Two decades-long studies link ultra-processed foods to cancer and premature death

While this upcoming long weekend may call for celebrations, this time around maybe reconsider breaking out the hot dogs, soda, and pre-packaged snacks. Two large-scale studies link overconsumption of “ultra-processed foods” to an increased risk of a number of ailments, including obesity, cancer, cardiovascular disease, early death, and more.

The authors defined ultra-processed food as “industrial formulations made entirely or mostly from substances extracted from foods (oils, fats, sugar, starch, and proteins), derived from food constituents (hydrogenated fats and modified starch), or synthesized in laboratories from food substrates or other organic sources (flavor enhancers, colors, and several food additives used to make the product hyper-palatable).” This definition is based on the NOVA Food Classification System.The paper published on August 31st in The British Medical Journal (BMJ) include two studies, one conducted in the United States and one in Italy.

The stateside study looked at 200,000 people (59,907 women and 46,341 men) for up to 28 years. Each study participant completed a questionnaire every four years, listing how often they ate about 130 different foods, ranging from non-processed foods like fruit all the way to ultra-processed like bacon. The long-range surveys found a link between ultra-processed foods and colorectal cancer in men, but not in women. Men in the highest quintile of ultra-processed food consumption had a 29 percent higher risk of developing colorectal cancer than those in the lowest quantile. The results of the Italian study found similar dangers in ultra-processed foods.

The reasons behind the differences between sexes is not yet clear.

[Related: Here’s why ultra-processed foods are so bad for your health.]

“We found an inverse association between ultra-processed dairy foods like yogurt and colorectal cancer risk among women,” said co-senior author Fang Fang Zhang, a cancer epidemiologist and interim chair of the Division of Nutrition Epidemiology and Data Science at the Friedman School, in a press release. Colorectal cancer is the third most diagnosed cancer in the US and is among the fastest-growing cancers in those under the age of 50.

Mingyang Song, co-senior author on the study and assistant professor of clinical epidemiology and nutrition at the Harvard T.H. Chan School of Public Health, added that, “Further research will need 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 other uncontrolled confounding factors in women that mitigated the association.”

A wide body of research has associated processed meats (bacon, salami, beef jerky, etc.) with a higher risk of bowel cancer in both men and women. The connection remained even when accounting for factors like dietary quality and body-mass index. This new study found that all types of ultra-processed foods, not just meats, played a role to some extent.

“We started out thinking that colorectal cancer could be the cancer most impacted by diet compared to other cancer types,” said Lu Wang, the study’s lead author and a postdoctoral fellow at the Friedman School of Nutrition Science and Policy at Tufts, in the press release. “Processed meats, most of which fall into the category of ultra-processed foods, are a strong risk factor for colorectal cancer. Ultra-processed foods are also high in added sugars and low in fiber, which contribute to weight gain and obesity, and obesity is an established risk factor for colorectal cancer.”

[Related: The truth about counting calories.]

The researchers recommend that ultra-processed foods be replaced with unprocessed or minimally processed foods to decrease the risk.

The Italian study began in 2005 and followed 22,000 people in the country’s Molise region. It was designed to assess rick factors for cancer, heart disease, and brain disease. The researched also published in the BMJ also compared the role of nutrient-poor foods (high in sugar and saturated or trans-fats) with ultra-processed foods in the development of early death and disease.

“Our results confirm that the consumption of both nutrient-poor or ultra-processed foods independently increases the risk of mortality, in particular from cardiovascular diseases,” said Marialaura Bonaccio, epidemiologist of the Department of Epidemiology and Prevention at the IRCCS Neuromed of Pozzilli and lead author of the study, in a press release.

When the team compared the two types of food to get a sense of which contributed the most, they found that the ultra-processed foods were “paramount to define the risk of mortality,” according to Bonaccio. “This suggests that the increased risk of mortality is not due directly (or exclusively) to the poor nutritional quality of some products, but rather to the fact that these foods are mostly ultra-processed.”