The risk of depression skyrockets when ultra-processed foods exceed 30% of a person’s diet

Many of the foods that are sold at the supermarket are ultra-processed. Pastries, ready-made pizzas, many sauces, salty snacks or cold cuts are only a few examples of this type of products, whose consumption continues on the rise; just in the United States, 58% of the people’s calorie intake comes from ultra-processed foods. And, as their consumption increases all over the world, so does the concern about their health effects. This week, the medical journal BMJ published an extensive review of studies that confirms the association between a higher consumption of these foods and diseases such as diabetes, mental health disorders and early death.

Among the review articles, which were all published in the past three years and involved almost 10 million participants altogether, the authors find “convincing evidence” that a greater intake of ultra-processed food is associated with a 50% increased risk of cardiovascular disease related death, an increase of approximately 50% in the risk of anxiety and other mental disorders and a 12% increase in the risk of type 2 diabetes. At a higher level of confidence, there was a 21% greater risk of death from any cause, an increase of around 50% in the risk of obesity or sleep problems and a 22% increased risk of depression. In a study by the same authors, they found that the risk of depression skyrockets when ultra-processed foods exceed 30% of a person’s diet. As for gastrointestinal health or cancer risk, the researchers believe that the evidence is still limited.

The meta-study, led by Melissa Lane and Wolfgang Max from Deakin University (Australia), concludes that the findings provide enough reasons to implement public health policies aimed at reducing the consumption of ultra-processed foods in order to improve the health of the population. Although their data does not allow them to compare the health deterioration caused by this type of food with that of tobacco or alcohol, Lane believes that some of the policies applied to these substances could help reduce the consumption of ultra-processed foods. “For example, warning labels like those on cigarettes could be effective,” says the researcher.

Miguel Ángel Martínez, professor of preventive medicine and public health at the University of Navarra (Spain), who did not participate in the study, believes that the evidence obtained by this review of studies is more than enough to propose “structural, not just educational” measures to reduce the consumption of ultra-processed foods. “We must make them more expensive through taxes and use that extra income to lower the price of healthy products such as olive oil or nuts, not for something else,” he points out. “The prices of healthy food cannot keep rising, because that will increase the health gap between social classes,” he emphasizes.

The article also emphasizes the importance of furthering the study of the mechanisms that explain why these types of foods are harmful. For now, it is known that they are less nutritious and worsen the diet of those who consume them because, in addition to providing too much salt, fat or sugar, they leave less space in the stomach for things like fruits, which contain beneficial compounds such as polyphenols or phytoestrogens. They also contain less fiber and protein and concentrate more calories. This combination can favor the development of chronic diseases that arise due to chronic inflammation or changes in the microbiota.

Martínez does criticize an aspect of the study that leads the authors to consider weak some evidence that might be stronger with another measurement method. “They use the GRADE system to evaluate the quality of the strength of the evidence and that was a mistake, because that method was designed for clinical trials, and we have known for a long time that the NutriGrade system, adapted to the specific characteristics of nutrition studies, is better,” he points out. “With the GRADE system, the evidence is going to be weak in many nutrition studies, because an observational study is going to be wrong, and in nutrition we cannot do randomized clinical trials like we do with drugs, giving people ultra-processed foods to see if they’re bad for them, as that would be unethical.”

Pablo Alonso Coello, researcher at the Sant Pau Research Institute of Barcelona and scientific coordinator of the Nutrimedia project, acknowledges the value of the large amount of information gathered in the review, its order and consistency, but warns that nutrition research will always have difficulty reaching a confidence level equal to that achieved with a drug in a clinical trial. “It is difficult to assess the influence of each factor, and the effects are small,” he explains. “We will never have the same certainty as with tobacco and cancer, which has a very significant effect, and the researchers themselves admit it in the limitations; there is no absolute certainty.” As an intermediate solution, the authors of the article propose short-term studies to test the effects of ultra-processed foods, measuring changes in weight, insulin resistance, microbiota or inflammation levels. Doing the same thing for long enough to find out whether they accelerate death, the onset of cancer or cardiovascular diseases will be impossible.

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