The case against so-called ultraprocessed foods just got a lot stronger, with the release of two large studies linking the products to an increased risk of heart disease and premature death.

Ultraprocessed foods are typically ready-to-eat or to pop into a microwave — think frozen meals, canned foods, sugary cereals, reconstituted meats and packaged baked goods. They generally contain high levels of fat, added sugars, salt and various additives.

The two new studies, from France and Spain, do not prove that ultraprocessed foods harm health, but do add to the mounting circumstantial evidence linking the products to a host of health problems. Both studies were published Wednesday in The BMJ, a medical journal.

In the French study, the researchers tracked more than 105,100 adults for a median follow-up period of five years. During that time, the participants filled out food questionnaires 5.7 times, on average.

The study found that, after accounting for factors such as age, baseline body mass index (BMI), smoking status, alcohol consumption and physical activity, there was a 12 percent increase in the risk of cardiovascular disease for every 10 percent increase in the amount of ultraprocessed food consumed.

In the Spanish study, the researchers tracked nearly 20,000 men and women from December 1999 to February 2014, checking in on them every two years. During that time, 335 of the participants died; the most common cause of death was cancer.

The researchers found that, compared with participants whose diets contained the least amount of ultraprocessed food, participants whose diets contained the highest amounts had a 62 percent increased risk of premature death from any cause during the study period. This study also accounted for factors such as gender, age, physical activity, baseline BMI and smoking history.

What makes ultraprocessed foods unsavory?

The two studies aren’t the first to show a link between eating ultraprocessed foods and health problems. For example, a small experimental study published this month that found that people ate an average of 500 calories more each day when eating ultraprocessed foods than when eating unprocessed foods like fresh meats, fruits and vegetables.

However, it’s unclear how exactly ultraprocessed foods do their damage.

Most likely, a lot of the problems associated with these foods are the result of an increase in calorie intake and weight gain, said Maira Bes-Rastrollo, a professor of preventive medicine and public health at the University of Navarra and the lead author of the Spanish study. But there are also “other problems related to ultraprocessed foods,” Bes-Rastrollo told NBC News in an email.

That’s because these foods don’t offer much by way of nutrients, and are calorie-dense. What’s more, the foods contain high amounts of added sugar, salt, unhealthy fat and additives, but are low in fiber. It’s unknown what health effects the additives, in particular, may have in the long term, Bes-Rastrollo noted.

Although the new studies show only an association, rather than proving that ultraprocessed foods lead to heart disease and risk of premature death, taken together with the previous experimental study, the studies build a good case.

“I think the growing body of literature focusing on ultraprocessed foods is tying lots things together,” said Dr. Rekha Kumar, an assistant professor of medicine at NewYork-Presbyterian and Weill Cornell Medicine and medical director of the American Board of Obesity Medicine. Kumar was not involved with the new research.

Indeed, the new studies highlight “an alarming trend,” said Dr. Erin Michos, an associate professor of medicine and epidemiology and associate director of the Ciccarone Center for the Prevention of Heart Disease at the Johns Hopkins University School of Medicine.

“We need to go back to what our ancestors ate: vegetables, fruit, whole grains, nuts,” Michos, who also was not involved with the new research, told NBC News. “That’s what we evolved to eat, and not stuff produced in a laboratory and designed to last on a shelf for a decade.”

The researchers from the French study — Mathilde Touvier, director of the Nutritional Epidemiology Research Team at the University of Paris 13, and Bernard Srour, a member of that team — agreed. While ultraprocessed foods may be convenient and fast, it’s possible to substitute healthier alternatives, senior author Touvier and lead author Srour told NBC News in an email.

“It does not take very long to use frozen fish and vegetables … and a serving of whole grain pasta,” they said. “It’s delicious and only takes 10 minutes to cook.”

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