It has been estimated that up to 30% of Australians are Vitamin D deficient and vitamin D supplementation has become a hot topic amongst health care professionals. Although, some current opinions support increases in supplementation dosage levels, there is also substantial evidence to suggest more caution should be used in relation to high dosage or long term vitamin D supplementation use.
Vitamin D is not like other vitamins and it is questionable if it should have been classified as a vitamin. Vitamin D is actually a pro-hormone; meaning it promotes or inhibits the effect of hormones. The major hormones that vitamin D influences includes; oestrogen, progesterone, testosterone, insulin, thyroid, parathyroid and adrenal hormones. As such, the role of vitamin D within the body is complex
Vitamin D is stored in the blood for a few weeks and in fat cells for a few months. The liver and kidneys help to convert vitamin D into it's more active form.
Vitamin D deficiency has been linked to the following conditions:
Bone Health:
Osteoporosis: Vitamin D facilitates bone mineralization of calcium
Rickets: a deficiency of vitamin D during pregnancy, breast feeding and early childhood, can result in this condition of decreased bone mineralization.
Cancer:
The latest research indicates a link between vitamin D deficiency and breast, prostate and colorectal cancer
Immune Function:
Type1 diabetes, asthma, psoriasis, multiple sclerosis, rheumatoid arthritis, systemic lupus and inflammatory bowel disease, are all auto-immune conditions that have been associated with a vitamin D deficiency.
Type 2 Diabetes:
Vitamin D is involved in pancreatic function and blood glucose metabolism.
Mental Health:
Fatigue, depression and seasonal affective disorder have been associated with low vitamin D levels. Perhaps, this is one of the reasons why our mood lifts, when we get some spring sunshine after the winter months
Fertility And Reproduction:
Male Fertility: receptors for vitamin D are present in sperm and are linked to sperm survival and their ability to bind to and fertilize the egg.
Female Fertility: vitamin D is essential for proper implantation of the embryo in the womb.
Pregnancy: vitamin D deficiency in pregnancy is associated with an increased risk of developing gestational diabetes and pre-eclampsia. The child is predisposed to low birth weight and rickets
How To Optimize Your Vitamin D Stores
Diet
We rely on dietary sources for only 10% of our vitamin D requirements. Rich sources of vitamin D are mackerel, herring, salmon, sardines, egg yolk and butter.
Sunshine
90% of our vitamin D is made from the cholesterol in our skin in response to UV-B penetration from the sun. So, the most basic way for us to get our vitamin D is through exposure to sunlight. Clothes, glass and sunscreen will block UV-B penetration and so inhibit vitamin D synthesis
UV-A rays destroy vitamin D and are linked with skin cancer risk. Unlike UV-B rays, UV-A rays are able to partially penetrate glass. So when we are outdoors we get a balance of both UV-A and UV-B rays. Whereas, indoors we get some exposure through glass windows to UV-A only.
Safe Sun Exposure
The success of the slip. slop, slap campaign has resulted in us becoming some what sun phobic. Hence, we are now seeing the re-emergence of rickets in Melbourne school children.
We have been taught that the safest time to spend in the sun is before 10.00am and after 3.00pm. More recent research [2008] dispels this by showing that UV-B ray exposure is highest between 10.00am - 2.00pm. Therefore, daily "sunscreen free" sun exposure between 10.00am- 2.00pm will provide you with the maximum vitamin D yield
The amount of time required will depend on your skin type. Those with darker pigmented skin or a tan will need longer in the sun than pale skinned people. Basically, sun exposure needs to be long enough to cause a slight pinking but not reddening of the skin. This can range between 10-20 minutes. The amount of skin exposed needed is face, arms and upper body or face, arms and legs.
Overdosing on vitamin D due to sun exposure is not likely. This is because there is a feedback loop and the body will shut down vitamin D production, when your vitamin D levels are optimal
Sunscreen
Please note, I am not advocating long periods of sun exposure without protection. As we approach the summer holidays, we are likely to be spending more time outdoors and slapping on the sunscreen lotion.
Unfortunately. most sunscreen lotions are a cocktail of synthetic chemicals; some of which will be absorbed into your blood stream and can impact on your health. Firstly, the chemicals used tend to produce a lot of cell damaging free radicals. Secondly, many of the chemicals are oestrogenic and can disrupt your hormone balance
Factors That May Reduce Vitamin D Synthesis
- Dry skin: excess soap and cleaning chemicals can change the barrier function of the skin and negatively impact on vitamin D conversion from cholesterol in the skin.
- Use of cholesterol reducing statin drugs.
- Imbalances or deficiencies of magnesium, zinc, boron or vitamin A and K. These all have a synergistic relationship with vitamin D.
- Bowel conditions such as crohn's disease, coeliac disease and irritable bowel due to reduced absorption abilities
NB
Please do not self-prescribe vitamin D supplements as this may lead to imbalances that impact on your health. However, the amount of vitamin D in a multi-vitamin is fine. Requirements are individual and the need for additional vitamin D supplementation is best assessed through a combination of your blood vitamin D levels and a mineral hair analysis, as well as taking into consideration your metabolic type and current health profile
