# Vitamin D: What is it good for? **URL:** \ **Category:** Factual Questions\ **Created:** [January 22, 2011, 3:10pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565 "2011-01-22T15:10:44Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [January 22, 2011, 3:10pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/1 "2011-01-22T15:10:44Z")
I’ve seen some articles in the media now and then, saying that many people have Vitamin D deficiencies - not enough to cause rickets, but lower than recommended. So, what is the recommneded level of vitamin D? is it true that lower levesl of Vitamin D may lead to more colds etc? are daily supplements a good idea? just what does Vitamin D do, anyway? ---
**Author:** ![Promethea](https://avatars.discourse-cdn.com/v4/letter/p/f9ae1b/32.png) [@Promethea](https://boards.straightdope.com/u/Promethea)\ **Post date:** [January 22, 2011, 3:14pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/2 "2011-01-22T15:14:46Z")
I heard an interesting programme on BBC Radio 4 a few months ago suggesting lower levels of vit D were indeed quite bad news. I’m not sure if their iplayer will work outside of the the UK but in case it doesn’t, there’s a transcript of the show in this link too. [Case Notes](http://www.bbc.co.uk/programmes/b00s0djn) From the programme: > [@](#): > > Traditionally lack of Vitamin D is linked with poor bone health, but new studies suggest that milder deficiency may also be linked to asthma, some cancers and diabetes. Dr Mark Porter investigates and hears from a night shift worker who had such excruciating pain in her hands she thought that she had arthritis - when her doctor checked for vitamin D levels, 3 weeks of supplements cured the pain. ---
**Author:** ![SanDiegoTim](https://avatars.discourse-cdn.com/v4/letter/s/85e7bf/32.png) [@SanDiegoTim](https://boards.straightdope.com/u/SanDiegoTim)\ **Post date:** [January 22, 2011, 3:32pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/3 "2011-01-22T15:32:12Z")
Couple of years ago y doc added a Vitamin D supplement to my daily intake. He noted relatively recent correlations to heart attacks. Good levels of D usually come from exposure to sunlight. ---
**Author:** ![iamnotbatman](https://avatars.discourse-cdn.com/v4/letter/i/858c86/32.png) [@iamnotbatman](https://boards.straightdope.com/u/iamnotbatman)\ **Post date:** [January 22, 2011, 3:46pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/4 "2011-01-22T15:46:49Z")
I was vit D deficient. Started taking 2000 IU/day about a year ago. Seems to have boosted my immune system, since I haven’t gotten a cold since (I usually get at least 2 colds per year). It’ll be interesting to see if the trend keeps up… ---
**Author:** ![Khadaji](https://avatars.discourse-cdn.com/v4/letter/k/9e8a1a/32.png) [@Khadaji](https://boards.straightdope.com/u/Khadaji)\ **Post date:** [January 22, 2011, 4:02pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/5 "2011-01-22T16:02:07Z")
There are many claims about it - helps prevent cancer and/or recover from cancer. Boosts energy. Helps prevent arthritis. Boosts immune system. Aids in calcium absorption. [Here](http://www.algaecal.com/vitamin-d/vitamin-d-benefits.html)are a list of claims. I read the [The Vitamin D Cure](http://www.amazon.com/Vitamin-D-Cure-James-Dowd/dp/0470455756/ref=sr_1_4?s=books&ie=UTF8&qid=1295711992&sr=1-4) years ago and the authors have a very detailed bibliography of the studies that they cite, if you have greater interest. ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [January 22, 2011, 4:15pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/6 "2011-01-22T16:15:17Z")
I started taking Vitamin D (D3 gel tabs 2000 IU from Costco) daily in the Fall and Winter months and noticed that I didn’t get colds as much as I used to. It could just be a coincidence. My doctor checked recently and verified that my Vitamin D was at a healthy level. Apparently during the Spring and Summer months I am outside enough, and exposed to the sun enough, to make my own Vitamin D. (Where I live now the winter days are short and the weather/temperature is not conducive to being outside during the day.) If you are concerned about it you should get tested and see where your levels are now and talk to your doctor before you decide to take supplements. ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [January 22, 2011, 4:26pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/7 "2011-01-22T16:26:39Z")
As a side not, like most adults, I now drink much less milk, which is fortified with Vitamin D, than I used to. ---
**Author:** ![racer72](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/racer72/32/3075_2.png) [@racer72](https://boards.straightdope.com/u/racer72)\ **Post date:** [January 22, 2011, 6:34pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/8 "2011-01-22T18:34:03Z")
I just had a full physical, besides needing to lose more weight (I had lost over 40 pounds since my previous visit to this doc), the only other issue was a vitamin D deficiency. He suggested Centrum Silver or it’s generic equivelant to maintain my vitamin D level, the other things would be a bonus. ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [January 22, 2011, 6:48pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/9 "2011-01-22T18:48:48Z")
I’ve noticed that in the past year or so, the multivitamin I take has increased the vitamin D content from 400 to 700 IU. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [January 22, 2011, 10:29pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/10 "2011-01-22T22:29:22Z")
It’s important to remember that all the evidence ostensibly showing a link between low vitamin D levels and things like diabetes, atherosclerosis (heart attacks, strokes), and cancer are simply observational\*, i.e. people with, say, cancer have, on average, lower vitamin D levels than those without it. To this point there are no “good” studies showing that vitamin D supplementation lessens the risk of diabetes, atherosclerosis, and cancer. - similar to the observational studies that consistently showed that women taking post menopausal estrogen had lower rates of heart attacks. In fact, when a “good” study was finally done, it became apparent that estrogen supplementation \*increased \*the risk of heart attacks. Same thing for vitamin E/vitamin A and cancer. Remember, \*association does not imply causation. - “good” = large number of patients, prospective, randomized, placebo controlled ---
**Author:** ![Surreal](https://avatars.discourse-cdn.com/v4/letter/s/eada6e/32.png) [@Surreal](https://boards.straightdope.com/u/Surreal)\ **Post date:** [January 23, 2011, 1:10am UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/11 "2011-01-23T01:10:01Z")
> [@KarlGauss](#): > > It’s important to remember that all the evidence ostensibly showing a link between low vitamin D levels and things like diabetes, atherosclerosis (heart attacks, strokes), and cancer are simply observational\*, i.e. people with, say, cancer have, on average, lower vitamin D levels than those without it. To this point there are no “good” studies showing that vitamin D supplementation lessens the risk of diabetes, atherosclerosis, and cancer. Not true. [http://www.ajcn.org/content/85/6/1586.long](http://www.ajcn.org/content/85/6/1586.long) > [@](#): > > Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial > > ABSTRACT > Background: **Numerous observational studies have found supplemental calcium and vitamin D to be associated with reduced risk of common cancers.** However, interventional studies to test this effect are lacking. > > Objective: The purpose of this analysis was to determine the efficacy of calcium alone and calcium plus vitamin D in reducing incident cancer risk of all types. > > Design: **This was a 4-y, population-based, double-blind, randomized placebo-controlled trial.** The primary outcome was fracture incidence, and the principal secondary outcome was cancer incidence. The subjects were 1179 community-dwelling women randomly selected from the population of healthy postmenopausal women aged \>55 y in a 9-county rural area of Nebraska centered at latitude 41.4°N. Subjects were randomly assigned to receive 1400–1500 mg supplemental calcium/d alone (Ca-only), supplemental calcium plus 1100 IU vitamin D3/d (Ca + D), or placebo. > > Results: When analyzed by intention to treat, cancer incidence was lower in the Ca + D women than in the placebo control subjects (P \< 0.03). With the use of logistic regression, the unadjusted relative risks (RR) of incident cancer in the Ca + D and Ca-only groups were 0.402 (P = 0.01) and 0.532 (P = 0.06), respectively. **When analysis was confined to cancers diagnosed after the first 12 mo, RR for the Ca + D group fell to 0.232 (CI: 0.09, 0.60; P \< 0.005) but did not change significantly for the Ca-only group.** In multiple logistic regression models, both treatment and serum 25-hydroxyvitamin D concentrations were significant, independent predictors of cancer risk. > > Conclusions: **Improving calcium and vitamin D nutritional status substantially reduces all-cancer risk in postmenopausal women.** I’m sure I could find studies for diabetes and atherosclerosis as well. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [January 23, 2011, 3:04am UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/12 "2011-01-23T03:04:17Z")
> [@Surreal](#): > > Not true. > > [http://www.ajcn.org/content/85/6/1586.long](http://www.ajcn.org/content/85/6/1586.long) That study may be unique. Certainly, its results have not been replicated as far as I know. It has also been roundly criticiized as can be seen in the following four analyses and comments published about the study: [link 1](http://www.ajcn.org/content/86/6/1804.long) [link 2](http://www.ajcn.org/content/86/5/1549.1.long) [link 3](http://www.ajcn.org/content/87/3/792.2.long) [link 4](http://www.ajcn.org/content/87/3/792.1.long) Among other things, the criticisms focused on the unexpectedly high cancer rate in the placebo group and the fact that the study was neither designed nor powered to answer questions about cancer prevention. I will add that many of the key results of the study are of marginal statistical significance, that huge conclusions are being drawn on the basis of **only 37 cancer cases** , and that [other, larger and “better” studies have failed to replicate its results](http://jnci.oxfordjournals.org/content/100/22/1581.long) (i.e. 36000 subjects _with 1100 cases of breast cancer alone_). Bottom line is that the thesis is hardly proven and that no “good” studies support the notion that vit D supplementation reduces cancer (with “good” defined as earlier). BTW, please note the calcium/colon Ca studies are an entirely different issue. > [@Surreal](#): > > I’m sure I could find studies for diabetes and atherosclerosis as well. I bet you can’t find any “good” ones. ETA: It is also revealing to note that the study you cite, containing what would appear to be unique proof of a new cancer prevention strategy was published in a rather lacklustre journal. ---
**Author:** ![Surreal](https://avatars.discourse-cdn.com/v4/letter/s/eada6e/32.png) [@Surreal](https://boards.straightdope.com/u/Surreal)\ **Post date:** [January 23, 2011, 5:11am UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/13 "2011-01-23T05:11:00Z")
> [@KarlGauss](#): > > I bet you can’t find any “good” ones. > > ETA: It is also revealing to note that the study you cite, containing what would appear to be unique proof of a new cancer prevention strategy was published in a rather lacklustre journal. Oh, please. How unbelievably petty of you to attempt to shift the goalposts like that. Let’s review. You made the following statement: > [@KarlGauss](#): > > It’s important to remember that **all** the evidence ostensibly showing a link between low vitamin D levels and things like diabetes, atherosclerosis (heart attacks, strokes), and cancer are simply observational\*, i.e. people with, say, cancer have, on average, lower vitamin D levels than those without it. Which is completely false. There are NUMEROUS studies showing benefits for vitamin D supplementation (mostly from D3 in sufficient quantities (i.e. \> 2000 IU/day)). I was easily able to link to one of them. A randomized, double-blind, placebo-controlled study with P \< 0.005 published in a major peer-reviewed journal. I’m not a doctor (I don’t even pretend to be one on the internet), but I know bullshit when I see it. Your GQ post was bullshit but I was easily able to debunk it with a citation. ---
**Author:** ![Surreal](https://avatars.discourse-cdn.com/v4/letter/s/eada6e/32.png) [@Surreal](https://boards.straightdope.com/u/Surreal)\ **Post date:** [January 23, 2011, 5:45am UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/14 "2011-01-23T05:45:49Z")
> [@KarlGauss](#): > > I bet you can’t find any “good” ones. Here’s another The Lancet, which FYI is one of the world’s leading medical publications: > **[Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study - PubMed](https://pubmed.ncbi.nlm.nih.gov/11705562/)** > > Dietary vitamin D supplementation is associated with reduced risk of type 1 diabetes. Ensuring adequate vitamin D supplementation for infants could help to reverse the increasing trend in the incidence of type 1 diabetes. > [@](#): > > Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study. > > Abstract > > BACKGROUND: Dietary vitamin D supplementation is associated with reduced risk of type 1 diabetes in animals. Our aim was to ascertain whether or not vitamin D supplementation or deficiency in infancy could affect development of type 1 diabetes. > > METHODS: A birth-cohort study was done, in which all pregnant women (n=12055) in Oulu and Lapland, northern Finland, who were due to give birth in 1966 were enrolled. Data was collected in the first year of life about frequency and dose of vitamin D supplementation and presence of suspected rickets. Our primary outcome measure was diagnosis of type 1 diabetes by end of December, 1997. > > FINDINGS: 12058 of 12231 represented live births, and 10821 (91% of those alive) children were followed-up at age 1 year. Of the 10366 children included in analyses, 81 were diagnosed with diabetes during the study. Vitamin D supplementation was associated with a decreased frequency of type 1 diabetes when adjusted for neonatal, anthropometric, and social characteristics (rate ratio [RR] for regular vs no supplementation 0.12, 95% CI 0.03-0.51, and irregular vs no supplementation 0.16, 0.04-0.74. **Children who regularly took the recommended dose of vitamin D (2000 IU daily) had a RR of 0.22 (0.05-0.89) compared with those who regularly received less than the recommended amount. Children suspected of having rickets during the first year of life had a RR of 3.0 (1.0-9.0) compared with those without such a suspicion.** > > INTERPRETATION: **Dietary vitamin D supplementation is associated with reduced risk of type 1 diabetes. Ensuring adequate vitamin D supplementation for infants could help to reverse the increasing trend in the incidence of type 1 diabetes.** ---
**Author:** ![Surreal](https://avatars.discourse-cdn.com/v4/letter/s/eada6e/32.png) [@Surreal](https://boards.straightdope.com/u/Surreal)\ **Post date:** [January 23, 2011, 6:05am UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/15 "2011-01-23T06:05:48Z")
> [@KarlGauss](#): > > ETA: It is also revealing to note that the study you cite, containing what would appear to be unique proof of a new cancer prevention strategy was published in a rather lacklustre journal. AJCN ranks **#3** out of 66 journals in the ISI’s category of “Nutrition & Dietetics”, placing it near the top of the heap. Do you have an actual citation to support your claim that it’s “lacklustre”? > **[The American Journal of Clinical Nutrition](https://en.wikipedia.org/wiki/American_Journal_of_Clinical_Nutrition)** > > The American Journal of Clinical Nutrition (AJCN) is a monthly peer-reviewed biomedical journal in the fields of dietetics and clinical nutrition. > The journal was established in 1952 as the Journal of Clinical Nutrition, edited by S.O. Waife and published by the Nutrition Press. It was continued in series under the present title from 1954 and was published by the American Society for Clinical Nutrition (ASCN). It is now published by the American Society for Nutrition. > The journal's editor-in-c... ---
**Author:** ![bardos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bardos/32/1069_2.png) [@bardos](https://boards.straightdope.com/u/bardos)\ **Post date:** [January 23, 2011, 7:02am UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/16 "2011-01-23T07:02:34Z")
Some medical folks are saying Vitamin D is not a vitamin, but a hormone. I am taking 4000 units per day D3. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [January 23, 2011, 11:00am UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/17 "2011-01-23T11:00:34Z")
> [@Surreal](#): > > Here’s another The Lancet, which FYI is one of the world’s leading medical publications: > > [Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study - PubMed](http://www.ncbi.nlm.nih.gov/pubmed/11705562) Talk about shifitng the goal posts! This is a non-randomized, non-controlled, cohort study - it is hardly a clinical trial, let alone a “good one”. I have no doubt that you can find all kinds of observational or retrospective studies to support the hypothesis. What are much harder to find (because they don’t exist) are prospective, randomized, placebo controlled trials with adequate power to prove the point. My point regarding AJCN being “lacklustre” is that of the world’s ‘medical research’ journals (and not ‘nutrition and dietetics’) it has a low impact and is not anywhere close to in prestige to journals like New England or JAMA or Lancet. Seriously, do you honestly believe that if someone had a “proof” of a new way to prevent cancer, they’d submit their results to AJCN? In terms of impact, NEJM, LANCET, and JAMA have impact factors of 47, 31, and 29 respectively ([cite](http://impactfactor.weebly.com/medicine.html)). OTOH, AJCN is less than 1.8 - at best, only one fifteenth of JAMA’s and only one twenty-fifth of NEJM’s. I, therefore, still stand by my characterization of AJCN as being “lacklustre” (or even mediocre). And, my point remains - reporting a new way to prevent cancer should be publishable in a high impact journal unless there are problems with the study. Since the study was reported in AJCN, it had problems. ---
**Author:** ![6ImpossibleThingsB4Breakfast](https://avatars.discourse-cdn.com/v4/letter/6/e19adc/32.png) [@6ImpossibleThingsB4Breakfast](https://boards.straightdope.com/u/6ImpossibleThingsB4Breakfast)\ **Post date:** [January 23, 2011, 12:11pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/18 "2011-01-23T12:11:35Z")
Vitamin D also aids calcium absorption, thereby lessening the likelihood of osteoporosis. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [January 23, 2011, 12:40pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/19 "2011-01-23T12:40:43Z")
I misstated the impact factor for AJCN. [It is actually 6.31](http://en.wikipedia.org/wiki/American_Journal_of_Clinical_Nutrition)which is much better than the “less than 1.8” I said earlier. Although the numbers are not as dramatic as I stated, a value of 6.31 is still far less than the 29, 31, and 47 for JAMA, LANCET, and NEJM respectively. One thing I can’t give a cite for is the “word on the street” by researchers about AJCN. In over 30 years of involvement in medicine and medical research, I have yet to hear anyone call AJCN a top flight journal. And, where I work, anyone who said that JAMA and AJCN, or NEJM and AJCN, or LANCET and AJCM were in the same league would be laughed at. ETA - I will point out the obvious and say that the many criticisms of the AJCN study in question (listed earlier) exist regardless of the journal’s impact factor. ---
**Author:** ![PandaBear77](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@PandaBear77](https://boards.straightdope.com/u/PandaBear77)\ **Post date:** [January 23, 2011, 2:54pm UTC](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565/20 "2011-01-23T14:54:08Z")
Purely anecdotal - I started Vitamin D therapy about 3 weeks ago. I’ve had only ONE headache since (used to be 4-5 times a week), I physically feel better (a little more energy - not way more, but enough to be noticeable), and it seems to have helped my (mild) depression symptoms. My skin looks better, too. My level was 8.6 when we found out I was deficient. On the lab results my doctor sent me it said a normal level is 32-100. However I’ve read different things since then that say 32 is the _minimum_ it should be and the optimal level is more like 50. Either way, a level of 8.6 is Bad News Bears. I put MrPanda on Vitamin D about a week ago, figuring he’s a walking risk factor for D deficiency, too (no sun, almost no milk drinking, big guy, etc). He’s been happier, emotionally, since. I have another friend who said his depression got better when he started D therapy too. We’ll definitely be taking it for years to come. YMMV, of course. [Next page](https://boards.straightdope.com/t/vitamin-d-what-is-it-good-for/568565.md?page=2)