The growing cancer crisis in young adults and a call to action

Over the past several decades, cancer has been predominantly viewed as a disease of aging. Conventional wisdom suggests that the longer we live, the more opportunities our cells have to accumulate genetic mutations that can eventually lead to malignancies. Yet, this paradigm is being upended by a disturbing trend: Cancer is increasingly striking younger adults.

Recent data show that rates of early-onset cancers—those diagnosed in individuals under 50—are rising across multiple cancer types, with colorectal, breast, pancreatic, and esophageal cancers showing some of the most dramatic increases. This shift is prompting urgent questions about what could be fueling the trend. While genetics plays a role, the rapid nature of this rise suggests that environmental and lifestyle factors, including changes in diet and the gut microbiome, may be contributing in ways we are only beginning to understand.

Historically, colorectal cancer was considered a disease of older adults, and screening guidelines reflected this assumption. However, in 2021, the US Preventive Services Task Force lowered the recommended age for colorectal cancer screening from 50 to 45 in response to mounting evidence of rising incidence in younger populations. Similar concerns are emerging for other malignancies, including breast and pancreatic cancer, which are also appearing at increasing rates in adults under 50.

While some researchers have suggested that improvements in early detection may be responsible for part of the increase, this explanation does not fully account for the trend. The data reveal a true rise in incidence, not merely better detection. Moreover, these cancers are often more aggressive when they appear in younger adults, leading to worse prognoses. This makes understanding the underlying risk factors an urgent priority.

Among the most scrutinized risk factors is the modern diet — specifically, the rise of ultra-processed foods. These highly refined, industrially manufactured products now make up over 50% of the average American diet. They are engineered for hyper-palatability and long shelf life but are often devoid of essential nutrients and fiber while being high in added sugars, unhealthy fats, and artificial additives.

Large-scale epidemiological studies have linked diets rich in ultra-processed foods to increased risks of obesity, type 2 diabetes, and cardiovascular disease—conditions that themselves are associated with elevated cancer risk. But beyond these indirect effects, emerging research suggests that ultra-processed foods may play a more direct role in cancer development. For example, they often contain emulsifiers, artificial sweeteners, and other additives that can disrupt gut bacteria, trigger chronic inflammation, and contribute to metabolic dysfunction, all of which may accelerate cancer-promoting processes in the body.

One concerning study published in The BMJ found that for every 10% increase in the proportion of ultra-processed foods in an individual’s diet, there was a significant increase in overall cancer risk. Another large-scale cohort study in JAMA Oncology linked high consumption of ultra-processed foods to an elevated risk of colorectal cancer, particularly in men.

One of the most compelling mechanisms by which diet influences cancer risk is through its effect on the gut microbiome—the vast community of trillions of microbes that reside in our digestive tract. The microbiome plays a crucial role in regulating immune function, metabolizing nutrients, and even influencing systemic inflammation. However, modern dietary shifts, particularly the increased consumption of ultra-processed foods and the decreased intake of fiber, have profoundly altered the composition of gut bacteria in ways that may increase cancer susceptibility.

A healthy gut microbiome is rich in diverse bacterial species, many of which produce beneficial metabolites like short-chain fatty acids (SCFAs), which have anti-inflammatory and anti-carcinogenic properties. However, diets high in processed foods and low in fiber promote the growth of harmful bacteria while depleting beneficial species. This imbalance — known as dysbiosis — can lead to increased gut permeability, allowing harmful bacterial byproducts to enter the bloodstream and trigger chronic inflammation, a key driver of cancer progression.

Studies have identified specific microbial signatures associated with increased cancer risk. For example, certain strains of Fusobacterium nucleatum, a bacterium found in high abundance in individuals with colorectal cancer, have been shown to promote tumor growth by suppressing the immune system. Other gut-derived metabolites, such as secondary bile acids produced from high-fat diets, have been linked to DNA damage and colorectal carcinogenesis.

While diet and gut health are critical factors, they do not operate in isolation. The modern environment exposes individuals to a growing array of endocrine-disrupting chemicals, including bisphenols, phthalates, and per- and polyfluoroalkyl substances (PFAS), which are found in everyday consumer products and food packaging. These chemicals have been implicated in metabolic dysfunction, obesity, and hormone-driven cancers such as breast and prostate cancer.

Metabolic health itself is an often-overlooked contributor to cancer risk. The rise in obesity and insulin resistance—both of which have been accelerating in younger adults—are tightly linked to increased inflammation, oxidative stress, and hormonal imbalances that create a more favorable environment for cancer development.

Addressing the rise in early-onset cancers requires a comprehensive approach that encompasses dietary changes, policy interventions, and increased public awareness. Public health initiatives should prioritize reducing the consumption of ultra-processed foods while promoting whole, nutrient-dense diets that support a healthy gut microbiome. Policies that regulate food additives, limit harmful ingredients, and improve food labeling transparency could help consumers make informed choices. Additionally, current cancer screening guidelines may need further revision to identify high-risk individuals earlier. Personalized risk assessments that consider dietary habits, gut microbiome composition, and metabolic health markers could refine early detection strategies and improve outcomes.

Education and public awareness also play a crucial role. Healthcare professionals should emphasize the importance of fiber-rich diets, probiotic and prebiotic intake, and minimizing exposure to processed foods and environmental toxins. The public must be made aware of how modern dietary patterns contribute to cancer risk, empowering individuals to make healthier choices. By implementing these strategies at both the individual and systemic levels, we can begin to slow the alarming trend of early-onset cancers and improve long-term health outcomes.

The rise in early-onset cancers signals a critical shift in the public health landscape. While genetics can play a role, the rapid increase in cases suggests that environmental and lifestyle factors—including dietary patterns and gut microbiome alterations—are the key drivers of this concerning trend.

We are at a pivotal moment in understanding how the modern food environment interacts with human biology to influence cancer risk. By shifting dietary patterns, promoting microbiome health, and reevaluating screening strategies, we have the opportunity to alter the trajectory of cancer trends in younger generations.

The next steps require action from researchers, healthcare professionals, policymakers, and individuals alike. Understanding and mitigating these risks today could mean fewer diagnoses and better health outcomes for future generations.

(Dr. Raphael Cuomo is a biomedical scientist and professor at the University of California San Diego School of Medicine, and is an expert in cancer epidemiology, tobacco control, and health disparities.)

(Opinion columns published in The New Lede represent the views of the individual(s) authoring the columns and not necessarily the perspectives of TNL editors.)

(Featured photo by Kateryna Hliznitsova for Unsplash +.)