"Not only are vitamin and mineral supplements a waste of money, they can in some instances actually harm the body," reports The Guardian.
A new Canadian review pooled the findings from existing research into the role of vitamin and mineral supplements for the prevention and treatment of cardiovascular disease (CVD). CVD is a general term for conditions affecting the heart or blood vessels, such as heart disease and stroke.
The review found that taking the most widely used supplements – multivitamins, vitamin D, vitamin C and calcium – had no significant effect on the risk of heart-related illnesses. And some supplements, such as vitamin B3 (niacin) may do more harm than good.
And while a large Chinese study did find that folic acid reduced the risk of stroke, these results may not apply to the UK population.
Current UK guidelines advise everyone to consider taking a vitamin D supplement during winter. Women who are trying for a baby or are in the first 12 weeks of their pregnancy should take folic acid supplements. And vitamins A, C and D supplements are recommended for children aged 6 months to 5 years.
You should be able to get most of the vitamins and minerals you need from your diet without having to take supplements. Read more about vitamins and minerals.
Where did the story come from?
The study was carried out by researchers from several institutions, including Toronto University and St Michael's Hospital in Canada, and the Paris Institute of Technology for Life, Food and Environmental Sciences in France.
It was funded by the Canada Research Chair Endorsement, Loblaw Companies Ltd and the Canadian Institutes of Health Research. Many of the authors reported links with the pharmaceutical and food industry.
The study was published in the peer-reviewed Journal of the American College of Cardiology.
Both The Guardian and the Daily Mirror singled out the finding that some multivitamins and supplements may actually increase the risk of death. However, this finding did not reach the threshold for statistical significance so may have been the result of chance.
What kind of research was this?
This was a systematic review and meta-analysis of randomised controlled trials (RCTs) looking at the role of vitamin and mineral supplements for the prevention and treatment of heart-related illnesses (cardiovascular disease).
Multivitamins are consumed by a significant proportion of the general population, who believe they have beneficial effects. However, there is not much expert consensus on whether taking supplements of vitamins and minerals is beneficial for the prevention and treatment of cardiovascular disease.
Systematic reviews are one of the best ways of analysing high-quality research to investigate a link between exposure and outcome. However, it's important to bear in mind that the strength of this review is dependent on the quality of the studies it included.
What did the research involve?
The researchers searched several databases to identify studies published between 2012 and 2017 that investigated the role of dietary supplements on cardiovascular outcomes and death.
The authors identified 179 individual RCT studies. After pooling the results, the researchers looked at the effect of specific vitamins and minerals separately. The following vitamins and minerals were assessed:
- vitamin A, as well as beta-carotene (a pigment found in food that the body converts into vitamin A)
- vitamin B1
- vitamin B2
- vitamin B3 (niacin)
- vitamin B6
- vitamin B9 (folic acid)
- vitamin C
- vitamin D
- vitamin E
They also looked at supplements that combined vitamins or minerals, such as:
- multivitamins (including some minerals)
- B-complex vitamins (2 or more of the B group of vitamins)
- antioxidants (2 or more of vitamins A, C, E, beta-carotene, selenium or zinc)
They assessed whether the supplements affected the following outcomes:
- death from any cause
- death due to cardiovascular disease
- risk of cardiovascular disease, such as a heart attack or stroke
The evidence was graded, and the researchers focused on the outcomes from studies that were graded as moderate- to high-quality evidence.
What were the basic results?
The study found that none of the most commonly used supplements had any significant effect on the risk of cardiovascular outcomes or death from any cause.
However, there were mixed results for folic acid. Pooling the results from 7 RCTs indicated that folic acid reduced the risk of stroke by 20% (relative risk [RR] 0.80, 95% confidence interval [CI] 0.69 to 0.93). It also reduced the risk of any cardiovascular disease by 17% (RR 0.83, 95% CI 0.73 to 0.93). However, both these results were mainly based on a single large Chinese study.
How did the researchers interpret the results?
The researchers wrote: "In general, the data on the popular supplements (multivitamins, vitamin D, calcium and vitamin C) show no consistent benefit for the prevention of CVD, MI [heart attack], or stroke, nor was there a benefit for all-cause mortality to support their continued use.
"At the same time, folic acid alone and B-vitamins with folic acid, B6, and B12 reduced stroke, whereas niacin and antioxidants were associated with an increased risk of all-cause mortality."
This review broadly found that vitamin and mineral supplements did not reduce the risk of cardiovascular disease or death. The one exception was folic acid: a large study in China found that it may reduce the risk of stroke.
This review was well designed, focusing only on RCTs, which are considered a source of high-quality evidence.
However, while the RCTs all had decent sample sizes, the number that could be pooled for each specific supplement and subsequent health outcome was not always high – in some cases, only 1 or 2 RCTs had investigated the link.
Although the results of this review do not support taking supplements to reduce the risk of cardiovascular disease, some supplements have other benefits and are recommended if people have deficiencies.
In general, you should be able to get all the vitamins and minerals you need through your diet. However, supplements that are recommended in the UK include:
- vitamin D supplements, especially during autumn and winter
- folic acid during pregnancy
- vitamins A, C and D for children aged 6 months to 5 years
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Guardian, 28 May 2018
Daily Mirror, 29 May 2018
Links to the science
Journal of the American College of Cardiology. Published online May 28 2018