Stomach cancer was a little less common in people who ate more vitamin B6. Then the researchers counted the vegetables

Stomach cancer is one of the world's most common cancers, and scientists have spent decades asking what diet has to do with it. Salt and preserved foods turn up again and again; individual vitamins much less clearly. A team led from the University of Milan has now looked at four B vitamins, thiamin (B1), riboflavin (B2), niacin (B3) and pyridoxine (B6), by pooling the original data of 13 case-control studies in the Stomach cancer Pooling (StoP) Project. The paper appeared in the European Journal of Nutrition on 7 October 2026.

A case-control study starts with people who already have the disease, the cases, and compares them with similar people who don't, the controls, asking both groups what they usually ate. Here that meant 5,252 people with stomach cancer and 11,397 without, with the research groups behind the studies spread across Europe, Asia and the Americas. Within each study the researchers split people into four equal groups by how much of each vitamin their diet supplied, then worked out how the odds of stomach cancer changed with each step up, allowing for the usual risk factors, before combining the studies.

Each step up in B6 intake came with 14% lower odds of stomach cancer, and each step up in thiamin with 7% lower odds. Niacin was borderline and riboflavin showed nothing clear. Allowing for Helicobacter pylori, the stomach bacterium most strongly tied to the disease, didn't change the main results. In men, the highest thiamin intakes looked more protective than in women. Riboflavin was linked with a higher, not lower, risk of the diffuse type of stomach cancer, though not the more common intestinal type.

The catch sits in one sentence of the summary: once the team also allowed for alcohol, meat, and fruit and vegetable intake, the links 'were weakened or no more apparent'. B6 comes from foods like chickpeas and other legumes, bananas, fish, poultry, nuts and whole grains, so people eating more of it are often simply eating more plants and fewer of the things already tied to stomach cancer. The vitamin may be a marker of a better diet rather than the active ingredient. Case-control designs add their own wobble: people diagnosed with cancer may remember their past eating differently, and the 13 studies measured diet in different ways, which the authors flag themselves when they call for more uniform methods. They conclude that B1 and B6 'might' lower risk. We read the abstract and the paper's funding record; the full text was not reachable for us. Nothing here suggests taking B-vitamin pills against stomach cancer, but it fits well with an ordinary plate built around legumes, whole grains, fish and fruit.