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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

A closer look: “Vitamin D no match for common cold”

Many of readers report a reduction (not absence) of colds and flu with 5,000 IU daily doses of vitamin D. However, hundreds of media outlets are reporting on a well-conducted JAMA study that showed no benefit for vitamin D in preventing the common cold.

The randomized controlled trial, led by Dr David R Murdock of the University of Otago in New Zealand, found that 200, 000 IU per month for two months followed by 100,000 IU per month of vitamin D for 16 months in 161 patients did not prevent either the diagnosis or complaint of the common cold. The study included viral cultures, rigorous efforts to capture all infections, vitamin D given during monthly doctor visits, and initial and follow up vitamin D levels. The average initial level in the treatment group was 29 ng/ml and 18 months later, the mean level was approximately 50 ng/ml, with no side effects.

However, only 13 of the 161 placebo patients had levels below 20 ng/ml and only 5 of the 322 total patients had levels less than 10 ng/ml to begin the study. That is, the placebo group had relatively high levels (mean of 28 ng/ml initially), compared to most populations, and all but 13 patients had levels above 20 ng/ml for most of the study, apparently from sun exposure.

Compare Dr. Murdock’s results to the result of another study, one in the Lancet by Dr Adrain Martineau and colleagues, who, as a secondary end-point, assessed upper respiratory tract infections over two months in patients given 2.5 mg (100,000 IU every two weeks for eight weeks for ancillary treatment of TB.

Martineau AR, et al. High-dose vitamin D(3) during intensive-phase antimicrobial treatment of pulmonary tuberculosis: a double-blind randomised controlled trial. Lancet. 2011 Jan 15;377(9761):242-50.

They found a six-fold reduction in upper respiratory infections, but their English population was severely vitamin D deficient to begin with.

In addition, two randomized controlled trials in children, one in Japan and one in Mongolia, both given daily vitamin D, showed a reduction in upper respiratory tract infections. Both studies had placebo arms. In the Mongolian study, the investigators measured vitamin D deficiency in the placebo arm, and it was much worse than in the JAMA study, a point the JAMA authors note.

In yet another secondary end point in a randomized controlled trial, 2,000 IU/day of vitamin D in African Americans with initial low levels reported a dramatic reduction in respiratory infections. Both the report and our group’s reply are free to read and download in its entirety.

Aloia JF, Li-Ng M. Re: epidemic influenza and vitamin D. Epidemiol Infect. 2007 Oct;135(7):1095-6; author reply 1097-8

Thus, the JAMA study leaves us with a number of possibilities:

  1. Vitamin D does not help prevent the common cold.
  2. Monthly doses of vitamin D do not help prevent the common cold while daily or weekly dosing does.
  3. Levels above 20 ng/ml (92 % of the placebo group) are all that is required to lower the infection rate.

I am unaware of any study that used significant daily doses for an entire winter that was negative. What is your experience with daily doses of vitamin D and infections?

  About: John Cannell, MD

Dr. John Cannell is founder of the Vitamin D Council. He has written many peer-reviewed papers on vitamin D and speaks frequently across the United States on the subject. Dr. Cannell holds an M.D. and has served the medical field as a general practitioner, emergency physician, and psychiatrist.

32 Responses to A closer look: “Vitamin D no match for common cold”

  1. Interesting discussion. My experience is this. I started supplementing with D3 three years ago….5000IU daily from Apr – Sept; 6000IU daily Oct – Mar. This gives me stable blood levels around 65 ng/ml. I test regularly. I haven’t had a flu since I started this regimen in 2009. The number of colds I get has reduced…from 2-3 per year before 2009, to 1 per year since. Moreover the severity of the cold I get is much, much less. Very few symptoms. Usually a few days of feeling tired and listless and…that’s it. No fever, no stuffed up nose, no headache, no chest involvement, etc. I attribute these improvements to the D3 since that’s the thing I’ve changed. My wife also reports the same. Fewer colds and when they do happen not nearly as bad as before.

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  2. JBG says:

    “What is your experience with daily doses of vitamin D and infections?”

    For at least ten years running, my wife and I had severe respiratory infections every February. Details varied, but somewhere between a *really* bad cold and the flu.

    Then we got the word about vitamin D, six or seven years ago. Since then, all happy Februaries, and only rare minor illness of any kind.

    I use this as a challenge to people unwilling to believe that an ordinary (to them) supplement can be of powerful benefit. Do it for a winter, and see.

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  3. Dan says:

    I don’t get flu vaccine shot since 2005. As far as colds, less severe symptoms and over more quickly and probably not as many episodes. My level has been around 50 ng/mL for over two years.

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  4. Dan says:

    I should add I used to get a moderate chronic cough in winter in the office with others coughing. Since bumping up my D level, I no longer get the chronic cough.

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  5. Raven says:

    My immune system isn’t as hardy as it could be due to Lyme disease (since treated with long term antibiotics and in remission). I tend to pick up viral infections. But if I feel like I have one coming on, I take 50,000 IU of D3 a day for two days plus lots of vitamin C and it never materializes.

    That’s all the evidence I need.

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  6. Rebecca Oshiro says:

    Vitamin D takes the edge off of my symptoms. If everyone around me has a cold or the flu, I just feel fatigued or slightly nauseated, not full blown symptoms.

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  7. I must wonder if they bothered to identify the time of onset of symptoms relative to the dosing regimen. In other words, were infections evenly distributed over time during the study or was there trending that could be identified, such as “X% (+ or – 10%) of infections occurred within 7 days (+ or – 10 days) of the next dose due date”.

    If the monthly dosing did not provide the right building blocks reliably on a day to day basis throughout the study, were cells that the body was replacing older cells with in some way deficient in Vitamin D receptors, reducing the immune-system effects of therapeutic levels of vitamin D.

    Many sophisticated systems in the human body (various immune responses, blood clotting mechanisms, endocrine secretory mechanisms, and more) rely on both triggers that cause and triggers that inhibit. Providing a one day HUGE insult of such mammoth dosing followed by literally weeks of NO new cholecalciferol into the system is a bizarre and illogical approach to an honest evaluation that skews the triggers, I would wager.

    How does such a dosing protocol in any way resemble what the human body routinely experiences? I find that this study comes closer to relevance than many yet once again FAILS as so many “D” studies do because of the lack of due consideration for appropriateness in the dosing protocol, and in the absence of apprehension of a full spectrum of data points possible.

    If you are going to the effort and cost to perform a clinical study, THINK about it before you actually do it, dang it…

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  8. http://jama.jamanetwork.com/multimediaPlayer.aspx?mediaid=4254617

    I just found this thanks to the council’s link. Most of my previous comment remains relevant, I think, though it is clear that at least one investigator recognizes such massive single-month dosing might not be the same as daily dosing (I read a lot into what he is saying, I confess). And another 20,000 patient study by the NIH? sure hope it is conducted with an intelligently/elegantly designed protocol!

    Conducting an analysis of capillary function in the big toe by first smashing it with with a ball-peen hammer is ludicrous. Yes it can reveal some interesting facts about leakage, but does it give you an adequate picture of the functions of “normal” vascularization? No more sledgehammers of 200,000iu dosing, please!

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  9. Jim Larsen says:



    Critical illness in kids and vitamin D: the first study

    Vitamin D is increasingly being recognized as important for good health. Vitamin D is a hormone made in the skin following sun exposure or acquired from diet and supplement intake. Previous medical research has shown that low body levels of vitamin D make people more susceptible to problems such as bone fractures, poor mental health and infections like the common cold. Until recently, there had been little consideration given to the role of vitamin D in more severe diseases, which is why Dr. Dayre McNally’s recent publication in the esteemed scientific journal Pediatricsis so compelling.

    “This is the first study to report on vitamin D levels in a large group of critically ill children,” said Dr. McNally, a clinical researcher and intensivist at the Children’s Hospital of Eastern Ontario (CHEO) and assistant professor in the Department of Pediatrics at the University of Ottawa.

    The study, led by Dr. McNally at the CHEO Research Institute, included over 300 children and teenagers at six hospitals in Ottawa, Toronto, Hamilton, Edmonton, Saskatoon and Vancouver. These children were admitted to an Intensive Care Unit (ICU) with severe infections, significant trauma or conditions requiring major surgery, such as congenital heart defects.

    Their study found that in three of every four critically ill children, blood vitamin D levels were below the target considered safe by many experts and medical societies. Further, those with lower vitamin D levels were noted to be sicker, requiring more life-sustaining therapies (breathing tubes, medications to support heart function) and staying in the ICU for longer periods of time.

    “Although these findings are of concern, we are very encouraged because we’ve discovered something that is modifiable,” explained Dr. McNally. “There are simple ways to prevent this problem, and it may be possible to rapidly restore vitamin D levels at the time of severe illness.”


    This study was conducted by Dr. Dayre McNally, Dr. Kusum Menon, Dr. Pranesh Chakraborty, Lawrence Fisher, Kathryn Williams, Dr. Osama Al-Dirbashi and Dr. Dermot Doherty. It was funded by the Canadian Institutes of Health Research (CIHR) and the CHEO Research Institute.

    About the CHEO Research Institute:

    Established in 1984, the CHEO Research Institute coordinates the research activities of the Children’s Hospital of Eastern Ontario (CHEO) and is one of the institutes associated with the University of Ottawa Teaching Hospitals. The Research Institute brings together health professionals from within CHEO to share their efforts in solving pediatric health problems. It also promotes collaborative research outside the hospital with partners from the immediate community, industry and the international scientific world. For more information, please visit http://www.cheori.org.

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  10. Four years ago, my husband and I increased our daily vitamin D3 consumption to 5000 IU. Since then, he hasn’t had a single cold and I have only had one. That’s enough evidence for me.

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  11. boston says:

    about seven years ago my hollistic MD tested all her patients for vitamin d deficiency. My results were very low. I’d had 4 bladder infections that year. She started me off with 5,000 units every other day…in three months my 25 hydroxy vitamin test did not budge. She increased me to 5,000 a day. a couple of months later my levels were 50 ng/ml…and has remained around that ever since….no flu shots, no colds or infections….However, because my weight has gone up substantially since those days, I increased the dosage to 8-10,000 units…..a day….

    Because i started a program of Chinese herbal supplements with a Chinese herbalist MD, I was told not to take other supplements at all….so I slacked off somehwhat on my vitamin D….

    wouldn’t you know it? I got the first cold in seven years….

    I went right back to taking my vitamin D—about 9,000 units a day….

    there is no doubt in my mind that the D saves me from getting sick….


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  12. PeterVermont says:

    While the two arms of the study were very well matched, there were two factors that would have predisposed the vitamin D arm to more infections:

    more contact with sick people

    more asthma/bronchitis

    On the other hand there were more smokers in the placebo group.

    Overall, though, I think the best explanation is that both arms were at sufficient levels — at least for this endpoint. I still prefer to keep my level > 30 ng/mL for the many other health benefits vitamin D has been associated with (I know ‘correlation is not causation’ — still waiting proof but I vote for ancestral levels of vitamin D as the better application of the precautionary principle).

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  13. I have been taking D3 for over five years. Prior to that, there was not one year, during the winter and spring that I never got a upper respiratory infection. My children and wife take D3 faithfully. Without question none of us get sick like we use too. With all the independent studies showing how critical the seco-steroid is for maintaining good health you would think everybody would make sure there levels were good. At the local gym people and friends thank me for educating them on this benevolent hormone. I have convinced doctors who don’t have time to read the medical journals to consider the test an important part of the patients blood work. Dr Chris Cugini an endocrinologist in Naples Fla. stated ” everyone of my patients who were severely ill had extremely low D3 levels. ” He increased there D3 levels coupled with other treatments and they improved. Everyone of his partners check there patients for D3 deficiency. I prefer my levels at 40 ng/ml or higher.

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  14. I began taking vitamin D about 6 years ago. I started with 1,000 iu., then worked my way up to 5,000 iu. which is my usual dose now. I do not get colds or infections of any kind. I am 65 years old and all my lab tests show a positive ANA and a leaning toward auto-immune problems. Both my mother and grandmother were diagnosed with Rheumatoid Arthritis in their 50’s. I do not not have it and believe the vitamin D is keeping it at bay. I do, however, have osteoarthritis. It seems to me that the common cold (and other viruses) show up when the immune system grows weak due to low levels of vitamin D? I have a friend from Africa who tells me he never had a cold in his life until he moved here.

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  15. gblock says:

    This is EXACTLY the same situation as for research on vitamin C and health outcomes — except that for vitamin D the situation is more favorable to finding an effect. At least for vitamin D the great majority of people have low levels. The same is not true for vitamin C. So over and over again they have done interventions on people with already good blood levels of vitamin C, and then declared that there was no effect of the intervention. In part this is a function of the population distribution of blood levels. Vitamin C is fortified in many many foods, and many people take multivitamins with useful levels, so many people are at least okay, if not optimal. But it is also a function of the type of persons who volunteer for this kind of study — well-off, well-educated, health-conscious. So they are a high-blood-level subset of an already not-awful population distribution. I said about 20 years ago that the window for vitamin intervention studies in the United States was closed. I was wrong about Vitamin D (there are a lot of low levels so), but it is certainly true for vitamin C. It would be awfully nice if researchers tested potential research subjects to make sure they were in need of the intervention they’re testing, before enrolling them in the study!

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  16. Ever since I started taking vitamin D (10,000 IU / day) 4 years ago, I haven’t had a flu and only one cold. The vitamin D does not protect from viruses, but it does give our immune system what it needs to do its job. Having said that, other factors can depress the immune system too, especially stress and sugar. In my case the 1 cold was due to being less careful with my diet. Vitamin D + a healthy diet = no colds or flus (in my case).

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  17. Ian says:

    I actually placed this in the wrong post so I am posting it here correctly.

    This is the sort of thing we are constantly being fed in the NZ news.


    The “scientist” interviewed states that their main aim is to provide information about science which has an impact on people.

    It is a bad review of a few studies to exemplify why you should not take vitamin supplements, vitamin D in particular, pointing out one study (NHANES) where only 3 people per 1000 had fractures prevented but 6 people died of “stroke or heart attack”.

    The interviewer asked “what about people who are deficient”?

    The answer is shocking: “problem is most people taking. . . . vitamin D . . . are not in that category . . . they are mostly older people . . . mainly women . . . with a healthy diet.

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  18. peterlepaysan says:

    I think it is a bit silly to link “cold” results to a single input.

    Susceptibility to a virus will never depend on a single factor.

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  19. Brant Cebulla says:

    @gblock, thanks for the insight.

    I think vitamin D researchers are starting to put that kind of care and attention into their research, to make sure their study has the best chance of finding something and getting it right. We see more and more studies where inclusion criteria is a vitamin D level less than 20 ng/ml. Obviously, not so in this study, something I am sure the investigators are kicking themselves over a little bit.

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  20. My Vitamin D level is 84 ng/ml, as many of you already know. And, I am sitting at my desk today with a (minor) cold….

    However, from colds of years past, my take is that if I were Vitamin D deficient this cold would be much worse….

    I was still able to run four miles this morning. And, my energy level, even with this cold, is awesome. I anticipate being able to run tonight as well.

    Previous colds, when my D level was much lower, would knock the socks off of me….:)

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  21. Jim Larsen says:

    200,000 iu/month is 6,666 iu/day. 100,000 iu/month is 3,333 iu/day. The sky is not falling.

    D half-life is roughly 2-3 weeks (http://www.annalsofepidemiology.org/article/S1047-2797(08)00002-1/abstract)(http://www.jci.org/articles/view/29449) although I’ve seen some sources say 7-14 days.

    Although monthly doses skew the perception of the doses (commonly used in nursing home studies), these doses only resulted in a mean 25(OH)D of 50 ng/ml (125 nmol). This reinforces the notion that D poisoning is extremely difficult to do.

    Single large loading doses/month don’t appear superior to daily doses. http://www.biomedcentral.com/1471-2474/12/135

    The 500,000 iu annual dose nursing home study suggested an increase in falls (Sanders KM, Stuart AL, Williamson EJ; et al. Annual high-dose oral vitamin D and falls and fractures in older women: a randomized controlled trial. JAMA. 2010;303:1815-1822.). I believe an analysis of the falls by month showed higher falls in the first quarter, etc.

    The suggested argument is that D levels and various diseases have a step function (i.e. there are no rickets cases above 20 ng/ml), therefore this population sample was skewed.

    Therefore, the conservation conclusion is that additional D may not affect cold/URI rates in a D replete population. Cold rates in a D deficient population might need more study.

    Even though high dose treatments may even out over time, I suggest daily doses are the best solution. The body is generally a real time system operating 24 hours a day. It controls its internal processes. Give it a month’s worth of magnesium and it dumps what it doesn’t need that day or so. The uneven D daily dose with the half life effect may be another variable.

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  22. Jim Larsen says:
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  23. John says:

    In my teens and twenties I got tons of sun and never got so much as a headache, must less a cold or the flu. I continued that in my thirties with the same result. In my forties I began to avoid the sun. I started getting one cold a winter. I became a conscientious sun avoider and sunscreen user and began to get multiple colds per winter. Mine were worse than other people’s. They lasted a full two weeks and the first week was awful. I began to stay in bed the first day or two to shorten the cold from fourteen to ten days.

    5k IU of D3 a day shortened my colds from 14 days to 3 or 4 and decreased the severity of symptoms by about 75%. I still went through all the usual stages of a cold, but in record time and I stopped feeling bad.

    I went up to 10kIU/day in an effort to shorten those 3-4 days. At the same time I tried staying in bed on Day 1. When I realize I have a slightly stuffy nose and a little sore throat that most people wouldn’t even notice, I stay in bed. If I go to bed and stay awake there is no change. But if I stay in bed and also get a one hour or longer nap, the cold is over when I wake up! This has happened three times in the last three years and twice I did not nap and there was no change. I am well versed in the symptoms so I am not imagining I have a cold when I don’t. For twenty years the same little sniffle and slightly sore throat were the harbingers of two weeks of misery. These ARE colds that are getting knocked out in one day! I have not tried the 5k D3 with bed and nap to see if I can produce the same results as with 10k.

    I have not found that taking D3 or getting sun exposure PREVENTS infection with cold viruses. How could it? I still forget and rub my nose or put my fingers in my eyes, so the viruses still come in. But now I fight them off so well and the symptoms are so mild and short lived that most people would never notice them. That’s why I thought I was never sick in my 20s and 30s. I zapped them right away!

    Reference the above study: Most of the studies I’ve read on this site that find Vitamin D does not work used something other than daily doses. In addition, I read on this site that we cannot process more than 50,000IU at a time, so the subjects getting these big monthly doses are not really using that much; in the above case, a quarter of that monthly dose. 50,000IU/30 days is only 1,667IU/day. Also, the sun produces many changes when it hits our skin only one of which is D3. They are giving only D3, not sunshine, a fundamental error. But then, these studies are being conducted by the same people who told the world to stay out of the sun and to use sunscreen if they couldn’t, without ever investigating whether doing so might do something bad. That we see flawed studies should not be surprising.

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  24. I started taking vitamin D in 2003. I have not had a cold or flu since then. Sorry the studies didn’t work out for others but I will keep taking it.

    Also had Hashimoto’s and took Armour Thyroid for several years. My temperature stayed at 96 degrees all the time I was taking it but, moved up to 98+ after taking D so I stopped taking the Armour and all Hashimoto symptoms are gone.

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  25. I agree that Vitamin D doesn’t prevent our bodies from being infected with viruses or bacterial infections.

    However, from my personal experience, having adequate Vitamin D levels (for ME, around 85 ng/ml) has enhanced by body’s ability to fight off infection. On October 10th I commented here that I had a minor cold. By the afternoon of October 11th all my symptoms had faded. I was up to speed once again. I will continue with my Vitamin D supplementation. And, this winter I will experiment with NOT receiving the flu vaccination. Wish me luck!!!

    May all your days be SUNNY!

    Rita C. Umile

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  26. Debbie says:

    I am a recovering smoker (5 years, yay!) diagnosed with COPD in 2007. I have been taking vitamin D for around 5 years now. I have not had a serious “exacerbation” since beginning the D and I used to get “something” every 3 or 4 months. I have had a couple of minor colds and only once did I see fit to stay home and not pass my germs around work. I am a true believer when it comes to respiratory issues and Vitamin D, whether it’s a cold or flu. As soon as I feel something coming on I load up. 50,000 iu every other day for 3 days…..keeps evil at bay.

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  27. wraywhyte says:

    Hi there I normally take 5000iu’s per day. But if I get run down, and there’s the slightest hint of a cold, sore throat etc, I use 100,000 iu’s per day for 3-6 days , it’s gone within a day or two. As a consequence I haven’t had a cold etc for years. Take care Wray

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  28. vlc says:

    I would say that it may only moderately reduce the frequency but going by my own experience and that of my four-year old daughter, it certainly significantly moderates severity and shortens duration of the infection.

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  29. SusanLinke says:

    My son got the West Nile Virus and was severely sick. I gave him 50,000 IU of vitamin D and got it knocked out in 3 days. If any of us gets the slightest hint of a cold, we take at least 20,000 IU of vitamin D, plus magnesium and K2. My daughter took 5,000 IU while pregnant and 6,000 IU while breastfeeding, and my grandson now takes 300 IU since he is no longer breastfeeding. He is 2 years old and has never been on antibiotics. I am a dietitian and ask all of my clients what their vitamin D levels are. I’ve seen it help with chronic pain, improved immune function and so much more. Thanks Dr. Cannell, you have made such an impact in my life as well as the life of my patients.

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  30. John says:

    Let’s have a Vitamin D challenge to prevent the flu this year!

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  31. Magic says:

    It is sad that such reports two years ago haven’t”busted wide open” the findings to the general public. The money saving personally and by our government would be BILLIONS. And our insurance rates would go down.

    I have said many times what it has done for my wife and me. We just do not get sick. And we are 80 and 78 years of age.

    There are about 60,000 hits on http://www.vitamindservice.com in Germany in a month..

    GREAT IDEA, JOHN!!!! Let’s all help…….


    Great idea, John….

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