A diet rich in vitamin A (retinol) may cut the risk of stomach cancer by 44 per cent, suggests a prospective study from Sweden.
The study, which analysed dietary data from over 36,000 women and 45,000 men, also reported that similar risk reductions are obtained from high dietary intake of both alpha- and beta-carotene.
"High intakes of vitamin A, retinol, and provitamin A carotenoids may reduce the risk of gastric cancer," wrote lead author Susanna Larsson from the Karolinska Institutet, Stockholm.
Stomach cancer is the fourth most frequent cancer in the world, according to the European School of Oncology, and there are 800,000 new cases every year. It is Japan's most common form of cancer.
The research by Dr. Larsson and colleagues from the Central Hospital, Vasteras, Örebro University Hospital, and University Hospital, Örebro prospectively investigated carotenoid intake from foods only (dietary intake) and from foods and supplements combined (total intake) and the incidence of stomach cancer amongst the 45,338 men of the Cohort of Swedish Men and the 36,664 women in the Swedish Mammography Cohort.
Dietary assessment was performed using self-administered 96-item food frequency questionnaires in 1997, and during the average 7.2 years of follow-up, 139 incident cases of stomach (gastric) cancer were determined.
Writing in the current issue of the American Journal of Clinical Nutrition, the researchers report that, the relative risk of gastric cancer between people in the highest versus lowest intake groups of total vitamin A was reduced by 47 per cent.
The relative risks between people in the highest versus lowest intake groups of retinol, alpha-carotene and beta-carotene were reduced by 44, 50 and 45 per cent, respectively.
No significant gastric cancer risk reduction associations were found for beta-cryptoxanthin, lutein and zeaxanthin, or lycopene intake, said the researchers.
The results are in-line with another prospective study by the same researchers that reported that carotenoid-rich green leafy vegetables or roots vegetables could reduce the risk of stomach cancer by between 35 and 57 per cent (Cancer Epidemiology Biomarkers & Prevention, Vol. 15, pp. 1998–2001).
It should be noted that high vitamin A intake is not advisable for all sections of the population. Indeed, women who are pregnant or thinking of having a baby are advised to avoid taking supplements containing vitamin A since too much of the vitamin can cause development defects in unborn babies. There have also been some concerns raised over the vitamin for people at risk of bone fractures, such as post-menopausal women and older people.
Source: American Journal of Clinical Nutrition
February 2007, Volume 85, Number 2, Pages 497-503
"Vitamin A, retinol, and carotenoids and the risk of gastric cancer: a prospective cohort study"
Authors: S.C. Larsson, L. Bergkvist, I. Näslund, J. Rutegård and A. Wolk