Researchers looked at whether eating foods with vitamin D could help prevent stomach cancer. They combined information from five different studies involving nearly 1,900 people with stomach cancer and almost 6,000 people without it. After carefully comparing how much vitamin D people ate, the scientists found no clear connection between vitamin D intake and stomach cancer risk. This means that while vitamin D is important for your health in other ways, eating more of it probably won’t reduce your chances of getting stomach cancer.

The Quick Take

  • What they studied: Whether people who eat more vitamin D-rich foods have a lower risk of developing stomach cancer
  • Who participated: Nearly 7,800 adults from five different countries and studies, including 1,875 people diagnosed with stomach cancer and 5,899 people without stomach cancer
  • Key finding: People who ate the most vitamin D had almost the same stomach cancer risk as those who ate the least (a 6% difference that could easily be due to chance). The researchers found no meaningful protection from dietary vitamin D.
  • What it means for you: You shouldn’t rely on vitamin D from food as a way to prevent stomach cancer. However, vitamin D remains important for bone health and other body functions, so continue eating foods like fatty fish, egg yolks, and fortified milk for overall wellness.

The Research Details

This research combined data from five separate case-control studies, which is a special type of research where scientists compare people who have a disease (stomach cancer) with similar people who don’t have it. By pooling all five studies together, researchers had a much larger group to analyze, making their conclusions more reliable. They looked at how much vitamin D each person ate through their diet and used statistical methods to see if there was any connection to stomach cancer risk. The researchers adjusted their analysis to account for other factors that might affect cancer risk, like how much total food people ate, whether they smoked, and how much alcohol they drank.

Combining multiple studies gives scientists a clearer picture than looking at just one study alone. This approach is especially important for rare diseases like stomach cancer, where individual studies might not have enough cases to find real patterns. By bringing together data from thousands of people across different countries, the researchers could be more confident in their answer about whether vitamin D really matters for stomach cancer prevention.

This study is fairly strong because it combined information from five separate research projects, giving it a large sample size. However, the studies showed some differences in their results (called heterogeneity), which means the answer wasn’t completely consistent across all five studies. The research relied on people remembering what they ate in the past, which can sometimes be inaccurate. The studies were case-control designs, which are good for studying rare diseases but can’t prove cause-and-effect the way some other study types can.

What the Results Show

When researchers compared people who ate the most vitamin D to those who ate the least, they found almost no difference in stomach cancer risk. The result showed a 6% higher risk in the highest vitamin D group, but this difference was so small it could easily have happened by chance. The confidence interval (a range showing where the true answer likely falls) included the number 1.0, which means no effect at all. This is the key sign that the finding is not statistically significant. The researchers tested whether the results were consistent across all five studies and found some variation, suggesting that vitamin D’s effect (or lack thereof) might differ slightly depending on the population studied.

The researchers also looked at whether vitamin D’s effect on stomach cancer risk was different for men versus women, younger versus older people, rich versus poor communities, smokers versus non-smokers, heavy drinkers versus light drinkers, and people who ate lots of vegetables and fruit versus those who didn’t. In every single one of these subgroups, vitamin D showed no meaningful connection to stomach cancer risk. This consistency across different populations strengthens the conclusion that vitamin D from food doesn’t appear to be an important factor in stomach cancer prevention.

Scientists have been uncertain about vitamin D’s role in stomach cancer for years, with some studies suggesting it might help and others finding no effect. This large pooled analysis provides clearer evidence that dietary vitamin D probably isn’t a major player in preventing stomach cancer. However, this doesn’t mean vitamin D is unimportant for health—other research shows it’s crucial for bone strength, immune function, and preventing other diseases. The finding also doesn’t rule out the possibility that vitamin D supplements (rather than food sources) might have different effects, since this study only looked at vitamin D from diet.

This study has several important limitations to consider. First, it relied on people remembering what they ate months or years earlier, which can be inaccurate. Second, the studies measured vitamin D intake in different ways, which might have affected the results. Third, the research only looked at vitamin D from food, not from supplements or sun exposure, so we can’t conclude anything about those sources. Fourth, the five studies showed some inconsistency in their findings, suggesting the answer might not be the same everywhere. Finally, case-control studies can’t prove that vitamin D prevents or causes cancer—they can only show associations.

The Bottom Line

Based on this research, you should not expect dietary vitamin D to prevent stomach cancer. However, continue eating vitamin D-rich foods like salmon, mackerel, egg yolks, and fortified milk because vitamin D is important for many other aspects of health. If you’re concerned about stomach cancer risk, focus on proven prevention strategies like not smoking, limiting alcohol, maintaining a healthy weight, and eating plenty of vegetables and fruits. Talk to your doctor about your individual risk factors.

This finding is relevant to anyone interested in cancer prevention, especially people with a family history of stomach cancer. It’s particularly important for people who were considering increasing vitamin D intake specifically to prevent stomach cancer—this research suggests that won’t help. However, the findings don’t apply to vitamin D’s other health benefits, which remain well-established. People in regions with high stomach cancer rates should focus on other proven prevention methods.

This research doesn’t suggest any timeline for benefits because it found no protective effect. If you’re making dietary changes for other health reasons (like bone health), you might notice improvements in bone strength or energy levels over weeks to months, but stomach cancer prevention isn’t a realistic expectation from vitamin D alone.

Want to Apply This Research?

  • Track your vitamin D intake from food sources (fatty fish, egg yolks, fortified milk) separately from other nutrients to monitor whether you’re meeting daily recommendations (600-800 IU for most adults), even though this study shows it won’t prevent stomach cancer.
  • Use the app to log vitamin D-rich foods as part of a balanced diet for overall health, but don’t use vitamin D intake as your primary stomach cancer prevention strategy. Instead, track behaviors with proven cancer-prevention benefits like vegetable and fruit consumption, avoiding smoking, and limiting alcohol.
  • Monitor vitamin D intake monthly to ensure you’re meeting general health recommendations, but pair this with tracking of other lifestyle factors known to reduce cancer risk. Use the app to set reminders for regular health check-ups and cancer screenings appropriate for your age and risk factors.

This research suggests that dietary vitamin D is not associated with stomach cancer risk, but it does not provide medical advice. Vitamin D remains important for bone health and other body functions. If you have concerns about stomach cancer risk, family history of cancer, or questions about your diet, please consult with your healthcare provider or a registered dietitian. This study looked only at vitamin D from food sources and cannot be applied to vitamin D supplements or sun exposure. Always discuss any major dietary changes or cancer prevention strategies with your doctor.