A sweeping and comprehensive new study involving more than 460,000 American adults is fundamentally challenging long-held assumptions regarding ultra-processed foods and their relationship with colorectal cancer. While public health messaging has increasingly cast ultra-processed foods as a monolithic threat to human health, researchers at the National Cancer Institute discovered that eating a high volume of ultra-processed food, when viewed as a single broad category, was not actually associated with a higher overall incidence of colorectal cancer.
However, the findings revealed a much more nuanced and critical distinction that could reshape how nutritional scientists and consumers think about modern diets: while total consumption did not move the needle on cancer risk, specific types of ultra-processed foods were sharply linked to contrasting health outcomes. Some categories of these foods were associated with significantly lower cancer rates, whereas others were clearly tied to elevated risks.
The landmark research, led by Erikka Loftfield of the National Cancer Institute and published in the open-access journal PLOS Medicine, suggests that the health effects of ultra-processed foods may depend far less on the industrial processing methods used to create them and far more on the actual nutritional ingredients those foods contain.
Ultra-processed foods currently account for more than half of all calories consumed by adults in the United States. In recent years, these convenient, ready-to-eat products have attracted intense scientific scrutiny and public concern because of their potential connections to a wide range of chronic diseases, including colorectal cancer, which remains one of the most diagnosed and deadly forms of cancer in the Western world.
Yet, as the researchers point out, the "ultra-processed" label captures a remarkably vast and diverse assortment of items. This broad classification sweeps everything from mass-produced sugary beverages and processed meats to fortified whole-grain breads and vitamin-enriched dairy products into the exact same bucket. This catch-all grouping has made it exceptionally difficult for epidemiologists and public health officials to accurately judge the actual health effects of these foods as a collective category.
For instance, prior dietary research has occasionally hinted that certain ultra-processed whole-grain items and dairy products might correlate with neutral or even beneficial health outcomes, while processed meats have consistently been linked to a heightened risk of gastrointestinal malignancies. This dichotomy raises a fundamental question for nutritional science: Is the sheer level of industrial processing truly a reliable indicator of a food’s potential health effects, or are researchers missing the forest for the trees by ignoring the underlying nutritional profile?
A Massive Study Tracks Cancer Risk for Nearly 19 Years
To investigate these complex differences and untangle the variables, researchers examined extensive health and dietary records from a massive cohort of 461,682 American adults. The participants were between 50 and 71 years old when they originally enrolled in the landmark NIH-AARP Diet and Health Study during 1995 and 1996.
At the very beginning of the multi-year investigation, participants completed detailed questionnaires describing how frequently they consumed a wide variety of different foods. Researchers used these self-reported dietary responses to estimate each individual’s baseline intake of ultra-processed foods, categorizing and quantifying how much of their daily caloric intake came from these manufactured sources.
Participants were then meticulously tracked through 2018, resulting in a median follow-up period of 18.8 years. This remarkably long observation window allowed the research team to examine how long-term dietary patterns were associated with the actual development of colorectal cancer over nearly two decades of life.
When the research team initially analyzed the broad data, the results showed no overall association between total ultra-processed food consumption and colorectal cancer incidence. In other words, participants who consumed higher quantities of ultra-processed foods did not, as a collective group, experience higher rates of colorectal cancer compared to those who ate fewer of these products.
However, a superficial glance at the top-line numbers missed a much more complicated and revealing underlying story. When the researchers peeled back the layers and examined individual food categories within the ultra-processed classification, the picture changed dramatically.
Some Ultra-Processed Foods Linked to Lower Cancer Risk
Diving deeper into the data, the research team found that higher consumption of specific sub-categories—namely whole grains, dietary fiber, dairy products, and calcium originating from ultra-processed food sources—was actually associated with a lower incidence of colorectal cancer. Far from being uniformly harmful, ultra-processed items that delivered essential nutrients long known to protect the colon appeared to retain those protective qualities.
Conversely, meat products obtained from ultra-processed sources showed the exact opposite pattern. Greater consumption of ultra-processed meats was consistently associated with a higher incidence of cancer, reinforcing longstanding warnings from public health agencies regarding the dangers of processed protein sources.
To further test these observations, the team examined what theoretical health impacts might occur if consumers replaced ultra-processed foods with less processed alternatives in their daily diets. Their rigorous substitution analysis found that swapping out minimally processed foods for just 10% of a person’s ultra-processed food intake by weight was associated with a modest but statistically significant 2% lower incidence of colorectal cancer.
These findings strongly suggest that the inherent nutritional characteristics of individual foods are far more informative than simply slapping a broad "ultra-processed" label on everything that comes in a package or undergoes industrial manufacturing. Foods placed in the exact same overarching category can possess profoundly different biological mechanisms and distinct associations with long-term cancer risk.
Why the Findings Come With Important Limitations
Despite the study’s exceptionally large sample size, its rigorous methodology, and its remarkably lengthy follow-up period, the researchers are careful to emphasize that its conclusions come with important caveats and may not apply universally to every demographic group.
Most notably, the vast majority of study participants were older, white Americans. This demographic makeup means the findings may not accurately reflect the dietary realities, genetic backgrounds, or disease risks of younger adults or more racially and ethnically diverse populations living in modern society.
Another critical limitation involves the methodology used for dietary data collection. Participants reported their eating habits only once, at the very beginning of the study in the mid-1990s. Consequently, researchers could not account for how individual diets naturally evolved, improved, or deteriorated over the subsequent two decades.
Furthermore, the commercial availability, formulation, and sheer variety of ultra-processed foods have expanded exponentially since the mid-1990s. As a result, the initial baseline dietary assessments may have inadvertently underestimated participants’ actual consumption of ultra-processed foods during the later years of the study period.
Because the research was observational in nature, it also cannot definitively establish direct causality—meaning it cannot prove whether particular foods directly cause or prevent cancer on an individual level, as other unmeasured lifestyle factors could theoretically influence the results.
What the Results Mean for a Healthy Diet
Rather than treating all ultra-processed foods as uniformly toxic or equally harmful, the study’s findings support evaluating foods based on their specific nutritional content and their demonstrated health associations.
The results also align neatly with existing, evidence-based dietary recommendations for colorectal cancer prevention. Current public health guidance consistently encourages individuals to consume adequate amounts of whole grains, dietary fiber, dairy products, and calcium-rich foods while actively limiting processed meat consumption, regardless of whether those foods have undergone industrial processing.
Lead researcher Erikka Loftfield summarized the clinical significance of the findings by noting that within this large population of older US adults, researchers did not observe a direct association between total ultra-processed food intake and colorectal cancer incidence. However, she emphasized that looking deeper into specific food groups—such as whole grains, dairy, and meat, broken down by their ultra-processed or non-ultra-processed sources—revealed associations that strictly align with current dietary guidance for colorectal cancer prevention, where higher whole-grain and dairy intakes, alongside lower meat intakes, correlate with reduced cancer rates.
Ultimately, this comprehensive research highlights why relying solely on the broad label "ultra-processed" fails to tell the whole story. When it comes to preventing colorectal cancer and understanding the complex interplay between diet and long-term health, the specific kinds of foods people choose to put on their plates appear to matter far more than their broad industrial processing category alone.
The study was funded entirely by the Intramural Research Program of the National Cancer Institute, part of the National Institutes of Health. Several authors are current or former employees of the National Cancer Institute’s Intramural Research Program, though the funding organization played no role in designing the study, collecting or analyzing the data, deciding whether to publish the findings, or preparing the final manuscript.