Study Finds Link Between Ultra-Processed Foods and Lung Cancer

The participants were followed for about 12.2 years and, during that time, 1,706 of them were diagnosed with lung cancer. While the overall risk of developing lung cancer was low (less than 2% across all groups), the researchers discovered that people who ate diets that were high in ultra-processed foods had a 41% higher likelihood of being diagnosed with lung cancer than those in the lowest group.

Meet the experts: Nilesh Vora, M.D., is an oncologist and medical director of the MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, Calif.; Danxia Yu, Ph.D., epidemiologist and assistant professor of medicine at Vanderbilt University Medical Center; Matthew Schabath, Ph.D., an epidemiologist at Moffitt Cancer Center; Scott Keatley, R.D., is co-owner of Keatley Medical Nutrition Therapy; Keri Gans, R.D.N., is author of The Small Change Diet

“Higher consumption of ultra-processed foods is associated with an increased risk of lung cancer,” the researchers wrote in the conclusion. “Although additional research in other populations and settings is warranted, these findings suggest the healthy benefits of limiting ultra-processed foods.”

While ultra-processed foods have been linked with cancer in the past, doctors say the lung cancer connection is surprising—particularly for non-smokers who developed lung cancer. Here’s what could be behind it, plus what doctors and dietitians recommend taking away from these findings.

What are ultra-processed foods?

Before we dive into the link it’s important to briefly touch on what ultra-processed foods are. The level of processing a food undergoes is classified on something called the NOVA scale. It breaks food into these four categories?

• Unprocessed and minimally processed foods: These foods are in their natural state or barely altered, like carrots, milk, and strawberries.
• Processed culinary ingredients: Foods in this category are minimally processed through steps like pressing or grinding. Those include things like olive oil and flour.
• Processed foods: Processed foods have been changed from their natural state, and typically include salt, oil, and sugar. Cheeses and canned fish tend to fall into this category.
• Ultra-processed foods: Ultra-processed foods are processed and include ingredients like artificial colors and flavors. They also typically have preservatives added for shelf stability and texture, and are usually packaged.

Why are ultra-processed foods linked to lung cancer?

It’s important to point out that the study didn’t prove that eating ultra-processed foods causes lung cancer. Instead, it found a link between people who have diets that are high in ultra-processed foods and a lung cancer diagnosis.

While the researchers adjusted the data for people who were smokers—a known risk factor for lung disease—it didn’t break down how much or how long people smoked, points out Nilesh Vora, M.D., an oncologist and medical director of the MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, CA. It could simply be that people who smoke often are more likely to eat more ultra-processed foods, and that the smoking (not the food) is what raised the risk, he explains. Worth noting: People who were non-smokers who ate high levels of ultra-processed foods were also diagnosed with lung cancer in the study.

Still, experts say it’s possible that there is something about ultra-processed foods themselves that may raise the risk of developing lung cancer. “Although ultra-processed foods are not—yet—classified as carcinogens, both epidemiological and laboratory data suggest they may be a potential cancer risk factor,” says Matthew Schabath, Ph.D., an epidemiologist at Moffitt Cancer Center. “Laboratory studies have shown that components of ultra-processed foods can alter gut microbiota, increase inflammation, damage DNA, and modify gene expression, among other effects. Diets high in ultra-processed foods also promote systemic inflammation and oxidative stress—both of which contribute to cancer development.”

The lack of nutrition in ultra-processed foods, contaminants from processing and packaging that may be carcinogenic, and additives that are often used with ultra-processed foods, like glutamate (an amino acid used in processed foods as a flavor enhancer) and carrageenan (an additive used to thicken and stabilize food), may also be an issue, according to Dr. Vora. The idea that packaging material and “unregulated glutamate” may raise the risk of lung cancer is “the most compelling” potential reason why someone may develop lung cancer from ultra-processed foods, Dr. Vora says.

Many ultra-processed foods are also engineered products, points out Danxia Yu, Ph.D., epidemiologist and assistant professor of medicine at Vanderbilt University Medical Center. “Ultra-processed foods are essentially industrial formulations that are extensively processed to be high in added sugars, saturated fats, and sodium, while low in fiber and micronutrients,” Yu says.

Yu also flags the food additives, particularly emulsifiers and preservatives, as being potentially problematic, along with chemicals from food packaging. Ultra-processed foods have been shown to impact blood sugar and the gut microbiome, as well as raise chronic inflammation, which is linked with a host of serious diseases, including cancer, she points out.

Still, Yu stresses that it’s hard to draw too many conclusions from this study. “Although there is biological plausibility and epidemiological evidence linking ultra-processed foods to disease risk like the results from this study, we cannot conclude that ultra-processed foods cause lung cancer,” she says.

Schabath agrees. “The study is one of the first cohort studies to identify an association between ultra-processed food consumption and lung cancer risk,” he says. “That said, the limited evidence doesn’t mean there’s no association—just that more research is needed.”

How to cut back on ultra-processed foods

While doctors stress that the link between ultra-processed foods and lung cancer is still being explored, a growing body of research suggests that it’s still best to limit how much of this food category you eat.

If you’re interested in eating fewer ultra-processed foods, it’s helpful to focus on more nutrient-dense foods first, says Scott Keatley, R.D., co-owner of Keatley Medical Nutrition Therapy. “Ultra-processed foods become a problem when they displace the fiber, protein, and micronutrients our bodies need to regulate inflammation and repair cells,” he says. “It’s not about swearing off convenience, it’s about making room for foods that do more for you.”

To start, it’s best to build your meals around whole ingredients like vegetables, fruits, whole grains, beans, nuts, and lean proteins, says Keri Gans, R.D.N., author of The Small Change Diet. “When those take center stage, there’s naturally less room for ultra-processed choices,” she says.