NHFT Libraries Health News: Vitamin pills have 'limited benefit', say researchers

Thursday, 19 December 2013

Vitamin pills have 'limited benefit', say researchers

Vitamin pills have 'limited benefit', say researchers “Vitamins are a waste of money,” reports The Daily Telegraph, while the Daily Mail tells us that multi-vitamins “do nothing to protect us from illness”.

The news is in part based on some high quality research on whether there were any benefits from taking vitamins among different – but specific – groups of people. But the main “waste of money” news headlines are, in fact, based on an opinion piece by a group of researchers, based on findings from these studies.

The underlying studies were two randomised controlled trials (RCTs) and a review summarising findings from previous RCTs. The review found limited evidence of any benefit from vitamin and mineral supplements to prevent cardiovascular disease or cancer. But it is important to note that the research looked at people who did not have any vitamin or mineral deficiencies or any chronic disease, so there may be benefits for these populations.

One RCT found high-dose multivitamins did not significantly reduce cardiovascular events in people who had previously had a heart attack, but that there was no evidence of harm either. The other RCT found that long-term use of a daily multi-vitamin did not provide cognitive benefits among a group of older men. The researchers noted that the dose of vitamins may have been too low for a benefit to be seen or that the men may have been too “well-nourished” to benefit from vitamin supplementation.

What is the basis for these current reports

The news coverage is based on four publications that appear in the current issue of the peer reviewed journal, Annals of Internal Medicine. The publications are:

a randomised controlled trial (RCT) that assessed whether high dose oral multivitamins reduced cardiovascular events in about 1,700 people who had previously had a heart attack (myocardial infarction) compared to a dummy treatment
an RCT that assessed whether long-term use of daily multivitamins affected cognitive function in later life among a group of about 6,000 male doctors aged 65 or older compared to a dummy treatment. The men were followed for up to 12 years
a systematic review looking at the benefit and harms of vitamin and mineral supplements in adults who did not have nutrient deficiencies for the prevention of cardiovascular disease and cancer
an editorial opinion piece written by a group of researchers based on the findings of the above three publications

A randomised controlled trial (RCT) is the best type of study design to determine whether a treatment is effective. It compares the effects of an intervention (in this instance, vitamin supplements) with another intervention or control (for example a dummy treatment).

A systematic review combines the findings from studies addressing a particular question. These sorts of reviews usually use set criteria which potential studies for inclusion must meet to be included, such as appropriate study design, and population size. A systematic review is considered one of the strongest forms of evidence. However, the strength of its conclusions are dependent on the quality and homogeneity (similarity) of the studies it pools together.

How accurate is the media reporting of the issue?

The research was widely reported in the UK media with a variety of headlines.

The news headlines appear to be based on the journal’s editorial, although most of the media do mention the underlying studies that this opinion piece was based on.

The systematic review hardly received any media coverage, which is disappointing as it summarises findings from multiple studies, and is one of the strongest forms of evidence.

Despite most of the media accurately reflecting the studies, the editorial piece is inaccurately reported by The Independent. Its reporting initially implies this was a study performed in people, when it is in fact the opinions of a group of researchers based on the findings from other research. Reassuringly, the other studies do get reported by The Independent on further reading.

What did the studies find?

One of the RCTs concluded that high-dose multivitamins and multiminerals did not statistically significantly reduce cardiovascular events in people who had previously experienced a heart attack. The researchers note that there was a high rate of people who stopped taking vitamins during the study (drop-out rate), but that there was no evidence of harm from taking vitamins.

The other RCT concluded that long-term use of daily multivitamins did not provide cognitive benefits among a group of male doctors aged 65 and older. The researchers noted that doses of vitamins may have been too low to detect a benefit and that the population may have been “too well-nourished” to benefit from multivitamins.

The systematic review that pooled the results of previous RCTs (not including the two RCTs above) concluded that, “limited evidence supports any benefit from vitamin and mineral supplementation for the prevention of cancer or cardiovascular disease. Two RCTs found a small but significant benefit from multivitamin supplementation on cancer in men only and no effects on cardiovascular disease”.

Importantly, this review only looked at the benefits of multivitamins in people living “in the community” (not in hospital or in a care home), who were known not to have deficiencies and who had no chronic disease, so were a healthy population. The review has not looked at the benefits in people known to have vitamin and mineral deficiencies.

The journal’s editorial offers an opinion by a group of researchers based on the above findings. It says the message is a simple one – “most supplements do not prevent chronic disease or death, their use is not justified, and they should be avoided. They say this message is especially true for the general population with no clear evidence of micronutrient deficiencies who represent most supplement users in the US and in other counties”.

The authors of the editorial added that some supplements may even be harmful for chronic disease prevention and that further research trials into this area are no longer justified. But it is important to note that these are just the opinions of a small group of researchers, they did not perform a study on whether or not multivitamins were harmful.

What’s the best way to get enough vitamins?

The best way for most of us to get enough vitamins is to eat a varied and balanced diet.

This includes:

plenty of fruit and vegetables
plenty of starchy foods, such as bread, rice, potatoes, and pasta
some milk and dairy foods
some meat, fish, eggs, and beans and other non-dairy sources of protein

Foods and drinks high in fat or sugar should be kept to a minimum.

Vitamin D is an exception. A small amount is obtained through diet but most of this vitamin is made under the skin when it is exposed to sunlight.

Who needs vitamin supplements?

Certain groups at risk of deficiencies are recommended to use supplements:

all pregnant and breastfeeding women should take vitamin D supplements
women trying to conceive and women in the first 12 weeks of their pregnancy are recommended to take folic acid supplements, which reduce their child’s risk of neural tube defects, such as spina bifida
people aged 65 and over should take vitamin D supplements
people with darker skin and people who are not exposed to much sun should take vitamin D supplements
all children aged six months to five years should be given a supplement containing vitamins A, C and D
your GP may also recommend supplements if you need them for a medical condition

Conclusion

Overall, the two randomised controlled trials provide evidence that there is little to no benefit from vitamin supplementation for reducing cardiovascular events in people who have previously experienced a heart attack. Nor that taking high-dose daily vitamins leads to cognitive benefits in a group of older men. These findings are in particular groups, so they may not be generalisable to other groups.

The large, good quality review provides limited evidence of a benefit from vitamin and mineral supplementation to prevent cardiovascular disease or cancer. However, it is important to note that it only looked at people who did not have any vitamin or mineral deficiencies or any chronic disease, so there may be benefits for these people.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.