Consumption of high levels of dietary iron appear to be associated with an increased risk of throat and stomach cancer, researchers report. However, the risk is decreased with higher levels of zinc.

In a study published in the International Journal of Cancer, Dr. David R. Jacobs, of the University of Minnesota, Minneapolis, and colleagues examined data from the Iowa Women’s Health Study involving 34,708 postmenopausal women (ages 55 to 69 years at study enrollment) who completed food consumption questionnaires.

The women were followed for 16 years. During that period, 75 cases of upper digestive tract cancer (52 stomach cancers and 23 throat cancers) were reported. The team found a positive association between iron intake and the risk of upper digestive tract cancer. However, an inverse association was observed between zinc intake and cancer risk.

The subjects were divided into groups based on dietary iron levels, and risk factors including age, total calorie consumption, cigarette smoking and alcohol consumption, were considered.

The increased risk of upper digestive tract cancers, from the lowest to the highest dietary iron levels, were zero to almost three-fold. The corresponding risks for dietary zinc levels were zero to less than 13 percent.

The results were not altered after consideration of other potential risk factors such as body mass index, physical activity score, hormone replacement therapy, multivitamin intake and intake of saturated fat, retinol, vitamin C, vitamin E, and folate from food and supplements.

“Our current and previous results strongly suggest that both iron and zinc play important roles in carcinogenesis of digestive tract, probably through the mechanism of oxidative stress,” Jacobs and colleagues comment.

SOURCE: International Journal of Cancer, November 2005.