The Latest on Vitamin D supplements: Are They Too Much of a Good Thing?

Vitamin D has been all the rage the past few years – the latest in a long line of cure alls – and touted for its ability to fight cancer, heart disease, autoimmune disorders, and diabetes. Along with calcium, vitamin D has also been hailed for its ability to build strong bones. But a new report released today says megadoses of vitamin D are unnecessary and may actually be harmful to one’s health.

The independent, non-profit Institute of Medicine (IOM) reviewed nearly 1,000 published studies on vitamin D and calcium at the request of the U.S. and Canadian governments in order to determine how much of each supplement people were getting, how much was needed, and how much was simply too much.

The IOM’s fourteen-member panel of experts concluded that most Americans and Canadians get enough Vitamin D and calcium in their regular diets.

“For most people, taking extra calcium and vitamin D supplements is not indicated,” Dr. Clifford J. Rosen, a member of the panel and an osteoporosis expert at the Maine Medical Center Research Institute, told The New York Times.

The panel did not debate the benefits of vitamin D in maintaining healthy bones, what it concluded was that most children and adults up to age 70 need no more than 600 IUs – or international units – a day, and those over 70 need as much as 800 IUs.

The panel said that only group that actually may be getting too little calcium is adolescent girls. Older women, however, may take too much — putting them at risk for kidney stones. 

So why all the confusion? Isn’t this, like so many medical studies where one report trumps the next, reminiscent of Woody Allen’s particularly prescient scene in his sci-fi sendoff Sleeper? Allen plays Miles Monroe, a health food store owner who was cryogenically frozen in 1973 and wakes up 200 years later. Two doctors are discussing his case. It goes like this:

“Dr. Melik: This morning for breakfast he requested something called wheat germ, organic honey, and tiger’s milk.

Dr. Aragon: Oh, yes. Those are the charmed substances that some years ago were thought to contain life-preserving properties.

Dr. Melik: You mean there was no deep fat? No steak or cream pies, or, hot fudge?

Dr. Aragon: Those were thought to be unhealthy — precisely the opposite of what we now know to be true.”

All joking aside, in this latest round of what-was-thought-to-be-good- for-you-is-now-bad-for-you, it seems that lab test numbers are at least a partial culprit. Dr. Rosen told MSNBC that most testing labs now use too high a cutoff when they test vitamin D blood levels. That, of course, would contribute to more doctors prescribing more supplements. The report says 20-30 nanograms of vitamin D per millileter is adequate for bone health. Some labs now report less than 30 nanograms as a deficiency, which Dr. Rosen says would mean 80% of the population lacks the proper levels.

In recent years some doctors have been prescribing upwards of 2,000 IUs a day for patients, but now there’s evidence that points to an association between extremely high levels of vitamin D and kidney stones, as well as kidney and heart damage.

Dr. Michael Holick of Boston University and who discovered the active form of vitamin D forty years ago is still a proponent of high doses. “My recommendation is very simple,” he told NPR. “I don’t see any downside to increasing your vitamin D intake. When I’ve been recommending for the past decade that people take more than the [officially recommended] 200 units, there was a lot of skepticism. Now they’re recommending three times what they recommended in 1997.” Holick still believes people need at least 3,000 IUs a day, and takes that much himself.

Perhaps not surprisingly, the vitamin D supplement industry has been booming. The New York Times reports that “vitamin D supplement sales have soared, growing faster than those of any other supplement,” with sales rising 82% from 2008 to 2009, reaching $430 million. 

“Everyone was hoping vitamin D would be a kind of panacea,” Dr. Dennis Black, a professor of the epidemiology and biostatistics at the University of California, San Francisco, and a member of the review panel, told the Times. 

Dr. Rosen called the state of vitamin D testing “the wild, wid west” on, and said that he hoped that “with this report, we can at least temper people’s enthusiasm for just taking tons of supplements.”

For in the end, it’s all about proper nutrition, and a healthy lifestyle, isn’t it? Get out in the sun a little, enjoy the outdoors, and eat well.

And for the record, here are a few ways to be sure you’re getting adequate vitamin D:

  • Sunlight is the best source of vitamin D – experts recommend exposure without sunscreen, varying from a minimum of 5 minutes for people with pale skin, to 15-20 minutes for people of color
  • A cup of D-fortified milk, soy milk, or orange juice contains about 100 IUs
  • A 3-ounce serving of canned tuna contains about 200 IUs
  • A 3.5-ounce serving of salmon contains about 360 IUs
  • An egg contains about 211 IUs
  • Other good sources are D-fortified cereals, mushrooms, and shrimp




Photo of calcium and vitamin D supplements by ragesoss


Warren Webber
Warren Webber6 years ago

Except for love, too much of anything can be a bad thing.

Sarah C.
Sarah C6 years ago

Vit D and Calcium supplements are basically unrelated, except in that we find them both fortifying certain foods.
We already know taking Calcium supplements has been proven ultimately inefffective. It can only be truly absorbed through natural food sources. (Absorption of Calcium & many other vitamins and minerals are aided by the simultaneous presence of Vit C. & the absence of caffeine).

Vitamin D (not technically a vitamin, but a steroid) is naturally produced by the skin when we are exposed to intense ultraviolet light (noontime summer sun) but we can't tolerate much of that without putting ourselves at risk, PLUS clothing blocks this effect from ever occurring.

Supplemental Vitamin D IS effective, but finding the "right" amount has been difficult. Too little and we get rickets and bone frailty among other things, and Overdose can be permanently harmful to our kidneys. We need further research into how much is appropriate, the Daily recommended values are only JUST enough for most people. Thorough testing has not yet been completed. The benefits could be much greater than merely staving off Rickets.

Vitamin D toxicity can occur when using large amounts ingested over time, but doesn't normally occur from sunlight exposure, since the excess D, that is not absorbed through the skin, degrades. But due to harsher and harsher unfiltered UV rays hitting Earth, this method will continue to become riskier as the ozone layer is slowly but surely destroyed.

Ayla M.
Ayla Meurer7 years ago

I have found an amazing difference in my health by taking vitaminD. I have not had a cold for the last 2 years let alone the pneumonia I was getting every year since taking vitamin D. Please know how amazing the health benefits are if you take vitamin D and except for vitamin A or iron your system will just slough off any extra so too much is not a valid health concern.

Jenny S.
J Stergiou7 years ago

Thanks for this! It's an issue that I've been concerned about lately.

jane richmond
jane richmond7 years ago


Amber M.
Amber Beasley7 years ago

if you go outside in the sunshine a lot, you won't hardly need to take and Vitamin D at all, you'll be getting it right there.

Eco Warriors SOS Rainfore

Thanks for the article.

Cat Neshine
Cat N7 years ago

People IBD need and should take, higher doses of Vitamin D than those with normal intestinal function.

Sharon Balloch
Sharon Balloch7 years ago

Mushrooms folks.. natural and no dead animals in them.. and they grow everywhere. But then us vegans have few choices.. but its an awful tasty choice.. in a salad.. yummy.

patricia m lasek
patricia lasek7 years ago

What are we supposed to believe?