A report published in the February, 2007 issue of the American Journal of Clinical Nutrition described the finding of researchers in Sweden that men and women who have a higher intake of vitamin A from food and supplements have half the risk of developing stomach cancer than that experienced by those whose intake is low.
Susanna C. Larsson of the Karolinska Institute and colleagues evaluated data from 82,002 adults aged 45 to 83 enrolled in the Swedish Mammography Cohort and the Cohort of Swedish Men. Participants in both studies completed identical dietary questionnaires in 1997 and were followed through June, 2005. Questionnaires were analyzed for preformed vitamin A (retinol from animal sources and fortified foods), provitamin A carotenoids alpha and beta-carotene, and other carotenoid levels.
Over the 7.2 year average follow-up period, there were 139 cases of stomach cancer. Subjects whose total vitamin A intake (including provitamin A carotenoids) from food and supplements was in the top one-fourth of participants had a 47 percent lower adjusted risk of developing stomach cancer than those whose intake was in the lowest fourth. When retinol from diet and supplements was examined separately, the risk was 44 percent lower for those in the highest intake group. For subjects whose alpha-carotene levels were in the top quarter, gastric cancer risk was 50 percent lower, and for participants whose beta-carotene levels were highest, the risk was 45 percent less than participants whose intake was lowest. No significant associations were determined for the carotenoids with no provitamin A activity. Further analysis of the data found that the reduction in gastric cancer risk associated with vitamin A was limited to nonsmokers or former smokers.
In their introduction, the authors remark that retinol plays a role in regulating cell proliferation and differentiation, and in modulating immune responses. The vitamin also has a healing effect on stomach ulcers, which have been associated with an increased risk of gastric cancer. The antioxidant activity of the vitamin neutralizes free radicals generated by H. pylori, a bacteria implicated in ulcers and stomach cancer.
The authors conclude that their results support the hypothesis of a possible protective role of vitamin A in gastric carcinogenesis.