How Much Vitamin D Should You Take?

Randomized, controlled clinical trials have found that vitamin D supplements extend one’s lifespan. What is the optimal dose? What blood level is associated with living longest? In my nine-part video series on vitamin D back in 2011, I noted that the relationship between vitamin D levels and mortality appeared to be a U-shaped curve—meaning low vitamin D levels were associated with increased mortality. But so were levels that were too high, with the apparent sweet spot around 75 or 80 nanomoles per liter [nmol/L], based on individual studies like this one.

Why might higher D levels be associated with higher risk? Well, this was a population study; so, you can’t be sure which came first. Maybe the vitamin D led to higher risk. Or maybe higher risk led to the vitamin D, meaning maybe those who weren’t doing as well were prescribed vitamin D. Maybe it’s because these were Scandinavian studies, where they tend to take a lot of cod liver oil as the vitamin D supplement, one spoonful of which could exceed the tolerable upper daily limit of intake for vitamin A—which could have negative consequences, even if you don’t inject it into your penis.

I was surprised to see cod liver oil listed among the long list of things men have tried to inject into themselves because they felt they were coming up short, though may have ended up shorter after all the reconstructive surgery.

Anyways, the U-shaped curve is old data. An updated meta-analysis has shown that as population vitamin D levels go up, mortality appears to go down, and stay down—which is good, because then we don’t have to test to see if we’re hitting just the right level.

Routine testing of vitamin D levels is not recommended. Why? Well, it costs money, and in most people, levels come right up to where you want them with sufficient sun, or supplementation. So, they figure what’s the point?

But also because the test is not very good—results can be all over the place. What happens when you send a single sample to a thousand different labs around the world? You maybe expect a little variation, but not this. Results from the same sample ranged anywhere from less than 20 to over 100. So, depending on what lab your doctor sent your blood sample to, the results could have placed you here, or here; so, not necessarily very helpful.

So, what’s a safe dose that will likely get us to the purported optimal level? 1,000 units a day should get most people up to the target 75 nmol/L (which is 30 ng/mL).

But by most people, they mean 50%. To get around 85% of the population up to 75 would require 2,000 a day. 2,000 international units a day would shift the curve from here to here. That way, we can take the average person into the desired range without fear of toxicity. You can take too much vitamin D, but you don’t tend to see problems until blood levels get up around 250, which would take consistent daily doses in excess of 10,000.

Note that if you’re overweight, you may want to take 3,000, or if obese, even more than that. If you’re over age 70, and not getting enough sun, it may take 3,500 units to get that same 85% chance of bumping your levels past the target. Again, no need for the average person to test and retest, since a few thousand a day should bring almost everyone up without risking toxicity.

Okay, but then why did the Institute of Medicine set the Recommended Daily Allowance at 600 to 800 units? In fact, official recommendations are all over the map—ranging from just 200 a day, all the way up to 10,000 a day. I’ll try to cut through the confusion, next.

In health,
Michael Greger, M.D.

Michael Greger, M.D., is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous “meat defamation” trial. Currently Dr. Greger proudly serves as the Director of Public Health and Animal Agriculture at the Humane Society of the United

The Latest on Vitamin D and Breast Cancer

Lastest Research on Vitamin D and Breast CancerBy: Rachel Pappas, Breast Cancer Survivor and Founder of

The link between Vitamin D deficiency, breast cancer, and breast cancer recurrence is not new. But now Vitamin D has actually been shown to kill breast cancer cells.

I was so intrigued by what I read, I had to get on the phone with the clinical investigator myself, especially since I, and most of the women I know with breast cancer have a Vitamin D deficiency, and I hear it more and more.

JoEllen Welsh, PhD, a professor at GenNYsis Center for Excellence in Cancer Genomics in Albany, NY, has studied Vitamin D and breast cancer for 30 years, but for the first time, has incubated fresh human samples with Vitamin D. She took samples of early and late stage tumors, those with and without receptors for estrogen, progesterone, and HER2.

“Within days, half the cells shriveled and died in every tumor,” she said.

“Eighty percent of people have a vitamin D receptor, and if they have a tumor with this receptor it has potential to respond to Vitamin D, just as estrogen-positive breast cancer responds to tamoxifen,” says Welsh.

Vitamin D actually becomes a hormone in the body, meaning it is transmitted through the blood to any and or all tissue.

Five human samples were tested, reflecting the following types and stages of breast cancer:

  • Stage IIIC ER and PR Negative
  • Stage IIIA HER2 Negative
  • Stage I ER and HER2 Negative
  • Stage IIA ER PR and HER Positive
  • Stage IIIC Triple Negative

What next?

Currently Welsh is doing genetic engineering in mice to understand the mechanisms that trigger a response.

“For example, we need to look at what levels you need? Is there a difference in how it works on triple negative breast cancer? Does it work in the presence of tamoxifen? What if the tumor has a BRCA mutation? Answering these questions is how we can predict who is most likely to benefit from optimal Vitamin D status,” says Welsh.

Caution: If you have breast cancer, you shouldn’t take vitamin D in place of your treatment medications. Talk to your physician for more advice about taking supplements.

Founder of  1UpOnCancer.ComRachel Pappas is breast cancer survivor. She is the founder of And the author of Hopping Roller Coasters, which tells the story of her and her daughter, both diagnosed with bipolar disorder.


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