Results from a questionnaire survey of a group of older American women's use of dietary supplements have been used to erroneously conclude that vitamin and mineral supplements would be ineffective or downright unhealthy. This is totally wrong.
The study, which is made by the Finnish researcher Jaakko Mursu and colleagues and published in the journal Archives of Internal Medicine in October 2011 and later mentioned in many media, suggests that older women who take vitamin and mineral supplements, may die before other women at the same age who are not taking supplements.
Not a controlled trial
Many health concerned experts in several countries has obviously pondered upon this study, and when it comes to quality, it certainly did not get good marks. This is because it is a highly uncertain survey that not even have had a placebo-controlled control group. A group of women with a mean age of 61 years, over a period of nearly 20 years were asked to write down their intake of certain vitamins and minerals 3 times. It required them to remember what dietary supplements they used approximately 10 years ago.
No statistical certainty
The main conclusion described a few percent excess mortality connected with the intake of multivitamin, B6, folate, iron, magnesium, copper and zinc. Apart from iron supplementation, none of these conclusions, however were significant, meaning that the results due to poor control could well be due to coincidences or factors which have nothing to do with dietary supplements. Calcium supplements however, lowered the risk. The supplements which gave the highest statistical certainty was calcium, which increased survival and iron supplements who appeared to lower it.
Basically, the uncertainty in this study is so great that nothing can be concluded with certainty!
Beware of iron
It is well known that it is unhealthy to take a supplement of iron, unless you lack this mineral. When the body's iron stores are full and you take extra iron, it creates a cascade of harmful free radicals.
Other causes of increased mortality
Many factors may have influenced the test result to give a misleading and negative image of dietary supplements. It has been pointed out that many people only start taking dietary supplements after they have got a disease. At the start of 1986 almost twice as many taking supplement also were receiving hormone treatment compared with non-supplement users. This trend was also present at the follow-up questionnaire in 2004.
In fact there is so much uncertainty about this study that it is surprising that it is worthy of publication. Much of the negative twist this study had in the media, seems not to originate from Mursu and colleagues but from a subsequent comment to the article written by two doctors: Bjelakovich and Gluud which has a highly negative attitude to dietary supplements.
It is worth mentioning that the main conclusion in the Mursu study does not mention either vitamin A, beta carotene or vitamin E as these two doctors do – from the obvious reason that there were no significant adverse effects of these vitamins in the study! Instead, they mention their own previous study in which they ignore more than 400 studies, also because there were some deaths! - In this way it's also much easier to scold at eg. Vitamin A, E and beta carotene (2).
However if you want a really thorough overview of the studies which have shown a beneficial effect of dietary supplements, you only need the discard list of studies from these two doctors.
Better quality studies
Studies of better quality have shown positive effects of the vitamins and minerals in question. In 2010 a research team led by Hans Biesalski did a reanalysis of the data Bjelakovich and colleagues had made of vitamin A, E and beta-carotene and which allegedly showed an increased mortality of 16% (2). The reanalysis found that 36% of the surveyed studies showed a positive effect of these antioxidants. 60% gave a neutral result (3).
Also the researcher Li and colleagues' study of vitamin and mineral supplements (4) concludes that supplementation with antioxidant vitamins may reduce the number of cancer incidents and all-cause mortality. Here they point out the statistical risk of corrupted data that might occur when people get sick and then start taking supplements without having participated in a possible pre-preventive effect.
Recently an article by researcher Bowman and employees (5) were published about development of Alzheimer's disease where the focus was on the content of nutrients in the blood of the trial participants, rather than relying on questionnaires. This analysis showed however that those with the most vitamin B, C, D and E in the blood did better on tests of memory and thinking. People with high blood levels of omega 3-fatty acids, primarily found in fish, also did well in the test.
The placebo-controlled SU-Vi.Max study showed that a daily intake of just 120 mg of vitamin C
, 30 mg vitamin E
, 6 mg beta carotene
, 100micrograms selenium
and 20 mg of zinc
lowered the number of cancer cases and deaths from all causes in men significantly (6).
The list of high quality scientific studies showing beneficial and life-prolonging effects of supplementation with vitamins and minerals is very long, and is still becoming longer.
Refs.1. Mursu J, et al. Dietary supplements and mortality rate in older women: the Iowa Women's Health Study. Arch Intern Med. 2011 Oct 10;171(18):1625-33.2. Bjelakovic G, et al. Mortality in Randomized Trials of Antioxidant Supplements for Primary and Secondary Prevention: Systematic Review and Meta-analysis JAMA. 2007;297(8):842-57.3. Biesalski HK, et al. Reexamination of a Meta-Analysis of the Effect of Antioxidant Supplementation on Mortality and health in Randomized Trials. Nutrients 2010, 2:929-49.4. Li, et al. Vitamin/mineral supplementation and cancer, cardiovascular, and all-cause mortality in a German prospective cohort (EPIC-Heidelberg). Eur J Nutr. 2011, Jul 22. Epub ahead of print.5. Bowman GL, et al. Nutrient biomarker patterns, cognitive function, and MRI measures of brain aging. FASEB 2011. E-pub ahead of print.6. Hercberg S, et al. The SU-VI.Max Study. Arch Intern Med 2004;164:2335-42.