Recently a post on “Precision Nutrition” talked about the dangers of high dose vitamin D supplementation. I wanted to address the post and talk about some of the risk factors that are mentioned. At the bottom of this post, I’ll talk about what my SPECIFIC recommendations are.
Lets look at the arguments made by the precision nutrition author:
1) High dose Vitamin D3 in rodents is a toxin. The problem I have with this argument is that the amount they give the rats is about 10-20x what a person would actually supplement with. Also, there’s no discussion about whether the biologics of rodent vitamin D metabolism mimic humans. Considering that they are nocturnal animals, the biology could certainly be different…
That said, lets say that based upon these results, you shouldn’t be taking extreme levels of vitamin D (above 30000 IU/day).
2) The Vitamin K/Calcium axis. This is actually a really important point that many people overlook. If you have a vitamin K issue, then high dose vitamin D could actually be a big problem. The problem I have is that the author goes on to basically state that if you’re vitamin K deficient you shouldn’t take vitamin D. Personally, if I was deficient in vitamin K, I’d fix my levels of vitamin K and not avoid taking vitamin D completely. This is like saying, well my car is low on oil so I stopped putting gas in the car to prevent it from overheating. Should people low in vitamin K avoid the sun?
I’ve looked and while some blogs like to say that vitamin K deficiency is common, the evidence out there to support this is pretty weak. You cannot just base levels off of food intake because vitamin K2 metabolism is tied to the microbiome. Nevertheless, if you are consuming leafy green vegetables, then you should be fine outside of rare genetic diseases. This leafy green vegetable thing is about to get very repetitive.
3) Magnesium: You’ll notice that in my supplements page, I list a magnesium supplement. Also, the same leafy green veggies I listed above are also really high in magnesium. I think the authors point is a good one, but again, I think the take home message should be to get your other nutrient levels to appropriate levels and NOT to avoid vitamin D if you are showing signs of deficiency.
4) Vitamin A: So vitamin A deficiency is a real problem but mostly in third world countries. In the United States, you’d be shocked at just how many foods are fortified with Vitamin A. As a result, people here are typically not vitamin A deficient. Now, if you eat an all natural organic diet, you aren’t getting any of those FORTIFIED vitamin A fortified foods of course, but the good news is that leafy green vegetables, grass fed beef and many other paleo-type foods which you are likely eating have TONS of vitamin A.
Now, there are in fact some really interesting new observations about vitamin D levels and health. One of these is a study with over 1 million people showing that the lowest mortality from a multitude of causes correlated with vitamin 25D levels between 20 ng/mL and 36 ng/mL. That’s somewhat surprising because the medical community says that the LOWEST your levels should be is about 30 ng/ml and that your better off with levels closer to 50 ng/ml. Interestingly, there are a couple other studies showing just the same thing… that optimal levels are around 30-35 ng/ml.
Now, there are a couple things to remember.
1) This data says that A correlates with B, not that A causes B… very important difference.
2) It does not mean that we should be avoiding vitamin D supplements, just that perhaps we don’t need to be driving levels so high by supplementing like crazy with 10000-50000 IU or more. Doctors are DEFINITELY doing this in some patients for 4-5 weeks. Not sure I’d want that much…
Ultimately, my recommendation is still pretty much the same as before.
1) GET IN THE SUN when possible. The body is (for the most part) capable of limiting its vitamin D levels much better when we use sunlight as our source.
2) If you live in the middle of winter for 6 months, I still think some supplementation is a good idea. 1000 IU/day is probably still pretty safe but I also would advise having your levels checked annually to make sure you’re in that ~ 35 ng/ml range.
3) You’ve GOT to be eating green vegetables for reasons that go way beyond anything to do with vitamin D, but also to mitigate any potential risks with the vitamin D supplementation.
Hope this helps.