Do certain vitamins increase your risk of cancer?

A study reports that taking too much beta-carotene and folic acid may increase your risk. Is there cause for concern?

27 May 2015
by Stefan de Clerk

Taking vitamins has become as much a part of our daily routines as brushing our teeth is. After all, in our ever-busier lives we’ve learnt that it’s important to boost our immune system not only with nutritional food but with dietary supplements too, so we can stay healthy, focused and productive.

However, a recent study conducted by Dr Tim Byers from the University of Colorado Cancer Center in the US suggests that vitamins may actually increase cancer risk if taken in excess of the recommended daily amount.

The evidence

Byers and his colleagues put dietary supplements under the microscope and reviewed 20 years’ worth of research into the relationship between vitamins and cancer prevention. They found that there is no scientific evidence that supports the claim that supplements fight cancer and that taking too many of them can potentially increase your risk of contracting the disease.

“We are not sure why this is happening at the molecular level but evidence shows that people who take more dietary supplements than needed tend to have a higher risk of developing cancer,” reported Byers, associate director for cancer prevention and control at the CU Cancer Center.

Beta-carotene and folic acid

Byers and his team singled out beta-carotene (also known as a carotenoid), which produces vitamin A and helps boost the immune system and improves vision. One trial they investigated showed that taking more than the recommended dosage of beta-carotene increased the risk for developing both lung cancer and heart disease by 20 percent.

They also reported that folic acid, which was thought to help reduce the number of precancerous polyps in a colon, actually increased the number in another trial.

Always take the correct dosage of vitamins

However, although the researchers concluded that taking more than the recommended dose of vitamins and minerals does more harm than good in their study, Dr Byers insisted that this didn’t mean that people needed to be afraid of taking vitamins and minerals. “If taken at the correct dosage, multivitamins can be good for you. But there is no substitute for good, nutritional food,” he reported.

It’s best not to generalise when it comes to cancer causes and risks, says Sister Andrea Brummer of The Mary Potter Oncology Centre in Tshwane. “What is still baffling is that what may contribute to one cancer may not contribute to another, so there is still a lot of research to be done, and we are just touching the tip of the iceberg. There are over 200 different kinds of cancer, so we have to be so careful of generalising,” says Sister Brummer.

“It is the oncologists' opinion that eating healthily is better than using supplements,” she advises. “It is all about balance, and if one vitamin is good, it doesn't mean more is better.”


For more info on this study

http://www.coloradocancerblogs.org/dietary-supplements-shown-to-increase-cancer-risk/

http://secure.oxfordjournals.org/our_journals/jnci/press_releases/martinezdjs195.pdf

Read More: Cancer Super Section