Vitamin D
Vitamin D is the term given to a group of secosteroids that can be ingested by the human body in a variety of ways. In addition to being ingested, the body can synthesise Vitamin D from cholesterol when sun exposure is adequate. Technically this means that Vitamin D is not an 'essential' dietary vitamin.
Vitamin D appears to affect bone health by assisting the body to maintain normal blood levels of phosporous and calcium, thereby ensuring strong bones. It may have other benefits in reducing high blood pressure, cancer and other autoimmune diseases but these are not yet proven.
Where do I get Vitamin D from?
In the diet, Vitamin D can be found in fish and fish oils, eggs, alfalfa, mushrooms and beef liver.
It is also speculated that as little as ten-fifteen minutes of sunlight a day is sufficient to allow the body to synthesise sufficient quantities of Vitamin D. Unfortunately sunscreen can reduce the body's ability to do this by 95% or more.
This appears to send a mixed message to the community. 80% of all newly diagnosed cancers in Australia are skin cancers and we remain a country with one of the highest incidences in the world.
Yet recent studies have also suggested that Vitamin D is deficient in many Australians, which may partly explain increased incidences of osteoporosis in the elderly.
If not supplementing Vitamin D artificially, it is recommended that people get 10-15 minutes of sun before 10am or after 3pm, to avoid the most damaging midday sun.
How much Vitamin D do I need?
The Australian Nutrient Reference guidelines suggest that healthy adults require 5mcg per day rising to 10mcg at 50 years old and 15mcg at age 70 plus. Some medicos recommend significantly more.
The upper limit for intake is recommended to be 100mcg. Some inconclusive evidence suggests it may cause atherosclerosis at these higher dosages, and as a result a cautious approach is recommended.
Additionally, certain medical conditions can make people very sensitive to high Vitamin D intake so for those people with specific medical problems or who are supplementing very heavily, personalised clinical advice is recommended.
Many Vitamin D supplements contain 20mcg or more per dose which seems adequate without getting anywhere near toxic levels.
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