Vitamin supplements do not reduce the risk of cancer
The prospect of reducing your risk of cancer through popping a simple pill is certainly attractive. But the big question about vitamin supplements is this: do they actually prevent the disease?
The latest study to address this question has just come out today, in the Archives of Internal Medicine.
The study’s US authors looked at data from over 161,000 women, all of whom had been through the menopause and forty per cent of whom used multivitamins. They collected detailed information about these women and any multivitamins they used.
Over the next eight years, they compared women who took the pills and those who didn’t, and noted whether any of them went on to suffer from health problems, including cancer or heart disease.
The results were very clear. The multivitamins didn’t reduce the risk of developing breast, bowel, womb, lung, kidney, stomach, bladder or ovarian cancers.
They didn’t reduce the risk of heart attacks, blood clots or strokes.
They didn’t reduce the risk of dying at any given age.
If those facts sound quite negative, there is some good news hidden among them – the multivitamins didn’t increase the risk of these conditions either.
That seems like a strange cause for celebration, but it’s a valid one. When scientists first started putting vitamin supplements through their paces in clinical trials, one of the most unexpected results was that some high-dose supplements could actually increase the risk of some types of cancer..
- Folate (vitamin B9) supplements could reduce the risk of developing bowel cancer, but there are concerns that they could also speed up the growth of existing cancerous cells.
- Two clinical trials recently showed that supplements of selenium, vitamin E or vitamin C do not reduce the risk of prostate cancer. One of these, the SELECT trial, was stopped early because hints of potentially harmful effects were starting to show.
- An analysis of 25 studies found that beta-carotene supplements do not protect against lung cancer. Another analysis of four clinical trials found that smokers who take these supplements are actually more likely to develop lung cancer.
- An analysis of 14 trials concluded that supplements of beta-carotene, vitamins A, C, E, and selenium do not reduce the risk of oesophageal, stomach, bowel, pancreatic or liver cancer. They could even increase the risk of dying from these diseases.
Now, we’ve just picked a few studies that have come out in recent years. It’s not meant to be a thorough review of the evidence. Fortunately, other organisations have done just that.
There are a couple of possible exceptions, for specific groups of people. Pregnant women, or those who are planning on becoming pregnant, are still advised to take folate supplements to reduce the risk of spina bifida.
And people who are likely to become vitamin D deficient may be advised to take vitamin D supplements. However, even for vitamin D, it is premature to advise that the wider population should start taking supplements.
The bottom line is that the best source of vitamins is the old-school, low-tech one – a healthy, balanced diet with a wide range of fruits and vegetables.
The benefits offered by these diets were the basis for the initial wave of optimism surrounding supplements. We now know that these pills, popular though they are, cannot substitute for vitamin-rich foods. They’re simply nowhere near as good for you. Some of them could even cause you harm.
Ed
Reference:
Marian L. Neuhouser, Sylvia Wassertheil-Smoller, Cynthia Thomson, Aaron Aragaki, Garnet L. Anderson, JoAnn E. Manson, Ruth E. Patterson, Thomas E. Rohan, Linda van Horn, James M. Shikany, Asha Thomas, Andrea LaCroix, Ross L. Prentice. (2009). Multivitamin Use and Risk of Cancer and Cardiovascular Disease in the Women’s Health Initiative Cohorts. Archives of Internal Medicine 169 (3), 294-304
Comments
Spencer Jackson February 23, 2010
Are these studies meant for the public or are they just meant to gradually alter the scientific control over such supplements? What I’m asking is why are these studies so readily available to the public when there always seems to be a conflicting study just around the corner. Surely, as the general public, we just wait for a government policy and not react to each and every confusing study. Surely the stress that they cause outweighs any value that they contain ;-)
Kismet December 22, 2009
No, it hasn’t. I’ve followed most studies since this article and I’ve seen both positive and negative results.
While the vitamin D hypothesis, especially relating to *overall* mortality is incredibly promising it remains unproven. We need RCTs before public policy may change.
However, based on the sum of the evidence it’d be foolish to go vitamin D deficient on an individual level… IMHO
Pete September 22, 2009
Given the research published on vitamin d and cancer since this was written would it not be better to amend this in the light of new evidence. Or put a notice at the top pointing to new work.
Vitamin d supplementation DOES reduce cancer risk. All the evidence points that way. It is also finally been accepted as important to MS, heart problems and blood pressure. It is also important in the function of the innate immune system
Kismet March 25, 2009
“even for vitamin D, it is premature to advise that the wider population should start taking supplements.”
Why so? All the experts on Vitamin D (William B. Grant is only one of them), actually, disagree with this statement (as far as I know).
It may be premature to advise it for overall cancer prevention (e.g. NHANES III results), but not for the dozens other benefits vitamin D exerts.
Your analysis of vitamin D effects seems highly biased. In your other post you mentioned “vitamin D as a marker of general health”, most studies actually adjust for BMI, activity, etc and the association of vitamin D with health was actually stronger not weaker in already healthy people in the NHANES III cohort. The most impressive data definitely does not come from ecological studies either.
I’m not sure if your dismissal of the heavily criticised paper by Lappe, et al was completely fair. Correct me if I’m wrong, but wasn’t the cancer incidence higher in both groups and not just the placebo group?
Well, now that I think about it, you actually (unintentionally?) advised almost world-wide vitamin D supplementation saying “people who are likely to become vitamin D deficient” should supplemet. You do know how wide-spread vitamin D deficiency (insufficiency) is?
Sorry, I believe your blog post was not in the best interest of your readers (and their health).
james March 20, 2009
US researchers studying the effect of beta carotene, vitamin C and vitamin E, either singly or in combination, on over 7,000 women found the supplements did not reduce their risk of getting cancer compared to women who did not take the supplements. However an expert who reviewed the study said that while the overall message was there was no link, it uncovered some interesting evidence that should not be overlooked. And other supplements such as creatine;
Hugh Turner March 9, 2009
What is key with many minerals and vitamins is the form in which they are presented. Mineral taken in an inorganic for are adsorbed into the body at a far greater rate than minerals that are contained in an organic form.
Because of this the majority of products on the market are ineffective.
There is also research that natural anti-tumour drugs might become available:
There are supplements with these ingredients on the market now. Maybe the authors might investigate these too.
Michelle March 1, 2009
Is it possible that this study merely reflects that most vitamin supplements are ineffective because they are inferior products or perhaps the vitamin ratios are incorrect? Maybe the conclusions to be drawn are that we should ensure we are taking effective vitamin supplements.
It seems obvious that you need vitamins, otherwise a ‘healthy’ diet would be equivalent to a non-healthy diet. If your diet is not providing certain vitamins, then getting them through a pill seems like a decent idea. However, if the vitamins you’re using are not absorbable or in less than optimal ratios, then perhaps you would not see benefits.
Is there any way to find out which vitamins are used in these studies?
Mike Barnes February 19, 2009
If you are going to test a substance as a cancer preventative you might first do some pharmacokinetic studies to determine the dose and frequency needed to maintain plasma levels. Giving subjects stat doses of vitamins ie 500mg vitamin C is hardly likely to do anything-and then conducting meta analysis of these studies will yield even less. You forgot to mention all the studies on vitamin D including the propective placebo controlled trial conducted by Lappe showing 60-77% reduction in cancer depending on how you analyze the data-also that the Canadian Cancer Society now recommend everyone takes vitamin D to prevent cancer.
connah callender April 26, 2010
my grandad took them when he had it but sadly passed away two day before my brithday R I P grandada matt
:( xxxxx