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Choosing the Best Form of Vitamin D

The Sun Herald, Biloxi, Miss.


Q: My doctor recommended I take supplemental vitamin D. Because of ongoing fatigue problems due to MS and fibromyalgia, she tested my vitamin D level. It was just above 20, which she said was too low. She made a point of looking up the specific type of vitamin D to take and recommended the ergocalciferol form over the cholecalciferol form. She said it was better absorbed. However, my own research indicates that cholecalciferol is recommended. Now I'm confused. After taking supplements for several months, my vitamin D level is 27, still lower than what she thinks is good for me. Can you advise?

A: Pat yourself on the back for being a good researcher. The cholecalciferol form of vitamin D is considered to be superior.

Ergocalciferol (vitamin D2) is present in plant sources. It's our primary dietary source of vitamin D and is the form used in vitamin D-fortified milk and cereal products.

Cholecalciferol (vitamin D3) is the form our body synthesizes when skin is exposed to sunlight.

Both forms are converted to active vitamin D by the body.

However, studies have determined that cholecalciferol is about three times more potent than ergocalciferol in the conversion process.

The test numbers you mention refer to blood levels of the major circulating form of vitamin D (in units called nmol/L).

Your current level of 27 is indeed on the low end.

It was once thought that blood levels of at least 40 were needed for optimal bone health. Vitamin D (along with calcium) is required to prevent the bone-thinning disease osteoporosis.

More recent research, however, indicates that higher levels of 70 to 80 might be optimal. So your doctor is on firm ground in wanting to push these numbers higher.

I'm taking the "MS" you mention to be multiple sclerosis. Some research suggests that long-term vitamin D supplementation might help prevent multiple sclerosis in women. Though you already have MS, your doctor could be hoping that raising your vitamin D levels might help this disease in addition to its other benefits.

To raise your levels to current recommendations, you may need at least 1,000 IU of supplemental vitamin D in the form of cholecalciferol (D3). I'd suggest talking with your doctor about this.

The safe upper intake level for vitamin D is currently set at 2,000 IU.

Vitamin D is available in both multivitamin and vitamin D-only supplements. Standard multivitamin supplements supply 400 IU of vitamin D, now considered a low-end amount.

The catch is, the vitamin D in supplement products may be either ergocalciferol are cholecalciferol.

The Supplement Facts label typically just says "Vitamin D." So how to tell which form you're getting?

You'll have to peruse the "Ingredients" section of the label, which is not alphabetized. The tiny print on some products calls for a magnifying lens.

Look for either "vitamin D3" or "cholecalciferol" as opposed to "vitamin D2" or "ergocalciferol."


(Richard Harkness is a consultant pharmacist, natural medicines specialist, and author of eight published books. Write him at 1224 King Henry Drive, Ocean Springs, MS 39564; or Selected questions will be used in the column.)


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