The risk increased to 15% for men and 14% for women once the data was adjusted, stated the study's principal author, Erikka Loftfield, an investigator at the National Cancer Institute in Bethesda, Maryland, CNN reports.

When asked about the consumption of 124 foods, 90% of those who consumed ultra-processed foods said that highly processed drinks were at the top of their list.

"Diet sodas are a key contributor to the consumption of ultra-processed foods. Second were sugar-sweetened sodas", said Loftfield. "Beverages are a very important component of diet and a contributor to the consumption of ultra-processed foods".

Refined cereals, such as ultra-processed bread and baked goods, ranked third in popularity, the study found.

"This is yet another large, long-term study confirming the association between UPF (ultra-processed foods) intake and all-cause mortality, especially due to cardiovascular diseases and type 2 diabetes", said Carlos Monteiro, emeritus professor of nutrition and public health at the University of São Paulo in Brazil.

Monteiro coined the term ultra-processed food and created the NOVA food classification system, which looks beyond nutrients to how foods are made. Monteiro was not involved in the study, but several members of the NOVA classification system were co-authors.

The NOVA classification system sorts foods from minimally processed - whole foods such as fruits and vegetables - to processed foods, such as cold cuts - to ultra-processed foods.

Ultra-processed foods contain ingredients "never or rarely used in kitchens or classes of additives whose function is to make the final product tastier or more attractive", according to the United Nations Food and Agriculture Organization.

The list of additives includes preservatives against mold and bacteria, emulsifiers to prevent the separation of incompatible ingredients, artificial colors and dyes, anti-foaming, bulking, bleaching, gelling and glazing agents, and added or modified sugar, salt and fats designed to make foods palatable.

The preliminary study, presented on June 30th at the annual meeting of the American Society for Nutrition in Chicago, analyzed food data collected starting in 1995 from nearly 541,000 Americans aged 50 to 71 who participated in the NIH-AARP Diet and Health Study.

Researchers linked the food data to death rates over the next 20 to 30 years. Compared to the 10% who consumed the fewest ultra-processed foods, those who consumed the most highly processed foods were more likely to die from heart disease or diabetes, according to the study. Unlike other studies, however, the researchers did not find an increase in cancer deaths.

Some ultra-processed foods present a higher risk than others, said Loftfield: "Highly processed meat and sodas were some of the ultra-processed food subgroups most strongly associated with mortality risk".

Diet sodas are considered ultra-processed foods because they contain artificial sweeteners like aspartame, acesulfame potassium and stevia, and additional additives not found in whole foods.

Diet sodas have been linked to a higher risk of early death from cardiovascular diseases, as well as the development of dementia, type 2 diabetes, obesity, stroke and metabolic syndrome, which can lead to heart disease and diabetes.

U.S. dietary guidelines already recommend limiting sugar-sweetened beverages, which have been linked to premature death and the development of chronic diseases. A March 2019 study found that women who drank more than two servings a day of sugary drinks - defined as a standard glass, bottle or can - had a 63% higher risk of premature death compared to women who drank them less than once a month. Men who did the same had a 29% increase in death risk.

Processed meats, such as bacon, hot dogs, sausages, ham, pastrami and deli meats, are also not recommended; studies have linked red and processed meat to intestinal and stomach cancer, heart disease, diabetes and early death from any cause.

"Evidence from this new study indicates that processed meat may be one of the unhealthiest foods, but people don't tend to see ham or chicken nuggets as UPF (ultra-processed foods)", said Rosie Green, professor of environment, food and health at the London School of Hygiene & Tropical Medicine.

The study found that people who consumed the most ultra-processed foods were younger and heavier and had an overall poorer diet quality than those who consumed fewer ultra-processed foods.

However, the increased health risk could not be explained by these differences, as even people of normal weight and with better diets also showed some risk of early death from ultra-processed foods, the study found.

A key limitation of the study was that the food data was collected only once about 30 years ago, said Green: "It's difficult to say how eating habits may have changed since then".

However, the production of ultra-processed foods has exploded since the mid-1990s, with estimates that nearly 60% of the daily calories of the average American come from ultra-processed foods. It's not surprising, considering that up to 70% of foods in any grocery store can be ultra-processed.

"If anything, we probably underestimate the consumption of ultra-processed foods in our study because we're very conservative", said Loftfield. "Intake has likely only increased over the years".

In fact, a study published in May, which found similar results - a higher risk of premature death and death from cardiovascular diseases in over 100,000 health professionals who consumed ultra-processed foods - accessed ultra-processed food consumption every four years and found that consumption had doubled between the mid-1980s and 2018.

"For example, daily intake of packaged salty snacks and dairy-based desserts like ice cream essentially doubled from the '90s", said Dr. Mingyang Song, lead author of the May study and associate professor of clinical epidemiology and nutrition at Harvard University's T.H. Chan School of Public Health.

"In our study, like in the new one, the positive association was mainly driven by a few subgroups, including processed meat and sugar-sweetened or artificially sweetened beverages", said Song. "However, all ultra-processed food categories were associated with an increased risk".

Choosing more minimally processed foods is one way to limit ultra-processed foods in one's diet, said Loftfield.

"We should really focus on diets that are rich in whole foods", she said. "And if foods are ultra-processed, then look at sodium and added sugar levels and try to make the best possible decision using the nutrition information label".