How Much Vitamin D is Enough?

By Craig Gustafson

In 2010, the USDA increased its Daily Recommended Intake of vitamin D from 400 IU to 600 IU for people younger than 70 years old, and to 800 IU for those who are older. This revision is a step in the right direction, but still pales in relation to the levels of vitamin D the human body is capable of producing.

It is no secret that sun exposure triggers the production of vitamin D3 in our skin. However, geography and skin pigmentation play a significant role in a person’s ability to produce vitamin D. For people living north of Altanta, Georgia, the sun is not strong enough for any vitamin D production from November through March. South of Atlanta, all the way to the equator, the oblique angle of the sun during the winter months causes most of the important UVB rays to be absorbed by the ozone layer.

If you can consistently get 15 to 30 minutes of sun exposure over 40 percent of your body two to three times each week (minding the above considerations), you are probably producing adequate levels of vitamin D.

If not, and you are not taking a supplement, you are probably vitamin D deficient. According to Dr. Michael Holick of Boston  University, one of the world’s foremost vitamin D researchers, vitamin D deficiency has reached pandemic proportions. Studies show that as much as 80 percent of the US population could be deficient.

The question is: How do you really know if you are getting enough? According to Dr. Joseph Pizzorno, ND and editor in chief of Integrative Medicine: A Clinician’s Journal, the only way to confirm adequate production and intake of vitamin D is a blood test. Furthermore, because of all the variables involved with vitamin D production, the only way to be sure that a supplement is bringing you to the optimum level is to continue periodic testing.

Blood tests measuring vitamin D should test calcidiol (25(OH)D) levels. A significant number of researchers maintain that this level should lie between 40–65 ng/ml (or 100–160 nmol/L).

For those who are identified as being deficient, both Holick and Pizzorno advocate supplementing at a higher level for two to three months to overcome the deficit, then reducing to a lower dosage for ongoing maintenance.

For example. Pizzorno suggests that initial doses of 10,000 IU per day and maintenance doses of 5,000 IU per day for adults who are not suffering from vitamin D hypersensitivity syndromes, such as sarcoidosis.

Additional nutrients are also needed for proper regulation of vitamin D at these levels including vitamins A and K, magnesium, and zinc.

Talk to your doctor about supplementation for infants, although their vitamin D level is very important to manage. For children, start supplementing with 1,000 IU per day. Dosage may safely rise as high as 1,000 IU per day for each 25 pounds of body weight.