Just How Important Is Vitamin D?
Today, we’re going to discuss vitamin D and its importance in the body.
What Is Vitamin D?
Vitamin D is a fat-soluble vitamin. Because the body can create its own vitamin D, it is technically not a vitamin, but a pro-hormone, a precursor to the hormones the body needs to function. Vitamin D has no active role in the body other than to be converted to usable hormones by the liver and kidneys.
This vitamin (we’ll stick with vitamin since that’s how it’s known commonly) is responsible for maintaining blood levels of calcium and phosphorus, growing bone, and shoring up the immune system. Let’s have a look at a few of the issues that are caused by a vitamin D deficiency.
What If I Don’t Get Enough Vitamin D?
Extreme deficiency of vitamin D during childhood results in a disease known as rickets. However, the importance of vitamin D in bone health doesn’t end in childhood. In adulthood, the bone softening diseases osteomalacia and osteoporosis have been associated with low vitamin D status. In fact, the Nurse’s Health Study found that vitamin D did more for bone health than did calcium.
But aside from the bones, how does vitamin D protect your health? Well, for starters, it appears to protect the brain against both Parkinson’s and Alzheimer’s.
These data support a possible role of vitamin D insufficiency in PD [Parkinson's Disease]. Further studies are needed to determine the factors contributing to these differences and elucidate the potential role of vitamin D in pathogenesis and clinical course of PD.
The results showed that vitamin D elicited a two-fold increase in nerve growth factor mRNA in both the hippocampus and cortex, suggesting a possible role in the treatment of neurodegenerative disorders such as Alzheimer’s disease.
It looks like it also helps protect against some skin infections:
A study led by researchers at the University of California, San Diego School of Medicine suggests that use of oral Vitamin D supplements bolsters production of a protective chemical normally found in the skin, and may help prevent skin infections that are a common result of atopic dermatitis, the most common form of eczema.
Rheumatoid Arthritis? Yeah, it handles that too.
Both dietary and supplemental vitamin D intake were inversely linked with rheumatoid arthritis risk, the authors found. High dietary (at least 290 IU/day) and supplemental (at least 400 IU/day) intake were associated with 28 percent and 34 percent reductions, respectively, in the risk of rheumatoid arthritis.
How’s this for irony? Vitamin D protects against skin cancer.
The results of the current study demonstrate that much of the geographic variation in cancer mortality rates in the U.S. can be attributed to variations in solar UV-B radiation exposure. Thus, many lives could be extended through increased careful exposure to solar UV-B radiation and more safely, vitamin D3 supplementation, especially in nonsummer months.
And here’s an interesting finding: Vitamin D may be protective against radiation.
Writing in the International Journal of Low Radiation, Hayes explains that calcitriol, the active form of vitamin D, may protect us from background radiation and could be used as a safe protective agent before or after a low-level nuclear incident.
This is all just the tip of the iceberg too. Congestive heart failure, numerous cancers, Multiple Sclerosis, Type I Diabetes, and high blood pressure have also been linked to low levels of vitamin D.
Where Can I Find Vitamin D?
For humans, there are two ways of getting vitamin D. The body can create vitamin D in the skin when it is hit with UVB radiation. Or the body can get vitamin D from dietary sources. Ultimately however, all vitamin D in the food-chain begins with some action of an organism with sunlight. So obviously, the first place you can turn to get some vitamin D action going on is the source of the UVB rays that help the plant and animal kingdoms make the vitamin in the first place. A little sunlight isn’t going to cause skin cancer. Recall above that vitamin D deficiency actually predisposes one to skin cancer. Of course, that’s not freedom to go sunbathe for hours on end.
Dietary Vitamin D Sources
So if you are either scared of the sun or live much above the sub-tropical zones, it’s going to be hard to get enough vitamin D from the sun. Luckily, there are some rich sources of the vitamin that fit perfectly into a lifestyle of eating real foods.
- Cod liver oil – 1tsp, 450IU
- Salmon, cooked, 3 1/2 oz: 360 IU
- Mackerel, cooked, 3 1/2 oz: 345 IU
- Sardines, canned in oil, drained, 3 1/2 oz: 270 IU
- Pork lard, 1 tbsp – 140IU
- Beef Liver, cooked, 3.5oz – 30IU
- Whole Egg – 25IU
An important thing to note on the fish though is that farmed fish is less likely to have those levels of vitamin D. Wild fish live on algae and other fish, which at the base of the food chain live on algae. Farmed fish live on grains and other such unnatural food.
Of course, I don’t typically advocate focusing on a single vitamin at the expense of others, and this one is no exception. But if you’re eating real foods and getting some sunlight in your life, you probably have little to worry about. Notice that a single teaspoon of cod liver oil gets you the recommended amount of vitamin D for two days. So it’s really not that hard to meet your vitamin needs when you eat foods that are naturally rich in vitamins.
How Much Vitamin D Do I Need?
There is technically no RDA for vitamin D as there is insufficient evidence to establish one. However, there are guidelines to give an Adequate Intake. They are:
- Ages 19-50: 200 International Units (IU)
- Ages 51-69: 400 IU
- Age 70 and older: 600 IU
It’s theoretically possible to overdose on vitamin D, but with natural sources of the vitamin, it’s unlikely. In the winter months, adding a teaspoon of cod liver oil to your diet can ensure that your sunless existence doesn’t lower your vitamin D intake.
EDIT: I want to add more information about optimal vitamin D intake. The above amounts are basically the RDA, which we all know are extreme low-level amounts to merely avoid gross deficiency. Much, much higher amounts can be taken to ensure vitamin D status is maintained at a sufficient level.
In his post How Much Vitamin D Should I Take?, Dr. William Davis recommends a blood level of D3 of 60-70 ng/ml and recommends getting as much D3 as is required to achieve such a level. That means getting out in the sun and letting the body make its own vitamin D as it is designed to do. Of course, to understand your current vitamin D level, you must have an inexpensive test run by your doctor. Here is part of Anna’s comment below to help you understand what test to get:
The test for the amount of Vit D3 stored in the body is called 25 (OH) D. It is increasingly common to have it ordered by primary care physicians (not the 1,25 (OH) D test; it isn’t the right level to test. Even if your doctor doesn’t offer Vit D testing, you may find they will order it without a problem if you ask; mine did. It’s a simple blood test.
Given all of the issues resulting from a lack of vitamin D, does it seem a good idea to slather every inch of your skin with sunscreen before walking to your car?
What are your main sources of vitamin D? Do you get unprotected sun exposure?
Table of contents for Understanding The Fat-Soluble Vitamins
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36 Reader Comments
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You are up on studies, so i’m curious why you havent’ linked the safety studies done by vieth et al (www.vitamindcouncil.org) showing that upper safe limits go as high as 10,000 i.us per day (the amount your body makes in the sun when given the right exposure), and most folks need way more than the reccomendations of 400 i.u. to meet all their vit D needs ( 400 will prevent rickets, but possibly not any of the other diseases you mention).
I urge all my clients to spend 20 min sunbathing at noon(full body) . If they wont or can’t, then 4000 i.u. via food, fish oil and supplements. the studies are showing that ou need at least 4000 i.u. a day to boost blood levels of 25hydroxy vitamin D.
The research on vit D has been extremely exciting in the past few years, and I suggest everyone read up on the new safety and reccomendations for vit D.
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Nice primer on “Vitamin D”, Scott. There is a plethora of information out there lately. Regarding Vit D activation by sunlight, Dr. William Davis at his blog has stated repeatedly that if you are over 40 years old, your ability to obtain Vit D from sunlight is severely muted. For more on Vitamin D and how much is enough, you might check out a couple of his posts here:
http://heartscanblog.blogspot.com/search/label/vitamin%20D
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Hey Scott,
Thanks for the post! This is a very cool reference guide to understanding Vitamin D and it’s importance in the body.
All the Best,
Andrew R
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Thanks for the bit about cod liver oil during winter months.
Right now I think eggs and pork and other animal fats (sorry, mammal friends) are probably the best sources of Vitamin D I get. I am okay with unprotected sun exposure–i believe sunscreen’s protective effect, at least for those getting less than an hour or so of sun, has been greatly overestimated, and that it prevents us from getting the beneficial effects of sun exposure–i think there is some research bearing this out.
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Check your cod liver oil label carefully. Many, if not most, brands of cod liver oil commonly sold in the US have some of the vitamin D removed, I guess to standardize the dose (which as a natural product, varies in amount). I understand that many companies may remove the natural vitamin D3 and replace with cheaper synthetic D2, I guess selling the more valuable natural vitamin in separate supplements.
D2 must be converted in the body in order to be used, so it is less efficient. Of course, D2 is what is added to industrial whole milk, so that may not be the best source of naturally bio-available D3. And of course, the foods that contain natural D3 are the same foods we are advised to limit consumption of: liver, butter, whole fat dairy, lard, tallow, bone marrow, etc.
Check out the Vitamin D Council, a non-profit group of researchers advocating more info on the benefits of Vit D, for more info. www dot vitamindcouncil dot org (remove the dot and spaces and replace with .)
And don’t assume that a sunny environment means adequate Vit D levels are a given. one needs to have an adequate supply of Vit D3 all summer long to ensure adquate tissue stores during the colder, short daylight months. Also, the higher the weight, the more Vit D3 is needed to maintain adequate levels.
Even though I live in So Cal, I’ve had levels tested twice (late summer without supplementation and mid-winter with supplementation) and was both times closer to the bottom of the reference range of 30-100 (ng/dL), no where near what is considered optimal (over 50 ng/dL).
I know three other women in the sunny San Diego area who have tested with truly deficient levels, in two cases despite a dark tan or plenty of weekend leisure time outdoors. Modern lifestyles of indoor living and indoor occupations, plus high rates of SPF sunscreen use (as well as the diminished consumption of outdoor-reared animal foods) makes Vit D3 inadequacy a real possibility anywhere in any season. I have a Seattle friend whose 25 (OH) D level was 17 ng/dL at the time of her diagnosis of breast cancer (breast and colon cancer, as well as other cancers, are strongly associated with low 25 (OH) D levels.
The test for the amount of Vit D3 stored in the body is called 25 (OH) D. It is increasingly common to have it ordered by primary care physicians (not the 1,25 (OH) D test; it isn’t the right level to test. Even if your doctor doesn’t offer Vit D testing, you may find they will order it without a problem if you ask; mine did. It’s a simple blood test.
And lastly, like most nutrients, Vit D3 does its job best when the other nutrients involved in the same processes are at adequate levels, such as Vit A, K2, etc. Not surprisingly, these fat-soluble vitamins are often found in the same foods, like liver from grassfed animals and wild fish, grass-fed butter, etc.
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Hi Scott,
Great article with the exception of recommended amounts to achieve therapeutic levels. Your recommendations are so low, it realistically cannot help anyone. Please read below…
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Dr. Bruce Hollis said in the Journal of Nutrition I Feb.2005 that “The current adult recommendations for vitamin D, 200–600 IU/d, are very inadequate when one considers that a 10–15 min whole-body exposure to peak summer sun will generate and release up to 20,000 IU vitamin D-3 into the circulation. We are now able to better identify sufficient circulating 25(OH)D levels through the use of specific biomarkers that appropriately increase or decrease with changes in 25(OH)D levels; these include intact parathyroid hormone, calcium absorption, and bone mineral density. Using these functional indicators, several studies have more accurately defined vitamin D deficiency as circulating levels of 25(OH)D less than 32 µg/L. Recent studies reveal that current dietary recommendations for adults are not sufficient to maintain circulating 25(OH)D levels at or above this level.â€
Recent evidence has shown that low vitamin D levels in forty years olds can increase the chances of dying by 26% in their next 8 years. To prevent law suits or egg on the face, this behooves all people recommending vitamin D to be sure and recommends enough vitamin D so that the customer is not left with a low blood level after taking the recommended amount. I have seen and heard of many people that felt much better in just a matter of days that started out taking 50 to 100,000 IU per day. This is most gratifying to see happen. This truly convinces people that vitamin D can alter the course of their life.
Thus if the sun can generate 20,000 upon striking the skin for just 20 minutes, wouldn’t it make sense to assume this is the minimum amount that normal, healthy people should take. Now if you are older and metabolize D slower, are fatter and D gets distributed amongst all that fat, or if you have pigmented skin, which blocks the action of the sun, wouldn’t it make sense to increase the dose way above 20,000?
Is their a downside to this advise? Could excess D cause problems? Not that anyone has reported, unless one is using millions of units of D on a high calcium/phosphate diet. On such a diet, one can get calcification in the arteries and joints. But if the calcium and phosphate are kept at the level seen in primitive people’s diet, which between 300 and 500 mg of calcium and phosphate, the risk of calcification is extremely low according published data.
The next question is, what is maximum safe level of vitamin D in the blood. Canadian researcher, Dr. G. Jones published in the Aug. 2008 issue of Amer. J Clin. Nutrition that maximum safe level of 25 Hydroxy D in the blood is 300 ng/ml. Depending on ones metabolism and length of taking vitamin D. one would probably have to consume 100,000 IU per day for months to achieve this level. His testing was done on Americans that consume “normal†levels of calcium and phosphate, which were probably over 1200 mg. per day. Notwithstanding that fact, he still said that 300 ng/ml is a safe level in the blood. This information should cause many vitamin D experts to raise their recommended safe input levels.
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Hey Scott,
Perfect timing on your vitamin D post with winter just about to set in (it already has in Anchorage, Alaska where I live). I notice some of the comments on your Blog replies recommending the Vitamin D Councils website–I highly recommend it too. By the way, it is a non-profit organization.
A few really worthwhile links from their site are two talks with PowerPoint presentations; both presentations are similar, but cover different material, and between the two you can really get an added understanding on vitamin D from what you’ve already posted. Dr Veth’s link: http://wildhorse.insinc.com/directms13oct2005/ Dr Hollick’s link: http://www.uvadvantage.org/portals/0/pres/
I find NOAA’s Climate Prediction Center UV Index sites valuable in determining my ability to make vitamin D in my favorite way–from solar energy. Link: http://www.cpc.ncep.noaa.gov/products/stratosphere/uv_index/uv_meanmax.shtml
Also, I think a follow-up article with the interactions between vitamins D, A, and K will be helpful–they have synergy and feedbacks too.
Thanks Scott and to all the great posters to this blog
Calvin
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Hi Scott,
I would agree with those who are suggesting a much higher daily intake. When vitamin A & D are in their natural form and at a ratio of 10 to 1, they work together in the body and also protect from toxicity. BTW, I’ve got it from a very good source that soon the only cod liver oil that WON’T have synthetic vitamin A & D are the ones that do not heat their oil at all. (There is a huge difference between synthetic and natural vitamins – synthetic can be very harmful, as I know you know.) The source for natural A & D that is normally added back in after cod liver oil is cleaned will soon not be available anymore. I take the fermented/unheated cod liver oil from Green Pastures. (They also have capsules.)
Kelly http://www.KellytheKitchenKop.com
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All, you can DEFINITELY go higher with vitamin D doses without worry. I was posting what is the standard recommendation. I’ll make an edit to add some of the information you’ve provided.
Cheers
Scott
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Btw, just in the past two weeks, the American Academy of Pediatricians doubled their recommended Vit D dose for children (still, the Vit D council recommends 1000 iU for every 25 pounds of body weight, which is the guideline I use for my son’s Vit D supplementation).
http://www.aap.org/family/vitdpatients.htm
The AAP is wrong about D only drops not being available in the US – Carlson makes a product for infants. The AAP is also wrong that Vit D fortified milk is the only food source of Vit D, though it is true that other than fish and liver, food isn’t typically a rich source (humans evolved to meet their Vit D needs from UV skin exposure). Also, modern industrial indoor animal production has reduced the amount of Vit D that would be contained in foods if the dairy cattle and poultry were raised outdoors.
I’ve been following Vit D issues for about two years. It seems every week for the past year or so there’s new news on the importance of adequate Vit D levels for good health. I remember ten years ago asking about vit D drops for my newborn son (born in late September) because I read breast milk had very little Vit D (plus I avoided sunlight due to a basal carcinoma history). The pediatrician chuckled and said he doesn’t worry about Vit D deficiency in San Diego (D drops are routine for babies in Scandinavia, for obvious reasons).
Turns out Vit D deficiency IS very possible, even in sunny San Diego, due to skin cancer fears, increased high SPF sunscreen useage, indoor lifestyles, low fat industrial food diets, etc. Everyone I know covers their babies up with umbrellas, clothing, and as soon as they hit 6 months, slathers on the sunscreen. Lots of very pale kids in Southern California now. No wonder kids are getting rickets again.
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Excellent post. Vitamin D is certainly the vitamin du jour, and no doubt it is important they we get enough. How much is enough? No one knows for sure. However, I am hestitant to go with the recommendations in the thousands, since these super quantities have not panned out for other vitamins.
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Good stuff, but don’t forget about Vit A. Love this blog btw. Found it through your post on Cressey’s site.
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[...] Just How Important is Vitamin D? — Modern Forager is my new favorite blog, so I hope you enjoy this, too. [...]
I get the majority of my vitamin D from dairy products and tuna. Need to start adding a bit more salmon back into my diet. I’ve not had it for ages and it is so tasty.
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[...] week, we discussed some of the various diseases that can result from vitamin D deficiency. Today, I want to look at the other three fat-soluble vitamins – A, E, and K – and see how these [...]
Wow that, pretty shocking. I never looked if I ever had enough vitamin B I will test myself for results!
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Dr. Hubbard,
I would just note that many of the other “megadose” vitamin recommendations have originated from poor associative evidence (e.g. epidemiological studies), often extrapolated with little or no biochemical evidence. This is not the case for Vitamin D. The effect of Vitamin D on a wide variety of critical biological processes is well-understood, with evidence continuing to be gathered. Unlike true vitamins such as C and E which are obtained from food, “Vitamin” D is made by the body, and the quantity manufactured for full sun exposure is also fairly well-understood. Thus it seems reasonable that any deficit due to lack of sun exposure must be compensated from diet at roughly the same magnitude. In this context, multi-thousand IU doses are at least nominally appropriate. The best way to ensure proper dosage is to get 25(OH)D tested, allowing one to find a supplement dosage that achieves the appropriate blood levels.
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Btw, I think it is getting pretty easy to get doctors to order the 25 (OH)D test these days.
My son paid a visit to the family practitioner’s office today because we thought he might have mumps (he probably does, despite being immunized when he was a baby). Since the doctor was ordering blood tests for mumps antibodies, amylase, a CBC and metabolic panel, I asked if he would order a Vit D level, too. No problem. Same happened when I asked for myself with my doctor.
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William Davis also says vitamin D in tablet form doesn’t raise your blood level. You have to use the gel caps.
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Carlson makes D Drops in 400, 1000, and 2000 iU per drop doses, 365 drops per small bottle. That’s an easy way to take Vit D – no capsules to swallow. My son still hasn’t learned to swallow pills and capsules, so he just chews the oil capsules and spits out the capsule.
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A lot of very useful information. Thank you for taking the time to provide all of the benefits and statistics
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We’re using a LOTTA vit D in the clinic — natural OTC NOW or Carlson’s or Nature’s Blend or NSI brand.
Often it requires 4000 to 8000 IU daily in the AM to reach therapeutic normal levels of 60-80 ng/ml require to prevent osteoporosis, proliferation, coronary calcification and C-A-N-C-E-R.
For me, a tan Asian female who wears mineral-makeup and sunscreen (to prevent wrinkles *wink* yes hey I’m vain too), I require 4000 to 5000 IU daily to maintain > 60 ng/ml, in Northern Cal where no UVB shines from Sep to Mar annually (only UVB activates vit D in our skin).
Let me tell you the improvements I’ve noticed (and not experienced for the last 20yrs of my 37 yr existence):
hey — u should get this for ur spouse Xmas!!
–warm extremities
–no SAD (seasonal affective d/o and moodiness)
–strength, conditioning, endurance and no more body aches
–better body recomposition
–less asthma and infections for my children
–less risk of autoimmune disease for my family/kids/friends/acquaintenances
–no intermittent mild-mod asthma
–no bronchitis
–no colds
–no infections
–treat my spouse better
–more blessings, bliss, and blithering happiness!!!
Kind regards, G
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Scott –
Great post on Vitamin D. Dr. Larry McCleary has also spotlighted Vitamin D and it’s role in neurological development and bone health:
http://www.drmccleary.com/2008/01/17/DBrainBossDBrain.aspx
Enjoying your blog as always.
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Thanks for the great tips.
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[...] Please check out more information on Vitamin D: (Source) [...]
I have diabetes, and a kidney transplant, and a Vitamin D and calcium deficiency as of 3 months ago. I am now taking 600 mg twice a dayof calcium and 400 iu vitamin D twice a day. My levels have returned to normal and my anooying back aches have stopped. Dion’t know if that directly correlates to the back.
But I CAN tell you my other chrionic diseases are being helped in ways that are too technical for me to explain. Trust me though.
Oh, and if your morbidly obese and over 35, the consequnces are horrendous. Get with the program or turn in your tickets. [I just made that up]
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Interesting info but I agree with some of the other comments that the dosing mentioned is way too low. 10,000IU per day has good safety data and a phase I study in MS used as high as 40,000IU per day with no side effects. It appears that the hypercalcemia everyone fears only occurs if you take excess calcium as well as vitamin D. Here is another good web site with lots of information especially in cancer: http://www.vitaminD3world.com
They also offer a free newsletter which is quite good
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Recently I have been diagonised as Ostereposis.My age is 50 and has been advised to dake Daily Calcium supplemet of 500 mg.The doctor has given me one injection of vitamin D3 600000 IU to increase bone build up.Is this sufficient or I need something more for increasing the weight.My current weight is only 46Kg with a height of 5ft 10 inch.
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Exciting new data has come out on the role of vitamin D in prostate cancer showing those with high levels do many times as well as those with low levels. Then most recently a prof in London published that he treated prostate cancer patients with only 1000IU and noted a marked decrease in PSA. Studies are running in Canada using as much as 40,000IU per day in this condition. Take a look at http://www.vitaminD3world.com which has the details of this work. This site has also recently anounced a new formulation of vitamin D and they are offering a free supply for customers children
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[...] of Vitamin D deficiency. This is known to be a potential cause of many disorders/diseases such as Depression, Chronic Pain, Arthritis, Fatique, and many more to list. Of course, you can easily take an over-the-counter Vitamin d3 to combat this deficiency, but did [...]
If you are interested in vitamin D you should take a look at http://www.vitaminD3world.com The Canadian Cancer Society now recommends that everyone take vitamin D to prevent cancer. The site has good summaries of the data and offers a new preparation of vitamin D in a micro-pill formulation. The pills have been formulated with cellulose which absorbs water very quickly. This ensures that the pill breaks up very quickly to provide for maximum absorption. The micro pill is tiny and tasteless. Many vitamin D pills on the market have very poor dissolution properties resulting in poor absorption.
The site also offers to supply customers with a free supply of 400IU for their children and it also has a good newsletter.
best regards
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[...] with your family or dog. Spend some time at the pool. Hang out in the sun to get some much needed Vitamin D. Point: Do something to actively recover and don’t push yourself. Recovery, among other [...]
In Britain, as much as 61 per cent of the population is Vitamin D3 deficient because of the limited exposure to sunlight. This rises to 87 per cent during winter. The current RDA for British people of 400IU is too low.
Interesting to note that sufficient levels of Vitamin D3 has been linked to helping the body fight flu and more topically, swine flu.
We’ve launched a new product to the market called SunVit D3 providing 1000IU of pure Vitamin D3 in a single tablet. See http://www.sunvitd3.co.uk (all research, Q&A’s and background listed on this site)
Our message here is to help you body have enough defence to help fight swine flu through gaining enough sunlight, vitamin D3-rich foods and vitamin supplements for those who can’t gain enough naturally.
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Here is link to a good article on how vitamin D protects you from colds and flu, a very topical subject as everyone is afraid of swine flu:
http://archive.constantcontact.com/fs026/1102452079631/archive/1102685428884.html
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