Are ultra-processed foods a public health hazard?

Short answer: Yes, the evidence strongly suggests they are — though the science is still evolving on mechanisms and specifics.

The observational evidence is substantial and consistent

The largest review to date — an umbrella review of 45 meta-analyses covering nearly 10 million people, published in The BMJ in 2024 — found 45 analyses published in the last three years, involving about 10 million people in total. The results were striking: the most convincing or highly suggestive evidence linked diets rich in ultra-processed foods with increased risks for premature death, cardiovascular disease, mental health disorders, diabetes, obesity, and sleep problems.

More specifically, that review found "convincing" evidence that a diet high in ultra-processed foods increases the risk of death from cardiovascular disease by 50% and the risk of anxiety by 48%. It also found "highly suggestive" evidence that greater consumption of these foods increases the risk of death from heart disease by 66%, the risk of obesity by 55%, sleep disorders by 41%, Type 2 diabetes by 40%, early death from any cause by 21% and depression by 20%.

A separate 2024 Harvard-led study reinforced this, finding that high intake of ultra-processed foods—particularly processed meats, sugary breakfast foods, and sugar- or artificially sweetened beverages—may increase risk of early death. And a 2025 updated meta-analysis of over a million people found that compared to the lowest, participants with the highest UPF consumption had a 15% increased risk of all-cause mortality.

Other systematic reviews have linked high UPF intake to a wide range of outcomes including all-cause mortality, overall cardiovascular diseases, coronary heart diseases, cerebrovascular diseases, hypertension, metabolic syndrome, overweight and obesity, depression, irritable bowel syndrome, overall cancer, postmenopausal breast cancer, gestational obesity, adolescent asthma and wheezing, and frailty, and in older adults specifically, the highest consumption of UPF was associated with incident frailty, incident dyslipidemia, renal function decline, and abdominal obesity.

Why scientists think this happens

Researchers point to several possible mechanisms: poor nutrient profiles of many UPFs, displacement of minimally processed foods from the diet, alterations to physical structure that impact how UPFs are consumed, exposure to potentially harmful additives or byproducts and contaminants from food packaging. A 2024 randomized crossover trial also found that ultra-processed foods cause weight gain and increased energy intake associated with reduced chewing frequency — suggesting the physical structure of these foods, not just their nutrient content, drives overeating.

A recent paper in The Lancet argues the evidence base is now very large: this hypothesis—that this pattern increases the risk of multiple diet-related chronic diseases through various mechanisms—is substantiated by more than 100 prospective studies, meta-analyses, randomised controlled trials, and mechanistic studies, covering adverse outcomes across nearly all organ systems.

Important caveats — the evidence isn't uniform or settled

Not every claimed link holds up equally well. The same 2024 umbrella review found weak to no evidence for many site-specific cancers, including breast, central nervous system, chronic lymphocytic leukemia, pancreatic and prostate cancer, and for conditions such as hypertriglyceridemia, low HDL cholesterol levels, Crohn's disease, ulcerative colitis, hyperglycemia, metabolic syndrome and non-alcoholic fatty liver disease.

A bigger limitation is the near-total reliance on observational data. A 2024 systematic review of actual randomized controlled trials found only a handful of studies, and three educational intervention studies and one controlled feeding trial were included, evaluating the effect of reducing the consumption of UPFs (455 participants, median follow-up, 12 weeks), with no significant effects observed in 30 out of the 42 outcomes evaluated. The one controlled feeding trial that did show effects found a reduction in energy intake, carbohydrates, and fat (low certainty of evidence), as well as in body weight, total cholesterol, and HDL cholesterol (moderate certainty of evidence) — supportive, but based on very limited trial data.

Researchers also acknowledge that determining the specific aspects of UPFs responsible for observed health effects is challenging, and additional research is needed to understand the mechanisms through which UPFs may contribute to disease risk. A review in Nature on policy implications similarly notes that while important questions remain about the relative contributions of specific UPF attributes, additive classes, and food matrix disruption—and while some UPFs continue to serve important roles in dietary adequacy, particularly in resource-limited settings—the weight of evidence is sufficient to act.

Bottom line

The weight of observational evidence — spanning dozens of meta-analyses and millions of participants — points clearly toward ultra-processed foods being a genuine public health concern, associated with higher risks of premature death, cardiovascular disease, type 2 diabetes, obesity, and mental health disorders. However, this is largely correlational evidence; causal proof from rigorous, long-term randomized trials is still thin, and not all claimed harms (e.g., many specific cancers) are well supported. Many public health bodies and researchers nonetheless consider the overall evidence strong enough to justify caution and policy action, even as the exact mechanisms are still being worked out.