Vitamin D deficiency is a common occurrence even in sunny Australia. We have been taught to ‘slip, slop, slap’ to the extent that 45-84% of Australians are effectively vitamin D deficient (NHMRC 2013). Mild vitamin D deficiency can be asymptomatic (meaning show no symptoms), but severe vitamin D deficiency is mainly seen in bone with such deficiencies causing rickets (a de mineralisation of bone causing bowing limbs in rapidly developing children) and oesteomalacia (soft bones) (Higdon 2003, pp75).
Very few foods contain significant amounts of vitamin D (Holick 2001, Vieth 1999), foods such as fatty fish, cod liver oil and eggs are the main sources however many dairy products and breads are now fortified with vitamin D (NHMRC 2003). The single most effective way to ensure adequate vitamin D levels is exposure to sunlight (Higdon 2003, pp73).
Vitamin D acts to regulate the calcium and phosphate levels in the body, thus promoting healthy bones. Once you have acquired the vitamin D either through sunlight or diet, the liver then processes this into the blood and raises the blood calcidiol levels, from there the parathyroid hormone (PTH) is stimulated and activates the kidneys to turn it into caltitriol (an active form of vitamin D3), which then releases calcium and phosphorus from the bone whilst simultaneously increasing absorption through the small intestine, both increasing serum calcium (Higdon 2003, pp74).
Healthy kidney, liver and thyroid function are clearly required for making vitamin D, yet another example of how we can be effective by on so many levels by a disfunctioning organ.
Vitamin D deficiency also plays a role on the emotional/mental body, stay tuned for how this is effected.
So make sure you get some rays in the middle of the day to keep your spirits high, your bones strong and your immune system fighting!
Higdon J, 2003, An Evidence-Based Approach to Vitamins and Minerals, Theime, New York
Holick M. Sunlight, 2001, ‘Dilemma: risk of skin cancer or bone disease and muscle weakness’. Lancet 357:4-6.
NHMRC, Australian Government Natural Health and Medical Research Council, Vitamin D, http://www.nrv.gov.au/nutrients/vitamin%20d.htm
Vieth R. 1999 Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr, 69:842-56.