Iron May Be Key Link Between Obesity and Colon Cancer

Researchers know that obesity is linked to an increased risk of colorectal cancer. But they are less clear about exactly why. Figuring out the why may be useful in creating strategies to help people who are obese lower their risk for getting colorectal cancer.

There are a number of existing hypotheses. One newer theory has to do with changes in the way the body processes iron when a person is obese, says Lisa Tussing-Humphreys, Ph.D., R.D., an American Cancer Society-funded researcher at the University of Illinois at Chicago. The basic idea is that obesity causes inflammation throughout the body, and this inflammation disrupts the body’s natural system for regulating iron.

Lisa Tussing-Humphreys

Tussing-Humphreys says that although iron is essential to many activities in the body – such as transporting oxygen – most healthy individuals only absorb small amounts of iron each day from what they eat, enough to replace natural losses.

Tussing-Humphreys explains that people who are obese seem to be absorbing even less iron, leading to a buildup of iron in the cells of the small intestine. These iron-laden cells eventually slough off and end up in the colon. Obesity itself is associated with underlying systemic and colonic inflammation, so over time this increased iron exposure could promote even more inflammation of the colon, which is linked to colorectal cancer. She is also exploring whether obesity-related changes in the way the body absorbs iron support the growth of harmful, cancer-promoting bacteria in the colon – and reduce the amount of good, protective gut bacteria.

Investigating Impact of Iron Levels in Various Diets on Colon Health

To see if iron is a factor linking obesity and colon cancer, Tussing-Humphreys is going to study the effect of different diets containing varying amounts of iron on colonic inflammation and the composition of gut bacteria.

She currently has plans (although she continues to tweak the specifics) to test three different diets:

  1. A typical American diet, with a higher level of iron
  2. A typical American diet, but with a lower amount of iron
  3. An anti-inflammation diet, similar to a Mediterranean-style diet, with a higher amount of iron

She is working with a colleague who is a registered dietician and a trained chef to design the test diets that all participants will get. She plans to kick off the study in April.

“I hope to find something that can help obese people protect against colon cancer; so if we find that eating a lower-iron diet has protective effects in this population, then that is an important message and very much modifiable.”

Even though researchers are not yet completely clear about all the specific reasons obesity increases a person’s risk for colorectal cancer – and other types of cancers – it is known that eating the right foods and getting enough exercise are two of the best ways to maintain a healthy weight and help lower the risk of getting cancer.

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