Are your vitamins actually killing you?
New research claims that too much Vitamin C is bad for your health, writes Lisa Jewell
Published 18/08/2010 | 05:00
It's less than a century since scientists first identified the different vitamins and discovered their effects. In a short space of time, we've learnt how important vitamins are to our health and this has led to vitamin supplements becoming a multi-billion euro business worldwide.
But questions have been raised as to whether vitamin supplements deliver all the benefits they claim to have. And most recently, a warning signal was sounded about the effect of taking high doses of vitamins -- that they could pose a threat to our health.
Dr Steve Kerrigan, Lecturer in Pharmacology at the Royal College of Surgeons Ireland, says there is still a lot more to be learnt about vitamins.
"One of the problems with vitamins right now is that it's an area that's under-researched," he says. "We had a problem with vitamin deficiency years ago and that's been sorted out. We realised that we need vitamins to get rid of disease but we haven't really looked at how much of the vitamin can cause problems in the body."
A study by scientists at the Cedars-Sinai Heart Institute in Los Angeles has shown that taking high doses of antioxidant supplements, such as Vitamins C and E, raises the risk of dangerous changes in human cells.
Lead researcher Dr Eduardo Marban says: "In simple terms, by taking high amounts of antioxidant supplements, you may be increasing your chances of cancer."
It's an alarming observation -- that taking too high a dose of a vitamin could actually harm your health rather than boost it.
The study's findings don't come as a surprise to Dr Kerrigan.
"I think there's very much a growing awareness that mega dosing of vitamins can be dangerous," he says.
"It's part of a much bigger problem -- people shouldn't really have to take any vitamins if they are eating properly. But we often hear about people tending to take three, four, five, even 10 times the amount of recommended daily intake and this seems to happen most commonly with Vitamin C.
"One of the problems with taking too much Vitamin C is that it enhances iron absorption and can lead to haemochromatosis. There are well-known effects for taking too many vitamins, including Vitamin A, B6, C, D and E along with taking too many of the other nutrients."
One of the major points of the Cedars-Sinai study, published in the Stem Cells journal, is that there is a fine balance in the body between antioxidants and free radicals.
The latter have often been painted as the bad guys in our bodies because they can raise the risk of cancer and can damage cholesterol molecules. But they have a role to play in the body and can fight off tumour cells.
"Free radicals are very important -- we need them in our body for many different reasons," says Dr Kerrigan. "It's a very complicated area. Free radicals can be dangerous, especially if they are hanging around long enough, but they are still needed in the body for many functions."
While antioxidants are often portrayed as the ultimate good guy, there is research into whether they have any downsides. Scientists debate whether chemotherapy patients should be taking antioxidants -- if they interfere with treatment and if they improve outcomes for patients.
Sarah Keogh, consultant dietitian at the Albany Clinic, agrees that there should be more research into vitamins.
"I think that people are becoming more aware of the science behind taking vitamins. When I give talks, people are asking about them and saying they don't want to be popping pills all the time.
"The research at the moment shows that taking high doses of vitamins is not a good idea.
"Unfortunately, Irish people tend to have a philosophy that if one is good, 10 must be better but that isn't the case with vitamins."
The Cedars-Sinai findings were discovered accidentally as part of another study being conducted into cardiac stem cells. Dr Marban wanted to limit the risk of oxidative damage to the cells and added antioxidant supplements (at the same level that someone taking high-dose supplements would have). He found that this action increased the level of genetic damage to the cells.
One advocate of taking high doses of some vitamins is nutritional therapist Patrick Holford. He isn't convinced by the Cedars-Sinai study.
"We don't have the full study available yet and I think it's significant that it is a cell study, rather than one carried out on humans," he says. "We have to know that it's a cell study and may have some limitations. The devil is in the detail."
Holford says there is existing research to support taking higher doses of antioxidants.
"We already have studies on people taking high dose Vitamin C, for example, and there is data out there on things such as high dose Vitamin C reducing cardiac risk."
Linda de Courcy, who is a nutritional therapist and an active member of the Irish Association of Nutritional Therapists, says she "never would have been a supporter of mega doses of vitamins. People should be getting their nutrients through food and supplements should only ever be supplementary".