Two large observational studies published in The BMJ this week highlight the dangers of a diet rich in ultraprocessed foods (UPFs).
The first links the diet to an increased risk for colorectal cancer; the second shows a heightened risk of death from heart disease or any cause over a 14-year period.
UPFs are highly manipulated and packed with added ingredients, including sugar, fat, and salt, and are low in protein and fiber. They include soft drinks, chips, chocolate, candy, ice cream, sweetened breakfast cereals, packaged soups, chicken nuggets, hot dogs, french fries, and many more.
Over the past 30 years, there’s been a steady increase in consumption of UPFs worldwide, coupled with mounting evidence that diets rich in UPFs raise the risk for several chronic diseases, including heart disease and cancer. Few studies, however, have focused specifically on the risk for colorectal cancer (CRC).
To investigate, researchers analyzed data on 206,248 American adults (46,341 men, 159,907 women) from the Nurses’ Health Study, Nurses’ Health Study II, and the Health Professionals Follow-up Study. Dietary intake was assessed every 4 years using detailed food frequency questionnaires.
During up to 28 years of follow-up, 1,294 men and 1,922 women developed CRC.
In Cox proportional models adjusted for confounding factors, men with the highest UPF intake had a 29% higher risk for CRC than men with the lowest UPF consumption. This association was limited to distal colon cancer, with a 72% increased risk.
Among subgroups of UPFs, a higher intake of meat/poultry/seafood-based, ready-to-eat products, and sugary drinks were associated with increased risk for CRC among men.
“These products include some processed meats like sausages, bacon, ham, and fish cakes. This is consistent with our hypothesis,” lead author Lu Wang, PhD, with Tufts University, Boston, said in a news release.
There was no association between overall UPF intake and risk for CRC in women, and the reasons for this are unclear, the researchers say.
However, among the subgroups of UPFs, there was a positive association between ready-to-eat/heat mixed dishes and CRC risk and an inverse association between yogurt and dairy desserts and CRC risk among women.
It’s possible that foods like yogurt help counteract the harmful impacts of other types of UPFs in women, the researchers say.
“Further research will be needed to determine whether there is a true sex difference in the associations or if null findings in women in this study were merely due to chance or some uncontrolled confounding factors in women that mitigated the association,” co-senior author Mingyang Song, MD, with Harvard T.H. Chan School of Public Health, Boston, says in the news release.
Hard on the heart too
The related study in The BMJ shows a joint association between a low-quality diet and high intake of UPFs and increased risk for death from heart disease or any cause.
In this study of 22,895 Italian adults (mean age, 55 years; 48% men), those with the least healthy diets had a 19% higher risk of dying from any cause and a 32% higher risk for death from cardiovascular disease, over 14 years, compared with peers with the healthiest diets.
Adults with the highest share of UPFs had similarly elevated risks for all-cause and heart disease mortality (19% and 27% higher risk, respectively).
When the two food dimensions (nutrients and food processing) were analyzed jointly, the association of poor diet quality with mortality was significantly attenuated, but UPF intake remained highly associated with mortality, even after accounting for poor nutritional diet quality.
“These findings suggest that highly processed foods are associated with poor health outcomes independently of their low nutritional composition,” Marialaura Bonaccio, PhD, with IRCCS NEUROMED, Pozzilli, Italy, and colleagues note in their paper.
The new studies linking UPFs to CRC and heart disease join a recent study that found high UPF intake is harmful for the aging brain, as reported by this news organization.