Wednesday January 6 2016

We get most of our vitamin D from sunlight on our skin

“Giving pensioners high doses of vitamin D to strengthen their leg bones may put them at higher risk of a fall,” The Times reports after a Swiss study suggested high doses of the supplement offer no benefits, but do increase the risk of falling.

This 12-month trial aimed to assess whether giving high doses of vitamin D to older adults with a history of falls increased their vitamin D levels and improved leg function in comparison with the lower recommended dose – in this case, 20 micrograms (mcg) a day. This is not the recommended UK dose, which is lower still, at 10mcg.

The study found the two higher vitamin D doses tested did result in a greater increase in vitamin D levels than 20mcg a day. However, it didn’t have any beneficial effect on leg function – in fact, it was actually associated with an increased number of falls over the study period.

This study does not provide evidence to suggest current UK government recommendations for older adults – a daily supplement of 10mcg – are “unsafe”. People in the UK who currently take vitamin D supplementation as recommended should have no concerns about the results of this trial.

The monthly dosage used in the highest dosage group, which had the greatest amount of falls (1,500mcg), is far higher than the recommend monthly dose of 300mcg.

These findings go on to suggest that taking more than 20mcg a day of vitamin D is not beneficial for older adults.  

Where did the story come from?

The study was carried out by researchers from University Hospital Zurich and the University of Basel in Switzerland, and Tufts University and the Harvard T H Chan School of Public Health in the US.

It was primarily funded by the Swiss National Science Foundation and The VELUX Foundations.

The study was published in the peer-reviewed medical journal JAMA Internal Medicine. The article is open access and can be read online.

The Times and the Daily Mail’s headlines slightly misinform the public, suggesting that taking vitamin D supplements as recommended by the government increases the risk of falls.

This isn’t the case. The study looked at taking higher doses than those currently recommended – these doses were associated with an increased risk of falls, not the current recommended dose.

The Mail also claims the increased risk of falls could be because “the pills make patients more active, meaning they have a higher chance of falling over”. This is pure speculation – the possible reasons behind the increased falls risk were not discussed in the study.  

What kind of research was this?

This randomised controlled trial (RCT) aimed to examine the effectiveness of high-dose vitamin D for reducing the risk of functional decline in older adults.

As the researchers say, vitamin D is believed to have a direct effect on muscle strength. Supplementation has been proposed as a way to maintain function in older adults. 

Several systematic reviews of previous trials are said to have consistently shown that this has a beneficial effect in preventing falls and hip fractures in those aged over 65. 

However, other evidence on whether it is associated with improved leg function is said to be cloudy, with some trials reporting a benefit, while others do not. A 2011 systematic review that pooled the results of 17 trials suggested the benefits were mainly limited to those with vitamin D deficiency.

This trial aimed to examine the theory that high-dose vitamin D – either given alone or in combination with its breakdown product, calcifediol – would increase blood levels to at least 30ng/ml. The researchers specifically studied a higher-risk population of those aged 70 or older who previously had a fall.

An RCT like this one is the best way of examining the effectiveness and safety of a treatment. However, the best evidence it will provide is for the main outcomes the study set out to look at, which in this case were vitamin D blood levels and leg function, not falls.  

What did the research involve?

This 12-month study compared the effects of three different vitamin D supplementation dosages in older adults who previously had a fall.

The researchers recruited adults aged 70 or over living in the community with a history of low-trauma falls in the past 12 months.

Participants were also required to be mobile (with or without assistance), have normal cognitive function, and not have taken vitamin D supplementation exceeding 800 international units (IU) a day (20mcg). The final trial sample included 200 adults.  

Participants were randomised to one of three study groups:

• group one – 24,000 IU of vitamin D taken as a 5ml drink a month, the equivalent of 20mcg a day, which is double the UK recommended dose; they also took three placebo capsules a month
• group two – 60,000 IU of vitamin D taken as a single 5ml drink, equivalent to 50mcg a day; they also took three placebo capsules a month
• group three – 24,000 IU vitamin D plus 300mcg of calcifediol a month taken as a 5ml placebo drink, two capsules of 12,000 IU vitamin D, and one capsule of 300mcg calcifediol

Participants and researchers were unaware of which group they were allocated to (the study was double-blinded) as all treatments appeared identical.

Participants attended three clinic visits at the start of the study and again at six and 12 months. At all visits, leg function was assessed using the Short Physical Performance Battery (SPPB) assessment, which assesses walking speed, balance and standing from a chair.

Researchers also took a general history and performed an examination, and took blood and urine samples. At the start of the study and at the 12-month mark, a dual X-ray absorptiometry (DEXA) scan was also performed to assess bone mineral density.

The main outcomes examined were SPPB score and the proportion of people who achieved blood vitamin D levels of at least 30ng/ml. The other outcome the researchers looked at was reported falls, which were assessed through participant diaries and monthly calls from nurses.

Nine participants dropped out during the trial, but all 200 were included in the analysis. The researchers adjusted their analyses for age, gender, body mass index (BMI) and SPPB score at the start of the study.  

What were the basic results?

The average age of the participants was 78, and two-thirds were women. Only 42% had adequate vitamin D blood levels at the start of the study – 58% were deficient (less than 20ng/ml) and 13% were severely deficient (less than 10ng/ml). There were no differences between the groups at the start of the study.

Vitamin D blood levels increased significantly more in both the 60,000 IU vitamin D and the 24,000 IU vitamin D plus calcifediol groups at both six and 12 months. At both of these time points, a significantly higher proportion of these two groups had also achieved the target of blood levels of 30ng/ml or higher.

There was no significant difference over the course of the 12 months between the three groups for changes in overall SPPB score. However, successive chair stands improved significantly more in the 24,000 IU only group than the other two treatment groups. Other functional components were similar.

Overall, 60.5% of participants reported a fall during the study. The rates at 12 months were significantly higher in the 60,000 IU vitamin D group (66.9%) and the 24,000 IU vitamin D plus calcifediol group (66.1%) compared with the 24,000 IU only group (47.9%).

The greater improvements in vitamin D levels in the two higher-dose treatment groups were only seen in those who had been deficient at the start of the study.

Significantly more people had falls in the two high-dose groups compared with the 24,000 IU only among those who had been vitamin D deficient at the start of the study.

However, when looking at the overall number of falls, more falls were seen in the two high-dose groups in people who had adequate vitamin D at the start of the study.  

How did the researchers interpret the results?

The researchers concluded that, “Although higher monthly doses of vitamin D were effective in reaching a threshold of at least 30 ng/mL of 25-hydroxyvitamin D [blood vitamin D levels], they had no benefit on lower extremity function and were associated with increased risk of falls compared with 24 000 IU.” 

Conclusion

This trial aimed to assess whether giving high-dose vitamin D to older adults with a high risk of falls increased their blood vitamin D levels to above 30ng/ml, as well as improving their leg function.

Vitamin D levels of 20ng/ml or more are generally considered adequate for bone health. But many people are deficient in vitamin D, with the elderly being particularly at risk.

Current UK recommendations say people aged over 65 should take a daily supplement of 10mcg. This is the equivalent of 400 IU a day – a lower level than the lowest dose used in this study (800 IU a day).

This study looked at taking two higher doses – with vitamin D alone or combined with its breakdown product, calcifediol – compared with the 800 IU a day control group.

As would be expected, those in the higher dosage treatment groups had higher levels of vitamin D in their blood compared with controls. Although the higher doses led to improved leg function, they were in fact linked to a greater number of falls than seen in the control group.

The trial has many strengths, including its double-blind design, the analysis of all 200 people enrolled, the relatively long duration of one year, and the use of valid assessment scales. It provides good evidence that high-dose vitamin D – alone or with calcifediol – does not benefit older adults with a prior history of falls.

Taking high doses of vitamin D may also increase the risk of further falls, but this result should be interpreted with some caution – it’s not the primary outcome the study set out to examine.

The trial had a sufficient sample size to reliably detect differences in blood vitamin D and function score, but it may not have been large enough to reliably assess whether there were true differences in the number of falls.

Importantly, though, this study does not provide evidence to suggest that current UK government recommendations for older adults are unsafe.

The low-risk group in this study in terms of falls was the 20mcg a day control group. This is the recommended supplementation for older adults in the US and other countries, but not in the UK, where it is even lower, at 10mcg a day.

This study also cannot tell us a lot about the effects of the dose recommended in UK guidelines, as this was not tested. Also, all the supplements were taken in the form of one big dose contained in a single drink each month, rather than as daily supplements, as recommended in the UK.

And as this study is only relevant to older adults, it cannot provide any evidence on the effects of supplementation in other recommended groups, such as pregnant or breastfeeding women (10mcg a day) or young children up to five years (7-8.5mcg a day).

This trial adds to the large body of evidence examining the effectiveness and safety of different forms of vitamin D supplementation in different groups.

Yet people currently taking vitamin D supplementation as recommended in the UK should have no concerns.

There are practical steps you can take to reduce your risk of a fall, such as removing clutter from around your home, wearing well-fitting, sturdy shoes, and doing regular strength and balance exercises.

Read more about how to prevent falls.