D-bunked: Vitamin D’s Benefits Are Overhyped, Study Says

By Gemma Tarlach | April 1, 2014 5:30 pm

vitamin d

For years, marketers have promoted vitamin D as a weapon against everything from brittle bones to cancer — often citing one study or another to back up their claims.

But the real benefits of the vitamin are anything but clear, say authors of an “umbrella study” appearing in today’s British Medical Journal.

Researchers reviewed more than 260 previously published papers, including observational studies and clinical trials, about the possible benefits of vitamin D both in the diet and as an added supplement. The earlier research had focused on finding any role the vitamin played in preventing or mitigating 137 different conditions, including osteoporosis, cardiovascular disease and autoimmune disorders.

Shaky Science

According to the new analysis, only ten of the previous studies met the bar for what the researchers felt was rigorous testing, including trials. Only one such study out of the hundreds reviewed suggested some evidence of a benefit, linking birth weight to a mother’s third trimester vitamin D levels. Researchers noted that some of the other studies examined in their umbrella review seemed to indicate “probable” links between vitamin D levels and a handful of conditions, including childhood cavities and hormone levels of dialysis patients.

But the authors noted that none of the studies they examined established definitive proof of a health benefit from vitamin D. Additional research to investigate vitamin D’s potential is not only needed, the researchers concluded, but must include better-designed trials.

BMJ‘s latest edition includes a second study questioning vitamin D’s value in disease prevention and an editorial weighing in on the ambiguous data.


Image by Stephen VanHorn / Shutterstock

CATEGORIZED UNDER: Health & Medicine, top posts
MORE ABOUT: personal health
  • Kpilk

    So, vitamin D deficiency is a lie?

    • C. G. Marshall

      No, vitamin D deficiency is definitely associated with adverse health outcomes. The conclusions of these studies just mean that taking supplements if your levels are relatively normal doesn’t necessarily have the disease-prevention benefits that manufacturers advertise. The studies did find evidence that higher Vitamin D levels do have a negative correlation with several cardiovascular conditions, which supports a preventive effect for these conditions.
      Basically, these studies generate data and avenues for further research; they aren’t meant to offer individual healthcare advice.

      • Kpilk

        Yeah. The only healthcare advice I follow is my doctor’s. So this follows the “if you are healthy, you don’t need supplements” thinking. I get that.

  • scott duncan

    Not a surprising conclusion for a meta-analysis done on hundreds of studies. These type of analyses can also be very flawed. Multiple in vitro studies with vitamin D suggest significant biological effects at the cellular level which suggests that vit D should still be studied using a PROSPECTIVE clinical study design with a more narrow disease focus.

    • Igpay Atinlay

      Such studies do exist for some outcomes- for shorter term outcomes like birth outcomes it’s easier to get that kind of data but ensuring long term adherence to supplements over the time period to capture chronic disease effects is notoriously difficult.

  • kulkarnic46

    Is Vitamin D deficiency associated with electromagnetic transmissions especially from Mobile Phone Towers & high tension power cables?
    Whenever a patient complaining of persistent / severe body pains comes to my clinic, I ask him ( or her) : whether his residential place is in the proximity of transmission towers. If the answer is ‘yes’, I ask him to get his ‘Vitamin B-12 & D in blood’ tests done from a pathological laboratory.
    Surprisingly, either one or both the tests are positive ( i.e. indicate deficiency).

    • Igpay Atinlay

      No-I can’t think of a mechanistic reason for why that would affect levels; the majority of americans are probably deficient in both nutrients. If the association had been shown in epidemiological studies (which it hasn’t), I’d hypothesize confounding: Maybe poorer people live near such towers+are therefore more likely to be deficient?

      • Chandrakant Kulkarni

        Okay, Sir.
        Thank you very much for the valuable info.
        Chandrakant Kulkarni. Pune, India.

  • JudyB202

    Holy bias Batman! You neglected to mention that the “second” study concluded in part “Supplementation with vitamin D-3 significantly reduces overall mortality among older adults…” For a more balanced review of these vitamin D studies, check out the Well Blog by Anahad O’Connor at the New York Times.

    • Brian Anseeuw

      Also MS, etc.

  • pnwfemale

    Vitamin D is a fat-soluble vitamin and can be stored in the fatty tissue of the human body. It’s not necessary to spend all day outdoors to absorb enough Vit D from the sun. If a person is overweight due to fat weight rather than muscle weight, it is possible that person will not experience any Vit D deficiency. However, the best way to determine the D level is through blood testing. My youngest son is tested deficient and has to take D3 supplements and he is outdoors often. My oldest son rarely goes outdoors, except to the car and back and he is not deficient.

    • roberta4343

      I am thinking some do not have the ability to make it in the skin. since I sunbathed without sunscreen for years and despite all the dietary changes and supplementation etc to get better never did. so maybe there is a genetic component here.

  • Sean

    It is well known that vitamin D dificiences and auto immune diseases coincide. Take for instance MS, there are no reported cases in warm sunny or tropical climates ( if born and raised there). Does this have anything to do with a lack of vitamin D?

    • roberta4343

      my sister had this, she got worse over time was obese (a sure sign of a d deficiency and glucose intolerance) and died at a young age, if I had known then what I know now I would of suggested trying to vitad3 megadose, couldn’t hurt after all she was basically dying. but alas we never learn something until after the fact.

  • Igpay Atinlay

    @Sean it certainty could. The evidence is somewhat ambiguous as the only way to really test it is through observational studies, not trials. And many seem to suggest a relationship between vitamin D and MS. There is also plausible mechanistic evidence for that outcomes.

  • William Supple

    The fact that this Discover Magazine article appeared on April Fool’s Day is in keeping with its conclusions. Since the human body uses 3500 IU vitamin D per day any study that examines dosages below this biological unit (3500 IU) will likely not find any therapeutic effect. Nothing new in the Discover article. I am concerned that about the title suggesting that vitamin D is ‘bunk.’ Smart people take vitamin D and stay healthy, and will go to the funerals of those that don’t.

    • roberta4343

      I thought vitd3 had a half life of 2 months, do you have any references to how much the body burns up a day? is it used per day or burned up per day? thanks

  • roberta4343

    figures, as soon as something is known to be beneficial they demonize it, personally I have had to take megadoses of the stuff to feel better to sleep better to normalize my appetite (I did everything else to do so, supplments like gtf, cinnamon immune supplements, vitamins and minerals absent d3 low carb low calorie., low fat, exercise programs, eating veggies nad fruits and avoiding grains you name it I tried it) nothing helped I just got worse for years gradually getting worse (symptoms to long to list) but eating a slow carb diet with vitad3 supplementation is really making a difference, not fast but gradually I am getting better. sleep has dramatically improved, (still needs work)my nervousness and anxiety attacks reduced and eliminated in some cases, my energy levels increasing, mental clarity is better but still needs work I sunbathed without sunscreen for years and never improved until I took supplements. even my periods are improving, more regular and less pms symptoms and less fatigue during it and I am in the throngs of menopause, and few if any hot flashes too. less headaches have not had a sinus infection in a very long time, which before I was always getting sick either sinus or bronchitis or asthma during exercise, this asthma still needs work but is better than used to. using less asthma medication. I mean the list is endless. so their study is bogus, they need to do real world studies instead of fabricated methods.

    • Samuella Samson

      you need to see a psychiatrist and a nutritionist.

  • Brian

    Eliminate all the studies that used low dose due to fear to toxicity do to build up, something that was a long held belief. Also eliminate any study using D2 and the picture changes. Look it’s cheap and you can go get a 40 dollar blood test to dial in your dose. Why not?


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