Do all ultra-processed foods pose the same health risks? A study involving more than 460,000 people invites us to take a closer look at what we eat.
Ultra-processed foods occupy an important place in our diet. This category includes very different products: biscuits, soft drinks, processed meats, but also certain packaged whole-grain breads and dairy products. What they have in common is that they have undergone several manufacturing stages and sometimes contain ingredients rarely used in home cooking.
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Researchers wanted to find out whether the total amount of these foods consumed was linked to the risk of colorectal cancer, meaning cancer of the colon or rectum. They studied the responses of 461,682 American adults aged 50 to 71 at the beginning of the survey. Their diet had been described in questionnaires completed in the mid-1990s.
These people were then followed for nearly 19 years on average. During this period, 10,075 participants developed colorectal cancer. The researchers compared these diagnoses with the dietary habits reported at the outset, taking into account factors including age, smoking and physical activity.
The result may come as a surprise: in this population, generally eating more ultra-processed foods was not associated with a measurable increase in the risk of this cancer. However, this does not mean that all these products are equivalent or that they have no consequences for health.
When the foods were examined separately, differences emerged. Higher consumption of processed meats was associated with more colorectal cancers. Conversely, whole grains, fiber and certain dairy products, even when they came from foods classified as ultra-processed, were associated with a lower risk.
This may explain why the overall result did not show a clear increase: the associations observed for different food groups pointed in opposite directions. An industrially produced whole-grain bread and processed meat do not become equivalent simply because they are both ultra-processed.
The researchers also observed dietary habits without asking participants to change their meals. Diet was reported through a questionnaire at the beginning and may have changed over the following years.
The results therefore do not challenge the prevention advice already established: favor foods rich in fiber and whole grains, and limit processed meats. Above all, they show that to understand the links between diet and colorectal cancer, we must also look at the composition of products, not just their degree of processing.