Are We Getting Enough Vitamin D In Our Day?
As we all know, too much sun can cause skin cancer and we in Australia and also in
New Zealand already have the highest rate of skin cancer in the world.
But the sun is also the main source of vitamin D and a significant part of our population
is deficient in this vital nutrient.
UNIQUE VITAMIN D
Vitamin D is a fat-soluble vitamin (which means it can be stored in the body) and
it is unique because unlike most vitamins which we get from foods and drinks,
most of our vitamin D is produced when a fatty substance in our skin reacts
with the sun rays.
The body then convert this into vitamin D and stores it for when we need it.
Circa 90% of our vitamin D is produced in this way and circa 10% comes from our food.
Are we getting enough?
It is important to get enough vitamin D for several reasons.
Healthy Bones
Vitamin D is essential for bone health because it helps to absorb calcium and other
minerals we need to build strong bones and teeth.
Over time, low vitamin D levels can lead to conditions like rickets in children and
osteomalacia (soft bones) in adults. Low levels in the adult years also increases the risk
of osteoporosis, a condition that’s characterized by porous bones which in turn
increases the risk of fractures and falls.
Healthy immune system
Low blood levels of vitamin D have been linked with a wide range of health problems
including polycystic ovary disease, multiple sclerosis, rheumatoid arthritis, muscle weakness, memory loss and some cancers.
Skin health
Although it is well known that too much sun exposure can cause skin cancer, vitamin D
and related compounds in our skin may actually protect against damage from UV radiation, according to a current research by Professor Rebecca Mason from the University of Sydney.
This is because vitamin D compounds in skin reduce DNA damage after UV exposure.
Low Levels in Australia
Low vitamin D levels are a proven problem, even in the sun-drenched southern hemisphere.
Generally there are few symptoms of deficiency except general aches, pain and tiredness.
When the deficiency is severe, extreme symptoms like bone deformities and intense
pain can be observed.
A large Australian Study (AusDiab) indicated that 40% of females and 27% of males have low levels of vitamin D in summer-autumn and these figures increase to 58% of females and 35% of men in winter-spring time.
Reasons for deficiency
Professor Mason explains: we use a target value for vitamin D based on a concentration of
vitamin D where most bone and muscle function are close to normal.
This is a little higher than the figure we used to use.
There are other reasons as well. There are more people in higher risk groups like older people (who are not going out in the sun much and may not be able to make vitamin D
quite so effectively. More people with naturally dark skin, as melanin absorbs the UVB
that converts a compound in the skin to vitamin D and/or who cover up with closing.
More obese people (vitamin D gets into fat, but doesn’t get out again until you break down
the fat). More people working indoors and entertain themselves indoors (Computers,
video games,etc.)
People with osteoporosis and babies of mothers who are low in vitamin D, especially
if they are being breast-fed, also fall into the high risk group for vitamin D deficiency.
The USA recently increased the recommended daily intake of vitamin D in order to reach
optimum blood levels of the vitamin. Our last NHMRC recommendations were made
about a decade ago and are currently being reviewed and it looks like the daily levels
are set to rise.
According to Professor Mason,’Most people agree that the minimum acceptable level
is 50 nmol/L’. At this level, bone and muscle function is close to normal and also the
handling of calcium by the body.
‘This is also the minimum level recommended by the AusNZ Bone and Mineral Society,
the Endocrine Society of Australia and USA, and the Institute of Medicine of USA.
Some groups recommend even higher levels, with some, though not conclusive evidence’.
Combination of safe sun and food.
As we know, our major source of vitamin D is the sun. We can also get it from food,
like oily fish (salmon, sardines) abd cod liver oil, eggs, butter and meat.
A combination of safe sun and vitamin D containing foods is wise.
The energetic UVB-rays that make vitamin D are there for most of the day in summer,
but only around noon in winter, particularly in southern parts of Australia.
When we expose the skin of our arms and hands during the peak UV periods, which is between 10 am and 3 pm in summer for 6 – 10 minutes should be enough for our body
to produce the required vitamin D. In winter we need to extend this for seven minutes
in Cairns to 40 minutes in Hobart and it has to be at noon.
Vitamin D Supplements.
Vitamin D supplements are suitable for people who are advised not to go outside,
people with sun-sensitive skin and those who are immune suppressed,
says Professor Mason.
People with naturally very dark skin may need three to six times this amount, so it may
not be possible to maintain vitamin D levels and supplementation may be needed.
Commenting on USANA’s Vitamin D supplement, Professor Mason said:
“Vitamin D3 supplements as cholecalciferol provide the same form of vitamin D
as we make in the skin and supplements are a reasonable way to improve vitamin D
status if more sun exposure is not practical.
For those with a higher degree of deficiency, more than 1000 IU per day might be required.