For years, conventional Government authorities assured us that our daily multivitamins contained plenty of vitamin D - around 400 IU.  And they told us we would get even more from fortified milk and from sunlight if we spent an hour or so outdoors every day.  Now we're seeing that this information was shortsighted.

   The medical community is finally taking Vitamin D seriously.  Until recently, all they were interested in was whether or not this vitamin/hormone caused rickets in children and osteomalacia in adults.  They told us that we needed our blood levels to be between 30 and 50 ng/ml.  Now we're finding this is much too low.

   Most people are still vitamin D-deficient. What's more, scientific studies have linked this deficiency to an increased risk of cancer, heart disease, diabetes, autoimmune diseases, and infectious diseases (including the flu).  We need much more vitamin D than the paltry amounts we get in our multi or from sunlight.

According to the Vitamin D Council, your blood level of vitamin D should be between 50 and 80 ng/ml.  That's significantly higher than the previously recommended level.  And you can't get to these levels from 400 IU a day, drinking milk, and spending time in the sun.  You need to take very high doses of vitamin D to get to these levels.

So, how much do you need to take - and can you take too much vitamin D?

   First, it is best to know if you're deficient.  Most of us are.  That's why I recommend you get a blood test, 25(OH)D, to check your vitamin D levels (usually about $65 - $100).  If your level is low — in the 30s or lower — you can take either 5,000 IU/day or 50,000 IU once a week for two months.  Then retest.

   But isn't 50,000 IU toxic?  Not according to a recent study conducted at Boston University School of Medicine.  In this study, patients who were vitamin D deficient took 50,000 IU of vitamin D once a week for eight weeks.  Their levels, which began at 19 ng/ml, rose to 37 ng/ml after two months of weekly supplementation.

   Then these patients took 50,000 IU every other week.  Their 25(OH)D level increased to 47 ng/ml.  This is still low if you're looking for vitamin D's protective effects.  However, it certainly shows that massive doses of vitamin D are safe.  In fact, researchers found that "While treating and preventing vitamin D deficiency, these large doses of vitamin D do not lead to vitamin D toxicity."

   (By the way, the vitamin D used in this study was synthetic.  If a synthetic vitamin isn't toxic, I certainly wouldn't worry about one from natural sources.)

   Another possibility for supplementation is to take 10,000 IU every day for two months and then re-check. Once your levels have reached 50 ng/ml, you may want to lower your dose to 5,000 IU/day. 

   Finally, it's always best and safest to get a baseline vitamin D blood test. But if you can't for any reason, 5,000 IU of vitamin D a day appears to be perfectly safe.  One doctor I know has taken 5,000 IU of vitamin D3 (the natural form) every day and has done so for nearly two years.  Her blood level is 67 ng/ml and she’ll continue to take this amount until it reaches 80 ng/ml.