Vitamin D, also know as calciferol, is a fat-soluble vitamin with properties of both vitamin and a hormone. It is required for the absorption and utilisation of calcium and phosphorus, and is especially important for the normal growth and development of bones and teeth in children.
Calcitriol, the active form of vitamin D, is considered to be a potent immune system modulator and has a variety of effects on immune system function. It may enhance innate immunity and inhibit the development of autoimmunity. It protects against muscle weakness and is involved in regulation of the heartbeat. It has been shown that vitamin D is important in prevention and treatment of breast and colon cancer, osteoarthritis, osteoporosis and hypocalcemia, it is also necessary for thyroid function and normal blood clotting.
Vitamin D Deficiency Syndrome (VDDS) is a newly designated disorder, diagnosed by low blood level of 25-hydroxyvitamin D and presence of at least two of the following conditions:
High blood pressure,
Psoriasis or eczema,
There are several forms of vitamin D. The one that comes from food sources is D2 (ergocalciferol). The best dietary sources are: sardines, salmon, tuna, butter, sunflower seeds, liver and eggs. This form of vitamin D requires conversion by the liver and then by the kidneys, to become fully active. This is why people with liver or kidney disorders are at a higher risk of deficiency.
The most active form of vitamin D is D3 (cholecalciferol) and it is synthesised in the skin in response to sun exposure. The darker the skin colouring the harder it is for vitamin D to be absorbed from sunlight. In addition, those who live above the 37th latitude obtain virtually no vitamin D from sunlight between November and March. Take a look at this very useful, but also quite depressing for people in the UK, sunshine calendar:
Studies have shown that vitamin D deficiency is very common, showing that at least 50% of general population and 80% of infants have less-than-optimal levels of the vitamin in their blood. Public Health England is advising that 10 micrograms of vitamin D are needed daily to help keep healthy bones, teeth and muscles. 10 micrograms is equal to 400 IU (International Units).
The ideal method for determining the optimal dosage requires a readily available blood test for 25-hydroxyvitamin D. While some people can achieve an optimal level with just 600 IU per day (or 20 minutes of sunlight exposure per day), other have a genetic requirement for as much as 10,000 IU per day.
Typically 2,000 to 4,000 IU per day is required to elevate blood levels to the optimal range. I personally take 3,000 IU daily from October until April, and my children take 400 IU daily, in a vitamin D3 oral spray. However, the only way to determine how much you need is by testing.
WARNING: People with the following health conditions should only take vitamin D with the doctor’s guidance:
- Primary hyperparathyroidism,
- Granulomatous tuberculosis,
- Some cancers.
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Murray, M.T. and Pizzorno, J. (2012). The Encyclopedia of Natural Medicine. 3rd edn. New York: Atria Paperback.
Osiecki, H. (2014). The Nutrient Bible. Ninth edition. Brisbane: Bio Concepts Publishing.
Public Health England (2016). PHE publishes new advice on vitamin D. Available at: https://www.gov.uk/government/news/phe-publishes-new-advice-on-vitamin-d (Accessed: 6th February 2017).
Vitamin D Day (2014). Sunshine Calendar. Available at: http://www.vitamindday.net/wp-content/uploads/2014/10/Sunshine-Calendar.pdf (Accessed: 6th February 2017).