Cancer has long been considered a disease of old age, but doctors are now seeing more young adults diagnosed with cancers that were once rare in people under 50.
Colon, breast, and other cancers are rising sharply in people in their 30s and 40s, leaving experts searching for answers.
Dr. Beatrice Dionigi, a colon and rectal surgeon at Columbia University Irving Medical Center, says she now routinely operates on young patients, many with advanced colon cancer.
“Every year, the patients are younger,” she says.
A recent study found that gastrointestinal cancers in Americans under 50 increased by 15% between 2010 and 2019, while breast cancer cases in young women rose by 8%.
Strangely, this is happening while cancer rates among older adults are declining.
Dr. Rebecca Kehm, a cancer epidemiologist at Columbia, says the rise isn’t due to better screening because many of these young patients aren’t old enough for routine colonoscopies or mammograms.
Genetics also doesn’t explain it, since inherited cancer mutations, like the BRCA gene for breast cancer, haven’t increased in the population.
“If this was purely genetic, we’d expect a gradual rise over many generations—not the sharp increase we’re seeing in just a few decades,” Kehm explains.
What’s causing early-onset cancer?
Scientists believe lifestyle and environmental changes may be fueling this trend.
Some experts point to rising obesity rates, as excess body fat can cause inflammation and tumor growth.
However, others argue that obesity may just be a symptom of deeper issues, such as unhealthy diets and sedentary lifestyles.
A new study led by Dr. Joel T. Gabre at Columbia suggests that ultra-processed foods may be playing a major role in early-onset colon cancer. His research found that certain fatty acids in processed foods, like soybean, corn, and sunflower oils, can damage gut health, cause inflammation, and trigger cancerous changes.
“Many of my patients with early-onset colon cancer are young and fit—some are marathon runners or ballet dancers,” says Dr. Dionigi. “It makes me think that what people eat as children may have long-term effects, even if they later adopt a healthy lifestyle.”
The role of exercise in cancer prevention
Dr. Kehm’s recent research shows that physical activity in adolescence and early adulthood can significantly lower the risk of breast cancer later in life. Her study of 26,000 women found that those who exercised regularly between ages 12 and 34 were 20% less likely to develop early-onset breast cancer.
Scientists believe exercise regulates estrogen levels, reduces inflammation, and lowers oxidative stress, all of which help prevent tumor growth. Kehm’s research suggests that staying active from a young age is key to reducing breast cancer risk—regardless of body weight.
“The message should be about maintaining a healthy lifestyle overall, not just focusing on body weight,” she says.
Can we detect and prevent cancer earlier?
Columbia researcher Lauren Houghton is studying how hormone levels in young women could be used to predict breast cancer risk. Identifying high-risk individuals early could allow for targeted prevention strategies, such as exercise programs, lifestyle changes, or earlier screenings.
While processed foods and inactivity are now under scrutiny, how these new risk factors compare to well-known cancer risks—such as smoking, alcohol consumption, and red meat intake—remains unclear. Researchers say long-term studies tracking children and young adults are needed to understand how lifestyle choices shape cancer risk over time.
“Most cancer studies have focused on adult exposures,” Kehm says. “We’re just beginning to understand how early-life factors play a role. The next step is to study young people more closely to find out when and how we can intervene to prevent cancer before it starts.”
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Source: Columbia University.
