In the U.S., ultra-processed foods are everywhere—found readily at local grocery stores and restaurants, they make up about 55% of people’s diets. Now, new research reveals these foods may also be putting people at a higher risk of lung cancer.
The study, published on July 29 in Thorax, found new lung cancer cases were more common in people whose regular diets were rich in ultra-processed foods (UPFs) such as soft drinks, hot dogs, and breakfast cereals. But the rate of new lung cancers was much lower in those who rarely ate those foods.
Lung cancer is the leading cause of cancer death in the U.S., and the majority of cases are caused by smoking. However, researchers have previously linked air pollution, secondhand smoke, radon, and asbestos to the disease—and it’s possible that diet plays a role somehow, too.
If you’re eating UPFs in higher quantities, you might be missing out on the cancer-protective benefits of healthier foods, the researchers explained.
Foods that fall under the UPF umbrella are, in general, highly manufactured. They contain small fractions of whole foods, additives, and chemical modifications, and have ingredient lists that contain things you wouldn’t normally use in your kitchen.
UPFs are not inherently bad for you—yogurt, hummus, and whole-grain bread are UPFs, for example.
But generally speaking, these foods tend to be easy to eat and high in calories, filled with significant amounts of salt, fats, and sweeteners. They’re also often low in dietary fiber and don’t contain many whole foods.
There are thousands of examples of UPFs, but this new study on lung cancer incidence called out a range of common food items you may very well have in your kitchen: hot dogs, pizza, store-bought hamburgers, soft drinks, sweetened fruit drinks, instant noodles, breakfast cereals, breads, baked goods and pastries, candy, store-bought sauces and soups, cream cheese, salty snacks, ice cream, and margarine.
And UPFs have been linked to more than a dozen different health issues, including cancer, all-cause mortality, poor sleep, anxiety, depression, heart disease, and obesity.
Knowing that UPFs have been tied to poor health, researchers wanted to see whether the foods might be associated with the development of lung cancer, too.
They used data from the U.S. Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, which includes participants ranging from 55 to 74 years old.
There were nearly 102,000 participants who completed a one-time dietary questionnaire, which researchers used to estimate their UPF consumption. About three UPF servings per day was average, while 0.5 servings and six servings were the low and high ends, respectively.
Based on their average UPF consumption, the participants were then split into four groups.
About one in 10 participants reported eating lunch meat, making it the most common UPF. Diet caffeinated and decaffeinated sodas were close behind (around 7% of people reported drinking one).
Over the course of about 12 years, 1,706 participants developed lung cancer. Consistent with national trends, the majority of those cases were non-small cell lung cancer, while 14% were small cell lung cancer (a faster-growing cancer).
After looking at the data and accounting for external factors, the researchers found that the group who consumed the most UPFs were 41% more likely to be diagnosed with lung cancer than participants who consumed the least amount of UPFs.
Specifically, that top group had a 37% higher chance of being diagnosed with non-small cell lung cancer, and a 44% higher risk of small cell lung cancer. The risk was greater for both non-smoker and smokers.
Previous research has shown that UPF consumption is associated with a greater risk of pancreatic cancer, breast cancer, and colorectal cancer—lung cancer may now be added to that list, too.
But the link between UPFs and cancer “remains early in its evolution,” said Tim Rebbeck, PhD, the Vincent L. Gregory, Jr. Professor of Cancer Prevention at the Harvard T.H. Chan School of Public Health and the Dana-Farber Cancer Institute. More research is needed.
Still, Rebbeck told Health, the results could be more evidence that what we eat could contribute to our cancer risk.
Our bodies were designed to metabolize naturally occurring and whole foods, but the same can’t necessarily be said for UPFs, explained Zhaoping Li, MD, PhD, chief of the Division of Clinical Nutrition at the UCLA David Geffen School of Medicine.
The idea is that highly processed and preservative-rich foods could cause inflammation and other adverse impacts in a way that an apple doesn’t, for example.
“We still do not know what the mechanisms [for lung cancer risk] might be, but it is possible that systemic inflammation is acting in some way,” Rebbeck added.
This latest study can’t answer that question definitively—and there were other limitations, too. Specifically, the research was observational, dietary information was collected from a survey (just once), the number of lung cancer diagnoses was small, and the research team didn’t take smoking intensity into account.
“They did try to correct for many factors, but the very small effect of UPF on lung cancer risk does not rule out the possibility that some bias remains,” said Rebbeck.
Even though many questions remain, Rebbeck said this research is “encouraging,” as it suggests that limiting UPFs in our diets could “decrease cancer risk.”
It’s important to remember that UPFs don’t appear to be as big of a risk factor for lung cancer as smoking, Li told Health—that’s the most crucial thing people should change if they want to lower their risk.
But focusing on the quality of your diet is also a good idea. It’s probably not possible to nix UPFs completely, but balance is key—don’t load up on ultra-processed foods for three meals, Li explained.
If you’re going to have cereal for breakfast, for example, skip the Beyond burger and deli meat at lunchtime. Instead, opt for salads, cooked vegetables, fish, or chicken, she said.
Cooking with whole foods can be less convenient, but it’s worth it. For her breakfast, Li said she took a bit of extra time to make an omelette with cauliflower and leftover chicken, rather than pouring a bowl of cornflakes.
“We know already that eating a diet rich in low processed foods, vegetables, fruits, grains, does reduce the risk of cancer,” Rebbeck added. “So as we learn about the role of UPF in cancer, the message will probably remain the same—eat a balanced, less-processed, plant-forward, and nutrient-rich diet.”
