Heme Iron Intake Linked to Risk of Upper Digestive Tract Cancer

NEW YORK DEC 12, 2005 (Reuters Health) - Higher intake of heme iron appears to be associated with an increased risk of esophageal and gastric cancers, researchers report.  However, the risk is decreased with higher intake of zinc.

In a study published in the November issue of 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 baseline) who completed food frequency questionnaires.  Heme iron was calculated as 40% of the total iron content of all meat items.

The women were followed for 16 years. During that period, a total of 75 cases of upper digestive tract cancer (52 gastric cancer and 23 esophageal cancer) were reported.  The team found a positive association between heme iron intake and the risk of upper digestive tract cancer.  An inverse association was observed between zinc intake and cancer risk.

Specifically, the relative risks for increasing quintiles of heme iron intake were 1.0, 1.53, 2.15, 3.05, and 2.83 (p for trend = 0.06) after adjusting for age, total energy intake, cigarette smoking, and alcohol consumption.  The corresponding relative risks for zinc intake were 1.0, 0.86, 0.42, 0.37, and 0.13 (p for trend < 0.01). 

The results were not altered after additional adjustment for 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 the digestive tract, probably through the mechanism of oxidative stress," Dr. Jacobs and colleagues explain.

"The body"s defense against oxidative stress may be accomplished by interconnecting systems of antioxidant micronutrients with a range of physical properties rather than the use of high doses of a single antioxidant," the investigators note.  "Therefore the roles of zinc and iron may partially depend on other nutrients or substances in the food that delivers the zinc and iron."

SOURCE:

• Int J Cancer 2005;117:643-647.