Bbbrrrrr, the Winter Solstice has just passed.
However there is still plenty of wild winter weather to come before we can really enjoy fresh-air activities in full daylight before and after work and so our Vitamin D levels may be suffering. There is an average drop of Vitamin D levels across Australia of about 23% (20 nmol/L) from Summer to Winter, with about 28% in Perth. 1
For those of you under 50 years old who had regular sun exposure last summer, there is good news, you have the ability to produce and store about 6 months worth of Vitamin D to get through this winter. 2
We often hear about the Sun providing Vitamin D, but what about foods? Only about 5% – 10% can be obtained from food 1 which is mainly found in fortified margarine, fatty fish such as salmon, herring, mackerel and eggs.2
Vitamin D must be converted by the liver to Calcidiol then into the active hormone primarily in the kidney, to Calcitriol. Vitamin D is referred to a hormone because it is processed in one area and then travels to exert its’effect in another.
The major function of Vitamin D is to maintain calcium levels by getting the small intestine to absorb calcium from the diet.2
However more recently it has been discovered that there is a Vitamin D Receptor (VDR) in every cell that houses a nucleus (DNA) which has the ability to convert Calcidiol to Cacitriol. This has promising outcomes with Auto-Immune disorders such as Hashimotos.1
In immunity, Vitamin D inhibits the Type 1 helper cells (Th1 cells) and enhances Type 2 helper cells (Th2 cells) creating a positive anti-inflammatory effect. It also decreases Type 2 helper cells (Th17) cells which are found in higher proportions in Hashimotos Thyroiditis. 3
In a study (2015) in Poland, perhaps a first for a low sunlight country, Vitamin D was assessed in those with Hashimotos Thyroiditis . The outcome was they had had a lower Vitamin D level than the controls in the same country.
It remains unclear if low levels of Vitmain D are a causative factor of Hashimotos or a result of the disease. 3 Although in an earlier study (2013) that compared Hashimotos patients on Levothyroxine with newly diagnosed Hashimotos patients, it was found that the lower levels of deficiency correlated with the duration of Hashimotos disease, thyroid volume and antibody levels. 5
In another recent study (May 2016) in India of 100 people showed that Vitamin D supplementation in therapeutic doses is associated with a big reduction in Thyroid Peroxidase Antibodies (TPO-Ab titers) in patients with Auto-Immune Thyroid Disease. After three months of Vitamin D and Calcium supplementation there resulted in a decrease of antibodies by greater than 25% in over half in the group.4
So how much sun? To produce about 10,000 IU a day it is recommended that 15% of the body – hands, arms and face be exposed to sunlight.1 In Perth Summer, from December to January at 10am or 2pm for 5-6 mins. Deliberate sun exposure between 10am and 2pm is not advised during summer. In the Winter, July to August at Midday for 15 minutes.1
When you are covering up for Summer, it is good to know that UVB does not travel through glass or clothing and sunscreens. Cloud cover reduces exposure by half and shade by 60%.1
The best blood test for Vitamin D levels is Serum 25[OH)D] as it covers both dietary and skin absorbed sources.2 and is the major circulating and storage form of Vitamin D1.
The optimum result to preventing chronic disease is ≥ 75 nmol/L.
A staggering 37% of requests to Clinipath Pathology in Australia shows deficiency.
Adequate for Bone health is ≥50 nmol/L but levels will need to be higher at the beginning of winter to allow for the natural decline by 10-20 nmol/L.
Moderate to Severe deficiency is regarded as <30 nmol/L.1
The names Vitamin D are referred to can be confusing. Cholecalciferol D3 Obtained through Sun Exposure2
Ergocalciferol D2 Obtained through Food 2
Calciferol D3 & D2 Combined
Calcidiol 25-hydroxyvitamin D [25(OD)H] Converted from D3 in the Liver1
Calcitriol 1,25-dihydroxy vitamin D [1,25(OH)2D] Made in the Kidneys from Calcidiol1
Medicare in Australia has now restricted it’s Vitamin D benefit of 25 hydroxyvitamin D, quantification in serum, for the investigation of a patient who:6
(a) has signs or symptoms of osteoporosis or osteomalacia; or
(b) has increased alkaline phosphatase and otherwise normal liver function tests; or
(c) has hyperparathyroidism, hypo- or hypercalcaemia, or hypophosphataemia; or
(d) is suffering from malabsorption (for example, because the patient has cystic fibrosis, short bowel syndrome, inflammatory bowel disease or untreated coeliac disease, or has had bariatric surgery); or
(e) has deeply pigmented skin, or chronic and severe lack of sun exposure for cultural, medical, occupational or residential reasons; or
(f) is taking medication known to decrease 25OH-D levels (for example, anticonvulsants); or
(g) has chronic renal failure or is a renal transplant recipient; or
(h) is less than 16 years of age and has signs or symptoms of rickets; or
(i) is an infant whose mother has established vitamin D deficiency; or
(j) is a exclusively breastfed baby and has at least one other risk factor mentioned in a paragraph in this item; or
(k) has a sibling who is less than 16 years of age and has vitamin D deficiency
So even it you have to pay for it, it is worth getting your Vitamin D levels checked.
Please feel free to contact me for a consultation if you have concerns about your Vitamin D and Thyroid health.
1. Clinipath Pathology (2014) SONIC Pathology Handbook
2. A guide to the interpretation of pathology tests Australia: The Buckner Group