Of all the vitamins, Vitamin D is the easy one to remember: it's the so-called "Sunshine Vitamin," the one your body makes when you enjoy bright sunlight on a summer's day.
Unfortunately, exposure to bright sun can also result in sunburn, which over time can lead to serious problems like sun-damaged skin and -- even worse -- melanoma (skin cancer).
Because of the danger, an increasing number of people use high-factor sun blockers or else remain in the shade or even indoors, away from the sun altogether. As a result they don't get any of the beneficial effects of sunlight, the most important of which is the way it triggers the production of Vitamin D.
Why We Need It
Vitamin D has a significant impact on how our bodies function. It plays a role in regulating the generation of the calcium and phosphate needed for strong bones and teeth.
Without Vitamin D, our bones become soft and breakable, our muscles become weak and stiff and we begin to suffer a general feeling of malaise. We know something's not right, but we may not be able to detect the cause.
Vitamin D Deficiency
A serious lack of Vitamin D leads to a specific condition known as Vitamin D Deficiency. In children it results in bone deformities such as rickets, which causes bowed legs and knock knees. In adults the lack of Vitamin D causes osteomalacia: severe bone pain in the legs, groin, thighs and knees.
(Note: we mustn't confuse osteomalacia and osteoporosis. The latter is not "soft bones" but "porous and brittle bones" and is not caused by Vitamin D deficiency.)
Vitamin D is really a group of vitamins known as "secosteroids," a subclass of steroids notable for their "broken ring" atomic structure in which there's a cleavage of the bond between carbon atoms.
Their complexity produces a curious anomaly. We get Vitamin D not only from sunlight but also from food, such as oily fish (sardines, herring, mackerel, etc.), red meat, liver and egg yolk. But whereas it's impossible to overdose on Vitamin D from exposure to the sun, it can become toxic if you take too much orally.
With sun exposure, Vitamin D production gets regulated by a negative feedback loop, but this doesn't happen when you deliberately supplement your intake.
The Preferred Option
So which is best, to get your proper amount of Vitamin D via sunlight, or by eating D-rich foods and topping up with over-the-counter supplements?
Here are some facts which may help you decide.
1. In the northern United States, northern Europe and the UK, most people can easily get all the Vitamin D they need via sunlight outdoors, from the end of March to the end of September.
2. At other times of the year, we need more Vitamin D from other sources.
3. People with darker skin (such as those of African, African-Caribbean and South Asian origin) need longer exposure to the sun.
4. Other people at risk from Vitamin D deficiency are children under 5, adults over 65, pregnant and breastfeeding women, teenagers and young women.
5. Body fat retains Vitamin D so that it becomes less available for bones and teeth. Obese people need to supplement their D intake (but go easy on the beef and liver!)
The Safe Way to Take the Sunny Option
If you take the sunny option during the late spring and summer, you need to judge your exposure carefully. People with pale skin can make Vitamin D quickly, before burning, by leaving forearms and lower legs uncovered.
If you're in the sun for only a few minutes, you won't need sunscreen on arms and legs. Where you need sunscreen the most is on your nose! Sunscreen blocks the rays you need, but your nose contributes very little surface area -- and when you're walking it's the first to burn.
Rays which activate the production of Vitamin D are UVB rays (or ultraviolet B), the same ones that cause you to tan and eventually burn. Remember: you can't get any benefit from the sun's rays if you sit by a window indoors. UVB rays do not pass through glass.
The Safe Way to Take the Oral Option
In North America, many foods -- such as cow's milk -- are supplemented with Vitamin D. This is not always true in the UK. However, you can check the side of your cereal packet to see if the manufacturer has added D. If so -- and if you eat it regularly -- you may be getting enough.
So how much is "enough"?
There are no official figures, mainly because of the variation between skin type and access to sun. However, here are some figures as a guide if you're taking supplements.
The consensus of medical opinion currently recommends 600 IU (international units) of Vitamin D per day for adults up to the age of 70. If you're 71 or over, you need a little more: 800 IU from your diet, especially in the winter months.
How Much Is "Too Much"?
As we've mentioned, too much Vitamin D taken by mouth can be dangerous, causing too much build-up of calcium in the body. Eventually it can damage the heart and kidneys, so it's vital to set some limits.
For normal adults, the upper limit is around 4,000 IU per day (as set by The Institute of Medicine). This translates as approximately 100mcg of Vitamin D per day, ten times more than the recommended supplement of 10mcg a day.
For children and pregnant mothers, always consult your doctor for advice.
Taking a Measurement
As you can see, there's plenty of leeway for error and you don't have to be too precise. However, if you think you have a deficiency it's feasible to measure the amount of Vitamin D in your body, via a blood test.
Typically, a blood test taken by a doctor measures a form called called 25-hydroxy Vitamin D produced in the liver. Your kidneys convert it to an active form for controlling the levels of calcium and phosphate.
Vitamin D deficiency has been linked to various heart conditions, diabetes, asthma and even dementia in older people. If you suffer from any of these conditions you'll certainly need your doctor to test your level of Vitamin D.
Do You Need a Vitamin D Boost?
You may have no symptoms whatsoever of Vitamin D Deficiency but your levels may still be too low, especially if you rarely go out in the sun. There are no obvious symptoms for a low level of Vitamin D.
The good news is: it's easy -- and safe -- to augment your diet or take a supplement. Apart from maintaining healthy bones you'll also lower your risk of colon cancer, according to recent studies.
Scientists are still investigating the role of Vitamin D in a range of illnesses. So far, the results are encouraging. Vitamin D can bring a ray of hope to millions. It's not called the Sunshine Vitamin for nothing.
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