in policy to promote vegetables, fruit, nuts and legumes.

While sugar and trans-fats are harmful, more deaths are caused by the absence of healthy foods in our diet, the study found.

The research is part of the Global Burden of Disease study by the Institute of Health Metrics and Evaluation (IHME) in Seattle, published in the Lancet medical journal.

Heart attacks and strokes are the main diet-related causes of death, followed by cancers and type 2 diabetes, say researchers.

The study found that eating and drinking better could prevent one in five deaths around the world. Although diets vary from one country to another, eating too few fruits and vegetables and too much sodium (salt) accounted for half of all deaths and two-thirds of the years of disability attributable to diet.

“Our findings show that suboptimal diet is responsible for more deaths than any other risks globally, including tobacco smoking, highlighting the urgent need for improving human diet across nations,” they write.

Rather than trying to persuade people to cut down on sugar, salt and fat, which has been “the main focus of of diet policy debate in the past two decades”, it would be better to promote healthy options, they say.

“Generally in real life people do substitution. When they increase the consumption of something, they decrease the consumption of other things,” said Dr Ashkan Afshin of the IHME, the lead author.

Countries that have a mainly Mediterranean diet eat more fruit, vegetables, nuts and legumes, said Afshin, naming Lebanon, Israel and Iran among the better performers. “But no country has an optimal level of consumption of all the health foods. Even in countries that have a Mediterranean diet, the current intake of many other dietary factors is not optimal.”

The paper is the most comprehensive analysis on the health effects of diet ever conducted, says the IHME.

It looked at 15 different nutrients – some good for health and some not so good. The main risk factors were eating too much salt and too few whole grains, fruit, nuts and seeds, vegetables and omega-3 fatty acids from seafood. Other risk factors considered were consuming high levels of red and processed meat and sugary drinks, low milk consumption and low fibre.

Poor diets were responsible for 10.9m deaths, or 22% of all deaths among adults in 2017. Cardiovascular disease was the leading cause, followed by cancers and diabetes. Nearly half – 45% – were in people younger than 70.

Tobacco was associated with 8m deaths, and high blood pressure was linked to 10.4m deaths.

Israel had the lowest rate of diet-related deaths, at 89 per 100,000 people, followed by France, Spain and Japan. The UK ranked 23rd, with 127 diet-related deaths per 100,000 and the US was 43rd with 171. Uzbekistan was last, with 892.

Prof Walter Willett from Harvard University, a co-author of the study, said that the findings were consistent with a recently published analysis of the benefits for cardiovascular health of replacing red meat with plant sources of protein.

“Adoption of diets emphasising soy foods, beans and other healthy plant sources of protein will have important benefits for both human and planetary health,” he said.

Tom Sanders, a professor emeritus of nutrition and dietetics at King’s College London, said the analysis put too much emphasis on individual components rather than the overall diet. “Obesity is a major driver for risk of type 2 diabetes as well as cancer and the health evidence for this relationship is strong. Obesity is caused by eating more food energy than required rather than specific dietary components such as sugar. The trend for populations to become increasingly sedentary is a major reason why there is an imbalance between energy intake and expenditure but increased availability of foods with a high energy density (more calories/gram) makes it too easy to overeat.”

Dr Christopher Murray, a director of the IHME and one of the authors, said: “This study affirms what many have thought for several years – that poor diet is responsible for more deaths than any other risk factor in the world.

“While sodium, sugar, and fat have been the focus of policy debates over the past two decades, our assessment suggests the leading dietary risk factors are high intake of sodium, or low intake of healthy foods, such as whole grains, fruit, nuts and seeds, and vegetables. The paper also highlights the need for comprehensive interventions to promote the production, distribution, and consumption of healthy foods across all nations.”