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How Much Vitamin D is Safe to Take for People with Multiple Sclerosis?

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Updated June 26, 2014

Many experts are convinced that there is a strong link between vitamin D and multiple sclerosis (MS), especially in terms of being a risk factor for developing MS.

One of the most compelling "clues" in this connection is the geographic distribution of MS. MS is much more prevalent in the northern latitudes, where there is less intense sunlight and colder weather, meaning that people get much less exposure to the sun (our bodies produce vitamin D from exposure to the ultraviolet B rays in the sun).

Studies have shown that vitamin D may not only play a role in who gets MS, but have some impact on how MS progresses; it may also reduce reducing relapses. There is also very solid evidence that vitamin D, especially when taken with calcium, can help prevent osteoporosis, which is more common in people with MS.

That is all wonderful news and I look forward to seeing many rigorous studies on the role of vitamin D in MS, as most of the studies done so far were done on mice.

However, I also frequently run across pieces of anecdotal evidence about how much vitamin D has helped people who have already been diagnosed with MS, which is particularly interesting to those of us for whom it is too late to prevent MS, as we already have it. I get statements such as these in my blog comments all the time:

"Several individuals I know are taking high doses (6,000-10,000 IU per day) of Vitamin D3 as part of their MD-regulated treatment regimen and claim that their disease has not progressed for several years."

"My neurologist has me taking 50,000 units once a week. I have not felt so well in years. Especially noticed that painful muscle spasms are mostly twitches now!"

"I started taking 10,000 units of vitamin D3 weeks ago. I feel wonderful. For the first time in 8 years, I can make it through the day without sleeping."

How Much Vitamin D is Safe for People with MS?

There are several theories about why vitamin D may be so beneficial for people with MS, as well as people with other disorders, which are beyond the scope of this article. I also am not going to cover what the "ideal dose" might be, as this depends on each person taking the vitamin D (what their plasma levels are, how they metabolize it, and what the goal levels are), as well as their doctor's approach to vitamin D supplementation (whether your doc wants to be aggressive and achieve certain plasma levels of vitamin D, whether he just wants you to take a regular supplement of a certain dose, or whether she really does not want to deal with the vitamin D question at all).

What I really wanted to find out (then tell you) is how much vitamin D is safe to take in supplement form, before it starts becoming toxic, a condition called "hypervitaminosis D."

I thought this would be a matter of looking in a couple of sources and typing out a quick little answer that everyone agreed upon. However, much like many things surrounding MS, there is plenty of controversy in the world of vitamin D supplementation.

Here is what a couple of sources say:

  • Reference Daily Intake (RDI): Formerly called the "Recommended Daily Allowance" or "RDA," this is what is used to determine the Daily Value on food and supplement labels. This value is determined by the Food and Drug Association (FDA) and is defined as is defined as "the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (approximately 98 percent) healthy individuals." This was my starting point, just for reference. The RDI of vitamin D is 400 IU per day. Many scientists are calling for this to be increased to 1,000 IU/day.
  • MedlinePlus: The website run by the National Institutes of Health says that, "Taking vitamin D for long periods of time in doses higher than 50 mcg (2000 units) per day is POSSIBLY UNSAFE and may cause excessively high levels of calcium in the blood. However, much higher doses are often needed for the short-term treatment of vitamin D deficiency. This type of treatment should be done under the supervision of a healthcare provider."
  • The limit set by the National Academy of Sciences in 1997 is 2,000 IU/day. However, the doses mentioned above are extremely conservative, according to studies that have looked at serum/plasma levels (the amount of vitamin D circulating in the blood). Since we all metabolize vitamin D differently, it is hard to pinpoint an exact dose that everyone should take to achieve and maintain a healthy level of vitamin D.

To confuse matters further, some experts say that toxicity occurs at blood levels over 220 nmol/L, while others insist that there are no reported cases of vitamin D toxicity until levels exceed 500 nmol/L. Most of the scientific studies on vitamin D toxicity are done in mice, anyway, so extrapolation is difficult.

Before I tell you which dosages could lead to plasma levels like this and, therefore are too dangerous, I will say this -- high-dose (more than 2,000 IU/day) vitamin D supplementation should only be done under the supervision of a doctor, preferably one who uses blood tests to monitor progress.

Here is the best that I can do, in terms of getting the facts about dosing to you: According to UpToDate, "some reports indicate that most cases of toxicity involve an intake of 25,000-60,000 IU daily for 1-4 months." Other sources suggest that anything above 10,000 IU daily is not advisable, as the potential for toxicity, although low at this dose, outweighs the benefits that one can expect from such a dose. It is pretty difficult to have an acute overdose of vitamin D, as even very high doses (exceeding 600,000 IU) still need to be taken over several days for blood levels to get high enough for toxicity.

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