Nutrition research is a fickle area of science in which no single study can definitively say what you should or should not eat. Yet over time, the evidence linking highly-processed foods to chronic diseases, cancer, and earlier mortality rates has mounted.
Now add a new piece of research to the pile. A study published Feb.11 in the Journal of the American Medical Association (JAMA) shows that people with diets heavier in ultra-processed foods—the kinds manufactured industrially from ingredients that often include additives for technological and cosmetic purposes—are more likely to die earlier.
Researchers used data from 44,551 adults participating in the ongoing French NutriNet-Santé Study, an observational cohort study launched in May 2009. Participants are asked to complete online-based surveys on what they eat over a 24-hour period. For the JAMA study, researchers picked participants who’d completed at least one set of three 24-hour diet diaries every six months for two years and surveys in which they submitted body-mass index, physical activity, and sociodemographic data.
After analyzing each person’s overall diet—and parsing out what percentage was comprised of ultra-processed foods—the researchers found that such foods were associated with younger age, lower income, lower educational level, a greater likelihood of living alone, a higher body-mass index, and lower level of physical activity. After adjusting for other health factors, including smoking, there was a 14% higher risk of early death for each 10% increase in the proportion of highly processed foods people ate. Over the course of the two-year period, 602 of the study participants died.
Put simply: The more junk food people ate, the greater risk they had of dying earlier than those who kept their ultra-processed intake to a minimum.
The study, which adds a contour to our overall understanding of the effects of junk food, is in no way definitive. Nutrition science is a notoriously difficult area of research from which to draw hard conclusions. This study is a good representation of why. It relied on people self-reporting their own diets, so there’s no way to be totally sure they didn’t omit or overstate what they were eating, how much they exercised, or miscalculate their body-mass index data. An observational study that drew from tens of thousands of participants can’t be ignored, though. It certainly adds to a growing body of evidence documenting the ill-effects of junk food.
The researchers wrote as much in their conclusion: “Further prospective studies are needed to confirm these findings and to disentangle the various mechanisms by which ultra-processed foods may affect health.”
Their findings aren’t the first to suggest that a bad diet can lead to chronic diseases and cancers associated with earlier deaths. Scientists from the University of Washington came to that conclusion. So did previous work based on the NutriNet-Santé Study, as well as research at Tufts University and in Great Britain. In other words, the latest JAMA study doesn’t exist in a vacuum.
The body of evidence suggests that, in a fast-paced world in which people are increasingly looking for foods tailored for convenience, it’s important to keep in mind the health benefits of choosing whole foods. Instead of sugar-laden granola bars, potato chips, frozen pizza, and pretzels, consider choosing carrots, apples, and bananas instead. And when you do eat manufactured foods, keep a close eye on the ingredients list—and consider how many of them are recognizable.