Pancreatic cancer is one of the most feared cancers in the US.
In its early stages, its symptoms are vague and easily dismissible: a dull back ache, abdominal pain, unexplained fatigue.
And just 12 percent of patients survive after five years, with the vast majority being diagnosed after the disease has already spread to surrounding organs.
Scientists are still working to uncover ways to prevent the devastating cancer, honing in on stripping out processed meats, implementing exercise and tackling obesity.
But a new study has found an unlikely silver bullet: sunlight.
Following 90,000 adults, researchers analyzed their average amount of daytime light exposure with wearable sensors. They then followed the participants for nearly a decade, tracking cases and deaths from gastrointestinal cancers, which includes pancreatic cancer.
The team found that being exposed to at least 1,900 lux of brightness – about the same as going outside on a cloudy day – between 7:30am and 8:30pm was associated with a 13 percent lower risk of developing gastrointestinal cancers, which also includes colon, stomach, esophageal and liver cancers.
The effects were particularly pronounced for pancreatic cancer. The team found that getting just two hours of exposure to light above 5,000 lux – the equivalent of an overcast morning or afternoon – was tied to a 42 percent lower risk of developing the disease.
A new study has pinpointed the exact amount of daytime light exposure that may lower pancreatic cancer risk
It’s unclear why exactly sunlight may be protective against pancreatic and other gastrointestinal cancers, but it’s possible the benefits lie with vitamin D, a vital nutrient the body produces when skin is exposed to sunlight.
Once the skin synthesizes vitamin D, it gets converted into a metabolite called 25-hydroxyvitamin D, which recent research suggests can promote the death of cancer cells and block the growth of blood vessels that feed tumors.
Daytime light also helps regulate the body’s internal clock – the circadian rhythm – which boosts the immune system and helps cell DNA repair itself.
‘Higher daytime light exposure was associated with lower risks of gastrointestinal cancer incidence and mortality, especially for pancreatic cancer, indicating a potential protective effect that warrants further investigation in prevention and prognostic contexts,’ the researchers, from Guangdong Medical University in China, wrote.
In the new study, published in the International Journal of Cancer, researchers looked at 89,069 adults recruited from the UK Biobank database between 2013 and 2015. Participants ranged from 44 to 79 years old.
Among them, 1,692 developed gastrointestinal cancer and 891 died from it.
The above chart shows the survival rate of pancreatic cancer by stage
The participants wore wrist sensors to track their lux sunlight levels between 7:30am and 8:30pm. The researchers then used UK health records to track cancer incidence and deaths over the course of nine years.
The team found higher daytime light exposure was associated with a 13 percent lower risk of being diagnosed with a gastrointestinal cancer overall and a 24 percent lower risk of dying from it.
Additionally, 2.4 hours of daytime light exposure greater than 5,000 lux was associated with a 42 percent lower risk of pancreatic cancer and 53 percent reduced chance of pancreatic cancer death.
There were no statistically significant differences with other forms of gastrointestinal cancer, including colon cancer, which the researchers note could suggest sunlight may have a particular impact on the pancreas.
Holly Shawyer of North Carolina was diagnosed with pancreatic cancer in her 30s despite being a marathon runner. Her main symptom was a stomach ache. ‘I was in great health before this,’ she said
Ryan Dwars of Iowa with his family. He was diagnosed with stage four pancreatic cancer at 36
‘The current investigation addresses a critical knowledge gap, as there has been limited direct evidence linking daytime light exposure with gastrointestinal outcomes,’ the researchers wrote.
The team, however, cautioned that the findings show associations rather than proof that sunlight directly lowers pancreatic cancer risk.
The findings come as pancreatic cancer strikes 67,000 Americans every year and kills 52,000.
And between 2000 and 2021, pancreatic cancer diagnoses increased by 4.3 percent per year among Americans ages 15 to 34, and by 1.5 percent annually among those ages 35 to 54, according to a 2025 analysis.
