Ultra-Processed Foods and Lung Cancer Risk

What a Large U.S. Cohort Study Shows—and What It Doesn’t

This article examines a large U.S. study on ultra-processed foods and lung cancer risk, explaining what the evidence shows, its limits, and what it means for everyday choices.

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🇪🇸 Spanish (Latinoamérica)

Este artículo analiza un gran estudio de Estados Unidos sobre los alimentos ultraprocesados y el riesgo de cáncer de pulmón, explicando qué muestra la evidencia, sus límites y qué significa para la vida diaria.

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🇨🇳 中文（简体）

本文解读一项美国大型研究，探讨超加工食品与肺癌风险之间的关系，并说明研究结果的意义与局限。

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Introduction

Lung cancer is still most strongly linked to smoking—but smoking may not be the whole story.
Over the past decade, researchers have begun to look beyond cigarettes to other modern exposures that might quietly influence lung cancer risk.

One of the most debated topics is ultra-processed food (UPF)—industrial food products designed for convenience, shelf life, and hyper-palatability. While UPFs are already linked with obesity, diabetes, and cardiovascular disease, their possible role in cancer, especially lung cancer, has been less clear.

A large new U.S. cohort study now asks a provocative question: could high consumption of ultra-processed foods be linked to lung cancer risk, even after accounting for smoking?

II. The Study at a Glance: What Was Asked and What Was Found

The study, titled “Association between Ultra-Processed Food Consumption and Lung Cancer Risk: A Population-Based Cohort Study,” was conducted by Wang et al. and published in Thorax in 2025.

Study design

• Population: 101,732 U.S. adults enrolled in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial
• Age at enrollment: 55–74 years
• Follow-up duration: Mean of 12.2 years
• Cancer outcomes:1,706 incident lung cancers, including
  • 1,473 non-small cell lung cancers (NSCLC)
  • 233 small cell lung cancers (SCLC) Association between ultra- proc…

Dietary intake was assessed at baseline using a validated Diet History Questionnaire (DHQ), and foods were classified into NOVA categories, with a specific focus on ultra-processed foods.

Main findings

After adjusting for a wide range of factors—including smoking status, body mass index (BMI), alcohol intake, physical activity, diabetes, hypertension, and overall diet quality (HEI-2015)—the researchers found a clear association between higher UPF intake and lung cancer risk:

• Participants in the highest quarter of UPF consumption had a 41% higher risk of lung cancer compared with those in the lowest quarter
  • Hazard ratio (HR): 1.41 (95% CI, 1.22–1.60)
• Similar associations were seen for:
  • NSCLC: HR 1.37 (95% CI, 1.20–1.58)
  • SCLC: HR 1.44 (95% CI, 1.03–2.10) Association between ultra- proc…

The authors also observed a non-linear dose–response relationship for overall lung cancer and NSCLC, suggesting that risk rises disproportionately at higher levels of UPF intake.

Why did this catch attention?

What makes this study notable is not just the size of the cohort, but the fact that the association persisted after accounting for smoking status and overall diet quality. In other words, the signal was not explained simply by “people who eat poorly also smoke more.” This raises an important question for both clinicians and readers: could ultra-processed foods be an independent, modifiable contributor to lung cancer risk in modern diets?

III. How Ultra-Processed Foods Were Defined and Measured

A major strength—or weakness—of any nutrition study depends on how diet is defined and measured. In this study, the authors made a clear attempt to systematically identify ultra-processed foods (UPFs), while also acknowledging the inherent limitations of dietary research.

How the diet was assessed

Participants reported their usual diet using the Diet History Questionnaire (DHQ), a detailed food-frequency questionnaire designed to capture typical intake over the previous 12 months. The DHQ asks about how often specific foods are eaten and in what portion sizes, allowing researchers to rank individuals from lower to higher intake patterns. While no questionnaire can perfectly capture real-world eating habits, this tool is widely used in extensive population studies.

How foods were classified as ultra-processed

Foods listed in the questionnaire were categorized using the NOVA food classification system, which groups foods by the degree and purpose of industrial processing, rather than by calories or macronutrients. Two trained dietitians independently assigned foods to NOVA categories and resolved any disagreements by consensus, reducing random classification errors.

Under this system, ultra-processed foods are industrial formulations made essentially from refined ingredients, additives, flavorings, emulsifiers, and preservatives, with little resemblance to whole foods. In this study, UPFs included items such as:

• Processed meats like lunch meats and sausages
• Soft drinks and sweetened beverages
• Cookies, cakes, pastries, and candies
• Salty snacks like chips and crackers
• Breakfast cereals
• Instant noodles and soups
• Sauces, margarine, and many fast-food items

Quantifying UPF intake

To avoid simply identifying people who eat more calories overall, the researchers adjusted UPF intake for total energy consumption. This approach allowed them to compare individuals based on the proportion of their diet from ultra-processed foods, rather than on total food intake.

Participants were then divided into four groups (quartiles) based on their level of UPF intake, from lowest to highest. Lung cancer risk was compared across these groups over the follow-up period.

Which UPFs contributed the most

Not all ultra-processed foods contributed equally. In this cohort, lunch meats and soft drinks accounted for the largest share of UPF intake. This is an important point for readers: the observed association was driven mainly by common, everyday foods, not rare or exotic additives.

Important limitations to keep in mind

The authors appropriately note several limitations in how UPFs were measured:

• The dietary questionnaire was not originally designed to classify foods by processing level, which may have led to some misclassification.
• Diet was measured only once at baseline, even though people’s eating habits can change over time.

These issues are common in long-term nutrition studies and generally bias results toward underestimating, rather than exaggerating, true associations.

IV. How Lung Cancer Was Identified—and Why This Part of the Study Is Strong

When evaluating any cancer–nutrition study, it is essential to separate dietary uncertainty from diagnostic certainty. While food intake is notoriously difficult to measure, this study’s handling of lung cancer outcomes is one of its strongest aspects.

How lung cancer cases were identified

Participants were drawn from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, a large U.S. research program specifically designed to track cancer outcomes over time. Incident lung cancer cases were identified through active follow-up, including periodic questionnaires, medical record review, and linkage to cancer registries.

Crucially, lung cancer diagnoses were confirmed through medical record abstraction, not self-report. Pathology reports and clinical documentation were used to verify each case, substantially reducing misclassification.

Classification by lung cancer subtype

The investigators went a step further by separating lung cancers into their major biological subtypes:

• Non–small cell lung cancer (NSCLC)
• Small cell lung cancer (SCLC)

This distinction matters clinically. NSCLC and SCLC differ in biology, growth patterns, and typical risk profiles. The fact that higher ultra-processed food intake was linked to both subtypes strengthens the argument that the association is not an artifact of a single disease category.

Why outcome ascertainment matters

Many observational studies rely on death certificates or self-reported diagnoses, which can be incomplete or inaccurate. In contrast, the PLCO framework provides:

• Prospective follow-up, reducing recall bias
• Pathologically verified diagnoses, improving accuracy
• Subtype-specific analysis, allowing more nuanced interpretation

Because lung cancer status was determined independently of dietary reporting, differential bias is unlikely—participants did not know their future cancer status when reporting diet. This temporal separation strengthens the credibility of the findings.

What this means for interpretation

Even though dietary exposure is imperfectly measured, the outcome side of the equation is solid. If an association is observed under these conditions, it is more likely to reflect a real signal rather than diagnostic noise.

In short, while skepticism is warranted when interpreting dietary data, the reliability of lung cancer diagnosis in this study supports taking the observed association seriously—especially when viewed alongside its consistency across cancer subtypes.

V. Why the Results Are Compelling—and Where Caution Is Still Needed

This study has drawn attention not because it proves causation, but because it raises a credible signal that persists even after extensive adjustment. At the same time, it illustrates the limits of observational nutrition research—especially for a disease as smoking-dominated as lung cancer.

Why the findings are compelling

1. The association survives heavy adjustment
The link between ultra-processed food intake and lung cancer risk remained after adjusting for:

• Smoking status (never, former, current)
• Body mass index
• Alcohol intake
• Physical activity
• Diabetes and hypertension
• Socioeconomic and demographic factors
• Overall diet quality (Healthy Eating Index–2015)

This is important. It suggests the signal is not simply a proxy for “unhealthy lifestyle” or poor diet quality overall. Even when two people had similar diet quality scores, the one consuming more ultra-processed foods still showed higher lung cancer risk.

2. Consistency across lung cancer subtypes
The association was observed for:

• Overall lung cancer
• Non–small cell lung cancer
• Small cell lung cancer

These subtypes differ biologically and clinically. Seeing a similar pattern across them reduces the likelihood that the result is a statistical fluke tied to one narrow diagnosis.

3. Presence in both smokers and never-smokers
Although smoking remains the dominant risk factor for lung cancer, the association with ultra-processed foods appeared in:

• Current/former smokers
• Never-smokers

The lack of a statistically significant interaction suggests that UPFs do not merely amplify smoking risk, but may represent a parallel exposure. For never-smokers in particular—where baseline risk is lower—dietary factors may be more detectable.

4. A plausible dose–response pattern
Risk did not rise linearly from the lowest intake upward. Instead, the data suggest a non-linear increase, with risk becoming more apparent at higher levels of ultra-processed food consumption. This pattern is biologically plausible and commonly seen with environmental and dietary exposures.

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Where caution is still needed

1. Smoking intensity was not fully captured
The study adjusted for smoking status, but not for smoking intensity or cumulative exposure (for example, pack-years). This is a critical limitation. Even small differences in lifetime smoking exposure can substantially affect lung cancer risk.

Residual confounding from smoking could partially explain the observed association—especially among former and current smokers.

2. Diet was measured once
Ultra-processed food intake was assessed only at baseline, yet participants were followed for more than a decade. Diets can and do change over time. This introduces misclassification, which generally biases results toward underestimating true effects—but it also limits precision.

3. Observational data cannot prove causality
No matter how well adjusted, this remains a cohort study, not a randomized trial. The findings show association, not proof that ultra-processed foods cause lung cancer.

That said, randomized trials assigning people to high-UPF diets for cancer outcomes would be neither ethical nor practical—so high-quality observational data may be the best evidence available.

4. Generalizability is limited
Most participants were older, predominantly White Americans. Results may not fully apply to younger populations or other ethnic and cultural dietary patterns.

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A balanced interpretation

Taken together, the results justify measured concern, not alarm. This study does not overturn decades of evidence showing smoking as the primary cause of lung cancer. But it does suggest that dietary processing may be an independent, modifiable contributor to risk, especially relevant in an era where ultra-processed foods dominate modern diets.

For readers, the message is not fear—it is risk stacking. Smoking, obesity, metabolic dysfunction, and dietary processing may act together. Reducing ultra-processed food intake is unlikely to eliminate lung cancer risk, but it may be one more lever—alongside smoking cessation and metabolic health—that tilts the odds in a healthier direction.

VI. Interactions with Smoking, Obesity, and Other Risk Factors: What the Data Actually Show

Given how dominant smoking is as a cause of lung cancer, a central question is whether ultra-processed foods (UPFs) simply track with smoking, or whether they appear to matter independently. The authors specifically explored this by examining whether the association between UPFs and lung cancer differed across major risk groups.

Smoking status

Participants were stratified into never smokers and current/former smokers. Higher UPF intake was associated with increased lung cancer risk in both groups. Importantly, statistical testing showed no significant interaction between UPF intake and smoking status.

What this means in practical terms:

• UPFs did not appear to raise lung cancer risk only among smokers.
• The association was also present in never smokers, where baseline lung cancer risk is much lower.

This finding argues against the idea that UPFs are merely a surrogate marker for smoking behavior. At the same time, the lack of detailed smoking intensity data (such as pack-years) means some residual confounding cannot be ruled out—particularly among former smokers.

Body weight and obesity

The researchers also examined body mass index (BMI). The association between UPF intake and lung cancer risk was:

• Numerically stronger in participants with BMI ≥25
• Still present, though weaker, in those with BMI <25

Again, no statistically significant interaction was detected. This suggests that excess body weight may magnify, but does not fully explain, the observed relationship. From a metabolic perspective, this aligns with the idea that UPFs may exert effects through pathways not captured by BMI alone, such as insulin resistance or chronic inflammation.

Other subgroups

The authors evaluated potential effect modification by:

• Age
• Sex
• Family history of lung cancer
• Length of follow-up

None of these factors significantly altered the association.

Clinical interpretation

For readers, this section carries an important message:
UPFs appear to function as a broad, background risk factor, rather than one that only matters if you smoke, are obese, or have a family history of cancer. This supports a “risk-stacking” model, where multiple modest exposures combine to influence long-term disease risk.

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VII. Possible Biological Mechanisms: How Might Ultra-Processed Foods Influence Lung Cancer Risk?

Because this is an observational study, any discussion of mechanism must be framed carefully. The authors do not claim proof—but they do outline plausible pathways that help explain why this association is biologically credible.

1. Diet quality displacement

Ultra-processed foods often displace whole and minimally processed foods. Diets high in UPFs tend to be:

• Lower in fiber
• Lower in protective phytochemicals
• Lower in naturally occurring antioxidants

Even after adjusting for overall diet quality scores, UPFs may capture qualitative differences that summary indices miss—such as food structure, additive load, and glycemic impact.

2. Metabolic and inflammatory effects

Ultra-processed foods are strongly linked to:

• Insulin resistance
• Postprandial glucose spikes
• Low-grade chronic inflammation

These metabolic disturbances can promote cellular stress, oxidative damage, and impaired immune surveillance—conditions that may facilitate cancer development or progression, even in tissues not directly exposed to food.

3. Additives and processing byproducts

UPFs frequently contain:

• Emulsifiers
• Preservatives
• Artificial sweeteners
• Flavor enhancers

In addition, industrial processing can introduce contaminants or byproducts such as nitrosamines, acrolein, and other reactive compounds. While individual exposures may be small, chronic, cumulative intake over decades could plausibly contribute to carcinogenic processes.

4. Shared pathways with smoking-related damage

Some of the biological stressors associated with UPFs—oxidative stress, inflammation, and impaired DNA repair—overlap with mechanisms known from tobacco exposure. This raises the possibility that UPFs do not replace smoking risk, but layer additional stress on already vulnerable systems.

A careful conclusion on mechanism

At present, these mechanisms remain hypotheses, not proven pathways. However, they provide a coherent biological framework that supports the observed epidemiologic signal and explains why the association persists even after adjusting for smoking, BMI, and overall diet quality.

VIII. What This Means for You

For most readers, the key question is not whether ultra-processed foods (UPFs) cause lung cancer, but whether this information should change anything they do in daily life. The answer is best framed with realism and proportionality.

1. This does not replace the smoking message

Smoking remains, by far, the strongest and most established cause of lung cancer. Nothing in this study challenges that fact. If someone smokes, quitting smoking will reduce lung cancer risk far more than any dietary change.

What this study adds is a broader view: lung cancer risk may be shaped by more than one exposure, especially in modern environments where UPFs dominate food choices.

2. Diet still matters—even for non-smokers

One of the most relevant findings for the general public is that the association between UPFs and lung cancer was also seen in never-smokers. For people who do not smoke, diet may represent a more visible modifiable risk, simply because major causes like tobacco are absent.

This does not mean UPFs are a major cause of lung cancer—but it suggests they may be one piece of a larger risk puzzle.

3. Focus on the biggest contributors, not perfection

The study found that lunch meats and sugary beverages were among the largest contributors to ultra-processed food intake. For readers, this is empowering:

• You do not need to eliminate all packaged foods
• You do not need to chase obscure additives

Instead, meaningful reductions can come from:

• Reducing processed meats
• Replacing sugary drinks with water, coffee, or tea
• Choosing simpler foods with recognizable ingredients more often

Examples of processed meat:

• Hot dogs
• Bacon
• Sausages
• Ham
• Salami
• Bologna
• Other deli meats

4. Think in terms of “risk stacking,” not single causes

Health risks rarely act in isolation. Smoking, obesity, metabolic dysfunction, physical inactivity, and diet quality often stack together over decades. Ultra-processed foods may contribute to risk by worsening metabolic health, increasing inflammation, or displacing protective nutrients.

Reducing UPFs is unlikely to eliminate lung cancer risk—but it may lower cumulative biological stress, especially when combined with:

• Smoking avoidance
• Weight control
• Regular physical activity
• Stable blood sugar and insulin levels

5. Small changes, long timelines

Cancer develops over many years. The relevance of this study lies not in short-term fear, but in long-term pattern shaping. Shifting even part of one’s diet away from ultra-processed foods toward minimally processed options is a low-risk, high-upside choice for overall health.

Final takeaway for readers

This study does not demand drastic dietary rules or alarmist conclusions. It supports a familiar, evidence-consistent message:

What we eat—especially how processed our food is—may quietly influence long-term health, even in organs far from the digestive tract.

For readers, the goal is not dietary purity, but steady movement toward simpler foods and fewer industrial formulations, alongside the well-established priorities of smoking avoidance, metabolic health, and physical activity.

IX. Limitations, Counterarguments, and How to Read This Study Responsibly

No study—especially in nutritional epidemiology—should be read without a critical lens. This one is no exception.

1. Association is not causation

This study shows a statistical association, not proof that ultra-processed foods cause lung cancer. Even well-adjusted observational studies cannot fully eliminate residual confounding, especially for behaviors that cluster together over decades.

That said, the absence of causality does not mean the signal should be dismissed. Many well-established cancer risk factors—including smoking itself—were first identified through observational data long before mechanisms or trials were possible.

2. Smoking confounding is reduced, but not eliminated

The authors adjusted for smoking status, which is essential. However, they did not account for smoking intensity or cumulative exposure (pack-years). This leaves open the possibility that:

• Heavier smokers may also consume more ultra-processed foods
• Some of the observed risk could still reflect unmeasured smoking behavior

Notably, the persistence of the association in never-smokers argues against smoking being the sole explanation, but it does not eliminate it entirely.

3. Dietary data are imperfect by nature

Diet was assessed once, at baseline, using a food-frequency questionnaire. This introduces two issues:

• People may misreport what they eat
• Diets change over time

Both tend to dilute true associations rather than exaggerate them, but they still limit precision.

4. UPF is a broad category

“Ultra-processed food” includes a wide range of products, from sugary drinks to processed meats to packaged snacks. The study cannot pinpoint which components—additives, processing methods, nutrient displacement, or metabolic effects—are most responsible for the observed association.

This means the findings are directional, not prescriptive.

5. Why the study still matters

Despite these limitations, the study is:

• Large
• Prospective
• Pathologically validated
• Consistent across lung cancer subtypes
• Aligned with broader literature linking UPFs to metabolic and inflammatory disease

That combination makes the findings clinically relevant, even if not definitive.

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X. Conclusion: What This Study Adds to the Bigger Picture

This study does not rewrite the lung cancer playbook. Smoking remains the dominant risk factor, and no dietary intervention comes close to the impact of smoking cessation.

What it does add is nuance.

It suggests that ultra-processed foods may be part of a modern risk environment—one where industrial food processing, metabolic stress, chronic inflammation, and environmental exposures interact over decades. Lung cancer, traditionally viewed almost entirely through the lens of smoking, may also reflect these broader lifestyle patterns.

For readers, the implication is not fear, guilt, or dietary absolutism. It is risk awareness.

Reducing ultra-processed food intake—especially common items like processed meats (hot dogs, sausages, bacon, ham, deli meats like salami and bologna) and sugary beverages—is a reasonable, low-risk step that aligns with cardiovascular, metabolic, and cancer prevention goals.

In medicine, we rarely get single causes or single solutions. Health is usually shaped by layers of exposure, accumulated quietly over time. This study supports the idea that how processed our food is may be one of those layers—small on its own, but meaningful when added to the rest.

Don’t Get Sick!

Medically Reviewed by Dr. Jesse Santiano, MD
Dr. Santiano is a retired internist and emergency physician with extensive clinical experience in metabolic health, cardiovascular prevention, and lifestyle medicine. He reviews all medical content on this site to ensure accuracy, clarity, and safe application for readers. This article is for educational purposes and is not a substitute for personal medical care.

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References:

• Wang, Kanran, et al. “Association between Ultra-Processed Food Consumption and Lung Cancer Risk: A Population-Based Cohort Study.” Thorax, vol. 80, 2025, pp. 810–818. BMJ, https://pubmed.ncbi.nlm.nih.gov/40730472/

Disclaimer:
This article is for educational purposes and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician before making health decisions based on the TyG Index or other biomarkers.

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