Vitamin D: Testing & quantity by Dr. Wendy Ross

Vitamin D: Do you need to get tested and how much should you be taking? The simple answers to these questions are — Yes! and “It depends..” The Mayo Clinic recommends testing vitamin D levels —both to establish the need for vitamin D supplementation and to guide appropriate treatment.

The main concern cited, is to avoid under-medication (not overdose). One of the reasons for this is that there are large variations between individual absorption with some people having a polymorphism (gene variation) which means they absorb far less than the general population. Being overweight and obese also decreases your available vitamin D as it is stored in adipose tissue (fat cells) and is therefore not available for use in the body.

Unfortunately across Canada, at least six provinces, including B.C., have stopped paying for vitamin D testing unless it is already known that the patient suffers from a vitamin D deficiency-related disease such as osteoporosis. Yes that’s right, you can’t be tested unless we already know you are probably deficient!

Well, you can be tested, but in B.C. be ready to pay the $65 fee unless you are lucky enough to have your rheumatologist order it, then the test is free to the patient. The BCMA Guidelines recommend against routine testing or screening for vitamin D deficiency and against testing levels during vitamin D supplementation. To educated physicians, this makes as much sense as guessing that one’s patient has a thyroid problem, then starting them on thyroid medication without checking their levels and also guessing at the starting dose.

The current reference range for vitamin D or 25(OH)D levels is 75 - 200nmol/L. Having a “normal” level, as defined by the reference range, does not necessarily mean this is optimal for health or prevention of multiple diseases discussed in last week’s column.

As far as supplementation goes, this remains controversial despite no cases of vitamin D toxicity ever being recorded even in people taking 40 000IU a day. Why then, are the medical authorities still recommending “routine doses” ranging from 400 -1000 IU?

As stated, individual needs vary hugely, with some people maintaining adequate levels at doses as low as 1000 IU daily and others needing 10 000 IU or more per day. For people taking the higher doses, these can also be given weekly or monthly.

Ideally, work with your doctor, check your levels every three months to establish your ideal dosing, and remember, even this will vary hugely from summer to the end of winter.

People with the highest levels of vitamin D are less likely to get cancer, dementia, heart disease, osteoporosis, autoimmune diseases including rheumatoid arthritis and multiple sclerosis, diabetes and certain eye conditions than people with the lowest levels.

Isn't it sad that our health authorities choose to save the several hundred dollars it would cost per person per year to establish optimal vitamin D levels, but are then happy to spend hundreds of thousands to treat the cancer, dementia etc, that may have been preventable?

Next week: Dr Ross will be away for two weeks, Health Matters returns November 7.