Iron and calcium may up risk of lung cancer

NEW YORK (Reuters Health) – Small amounts of iron and
calcium in the diet or in the form of supplements may play an
important role in the development of lung cancer, especially
among smokers, a study suggests.

Iron, zinc, and calcium are micronutrients that participate
in the metabolism of damaging forms of oxygen, known as
reactive oxygen species. Intake of these micronutrients has
been associated with higher risks of certain cancers, such as
colorectal, breast, and prostate cancers.

“Some recent literature has associated these micronutrients
with disease including cancer, but nobody had looked into it in
the lung,” Dr. David C. Christiani from Harvard School of
Public Health and Harvard Medical School told Reuters Health.

Christiani and his colleagues looked for associations
between dietary iron, zinc, and calcium intake and the risk of
lung cancer in 923 patients with lung cancer and 1125 healthy
controls. To assess micronutrient intake, they used a 126-item
food-frequency questionnaire that took into account potential
risk factors such as smoking history.

When the team analyzed the 3 micronutrients separately,
iron and calcium were associated with a higher risk of lung
cancer but zinc was associated with a lower risk of lung
cancer. However, the associations were stronger when all 3
micronutrients were analyzed in the same model.

“The associations hold true, no matter the source of the
micronutrients,” Christiani said. “Iron and calcium in
particular, both dietary and in supplements, are associated
with increased risk of lung cancer.”

The investigators also found differences related to smoking
history, with the effects being particularly strong in current
smokers, and less so in former smokers.

“The message here for smokers and for former smokers is,
don’t take large amounts of supplements, particularly those
with iron or calcium, unless you have a medical indication for
them,” warned Christiani. “People tend to take lots of vitamins
and minerals thinking that they are good for them. We don’t
recommend large dietary shifts until these results are
confirmed in further studies.”

SOURCE: Epidemiology, November 2005.