Vitamin D Quantitative Status test & Consultation




This option includes a consultation with Mary Carmody where she will do the test and follow up with you.

D25-hydroxyvitamin Vitamin D (25-OH) Status Test

Vitamin D, a fat soluble vitamin, is more appropriately categorized as a prohorm-one which is a collective term for a group of seco-steroids. Vitamin D is metabolis-ed by hepatic 25-hydroxylase into 25-hydroxy-vitamin D and by renal 1α- hydrox-ylase into the active form 1,25- dihyroxyvitamin D. This is responsible for the modulation of calcium absorption and inflammatory responses. Low circulating levels of 25-hydroxyvitamin D Is the most reliable marker of Vitamin D deficiency.

Why test for Vitamin D Deficiency

Vitamin D deficiency can be a serious problem. It doesn’t have obvious symptoms but increases susceptibility to more serious conditions. Epidemiological data supports the view that maintaining Vitamin D levels protects against a wide range of diseases including viruses, cardiovascular disease, bone diseases such as osteoporosis, rickets and osteomalacia, autoimmune disease (such as multiple sclerosis, Hashimoto’s Thyroiditis and rheumatoid arthritis), strokes, nervous system disorders (such as Parkinson’s Disease) and type 1 & 2 diabetes. Depression and breast, prostate and colon cancer have also been linked to Vitamin D deficiency.

Causes of Vitamin D Deficiency

  • Deficient production
  • Increased metabolism
  • Decreased input due to seasonal lack of exposure to sunlight
  • Anything that interferes with the penetration of solar ultraviolet radiation into the skin will diminish the cutaneous production of Vitamin D3
  • Dietary intake is low
  • Decreased capacity of human skin to produce vitamin D in the elderly
  • Impaired absorption due to kidney or digestive diseases

Which foods contain Vitamin D

Only a few foods naturally contain Vitamin D therefore adequate levels are largely dependent on exposure to sunlight. The flesh of fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best sources. Small amounts of vitamin D are also found in beef liver, cheese, and egg yolks. Vitamin D in these foods is primarily in the form of vitamin D3 (cholecalciferol) and its metabolite 25(OH)D3. Vitamin D2 will also raise blood levels and can be found in sun-exposed mushrooms (including purchased mushrooms placed in sunlight) as well as seaweeds (e,g, kelp) and yeast products (reportedly even in some beers). While less desirable as sources, fortified processed foods such as breakfast cereals, yogurt, margarine contain added Vitamin D.

Vitamin D maintains levels of calcium and phosphate. These are needed for normal bone mineralisation, muscle contraction, nerve conduction & general cell function. More specifically 1, 25-dihydroxyvitamin D is a strong steroid hormone with a crucial role in calcium homeostasis, bone metabolism, cell growth and replication.

How does the test work?

CNS uses conventional ELISA based technology to determine levels of 25-Hydroxy-vitamin D and other metabolites in serum or plasma. Calibrators, controls and samples are diluted with biotinlabelled 25-OHD. Diluted samples are incubated for 2 hours at room temperature before washing. Enzyme labelled Avidin is added and binds selectively to complexed Biotin and following a further wash step colour is developed using TMB. The colour is proportionate to the concentration of 25-OH D.

Research is showing what a key player vitamin D is for multiple body systems. It bests biological function is that it increases calcium and phosphorus absorption and thus directly influences bone health metabolism. It also influences our immune system, heart health, mood, autoimmune conditions and cell differentiation.

Risk Factors for Deficiency include

    • Vitamin D production in the skin depends on the incident angle of the sun and thus latitude, season and time of day. Consequently people with dark or covered skin and users of sunscreen, synthesise less vitamin D.
    • Sun exposure during the winter months at latitudes above approximately 33 degrees north or below 33 degrees south is insufficient for production of vitamin D3 in the skin. Ireland is above 40ºN.
    • People taking medication can significantly deplete vitamin D status e.g. steroids, metformin, anti-convulsants and medications that interfere with digestion/absorption such as proton pump inhibitors.
    • People who are obese( as vitamin D is deposited in body fat stores, making it less bio-available) and/or have a sedentary lifestyle(likely to have reduced sun exposure)
    • People with digestive impairments such as IBD, especially those who have had small bowel resections, or fat malabsorption disorders.
    • Pregnant and breastfeeding women
    • Babies( particularly exclusively breastfed) and young children under 5 years of age.
    • The elderly, due to reduced capacity to synthesise vitamin D in the skin when exposed to UVB radiation

Also did you know that studies have shown distinct demographic differences in rates of vitamin D insufficiency and deficiency with people with darker skins/skin tone.

What you can do now?

  1. Get tested
  2. When the sun shines, jump out into it, we should get at least 15 mins three times a week.
  3. Resistance exercise, [lifting weights in the gym, using your body weight in yoga] are useful for promoting bone growth.
  4. Eat more Oily fish like salmon, mackerel and herring [wild!]
  5. Eat good quality eggs
  6. Supplementation with a good quality Vitamin D3 supplement.

What is the optimal range on a blood test?
Optimal range is 50-100 ng/mL (125-250 nmol/L). I like to see readings over 80ng/mL.

Having blood tests to measure the amount of vitamin D in your blood is the only way to know if you’re getting enough vitamin D or not.

Sample requirements & test turnaround

The test requires a pin-prick blood sample. Results are available within 15 working days.

This Vitamin D test has not been verified for use with clients under the age of 18. In some cases, under 18s may have different blood protein levels which may affect the results of most Vitamin D tests currently available.

What do I do next?

This test is a post-away test. Mary also offers this test without a consultation where you can do the test at home yourself. Click here to choose that option.

The steps involved are:

  1. Order online here and Mary Carmody Nutrition will contact you to arrange your appointment.
  2. Following your appointment, Mary will contact you within 2-3 weeks of testing with your results.


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