Wednesday, January 28, 2009

Don't Doubt Vitamin D !

Experts in the field are convinced we are not getting enough vitamin D and the evidence is pretty convincing. There is a growing list of health conditions and diseases that vitamin D deficiency/ insufficiency* has been linked to, such as
Osteoporosis
Type 2 Diabetes Mellitus
Cardiovascular Disease
Muscle weakness
Fractures
Cancers
Autoimmune diseases
Dementia
Hypertension
To mention just a few...

*criteria for deficiency is a serum 25(OH)D [25 hydroxyvitamin D] less than 50 nmol/L, and vitamin D insufficiency is a serum 25(OH)D between 50 and 80 nmol/L (experts believe this reflects a vitamin D status that is too low to prevent some disease).


Last year I was vitamin D deficient. I suspected that I was deficient for several reasons:

(1) I live on the East Coast.
(2) I lather myself in sunscreen from May to September (tanning is not an option for most Irish).
(3) I don't drink any milk (there is a story behind that one).
(4) Like most, I only consume fish once a week.

A simple request to my Dr. asking that she test my serum 25(OH)D levels confirmed what I had suspected and so now I take a vitamin D supplement.

Nutrition 101:

Upfront, there are two points you need to keep in mind. First of all, there are three ways you can get vitamin D (1) through sunlight exposure, (2) from food, and (3) from supplements. Second, there are 2 forms of vitamin D: D3 (cholecalciferol) and D2 (ergocalciferol). Vitamin D3 is the most potent form of vitamin D. It is more effective at raising serum 25(OH)D than vitamin D2 and, it is more effective at maintaining those levels for a longer time. Most supplements now contain vitamin D3, rather than vitamin D2 (but make sure to check the label).

Sources of vitamin D:

Most people know we get vitamin D from sunlight. If like me however, you use sunscreen, you block the UV rays and therefore prevent the absorption of vitamin D in your body. Also, keep in mind the further from the equator you live, the weaker the UV light (note to Irish friends....even on those sunny days you're at a disadvantage!)

With respect to diet, there are few foods that are naturally rich in vitamin D. These include fatty fish, some fish liver oil, and eggs from hens fed vitamin D. Milk products, breakfast cereals, infant formula, and juice can be good sources if fortified with vitamin D. Contrary to what you may believe, most cheeses and other dairy products are not fortified with vitamin D.

**NOTE: THIS SECTION IS NOT NECESSARY TO READ IF YOU'D RATHER SKIP AND GO STRAIGHT TO THE BOTTOM LINE (SEE BELOW).
Regardless of where vitamin D is obtained (sun exposure, food, and supplements) it is biologically useless! It needs to go through 2 steps in the body to become active. The first step occurs in the liver where vitamin D3 is converted to 25-hydroxyvitamin D [25(OH)D]. As mentioned above 25(OH)D is a blood measure of vitamin D status. The second step occurs primarily in the kidney, where 25(OH)D is converened into the physiologically active form 1,25-dihydroxyvitamin D [1,25(OH)2D]. This is a hormone and it plays many roles in human health. One of the most important roles of vitamin D is in promoting calcium absorption in the gut and maintaining adequate serum calcium and phosphate concentrations to enable normal mineralization of bone.

How much vitamin D should I have in my diet?:

Most experts are recommending 1,000 international units (IU) a day. Check to see how much you are getting from your multivitamin, calcium supplement (most include vitmain D) and then from foods.

(Go to: http://ods.od.nih.gov/factsheets/vitamind.asp#h3).

You should be aware that there is a current recommended tolerable upper intake level (ULs) for vitamin D (i.e. the maximum that is considered safe). This is set at 2,000 IUs a day. Most experts however believe this is set too low and that higher intakes appear to be safe. If you are prone to kidney stones or kidney problems I suggest you seek advice from your doctor. The main reason is that too much vitamin D will cause your body to absorb too much calcium and this can lead to kidney problems.

BOTTOM LINE:
So, here is my advice:
Get your serum 25 (OH) D levels measured at your next physical examination.

Aim to consume 1,000 IU daily (most multivitamins contain 400 IU).

If your serum 25 (OH) D levels are low at your follow up visit, discuss taking a vitamin D supplement.

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