Wednesday, February 4, 2009

Vitamin D & other vitamins

I'm re-posting this as a separate entry, because I think it's important.

I recommend multivitamin supplements as standard advice, because I think there is negligible evidence of risk (other than the effect on your wallet), and potential benefit.

The role of vitamin supplements ought not to be overvalued -- I think they are unlikely to cause a pronounced change in any symptom. But a vitamin deficiency could possibly prevent other treatments for depression from working optimally. Many people with psychiatric symptoms have less than optimal nutrition, for various reasons; therefore I feel that vitamin and mineral deficiencies are more likely.

There is some evidence of vitamin supplements being used to augment antidepressant medications, but the level of evidence is quite weak.

Vitamin D in particular is probably important to supplement, particularly for those of us who experience dark, cold northerly winters (vitamin D is normally produced in the body when our skin is exposed to the ultraviolet rays from direct sunlight). Furthermore, most of us wisely use sunscreen when it is sunny and warm, so most of us are getting less vitamin D from the sun. There is some evidence that the RDA for vitamin D (200-400 IU per day) is too low, particularly when we consider that brief whole-body skin exposure to sunlight generates an equivalent of perhaps 10 000 IU.

Here is a reference to a very interesting and promising recent study suggesting beneficial mood effects from higher-dose vitamin D supplementation (people received the equivalent of about 3000-6000 IU per day, for a whole year); the study is from a major, highly respected internal medicine journal:
Here is an excellent reference examining the issue of vitamin D safety, dosage, and toxicity:

Vieth, Reinhold. "Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety", American Journal of Clinical Nutrition 1999;69:842–56

A recent study by Bischoff-Ferrari et al. (2009) showed that elderly hip fracture patients given 2000 IU per day of vitamin D for 12 months, had a 60% reduction in fall-related injuries and a 90% reduction in infections leading to hospitalization, compared to a group given only 800 IU per day of vitamin D.

Here's a reference to a 2008 study from a clinical biochemistry journal showing toxicity from prolonged very high-dose vitamin D, of over 40 000 IU/day over several years. It concludes that the lowest dose at which hypercalcemia can occur is about 3800 IU per day:

Based on the evidence I recommend supplementing with an extra 2000 IU of vitamin D daily (possibly up to 3000 IU), in addition to the 400 IU that is present in most vitamin supplements, unless you have a medical condition associated with abnormal calcium metabolism or abnormal sensitivity to vitamin D (e.g. sarcoidosis).

If you are taking high-dose vitamin D you should have serum calcium levels checked periodically, and possibly a serum vitamin D level.

I do not recommend "mega doses" of any other vitamin, since I do not see a good evidence base for this being helpful, and higher doses of many such nutrients can be toxic or dangerous. A few recent studies have shown that people taking certain vitamin supplements, such as vitamin A or E, actually do more poorly than the control group.


Anonymous said...

Waiting for the full report.

New DRIs for Vitamin D by IOM.

GK said...

I suspect the content of this report makes a very conservative interpretation of existing evidence, which is understandable given that it is meant to be advice for the entire population. I do think that higher dose vitamin D, in the 1000-3000 IU per day, presents negligible risk of toxicity (see references in this post), and some promise of various positive health effects, including mood benefits. Because so many treatments for mood problems carry a less favourable risk:benefit ratio, simple nutrient supplementation, such as with vitamin D, could be considered a very simple, convenient, and safe augmentation.

Anonymous said...

I'm curious as to your thoughts on "megadoses" of Vitamin B12. I had always thought that it was difficult to become deficient in this vitamin, especially because the RDA for this vitamin is so small. However, I've been reading up on vegan/vegetarian nutrition because I'm trying to avoid most animal products, and everything I've read so far seems to suggest that it is very possible for vegans/vegetarians to become deficient in this vitamin, even while taking a supplement. For example, several well-respected vegan dietitians are recommending that vegans take up to 100 mcg of Vitamin B12 daily (one recommendation said to aim for at least 25 mcg/day; or to take 1000 mcg 2-3 times a week) in order to ensure that a deficiency does not develop. This seems much higher than the RDI (which I think is under 3 mcg/day). It seems that this is a kind of "megadosing", at least if the RDA really is 3 mcg.

I've noticed that every vegetarian multivtamin that I've seen provides at least 50 mcg of Vitamin B12; some sublingual Vitamin B12 tablets that I purchased were for 1000 mcg, and the recommended dosage was 1 tablet/day. I doubt that many dietitians/physicians would recommend taking 1000 mcg/day unless there was a pre-existing deficiency, but it does seem strange to me that the typical recommendations for vegans are so much higher than they are for everyone else.