Vitamin D – Where do we get vitamin D from?
Vitamin D is manufactured from a particular wave length of ultraviolet light from the sun hitting the skin. It then travels to the liver where it is converted to caclcidiol. The active form of vitamin D is calcitriol. A small amount of vitamin D is also obtained from food such as oily fish, eggs and fortified cereals.
What does vitamin D do?
The main function of vitamin D is to check calcium and phosphate levels in the blood. They in turn are responsible for laying down healthy bones.
Is there a test for vitamin D?
There is a test available for checking vitamin D but the controversy surrounding whether people generally should be tested is raging on. The test that is carried out is to measure 25- hydroxyvitamin D (25OHD) in the blood. There is another test available and that is to determine 1.25-dihydroxyvitamin D. If you are getting tested privately then make sure that the lab is measuring (25OHD). This is because the calcidiol or 25OHD is produced in the liver first and gives a much clearer picture of vitamin D levels than waiting for the kidneys to convert to calcitriol. Because demand is so great now for vitamin D tests, pharmaceutical companies such as Roche, Abbott and Siemens are developing new tests involving immunoassays.
Can you overdose with vitamin D from the sun?
The answer is no because there is a built in feedback mechanism that does not allow that to happen. You can however get cancer of the skin if you allow the skin to burn. The best way to get an adequate amount of vitamin D is to allow about 65% of your skin to be exposed to the sun when it is high in the sky. This is between 10am and 2pm and will produce enough vitamin D after about 10 minutes or until your skin goes pink.The darker your skin the longer will need to be the sun exposure. In the UK and particularly the further north you go it becomes more and more difficult to obtain adequate vitamin D levels naturally from the sun since the particular wavelength of ultraviolet light needed is only available in the summer months and is not effective through cloud.
What about overdose from taking vitamin D supplements?
Because vitamin D is a fat soluble vitamin then it is possible to overdose but the reported overdose cases have involved many thousand and in some cases millions of international units.
One family had been poisoned with white table sugar that had been contaminated with pure vitamin D3. Each gram of sugar contained 21.4mg of vitamin D3. The father and son had consumed more than 1.3g of vitamin D3 per month –one million seven hundred thousand iu per day. If you note above the UK chief Medical Officers suggest about 400iu for pregnant mothers you can see why these individuals were experiencing toxic symptoms. They both had increased thirst, vomiting and kidney failure.
In another example researchers reported a massive acute vitamin D intoxication when a family accidently ingested 2 million iu/G of oil based supplements mistakenly used as cooking oil.
In 2005 A mother gave her child –a two year old- an accidental overdose of 60,000iu/day Initially the child had colic and constipation and calcium levels were found to be raised. In 4 days the child had been given 2400000iu.Despitre high calcium levels and raise blood pressure the child made a complete recovery.
So what dose of vitamin D supplements should you take ?
If you are pregnant or breastfeeding then you should take 400iu of vitamin D3 daily.Most adults should take between 1000 and 5000iu of vitamin D3.
Who should not take vitamin D?
People who have a condition called sarcoidosis should not take vitamin D without monitoring.
We don’t know the cause of sarcoidosis but it is an inflammatory disease. It is thought to be one of the autoimmune diseases where the body attacks itself. The inflammatory immune cells form granulomas (or lumps). If these lumps form on a particular organ they can impact on the workings of the organ. Signs and symptoms can vary from causing no symptoms to breathlessness, blurred vision, painful joints and inflamed lymph nodes. Chronic sarcoidosis affects the lungs with coughing and shortness of breath.
Patients with sarcoidosis are often told to stay out of the sun and avoid taking calcium and vitamin D products such as oily fish in the diet.
The message is not to take calcium and vitamin D supplements unless instructed to do so by your doctor and to avoid overindulgence in sun exposure.
So the overall message is since most of our vitamin D production is from the sun then it is possible that many people in the UK are vitamin D deficient. It is very important to take vitamin D if you are pregnant or breastfeeding, over 60 or spend most of your day indoors out of the sun’s rays.
