How processed your food is could put you at higher risk for lung cancer, study suggests

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There are many reasons to avoid ultraprocessed foods, including a link with heart disease, diabetes and obesity, but an increased risk of lung cancer may be yet another, a new study suggests.
Ultraprocessed foods contain ingredients 'never or rarely used in kitchens, or classes of additives whose function is to make the final product palatable or more appealing,' according to the Food and Agriculture Organization of the United Nations.
Those ingredients — found in items such as sodas, chips, packaged soups, chicken nuggets and ice cream — can include preservatives against mold or bacteria, artificial coloring, emulsifiers to stop separation, and added or altered sugar, salt and fats to make food more appealing.
People who eat the most ultraprocessed foods are 41% more likely to be diagnosed with lung cancer than those who eat the least, even after accounting for other factors such as smoking, according to the study published Tuesday in the journal Thorax.
For this study, researchers analyzed data from more than 100,000 people who completed the National Health and Nutrition Examination Survey's Food Frequency Questionnaire on their dietary habits and compared the information with medical records for lung cancer diagnoses.
On average, people had nearly three servings a day of ultraprocessed foods, most commonly lunch meat, diet or caffeinated soft drinks, or decaffeinated soft drinks, the study authors wrote.
'Industrial processing alters the food matrix, affecting nutrient availability and absorption, while also generating harmful contaminants,' the researchers added. They specifically highlighted acrolein, which can come from burning tobacco, wood, plastics and gasoline and from cooking fats and oils at high temperatures, according to the US Centers for Disease Control and Prevention. Packaging materials also may be part of the problem, they suggested.
The study is observational, meaning that while the methods were clear and strong, the research still can't definitively prove that the foods cause lung cancer –– just that there is a connection between the two, said Dr. David Katz, a specialist in preventive and lifestyle medicine and founder of the nonprofit True Health Initiative, a global coalition of experts dedicated to evidence-based lifestyle medicine. He was not involved in the research.
'This study strongly suggests that (ultraprocessed foods) may contribute to lung cancer risk,' he said.
Lung cancer is a common form of cancer, with an estimated 2.4 million new cases worldwide in 2022, according to the World Health Organization.
Smoking is the main contributor to lung cancer risk, but people who don't smoke can still get it, which suggests other factors are at play, Katz said.
The authors adjusted for factors, meaning that they accounted for other possible things that could increase lung cancer diagnoses, including whether or not a person smoked, but it's important to note that the measurements were not nuanced, said Dr. Fang Fang Zhang, The Neely Family Professor and chair of the division of nutritional epidemiology and data science in the Friedman School of Nutrition Science and Policy at Tufts University in Boston. She was not involved in the research.
'Because smoking is a very important risk factor for lung cancer, adjusting smoking in a crude way could leave a large room for residual confounding,' she said in an email. 'It will be important to adjust for the intensity (e.g., cigarettes/day) and duration (e.g., years of smoking) or the cumulative exposure of smoking (e.g., pack-years). However, the authors found that the association between ultra-processed food consumption and lung cancer risk was stronger among never-smokers.'
There hasn't been a lot of research into ultraprocessed foods and lung cancer risk, but a lot of existing evidence shows how important diet quality is for predicting premature death from all causes in the United States, Katz said.
Often, ultraprocessed food consumption is associated with a lower diet quality, such as a higher intake of saturated fats, chemicals, salt and sugar, as well as higher calorie consumption, he added.
These factors 'can drive inflammation –– a primary pathway in the development and progression of cancer –– and damage the microbiome, impairing immune system function,' he said in an email. 'This combination of excess inflammation and impaired immunity gives rogue cells the upperhand. … This scenario is where cancer begins.'
Ultraprocessed foods tend to be low in omega-3s, said Dr. Tom Brenna, professor of pediatrics, human nutrition and chemistry at Dell Medical School of the University of Texas at Austin. Omega-3s are essential, healthy fats that the body can't produce on its own, according to the National Institutes of Health Office of Dietary Supplements.
'Omega-3s limit shelf life, so if you're going to ultraprocess something … then you kind of want to get rid of omega-3s,' said Brenna, who was not part of the research.
Additives in ultraprocessed foods, carcinogens formed during processing or chemicals from food packaging might also be at play, Zhang said.
'However, these pathways are not well understood and warrant further investigations,' she said.
The study adds lung cancer risk to the list of reasons to avoid ultraprocessed foods and increase diet quality, Katz said.
Health and diet quality improve when people eat mostly whole, unprocessed foods and largely plants such as vegetables, fruits, whole grains, beans, lentils, nuts and seeds, he added.
If you want to make a change, Zhang recommends starting by reading food labels.
'Avoid foods with long ingredient lists with unfamiliar names — these are more likely to be additives, preservatives, and artificial flavors,' she said. 'Prioritize whole food and prepare meals using whole or minimally processed ingredients whenever possible.'
Instead of focusing on what you won't eat, try prioritizing adding foods directly from nature into your diet, Katz added.
'If you are used to eating a lot of UPFs, transition to less of them, more 'real' foods one better choice at a time,' he said in an email.
It may take a minute for your taste buds to adjust to more wholesome foods, but if you give yourself a couple of weeks to get used to it, you can come to prefer the taste of more natural ingredients, he said.
'Once that happens, maintaining a healthier diet becomes much easier,' Katz added.
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