If you’ve been following the news lately you could believe vitamin and mineral supplements are either a waste of money or worse. According to reports of one study, they’ll even shorten your life.
Popping vitamins may do more harm than good, according to a new study that adds to a growing body of evidence suggesting some supplements may have health risks…Women who took supplements had, on average, a 2.4 percent increased risk of dying over the course of the 19-year study, compared with women who didn’t take supplements”. Yahoo news
But was that the actual conclusion the researchers made? Hands up the shock jocks, journalists or even medical reporters who have read the original research? I’ve spent the past few weeks reviewing the paper and discussing it with scientists to get to grips with the statistical world of “hazard ratios” and the drawing of such devastating conclusions.
Almost 39,000 older women (average age 62 years old) initially took part in a longitudinal study but at its completion 19 years later less than 17,000 remained. As would be expected from this demographic, some had died but a number had dropped out or were excluded for other reasons.
The group was not double blind. This means there were no placebos. Everyone involved took their own self selected supplements. This is very unusual in an era of research where the double blind study is considered to be the “gold standard” in medical research.
The participants self-reported the supplements they took when surveyed in 1986, 1997 and 2004. The survey did not include how consistently they took the supplements. For example whether it was an impulse buy of a single bottle or had they taken the supplements every day for 19 years?
The dosage of each vitamin or mineral was also not included. Women took different brands and combinations. Keep in mind that the United States does not have stringent therapeutic goods laws or the same codes of good manufacturing practice as we have in Australia. The majority of supplement products on the shelves in that country would not be able to be sold here.
The two nutrients associated with the greatest negative impact on life expectancy were copper and iron. Excess iron intake has known risks. None of the women were screened for haemochromatosis, a common metabolic condition that causes the body to deposit iron in vital organs, which if not controlled can be fatal. Copper is an unusual single supplement to take. In 20 years of practice I have never prescribed it. In fact very few of the women in the study took a copper supplement. In 1986 there were only 30, which is less than 0.01 percent of participants. Not the “40,000” women some media source alluded to. Most scientists would consider this too small a sample to draw any conclusions.
The supplement that hit the headlines was the multivitamin. The researchers concluded that taking a multivitamin was associated with a 2.4 percent increased mortality (death) risk. What these vitamins consisted of and how long and consistently they were taken was not included in the study. It certainly includes a wide variety of possibilities. While some screening of existing health conditions was used in the study, the authors admit that they didn’t “exclude the possibility that some supplements were taken for reasonable cause in response to symptoms or clinical disease”. In other words some participants may have had unreported pre-existing deficiencies or diseases that may have been related to increased death rates.
The scientists I consulted said the study was too poorly designed to jump to the conclusion that multivitamins “can kill you”, as many media outlets reported.
The paper also does not mention any prescribed medication the women were taking during the study. While the research has been criticized for not ruling our many major health issues, there is no mention of arthritis or menopause-related medications being included. The anti-inflammatory drug Vioxx was withdrawn from the market in 2004 and is considered to have caused around 60,000 deaths. Premarin, a form of Hormone Replacement Therapy associated with increasing the risk of breast cancer, was in common use during much of the survey period. As women aged 55 year and older were a target market for these drugs, it raises more issues about the study.
Selective reporting in the media
Although it appears that almost all journalists ignored the flaws in the research, their reports focused on particular findings. Most concentrated on the negative outcomes, ignoring or underplaying the many positive results.
The study concluded that many of the women taking certain supplements lived longer. In particular taking a B vitamin complex, C, D, E and calcium were positively associated with decreased mortality.
“In agreement with our hypothesis, most of the supplements studied were not associated with a reduced total mortality rate in older women.” ”Mursu et al, Dietary Supplements and Mortality Rate in Older Women: The Iowa Women’s Health Study
Do you still think that your vitamins are killing you?
It all depends on what studies you read, or what media you listen to. As a regular multivitamin user of over twenty years, the Iowa Women’s Health Study has not changed my supplementing habits. For me the jury is out until a better designed study can reproduce their results.
Whether you need the vitamins your take, or are taking the best product for your requirements is another question entirely. The majority of clients whose supplements I review are taking more than they need or are under-dosing on the nutrients their specific condition requires.
For a free pdf of the study, click “study” in the first paragraph in Junk Science.
A good, plain English analysis of the study in the Huffington Post.
An older analysis of vitamin research suggests How to Fake a Vitamin Study.