WARNING!
This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.
By Dr. Mercola
For the last ten years, I've regularly reported on the benefits of vitamin D, especially for combating colds and flu. But according to a new study in the Journal of the American Medical Association (JAMA), vitamin D supplements appear to be useless for reducing the number or severity of colds or upper respiratory infections.
The randomized controlled trial – led by Dr. David R. Murdock of the University of Otago in New Zealand – included 322 healthy adults. Half of the participants received 200,000 IU's of oral vitamin D3 at the outset of the study, followed by another mega-dose of 200,000 IU's a month later. For the next 16 months, the vitamin D group received once-monthly mega-doses of 100,000 IU's of vitamin D. The control group received a placebo throughout.
At the beginning of the study, the average vitamin D level for the treatment group was 29 ng/ml, which is still far below an optimal range. This is not surprising in light of the bizarre dosing regimen that was prescribed.
At the end, 18 months later, the group averaged 50 ng/ml. Still, at the end of the trial, 593 incidences of upper respiratory infections had been reported among the vitamin D group, while the control group reported 611 colds – a reduction of just around 10 percent.
So why didn't vitamin D do a better job of reducing colds?
Placebo Group had Higher than Normal Vitamin D Levels
Dr. John Cannell, founder of the Vitamin D Council first introduced the hypothesis that influenza is merely a symptom of vitamin D deficiency in the paper "Epidemic Influenza and Vitamin D," published in the journal Epidemiology and Infection1 in 2006, followed up with another study published in the Virology Journal2 in 2008.
In response to the featured study, Dr. Cannell points out that only 13 of the 161 placebo patients had levels below 20 ng/ml and only five of the 322 total patients had levels less than 10 ng/ml at the beginning of the study. In essence, to say that vitamin D supplementation is ineffective against upper respiratory infections is misleading, due to the simple fact that the placebo group had relatively high levels of vitamin D (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). Hence the similarity in outcome between the two groups.
In his recent blog on the topic, Dr. Cannell commented:
"Compare Dr. Murdock's results to the result of another study in the Lancet3 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. 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 Japan4 and one in Mongolia5, 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. The figure below shows the reduction in reported colds and flu with daily doses of vitamin D for a two-year period.
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| (colds and flu)6 |
Thus, the JAMA study leaves us with a number of possibilities:
- Vitamin D does not help prevent the common cold.
- Monthly doses of vitamin D do not help prevent the common cold while daily or weekly dosing does.
- 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."
Further evidence supporting the third possibility on his list is a 2009 analysis,7 which examined the association between vitamin D levels and recent upper respiratory infections (URI) in nearly 19,000 subjects over the age of 12. Recent URI's reported by:
- 17 percent of participants with vitamin D levels of 30 ng/ml or higher
- 20 percent of participants with vitamin D levels between 10-30 ng/ml.
- 24 percent of participants with vitamin D levels below 10 ng/ml
Results Do Not Negate Benefits of Sun Exposure
Two additional factors worth mentioning, as they may bear upon the final evaluation, are that the featured study used a bizarre and rarely ever recommended regimen of just ONE massive ORAL dose of 200,000 units once a month for two months and then decreasing to 100,000 units once a month. While this may be convenient, it seems reasonable to expect that more frequent dosing with lower amounts of vitamin D would help you maintain a more consistently even vitamin D level, which is what you want.
One massive dose once a month may be beneficial in an acute situation, but, since vitamin D is an oil soluble nutrient, it is highly unlikely to optimize D levels and help you maintain robust immune protection long-term. Also there is strong evidence to suggest 50 ng/ml may be reflective of optimized levels of vitamin D and these subjects were nearly half that level.
Additionally, mounting evidence now suggests that elevating your vitamin D level with an oral supplement is unlikely to provide you with the identical health benefits of obtaining your vitamin D the way you were designed, and that is from safe sun exposure. So the fact that the control group had higher than normal vitamin D levels compared to most populations (the late-winter average in the US is around 15-18 ng/ml) attributed to sun exposure may also help explain why vitamin D supplementation didn't yield a greater difference in cold incidence.
For example, when you expose your skin to sunshine, your skin synthesizes not only vitamin D but also vitamin D3 sulfate, although not all studies agree. This form of vitamin D is water soluble, unlike oral vitamin D3 supplements, which is unsulfated. The water-soluble form can travel freely in your blood stream, whereas the unsulfated form needs vitamin D binding protein, a protein similar to LDL (the so-called "bad" cholesterol) as a vehicle of transport.
As reviewed in a previous interview with Dr. Stephanie Seneff (a senior scientist at MIT), it is her opinion that the oral non-sulfated form of vitamin D will not provide the same benefits as the vitamin D created in your skin from sun exposure, because it cannot be converted to vitamin D sulfate.
And based on her research, Dr. Seneff believes many of the health benefits generally attributed to vitamin D are actually due specifically to the sulfated form, which you can only get from sun exposure. Such benefits include the natural optimization of your immune system, which of course is a vital component of combating or preventing any infection, not just upper respiratory infections. This is just one of many compelling reasons to make a concerted effort to get your vitamin D requirements from safe sun exposure.
Benefits of Sun Exposure Beyond Vitamin D Production
Evidence presented in the April-June issue of Dermato-Endocrinology8 confirms that exposure to the sun in appropriate and measured timeframes has a number of health benefits unrelated to vitamin D production, including:
| Enhancing mood and energy through the release of endorphins |
Protecting against and suppressing symptoms of multiple sclerosis (MS) |
| Treating skin diseases, such as psoriasis, vitiligo, atopic dermatitis, and scleroderma. UV radiation also enhances skin barrier functions |
Inducing nitric oxide (NO), which helps protect your skin against UV damage and offers cardiovascular protection, promotes wound healing through its antimicrobial effect, and has some anti-cancer activity |
| Melatonin regulation through the "third eye" of the pineal gland photoreceptors |
Relieving fibromyalgia pain |
| Standard treatment for tuberculosis 100 years ago, long before the advent of antibiotics |
Treating neonatal jaundice |
| Can be used to sterilize your armpits and eliminate the cause of most body odor |
Treating Seasonal Affective Disorder (SAD) |
| Synchronizing important biorhythms through sunlight entering your eye and striking your retina |
Regulating body temperature |
| Protecting against melanoma and decreasing mortality from it |
May be effective in treating T Cell lymphoma |
Low Vitamin D May Increase Your Alzheimer's Risk
In related news, a new analysis published in the journal Neurology9 found that low concentrations of vitamin D may increase your risk of cognitive decline and Alzheimer's disease. The review included 37 studies. Eight of them compared the Mini-Mental State Examination (MMSE) scores of subjects with less than 20 ng/ml vitamin D and those with greater than 20 ng/ml. Those with higher levels scored better. Six studies also confirmed that those with Alzheimer's had significantly lower levels.
According to the authors:
"These results suggest that lower vitamin D concentrations are associated with poorer cognitive function and a higher risk of Alzheimer's disease. Further studies are required to determine the significance and potential public health benefit of this association."
Guidelines for Safe and Effective Sun Exposure
While sun exposure is your best source for vitamin D, it's important to understand that not all sun exposure will allow for vitamin D production. Sunlight is composed of about 1,500 wavelengths, but the only wavelength that makes your body produce vitamin D are UVB-rays when they hit exposed skin. The UVB-rays from the sun must pass through the atmosphere and reach where you are on the earth in order for this to take place. This obviously does not occur in the winter for many of us in the U.S., but the sun's rays are also impeded during a fair amount of the year for people living in temperate climates.
Due to the physics and wavelength of UVB rays, they will only penetrate the atmosphere when the sun is above an angle of about 50° from the horizon. When the sun is lower than 50°, the ozone layer reflects the UVB-rays but let through the longer UVA-rays.
So how do you know if you have entered into the time of year for your location where enough UVB is actually able to penetrate the atmosphere to allow for vitamin D production in your skin?
The first step is to determine the latitude and longitude of your location. You can easily do this on Google Earth, or if you are in the U.S. you can use the TravelMath Latitude Longitude Calculator to find your latitude and longitude. Once you have obtained that you can go to the U.S. Navy site to calculate a table to determine the times and days of the year that the sun is above 50 degrees from the horizon.
Translated to the date and time of some places on the globe, it means for example: In my hometown of Chicago, the UVB rays are not potentially present until March 25, and by September 16th it is not possible to produce any vitamin D from the sun in Chicago. Please understand it is only theoretically possible to get UVB rays during those times. If it happens to be cloudy or raining, the clouds will also block the UVB rays. For a more detailed understanding of this, please view the following video, and/or read through the corresponding article.
Yes, There's an App For That!
Alternatively, if you have an iPhone or iPad you can download a free app called "D Minder," which will make all the calculations for you. It was made by an Apple developer who was motivated to simplify the process after he watched the video above.
From a health perspective, it doesn't make much sense to expose your skin to the sun when it is lower than 50 degrees above the horizon because you will not receive any valuable UVB rays, but you will expose yourself to the more dangerous and potentially deadly UVA rays. UVA's have a longer wavelength than UVB's, and can more easily penetrate the ozone layer and other obstacles (like clouds and pollution) on their way from the sun to the earth. UVA is what radically increases your risk of skin cancer and photoaging of your skin. So while it will give you a tan, unless the companion UVB rays are available you're likely doing more harm than good and should probably stay out of the sun to protect your skin.
During the times of the year when UVB rays are not present where you live you essentially have two options: You can use a safe tanning bed or oral vitamin D3.
Take Action: Please Support Critical Research
If you would like to support critical vitamin D research, I recommend supporting the Vitamin D Council and Grassroots Health's D*Action Project. Right now, Grassroots Health has a matching funds campaign for vitamin D and breast cancer research.
If you're a woman aged 60 or over and do not currently have cancer or being treated for cancer, you can sign up to participate in the D*Action Breast Cancer Prevention Study. The aim of the D*Action Project is to demonstrate the significance of vitamin D on human health and, of course, in the prevention of many diseases, including cancer.
You can also give a tax deductible donation to GrassRootsHealth.org by clicking HERE!
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