I
n the darker months between
October and March, there’s
insufficient sunlight in the
UK for the human body to make
vitamin D. According to the 2018
National Diet and Nutrition Survey,
around 17 per cent of British adults
have inadequate levels of vitamin
D, which is why Public Health
England advises people to take
vitamin D supplements for at least
part of the year.
Doctors agree vitamin D helps
maintain healthy bones, teeth and
muscles, but beyond this, opinions
differ. Many doctors and dietitians
believe supplements are a good
idea because vitamin D needs are
difficult to meet through diet alone
during the darker months. Others
argue supplements are unnecessary
for healthy people and might in fact
be harmful for certain age groups.
To compound the confusion,
vitamin D supplements are widely
touted as a near-miracle cure for a
range of conditions from multiple
sclerosis and dementia to
cardiovascular disease and cancer.
So, what’s the truth?WHAT IS VITAMIN D?
Vitamin D is unlike any other
vitamin: we make it in our skin
using the sun’s ultraviolet B rays
(UVB). During the autumn and
winter in northern climes, including
the UK, the angle of the sun is too
low for enough UVB to reach theearth’s surface, so our vitamin D
stores decline. This is a problem
because very few foods contain
vitamin D: oily fish, cod liver oil
and some fortified foods contain
good amounts, while small
quantities are found in egg yolks,
liver and wild mushrooms.
“It’s pretty unrealistic to get all
our vitamin D from food, unless
it’s fortified,” says Clare Thornton-
Wood, registered dietitian and
spokesperson for the British Dietetic
Association. “We are designed to get
it from sunlight.” But how much
vitamin D do our bodies need?HOW MUCH IS ‘ENOUGH’?
In 2016, after reviewing the evidence
on vitamin D, the government issued
new advice that adults and children
over the age of one should consider
taking a daily 10mcg supplement
during autumn and winter (mcg is
sometimes written as μg). Those at
a higher risk of deficiency (whose
skin has little or no exposure to
the sun or who have dark skin) are
advised to take a supplement all
year round. It’s also advised that
babies under one should take a daily
8.5-10mcg vitamin D supplement,
except those fed infant formula, as
it’s already fortified.
Not all experts agree that 10mcg
is right for everyone, or that there’s
one ideal standard dose. In the US,
for example, 10-20mcg per day is
recommended, dependent on age.And some studies suggest older
people, particularly women, need
more than 10mcg, as the ability to
synthesise vitamin D diminishes
with age. “Some groups may need
more than the recommended
dosage, but this should be advised
by a pharmacist or other suitably
qualified healthcare professional,”
Thornton-Wood says.CONTESTED HEALTH CLAIMS
Vitamin D’s role in human health
is complex, not completely
understood and hotly debated.
Severe deficiency is known to cause
rickets (a condition that affects
bone development in children) and
osteomalacia (soft bones) in adults.
Some research suggests a link
between low levels of vitamin D
and certain health conditions.
A study published in The BMJ
in 2017 suggested a small benefit
in taking vitamin D supplements
to reduce the risk of respiratory
infections. In 2018 the VITAL
study of 25,000 adults in Boston,
Massachusetts, in the US found
a potential link between taking
supplements and a slightly reduced
risk of death from cancer (but not
the actual risk of getting cancer).
However, researchers stressed that
further trials were needed.
Elsewhere, studies linking
vitamin D and conditions including
heart disease, cancer, multiple
sclerosis, inflammatory bowelShould we ALL
be taking vitamin D?
The bone-strengthening nutrient is made mainly in our skin when it’s exposed to sunlight.
But should we be taking supplements in the dark UK winter or can we get enough from our
food – and is vitamin D really a cure-all? Sue Quinn ups your knowledge intake
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