Vitamin D, Or: You're Not Getting Enough Sun

Over the past few months I’ve been hearing more and more about vitamin D deficiency.  Then a few weeks ago Steve Gibson, the guy who does the Security Now podcast, took a rare diversion from security to talk about vitamin D (podcast here).  He created a page about vitamin D explaining everything and citing all the research he’s read, and that page also links to some good videos on the topic: a 90-second video focused on cancer; another 90-second video on cancer and sun exposure; a 6-minute video on vitamin D’s effect on general health (money quote: people who take sufficient vitamin D supplements just don’t get sick anymore); and finally a 1-hour video full of tons of vitamin D science.

Certainly watch the 2-3 shorter videos, and watch the longer one if you have time.  But the bottom line is this: many and probably most people are vitamin D deficient, especially in the winter months; and vitamin D deficiency is linked to not only many forms of cancer but also autism, bone diseases, tuberculosis, psoriasis, and many other diseases.  And in particular, vitamin D deficiency during pregnancy and after birth can cause lots of problems for babies, most famously the disease rickets.

Crucially, vitamin D is not actually a vitamin at all; it’s a hormone.  So it’s impossible to get a sufficient amount of vitamin D from your diet, unlike most real vitamins.  The only way to get sufficient vitamin D is from the sun, or via supplement -- but a multivitamin will not give you nearly enough.  For example, in milk that’s fortified with vitamin D, and in most multivitamins, there’s only a few hundred IU of vitamin D, whereas 10-20 minutes of noontime sun exposure will cause your body to create around 10,000 IU of vitamin D.

The problem is that in recent decades, due to the problem of skin cancer caused by overexposure to the sun, we have massively overcorrected, with the scientific, medical, and governmental guidelines generally recommending that we avoid the sun entirely, never being exposed to it without sunblock.  But since sunblock blocks virtually all UVB, your body doesn’t make any vitamin D when you’re covered in sunblock.

The solution is to get a moderate amount of noontime sunlight on a daily basis.  As mentioned above, just 10-20 minutes will boost vitamin D levels into the healthy range, and will not give you a sunburn.  It must be within about 2 hours of solar noon though -- which is 1 PM in the northern hemisphere -- because outside that range, the sun’s angle in the sky forces it to travel through much more atmosphere, which totally blocks UVB outside of about 10AM-4PM.  That’s also the reason it’s much harder to get a sunburn except within a couple hours of solar noon.

But during the winter, unless you live very close to the equator, the sun’s angle again prevents it from delivering enough UVB to generate healthy amounts of vitamin D in your skin.  Because of this, and because you can’t get sufficient vitamin D via diet, I plan to start taking a vitamin D supplement soon; Steve Gibson’s vitamin D page has his recommendations about halfway down the page, and in terms of dosage it appears that 2000 IU/day is a good amount.  And that’s about an order of magnitude below the level at which toxicity begins to become an issue.

This topic fascinates me partly because of its obviousness: for all of human history we’ve been exposed to at least some sun nearly every day, so the idea that we should now suddenly start avoiding it altogether is just insane.  It appears that we’re now suffering many unintended consequences of that advice.  There are lots of interesting statistics in the videos above, but one that sticks out to me is that, for some forms of cancer, vitamin D deficiency causes a doubled risk of metastases and a 75% increased risk of mortality.

Posted by Anthony on 9 replies


01. Sep 4, 2009 at 02:51pm by Mom:

This is quite interesting and makes sense.  Of course the exception to the rule is Dad.  He worked 36 years in the sunlight 6 days a week in his roofing and siding business; never, ever used sunscreen (that was for sissies); develops kidney cancer (probably from smoking) and it metastasizes to his spine.  I know nothing works out exactly as research states.  So I agree, the Rx for this is to get to the beach early and often!

02. Sep 4, 2009 at 05:02pm by Anthony:

Yeah, dad almost certainly was not D-deficient during all those summers working on roofs -- although it’s also true that the tanning of your skin is a defensive response which serves to limit further UVB absorption.  And it’s likely that the smoking and the continuous exposure to petrochemicals in roofing tar were the primary causes of his cancer.  But it seems likely that now he would be D-deficient, and it’s probably worthwhile to ask the doctors to check his D levels on his next blood test.

03. Sep 9, 2009 at 01:43pm by Tasha:

I’ve been hearing a lot about this on the news lately.  I definitely get the winter ’blues’ and have heard that there are some kind of light box type things that are available that will help supplement vitamin D in the winter.

04. Sep 10, 2009 at 12:29am by Anthony:

I guess that’d be similar to a tanning bed in its effect.  I’ve never used a tanning bed and I don’t think I ever would; that seems more risky and scary to me than taking a dietary supplement.

05. Oct 2, 2009 at 05:22am by Anthony:

A New York Times article from last week on vitamin D:

A growing body of research suggests that [Vitamin D]’s vital in multiple different bodily functions, including allowing body cells to utilize calcium (which is essential for cell metabolism), muscle fibers to develop and grow normally, and the immune system to function properly.  "Almost every cell in the body has receptors" for Vitamin D, Anderson says.  "It can up-regulate and down-regulate hundreds, maybe even thousands of genes," Larson-Meyer says.  "We’re only at the start of understanding how important it is." [...]


A major study published online in the journal Pediatrics last month concluded that more than 60 percent of American children, or almost 51 million kids, have "insufficient" levels of Vitamin D and another 9 percent, or 7.6 million children, are clinically "deficient," a serious condition.  Cases of childhood rickets, a bone disease caused by lack of Vitamin D, have been rising in the U.S. in recent years.

Here’s more from a long and detailed Scientific American article from November 2007:

Extensive evidence now shows that D has potent anticancer actions and also serves as an important regulator of immune system responses.  Moreover, many of D’s newly recognized benefits are maximized when it is present in the bloodstream at levels considerably higher than those found in many populations.  These findings, together with epidemiological data linking low vitamin D levels to disease, support the possibility that widespread vitamin D deficiency is contributing to a number of serious illnesses.


After reviewing multiple studies comparing vitamin D intake and the serum concentrations of 25D produced, Harvard School of Public Health researchers and others concluded last year that the current [Recommended Daily Intakes] are inadequate.  They suggested that no less than half of U.S. adults needed to consume at least 1,000 IU of vitamin D3 daily to raise their serum 25D concentrations to the minimum healthy level of 30 ng/ml.  No rule of thumb exists for calculating the serum 25D levels generated by supplements, because individual responses can vary and may depend in part on the extent of deficiency.  A study of pregnant women showed, for example, that daily doses of 6,400 IU raised serum 25D levels dramatically until they reached about 40 ng/ml and then leveled off.

From the Vitamin D Council:

Healthy children under the age of 2 years should take 1,000 IU per day -- over the age of 2, 2,000 IU per day.  Well adults and adolescents should take 5,000 IU per day. ... But remember, these are conservative dosage recommendations.  Most people who avoid the sun -- and virtually all dark-skinned people -- will have to increase their dose once they find their blood level is still low, even after two months of the above dosage, especially in the winter.

I ordered a pack of 2000 IU Vitamin D3 capsules from a few weeks ago, and have been taking them daily.  But I’ve been continuing to research (and come across news about) vitamin D, and I’m seeing more and more statements saying that less than 5000 IU is probably not sufficient for adults.  Considering that your body makes ~10,000 IU from ~15 minutes in the sun during the summer, 2000 IU does seem low.  So I just ordered a pack of 5000 IU capsules that I’ll take instead.  They’re dirt cheap: around $7 for a half-year’s supply.  Ironically, that’s apparently part of the problem: "vitamin" D is such an old and well-known substance that drug companies can’t patent it, so they have little incentive to spend the vast amounts of money and time required to do research and trials related to vitamin D.

06. Oct 21, 2009 at 09:52pm by Anthony:

Quoting Susan Male-Smith for ABC 13 in Houston:

An alarming three out of four Americans are seriously short of vitamin D, according to the results of a recent study conducted at the University of Colorado. [...]

Researchers have found that insufficient vitamin D has serious, far-reaching ramifications, including: Higher rates of cancer ... Increased risk of heart disease and diabetes ... More colds and flu ... a host of maladies, including pregnancy-related complications, Parkinson’s disease, multiple sclerosis, arthritis and even dementia. [...]

While the recommended dietary allowance (RDA) is still 400 international units (IU) of vitamin D per day, nearly every expert will tell you that’s simply not enough, and you can bet the RDA will change next year when a government panel weighs in.  "Most Americans need at least 1,000 IU a day," says [lead researcher Adit Ginde, M.D.], "and many require even higher doses." [...]

Michael Holick, M.D., Ph.D., director of the Vitamin D Laboratory at Boston University, recommends 1,000 to 2,000 IU daily, especially in the fall, winter and spring.  And don’t worry about getting too much; one study found that 10,000 IU a day is safe, even when taken for a year.

07. May 20, 2010 at 07:54pm by Pennie:

At the latitude of Seattle, the recommendation for vitamin D is 5000 IU a day, more for treating various deficiency diseases.  I am on 20,000 IU per day for blood sugar control.

08. Apr 13, 2013 at 01:12pm by colleen:

some one has mentioned to me that due to the "tilt" of the sun in Colorado, it is difficult to absorb or make any vitamin D (even though we are closer to the sun in Colorado) is there any truth to this????


09. Apr 13, 2013 at 05:14pm by Anthony:

Not quite.  It’s the Earth that’s tilted, not the sun.  The Earth’s tilt is the reason that we have seasons: more sunlight reaches the surface of the Earth (warming it up more) in your location during the half of the year when your hemisphere is tilted towards the sun (i.e. the summer), and conversely when your hemisphere is tilted away that’s winter because less sunlight reaches the surface.

But regardless of all that: anytime you can get a suntan or a sunburn, you can make vitamin D.  It’s UV light that causes both tans/burns and vitamin D production.

Reply to this message here:

Your name
Website (optional)

HomeCreate PostArchivesLoginCMS by Encodable ]