VITAMIN D at High-Dose - Caution

[Guest guest]

High-Dose Vitamin D Supplementation, Too Much of a Good Thing?

Researchers have investigated the effect of oral vitamin D on falls and

fractures in older women.

They found that how you take it might make a difference. Also, frailty is a huge

health problem for

older people. However, what actually is frailty, is it inevitable and can it be

reversed?

Transcript

(This transcript was typed from a recording of the program. The ABC cannot

guarantee its complete

accuracy because of the possibility of mishearing and occasional difficulty in

identifying

speakers.)

Norman Swan: Today on the Health Report: delving into the used and abused

concept of frailty -- what

exactly does it mean and why does it occur, and an extraordinary program that

looks like preventing

it.

And the vitamin of the moment, vitamin D. The Health Report was probably the

first place in

Australia to cover research showing the widespread benefits of vitamin D, from

cancer prevention to

reduced falls and fractures set against the widespread extent of vitamin D

deficiency even in a

sunny country like Australia.

But Australian research recently published internationally has sounded a note of

warning. It relates

to the way vitamin D may be increasingly given by doctors. Professor Geoff

Nicholson is head of

Clinical and Biomedical Sciences at the University of Melbourne and director of

Endocrinology at

Barwon Health in Geelong. He and his team have had a long interest in bone

health in the community.

Geoff Nicholson: We've done a survey in Geelong amongst women, and up to half of

the women of all

ages have some degree of vitamin D insufficiency. In the case of elderly women

in the middle of

winter it can be quite significant.

Norman Swan: And people have related this to falls?

Geoff Nicholson: Yes, vitamin D deficiency is associated with instability of

gait and weakness of

the proximal muscles and increased falls.

Norman Swan: And the proximal muscles are the ones that are at the top of the

leg?

Geoff Nicholson: Yes, and perhaps also the speed of muscles because people

recover from a little

trip by quickly moving their legs to replace them and get back their balance but

if they can't move

them quickly then they fall over.

Norman Swan: So you decided to test supplementation which has been tested in

other situations.

Geoff Nicholson: Yes, one of the problems with many of the studies has been

compliance, people are

asked to take vitamin D every day usually with calcium and in a number of large

studies the

proportion of people actually taking the therapy at the end of the study has

been down to 50%. There

was a very famous study done in French nursing homes where compliance is high

because medication was

administered by the staff and that showed a reduction in fractures and that was

really the landmark

study. Subsequent studies have had quite mixed results.

So what we decided to do was to address the problems of compliance, we decided

to give the vitamin D

once a year. Now vitamin D is stored in the body and it was previously thought

to be quite safe to

give a loading dose. We focused on the people most at risk, so these were older

women over 70 who

were actually living in the community. We recruited 2,256 women who participated

for between three

and five years, so it's a very large study over a long time.

Norman Swan: And a very large dose, 500,000 units of vitamin D.

Geoff Nicholson: That's right but in a daily dose it's a little bit less than

1,500 units a day

which is not really an extraordinary daily dose.

Norman Swan: And they got this at the beginning of winter?

Geoff Nicholson: Yes. We had some other data where we measured vitamin D levels

throughout the year

and we found the vitamin D levels dropped during winter. We also observed that

as the vitamin D

levels dropped the number of fractures went up so we had more fractures during

the winter months

than we had during the summer months. So we estimated that if we could stop that

drop in the vitamin

D levels during winter we would have up to a 22% reduction in fractures.

Norman Swan: So what did you find?

Geoff Nicholson: Well we found exactly the opposite. We got a 26% increase in

fractures.

Norman Swan: No particular women were more likely than others?

Geoff Nicholson: No, there were no characteristics that selected whether people

were more likely to

have a fracture or not including their calcium intake.

Norman Swan: This must have shocked the living daylights out of you?

Geoff Nicholson: It did indeed so we went back and made sure that there hadn't

been any errors, we

actually tested the study drug to make sure that it was correct. There was some

confirmation in that

about 130 of the ladies were involved in an intensive study and we measured a

whole bunch of

functions and were able to track the vitamin D levels and that confirmed that

the people who were on

the active study medication actually got a significant rise in vitamin D.

Norman Swan: So what could be going on? I mean people have given various

explanations for this

including that you actually might have made them so well with their vitamin D

that they go out more

and put themselves more at risk.

Geoff Nicholson: Well we did an analysis of that and there were not increased

fractures in people

who were active.

Norman Swan: You didn't have an epidemic of well being and people squash

playing?

Geoff Nicholson: No. What we also found is an increase in falls, a 15% increase

in falls amongst the

group taking the vitamin D.

Norman Swan: So what's happening?

Geoff Nicholson: That was a great puzzle. We did a post hoc analysis looking at

when the falls and

fractures were occurring and we found that the increased rate of falls and

fractures was much higher

in the first three months. So that tells us that it's got something to do with

the sudden rise in

vitamin D levels.

Norman Swan: And what could that be doing?

Geoff Nicholson: It could be interfering with vitamin D signalling, there are

vitamin D receptors

basically in every cell in the body.

Norman Swan: And we should say here that vitamin D is not really a vitamin it's

a hormone, it's a

chemical messenger.

Geoff Nicholson: Yes, that's right, it interacts with the receptor in the cells

and whether that

interaction is interfered with by the presence of high levels of other vitamin D

metabolites is

unknown.

Norman Swan: So what do you think the message is at this state of knowledge

here, it is only just

one study, that if doctors attempted to give a whopping great dose of vitamin D

because they don't

think people are going to take it on a daily basis, just be a bit careful?

Geoff Nicholson: Oh I think they should severely rethink that strategy. It's not

the only study,

there's another study, they gave a large group of elderly men and women once a

year vitamin D as an

intramuscular dose. There was a clear effect on increasing fractures in the

older women.

Norman Swan: And why should it be different for men and women?

Geoff Nicholson: Excellent question. No idea.

Norman Swan: Are you starting to question whether daily doses of vitamin D may

be toxic as well?

Geoff Nicholson: No, I don't think so, I think there are a couple of studies

with daily doses of 400

to 800 units per day and a couple of those have shown a clear benefit and

reduction in fractures.

Norman Swan: But some people are giving 4,000 units a day.

Geoff Nicholson: Yes, well I think that one needs to question that. The

situation gets even more

confusing because there was one study where the subjects were given 100,000

units every four months

and that showed a reduction in fractures.

Norman Swan: So the bottom line here is that the vitamin D story and falls may

still be right but

only for moderate daily doses of vitamin D. The king hit to save you taking

daily vitamin D is to be

avoided, at least at this state of knowledge.

Geoff Nicholson: Yes, I'd agree.

Norman Swan: Is there any evidence that this practice of giving the one big dose

a year is prevalent

in Australia?

Geoff Nicholson: I don't know the statistics of that but certainly I'm aware and

I do see patients

who are given doses for example of 50,000 a week or more. These high doses are

available and are

becoming increasingly available. Now there are people who have more severe

issues, for example fat

mal-absorption or have had bowel surgery where one needs higher doses because

this is a fat soluble

vitamin, it is absorbed through the gut and if the patients have mal-absorption

and you have to give

higher doses - that's a different matter.

Norman Swan: Because they are losing a lot of it in their poo.

Geoff Nicholson: Exactly yes.

Norman Swan: Professor Geoff Nicholson is Head of Clinical and Biomedical

Sciences at the University

of Melbourne. You're with the Health Report here on ABC Radio National, I'm

Norman Swan.

References:

KM et al. Annual High-Dose Oral Vitamin D and Falls and Fractures in

Older Women. JAMA

2010;303(18):1815-1822

Bess Dawson- and S. High-Dose Vitamin D Supplementation, Too

Much of a Good

Thing? (Editorial) JAMA 2010;303(18):1861-1862

http://www.abc.net.au/rn/healthreport/stories/2010/2942983.htm