I’m asked this question regularly, and my answer is very consistent: ‘It depends.’
I’ve brought this up today because new guidelines were recently set for Vitamin D’s Recommended Dietary Allowance (RDA). Previously, the guidelines were 200 IU per day for adults under 50, 400 IU per day for adults 50-70, and 600 IU for adults over 70. Most naturopathic physicians viewed these guidelines as woefully inadequate. The revised RDAs now recommend 600 IU per day for all people under 70, and 800 IU per day for adults over 70. These new guidelines are a step in the right direction, and are an indication that large organizations are paying attention to emerging data about Vitamin D. Most naturopaths would, however, still argue that these numbers are low, and that most people should take more.
Despite changes in the RDA, and despite calls to increase the number, I’m going to stick to my strict guideline of ‘It depends.’ The IOM’s decisions are based on a public health model, where they are trying to establish a baseline dose that will supply the majority of people with enough of a nutrient to ward off disease. To that end, they do not take into account the individual needs of a given person, but instead look for the peak of the bell curve, and how much that population needs. The needs of an individual person at a given time can and will vary.
As a consumer, though, how do you decide how much to take? The best way to determine this is to have a blood test done and to work with a doctor to bring your levels back into an optimal range. Many naturopaths will run this as a routine test along with cholesterol, blood sugar, iron, etc., because of increased knowledge of its importance in health. Most frequently, I have seen doctors initially recommend high doses of Vitamin D for a period of a few weeks or months in order to bring blood levels up to an optimal range, and then back off to a lower maintenance dose.
As we learn more about this as yet poorly understood nutrient, we will likely see greater and greater benefit, and RDAs will increase. At some point in the future, though perhaps not soon, we will also see a more individualized system of dosing develop. We’ll likely see recommendations altered for people living in more northerly climates, where the body’s own Vitamin D production drops in winter months. Additionally, we may see recommendations come out based on ethnic background and skin color, as people with darker skin may make less Vitamin D than lighter skinned people when exposed to the same amount of sunlight. Fortunately for all of us, Vitamin D continues to be one of the least expensive nutritional supplements around. For pennies a day, one can gain immense health benefit from this unique nutrient.