Warning: math and chemistry discussion (with units!)
If you’ve been living under a rock, you’ve missed the new fad that vitamin D can solve all your health problems. Just keep taking more. But then occasionally we hear things about people like Gary Null taking too much (his supplement was off by a factor of ten).
So how much vitamin D should you take? Short answer, we don’t know. The problem is that the amount you take and the amount you absorb are different. But in general, a ball park estimate for Vitamin D would be (much handwaving here):
About (maybe) 100 IU for every 1-2 nmol/L in your blood.
So what’s the optimum dose for nmol/L of vitamin D in your blood? The cutoff is 20 nmol/L. Below that you’re deficient. To get that amount of vitamin D:
100 IU = 1 nmol/L (conservative here, because we don’t want deficiency)
Now, if your absorption is better, then you need less, but by the best standards we have, the current RDI from the U.S. government is not sufficient to maintain people at sufficient levels. So, they’re estimating that your dietary intake will be sufficient to make up the difference. But that’s not a safe assumption, because not everyone is sucking down quarts of milk these days. Or getting out into the sun to activate their vitamin D.
What about the upper range? Again, someone taking 100,000 IU of vitamin D is going to end up with theoretically 1,000 nmol/L in their blood. That’s what made Null sick. It’s way too much.
Somewhere between 30 nmol/L (3,000 IU daily) and 80 nmol/L (8,000 IU daily) have not been shown to kill you. But we also have scant evidence of any health benefits at that level. Until the advocates do the studies to show that this much vitamin D doesn’t just suppress your hormonal response, we’ve only got evidence for something less.
Oh, and before you send me comments about how your particular brand of exotic coral reef derived plankton Vitamin D is better/nontoxic, have a look at the abstract below.
I hope this was helpful. If you want to change your Vitamin D levels, please talk to your doctor. Don’t use a blog post to determine your health. That’s just loco.
- Mother’s Vitamin D Status and Childhood Obesity (smartypantsvitamins.com)
- High Vitamin D Levels Linked to Early Death (extremelongevity.net)
- Optimal Vitamin D Levels Can Significantly Reduce Heart Disease Risk in Adults Suffering from Metabolic Syndrome (smartypantsvitamins.com)
- Too much vitamin D can be as unhealthy as too little (eurekalert.org)
- Is too much vitamin D a health risk? Finding surprises researchers (examiner.com)
- Vitamin D (throughthepuzzle.com)
- The Sunshine Vitamin: Get Your Vitamin D (everydayhealth.com)
- Sunscreen Guide for the Summer – But Don’t Block Out The Vitamin D! (smartypantsvitamins.com)
- More Vitamin D Might Help Older People Stay Active (nlm.nih.gov)
- Vitamin D Fracture Risk Questioned in New Government Recommendations (inquisitr.com)