Translated from the original Italian version.
Stomach cancer is the fifth most common cancer worldwide. The risk of developing this type of cancer increases with age, but the latest statistics show a worrying increase in adults under the age of 50. Risk factors include tobacco and alcohol consumption, Helicobacter pylori infection, overweight and obesity.
Studies of Asian populations that frequently consume salt-cured foods, heavily salted fish or marinades, and extremely salty sauces have already shown that a high-salt diet increases the risk of stomach cancer. Salty foods increase the likelihood of developing stomach cancer by 41 per cent.
This prospective study (DOI: 10.1007/s10120-024-01502-9) had a large cohort of 471,144 adults included in the UK Biobank database. The study found that those who always added salt to their food had a 41 per cent higher risk of developing stomach cancer than those who almost never did so. This association was confirmed even after taking into account demographic, socioeconomic and lifestyle factors, as well as pre-existing comorbidities. Furthermore, adding salt to food at the table was associated with increased urinary sodium, both at a single point in time and over a 24-hour period, calculated using the INTERSALT formula.
However, when only 24-hour urinary sodium was considered as exposure, no association with gastric cancer risk was detected, probably due to the already known dilution effects of sodium measurements based on urine spot samples compared to those over a 24-hour period. Furthermore, the data analysis suggests the presence of a possible reverse causal mechanism, whereby individuals with gastric symptoms prior to cancer diagnosis may have lower salt intake.
These results are consistent with previous large-scale studies in America, Asia and some European countries that have shown a positive association between consumption of added salt and gastric cancer. However, previous studies in Europe have not shown an association between total salt intake, as assessed by food frequency questionnaires, and gastric cancer risk. This suggests that the difficulty of measuring total salt intake with food questionnaires may account for the discrepancies in the results.
The study suggests that the habit of adding salt at the table may be a good indicator of habitual salt intake and is less dependent on daily fluctuations than salt estimated from 24-hour dietary records. However, the study has some limitations, including the limited number of gastric cancer cases to evaluate potential confounding factors such as sex, age, ethnicity, H. pylori infection or smoking status.
Furthermore, the stratified analysis by anatomic location of gastric cancer was limited due to the small number of cases. Further research is needed to evaluate possible differences between individual cancer types. More studies are needed to better assess the association between salt intake and gastric cancer risk, particularly in non-Asian populations and using repeated 24-hour urine sodium measurements.