Is excessive iron intake associated with cancer?
The straight answer: Yes.
The facts: Just as there are diseases associated with low body iron, an excessive amount of iron can also cause problems. Your body needs iron - for the production of red blood cells and to facilitate the transport of oxygen around your system - but too much of this mineral is toxic.
In addition to causing stomach upset, heartburn and nausea in some people, a high iron intake can also hinder the absorption of zinc, a trace mineral that helps support a healthy immune system by fighting off free radicals and promoting healing. In some studies, too much dietary iron has also been linked to cancer.
A study published in the European Journal of Cancer Prevention in November 2013 found an association between dietary and supplementary iron and colorectal cancer. Another study, published in 2008 in The Lancet Oncology showed that excessive iron plays a role in the development of breast cancer.
According to Dr Victor Hsue Chan-chee, president of the Hong Kong Association of Community Oncologists, iron is thought to be carcinogenic in that it accelerates the formation of the most dangerous type of free radical - hydroxyl radicals. In addition, excessive dietary iron suppresses your body's immune system, lowering your body's defences against the disease.
Unlike other nutrients, iron cannot be excreted naturally and any excess accumulates in the tissues and organs. Since cancer cells need iron to grow and multiply, a lifelong intake of iron can therefore increase the development of cancer, says Hsue.
While iron is occasionally detected at higher levels in the serum of cancer patients, which may correlate with aggressive disease and poor clinical outcome, it has never been proven to be a good cancer marker or prognostic marker. And, although many studies have shown the connection between body iron status and cancer, Hsue says that more solid evidence is still needed to prove the claim that an excess of this mineral increases an individual's risk of the disease. Genetics and certain lifestyle factors also play a role in the development of cancer.
Despite the controversy surrounding the issue, Hsue says that no one should take iron supplements unless there is a deficiency, with the possible exception of pregnant women. It is also important to watch your intake of heavily iron-fortified foods.
Bottom line: as long as you enjoy a balanced diet, your body's iron needs should be met. And to improve iron absorption, remember to also consume vitamin C-rich foods during meals.