A comprehensive review of 50 high-quality studies finds a meaningful link between higher vitamin D levels and lower colorectal cancer risk. Some studies suggest up to a 58% reduction among individuals with the highest intake, a finding that could influence cancer prevention strategies in Thailand and beyond. The research, published in Nutrients in 2025, emphasizes vitamin D as a practical and accessible tool in public health.
Colorectal cancer remains a major global health challenge, ranking among the most common cancers for both men and women. In Thailand, the disease has become more prevalent in recent years, with dietary shifts toward processed foods and lower fiber intake contributing to risk. Public health leaders are urging culturally appropriate prevention efforts that align with Thai lifestyles and dietary patterns.
The Nutrients review analyzes data from representative cohorts and clinical studies, including the Nurses’ Health Study in the United States, which linked higher vitamin D intake to a substantially lower colorectal cancer risk among women. Additional large studies found similar protective effects when considering calcium together with vitamin D. Importantly, vitamin D from both foods and supplements appears beneficial. A Canadian study involving more than 1,400 participants showed that vitamin D supplementation reduced the likelihood of developing colon polyps, precursors to cancer, and lowered risky polyp formation.
Researchers describe several mechanisms by which vitamin D may protect against cancer: modulation of immune responses, reduction of chronic inflammation, improved cell signaling, and promotion of programmed cell death in abnormal cells. It may also limit tumor growth and curb the growth of blood vessels feeding tumors, known as angiogenesis.
While some results in the broader literature vary—particularly regarding optimal dosage and whether food or supplements are most effective—the overall message supports a protective role for vitamin D. A Norwegian nested case-control study highlighted heightened proximal colon cancer risk at low vitamin D levels, underscoring the importance of maintaining adequate vitamin D, especially for women. In addition, a five-year retrospective study from California linked higher post-diagnosis vitamin D levels with improved survival among colorectal cancer patients.
Thai nutrition experts note a dual role for vitamin D: prevention and improved outcomes for those diagnosed with cancer. A Bangkok-based nutritionist explains that vitamin D is commonly undervalued in a country with abundant sunshine, yet many populations experience deficiency. Urban lifestyles, sun-avoidant behavior, and skin health concerns can limit natural production. Thailand’s tropical climate does not guarantee adequate vitamin D without intentional exposure and dietary choices.
Vitamin D is often called the “sunshine vitamin” because skin synthesis depends on sunlight. In Thailand, many people spend substantial time indoors, and sun exposure may be limited by work demands, urban living, and skin health norms. The interplay of pollution, aging, obesity, skin pigmentation, and sunscreen use can further reduce vitamin D production. Traditional Thai cuisine does not always provide sufficient vitamin D-rich foods, though fatty fish, egg yolks, and some mushrooms offer sources when included regularly. Fortified dairy products can contribute as well, but dietary patterns vary widely.
For individuals concerned about vitamin D status, a blood test measuring 25-hydroxyvitamin D is the standard check. Aiming for sufficiency typically means levels above 50 nmol/L, though guidelines differ by region. If levels are low, safe sunlight exposure and dietary adjustments are advised, with careful consideration of upper intake limits to avoid adverse effects.
Thailand’s Ministry of Public Health already emphasizes vitamin D for bone health in older adults. The potential cancer-prevention implications may prompt new public health campaigns and broader education about vitamin D in schools, workplaces, and communities. Health officials stress a practical approach: emphasize fish, eggs, fortified dairy, and regular, safe sun exposure, alongside accessible vitamin D testing and dietary guidance.
Globally, vitamin D deficiency affects a sizable portion of populations, with higher prevalence in certain communities. Shared risk factors with colorectal cancer—age, diabetes, sedentary lifestyles, poor gut health, high processed food intake, and lower socioeconomic status—make vitamin D optimization particularly relevant for Thailand’s aging and rapidly urbanizing society.
Thai cultural practices can support broader adoption of vitamin D optimization. Encouraging early-morning outdoor activity and mindful sun exposure resonates with local values and can be integrated into school and workplace routines. Public health planners may consider fortifying staple foods and expanding nutrition education to promote Vitamin D awareness as part of cancer prevention strategies.
Future research should include large-scale randomized trials focused on Southeast Asian populations to refine optimal intake levels and delivery methods. Policymakers may ultimately incorporate cancer prevention into vitamin D guidelines and public health messaging, influencing clinical practice and community health initiatives across Bangkok, Chiang Mai, and regional provinces.
Actionable steps for Thai readers: check your vitamin D status if you are over 50, have cancer risk factors, or spend most days indoors. Adopt a diet that includes more fatty fish, eggs, and fortified dairy. Where safe and appropriate, seek sun exposure as part of a daily routine. Schools and workplaces can support health by offering vitamin D–rich meal options and creating opportunities for outdoor activities.
Experts conclude that vitamin D is a low-cost, safe, and accessible intervention with significant potential for improving colorectal cancer prevention and outcomes. As more research becomes available, the Thai population can leverage the sunshine vitamin to support long-term health, complemented by broader public health strategies.
In summary, vitamin D shows promise as part of a comprehensive approach to colorectal cancer prevention and patient care. This evidence invites Thailand to consider practical, culturally attuned strategies to improve vitamin D status across the population.