Vitamin D Supplements May Offer Cheap And Effective Immune System
Boost Against TB
Science Daily - Scientists have shown that a single 2.5mg dose of
vitamin D may be enough to boost the immune system to fight against
tuberculosis (TB) and similar bacteria for at least 6 weeks. Their
findings came from a study that identified an extraordinarily high
incidence of vitamin D deficiency amongst those communities in London
most at risk from the disease, which kills around two million people
each year.
Whilst a diet of oily fish can provide some vitamin D, the main source
of the body's vitamin D comes from exposing the skin to sunlight. In
Britain, however, the amount of sunlight is usually insufficient to
make vitamin D in the skin between October and April, and much of the
population becomes deficient during the winter and spring.
Researchers from Queen Mary's School of Medicine and Dentistry,
London, and the Wellcome Trust Centre for Research in Clinical
Tropical Medicine, Imperial College London, studied patients at Newham
University Hospital and Northwick Park Hospital in London who had been
exposed to TB. They found that over 90% of such patients had a vitamin
D deficiency.
Vitamin D was used to treat TB in the pre-antibiotic era, when special
sanatoria were built in sunny locations, such as the Swiss Alps. But
until now, no study has evaluated the effect of vitamin D
supplementation on immunity to mycobacteria, the family of bacteria
that cause TB.
The researchers performed a randomised control trial on a group of
volunteers who were given either a 2.5mg supplement or a placebo.
Samples of the volunteers' blood were then tested in Dr Robert
Wilkinson's Wellcome Trust-funded laboratory at Imperial College, to
see whether the supplement affected the immune system's ability to
withstand infection by mycobacteria.
"We found that a single large dose of vitamin D was sufficient to
enhance a person's immunity to the bacteria," says Dr Adrian
Martineau from the Division of Medicine at Imperial College London,
who co-ordinated the study. "This is very significant given the high
levels of vitamin D deficiency in people at the highest risk of TB
infection, and shows that a simple, cheap supplement could make a
significant impact on the health of people most at risk from the
disease."
According to the Health Protection Agency, the incidence of TB in the
UK is increasing, with around 8,000 new cases a year. Cases in the UK
are predominantly confined to the major cities and about 40 per cent
of all cases are in London. TB is also a major global problem: an
estimated one-third of the world's population - nearly two billion
people - are infected. Nine million people a year develop the active
disease worldwide, which kills two million each year.
"Most cases of TB in London arise from people who have already become
infected with the bacteria but in whom it lies latent," says Professor
Chris Griffiths from Queen Mary's School of Medicine and Dentistry.
"Our results indicate that vitamin D supplementation may prevent
reactivation of latent TB. Identifying people with latent TB and
providing supplements could be an important strategy for tackling the
disease."
Treatment is both very cheap - about 60p per dose or 10p per week -
and safe. Vitamin D supplements could be prescribed for patients with
or at risk of latent TB through GP surgeries.
Dr Martineau points out: "Our work adds to the growing evidence that
vitamin D may have a wide range of important health benefits,
including preventing falls and fractures and reducing risk of cancer
and diabetes, as well as boosting the immune system against infection.
Population-wide supplementation needs to be considered by public
health planners."
"Milk and orange juice could be fortified with vitamin D, as in the US
and Canada," he says. "At present only margarine is supplemented in
the UK, and recent studies show that this is not an effective way to
prevent vitamin D deficiency."
The research, funded by the Wellcome Trust, the Department of
Environmental Health at Newham Council and Newham University Hospital
NHS Trust Respiratory Research Fund, is published online in the
American Journal of Respiratory and Critical Care Medicine.
* * *
A Single Dose of Vitamin D Enhances Immunity to Mycobacteria
Martineau et al., Published ahead of print on April 26, 2007 Am. J.
Respir. Crit. Care Med. 2007, doi:10.1164/rccm.200701-007OC
Rationale: Vitamin D was used to treat tuberculosis in the pre-
antibiotic era. Prospective studies to evaluate the effect of vitamin
D supplementation on antimycobacterial immunity have not previously
been performed. Objectives: To determine the effect of vitamin D
supplementation on antimycobacterial immunity and vitamin D status.
Methods: A double-blind randomized controlled trial was conducted in
192 healthy adult tuberculosis contacts in London, UK. Participants
were randomized to receive a single oral dose of 2.5 mg vitamin D or
placebo and followed up at 6 weeks. Measurements and Main Results: The
primary outcome measure was assessed with a functional whole blood
assay (BCG-lux assay) that measures the ability of whole blood to
restrict luminescence, and thus growth, of recombinant reporter
mycobacteria in vitro; the read-out is expressed as a luminescence
ratio (luminescence post-infection/baseline luminescence). Interferon-
gamma responses to the M. tuberculosis antigens early secretory
antigenic target-6 and culture filtrate protein 10 were determined
with a second whole blood assay. Vitamin D supplementation
significantly enhanced the ability of participants' whole blood to
restrict BCG-lux luminescence in vitro compared to placebo (mean
luminescence ratio at follow-up 0.57 vs. 0.71 respectively, 95% CI for
difference 0.01 to 0.25; P=0.03) but did not affect antigen-stimulated
Interferon-gamma secretion. Conclusions: A single oral dose of 2.5 mg
vitamin D significantly enhanced the ability of participants' whole
blood to restrict BCG-lux luminescence in vitro without affecting
antigen-stimulated Interferon-gamma responses. Clinical trials should
be performed to determine whether vitamin D supplementation prevents
reactivation of latent tuberculosis infection.
* * *
Someone help me out here. How can 2.5 mg be considered a high dose?
I am wondering if there is a typo in the abstract.
Marilyn