Vitamin D is the collective term for five
different fat-soluble vitamins, of which the most important for human health
are vitamin D3, which is found in animals, and vitamin D2 which is found in
Vitamin D is made in the skin
by the action of sunlight, and this is the main source of vitamin D for most
people. During the summer months in Europe, about
fifteen to thirty minutes of sun exposure to the arms and legs should allow you
to make sufficient vitamin D3. In autumn and winter months when
there is less sunlight, and we are covered up when we are outdoors, it is
difficult to make enough to meet your needs. As you age, your ability to sythesise vitamin D also
As only a limited number of
foods contain vitamin D3, it is difficult to obtain enough vitamin D through
diet alone. Good sources include oily fish
such as salmon and sardines, red meat, liver, egg yolks, and fortified foods
such as fat spreads and some breakfast cereals.
Following an extensive review by the Scientific Advisory Committee
on Nutrition, Public Health England therefore advises that everyone takes a
daily supplement of 10 micrograms (mcg) of vitamin D to help maintain healthy
bones, teeth and muscles [i]. To obtain
this Government recommendation from food alone, you would need to eat the
equivalent of 10 egg yolks a day.
Maintaining good intakes of vitamin D contributes towards the
prevention of rickets and asthma flare ups, as well as towards the maintenance
of a healthy immune system which, according to Dr. Sarah Brewer, GP and Medical
Director at Healthspan, ‘is backed by extensive medical research’.
What you may not be familiar with
is the continued emergence of science that underpins the benefits of
vitamin D3 for optimal health.
So what is this emerging science?
Vitamin D intake is linked to a
reduction in falls in people aged sixty and over
Researchers in the UK have calculated that, if everyone over
the age of 60 was treated with 20mcg (800iu) of vitamin D3 daily for five
years, this simple intervention would prevent over 430,000 minor falls, avoid
190,000 major falls and save 1579 lives. [ii]
A link between vitamin D3 deficiency and falls in older people may
seem odd, but Dr. Sarah explains the science behind the research: -
‘Vitamin D3 binds to receptors in muscle cells to increase gene
activity and protein production in ‘fast twitch’ muscle fibres. These muscle
fibres help to maintain balance and co-ordination and rapidly respond to
instability to help prevent a fall. This effect means supplements could help
older people who are vitamin D deficient.’
Dr. Sarah adds, ‘A large analysis of data from ten studies in older
adults also showed that vitamin D supplements
of 5mcg to 25mcg daily reduced falls by 14% compared with inactive
Another recent trial[iv] suggested that a combination of low
frequency exercise and high dose vitamin D supplementation could help reduce
the risk of falls in the elderly by more than 70%.
There is yet more evidence linking vitamin D
deficiency to Alzheimer’s disease
In 2014 the medical journal of the American Academy of
Neurology compiled a study, the largest of its kind, to investigate a possible
link between vitamin D deficiency and the risk of developing Alzheimer’s
disease and other forms of dementia. Though scientists expected to find an
association between the two, they were surprised to find that not
getting enough vitamin D could double the risk of developing these
Almost three years on and another link was found. This time, researchers
from Duke University and Duke-NUS Medical School looked at the effects of
vitamin D on cognitive decline, based on previous research suggesting that
vitamin D protects against neuron damage and loss. They measured vitamin D
levels in people aged 60 and over and assessed their mental abilities over two
years. Those with low vitamin D levels at the start of the study were around
twice as likely to show significant cognitive decline over time as those with
Should my vitamin D daily
intake amount change in accordance with my age?
'With increasing age, your
ability to synthesise your own vitamin D reduces. In one study, people aged 62
to 80 years synthesised four times less vitamin D than those aged 20 to 30
years’, says Dr. Sarah Brewer.
‘If you’re only interested in
protecting the future health of your bones, then the Government
recommended daily dose of 10mcg is probably fine. But, if you want to
maintain optimum blood levels that boost your immunity and protect against
other health issues, a higher dose is needed.
In any case, to suggest that the
same 10mcg dose will suit everyone, from a tiny infant to a strapping
body-builder and a frail, elderly lady is illogical.’
Dr. Sarah says, ‘If you are under
the age of 50, many experts suggest that, in the absence of sun exposure, an
intake of 25mcg (1000iu) vitamin D is more appropriate than 10mcg for optimum
adult immune health. If you are over the age of 50, a higher intake of at least
50mcg vitamin D3 may be needed.