There is solid scientific evidence that vitamin D improves immunity to respiratory infections and prevents cavities. Despite excellent dental care, I got a new cavity at least once every 3 years. At my worst after my kids started daycare, I caught cold after cold and was unwell for a whole year with either a cold or a secondary bacterial infection caused by a cold. In 2007 I learned that vitamin D might help me. I started with vitamin D supplements, 4000 IU/day, and soon began feeling better. Unfortunately, I soon experienced vitamin D side effects. Over the course of a year, I gradually switched from supplements to sunshine. Over the next two years I steadily increased my sun exposure in an effort to maximize vitamin D production. Starting about a year ago, to further increase vitamin D production, I started using a UVB lamp in addition to sun bathing.
Using the lamp made me nervous. It is an unnatural behavior. So I started reading up on using UVB lamps to produce vitamin D. To my surprise, despite spending hours looking for information and reading, I still don't know how much vitamin D I can make using UVB light from the lamp and the sun. Here's the best data I found, not surprisingly from John Cannell (The Vitamin D Council):
"Despite robust skin production, vitamin D toxicity
cannot occur from skin production. Once maximum
cutaneous production occurs, additional sun exposure will
not result in additional net input to the system. The same
UVB that produces vitamin D in the skin also degrades it,
causing a steady-state that generally limits cutaneous
production to a maximum of ∼ 20,000 IU/day. For this
reason, in spite of such robust cutaneous production, no
one has ever reported vitamin D toxicity from either sun
exposure or from exposure to artificial UVB light."
Cannell did not show any data to support his 20,000 IU/day number. I'm certain this number is based on a limited amount of data from a small number of racial groups. I was disappointed to read the "light therapy" page at Wikipedia and find no mention of vitamin D. I had to narrow my "light therapy" search at Google to "light therapy and vitamin D" to find much of anything at all. Medical science had the tools required to answer basic questions about vitamin D by at least the 1950's. Today's tools are fantastically superior and still the data has yet to be collected to answer basic questions about vitamin D. Even worse, some of the basic data we do have is being ignored.
Vitamin D supplements, even in low doses, cause side effects. Vitamin D made by skin exposure to sunlight does not cause side effects. I do not know why these facts are both true. Neither does anyone else. We are unlikely to get an answer until someone besides me recognizes these facts as facts. I could come up with at least a dozen plausible reasons. I can wait for the answer to emerge. Finding the answer is pretty far down my list of important questions about vitamin D waiting to be answered.
It really is difficult for me to understand why every physician and scientist isn't nervous about the safety of vitamin D supplements. Let's start with a quote from what I regard as the most authoritative study of vitamin safety. The book is called, "The Right Dose - How to Take Vitamins and Minerals Safely".
"You might say that an intake of 1,000 IU of vitamin D can be considered relatively untainted by current knowledge. The critical level for increased risk of heart attack, for instance, seemed to be 1,200 IU. In the study of kidney stones, the average intake was 1254 IU among those with no condition predisposing to stones. So an intake of up to 1,000 might seem like a safe bet. In fact, supplements containing 1,000 IU can be found easily. Count me out as one who will endorse this level of supplementation as a general measure. it lacks something that i spoke of only a chapter ago - a margin of safety."
Next consider the fact that pure vitamin D is acutely toxic. It is on the "particularly hazardous substances" list in the laboratory where I work. I can not purchase vitamin D or use it in the lab without special safety training. Extreme doses (the equivalent of a person taking millions of IU per day) are used as rat poison.
I want readers to know that I'm really struggling with the disconnect between the many published studies using 4,000 IU or higher doses of vitamin D that report no side effects and my own personal experience. I'm looking at a very small number of individuals, but every single person I know who took 4,000 IU or more of vitamin D per day stopped because of side effects. This information is supplemented by the outpouring of testimonials at my blog item titled "Overdosing on Vitamin D: Side Effects, Toxicity, Symptoms, Poisoning."
So here are the uncomfortable facts. Vitamin D is essential for good health. Supplement doses of >4000 IU/day are needed to elevate blood levels of vitamin D and to achieve obvious benefits. Supplement doses as low as 1000 IU/day are associated with serious health risks, and uncomfortable side effects are commonplace at daily doses at or above 4,000 IU.
Vitamin D supplements are amongst the oldest known supplements. The healing powers of fish oils, and cod liver oil in particular, have been exploited for centuries. Unlike the "Blue Zone" cultures, fish oil taking cultures are not known for exceptional health and longevity. These cultures did not land on vitamin D daily doses of 4,000 IU/day or higher - the amount now proven to be the minimum required for maximum benefit. A typical dose was closer to 1,000 IU. Vitamin D has been used for decades to treat osteoporosis. The calcium plus vitamin D supplements typically have 400 to 800 IU/day - not higher and not lower. Again, it is simply a fact that doses >4000 IU/day are required for optimum benefits. So why the much lower typical doses in the supplements used starting centuries ago and right up through the end of the 20th century? Side effects sure look to me like a logical explanation.
Unlike supplements, there is no evidence that vitamin D produced in the skin by exposure to sunlight or man-made UV light causes side effects or toxicity. Cultures of the world known for health and longevity all spend lots of time outdoors in the sun. Some of these cultures were recently reviewed in a book called "The Blue Zones". Responding to these facts, I stopped taking vitamin D supplements and started sun bathing and using a UVB lamp. I don't know how much vitamin D I can make this way, and if I did, I wouldn't know what it meant. I don't think it is safe to assume that vitamin D produced in the skin and taken as a supplement have the same potency.
I assumed that as I increased the amount of time I spent in the sun every day, that I would get more tan and therefore require more time to synthesize the same amount of vitamin D. For me, this assumption was wrong. Where I live, the UV index at noon varies from 3 at winter solstice to 10 at summer solstice. In the summer I found I could only stay out in the sun for 2 minutes on each side before I started to burn. So - I assumed that 4 minutes on a side at a UV index of 5 would initiate burning. It doesn't. I can stay out in the sun all day when the UV index is 5 without burning. When I figured this out, I started sun bathing multiple times on sunny days. Just a few minutes. Then I'd wait an hour or so and get another few minutes. I sometimes do this as many as 5 times. I don't get any side effects that I associate with sunburn. But I do feel like the increased sun exposure is changing me. I'm hesitant to characterize my sensations as side effects from sun and UV lamp exposure because they aren't severe and don't get worse and aren't entirely consistent. But I feel very different. That's why I was hoping to find information about the benefits and side effects of sunbathing and UV light exposure.
The UV light I use is sold as a "lizard lamp". The manual that came with the light instructs lizard owners to watch the behavior of their lizards. If they starting acting sick, then removing the lamp is recommended. The manual further instructs owners to make sure that the lizard always has access to shade so that the lizard can self dose on the light. If a lizard can "feel" the effects of UV light, why shouldn't I. Again, how can it be 2011 and I can't find any solid information to use to intelligently select a dosage of UV light to optimize the amount of vitamin D made in my skin?
The stakes are high. Since I started supplementing with vitamin D, my teeth have healed along with some serious joint pains. There is every reason to believe that vitamin D is responsible for these benefits. Almost a third of American adults suffer from osteoporosis, osteopenia, or hypertension. What if lack of UV exposure is the cause?
For me, the choice is an easy one. My teeth were in ruins and I was afraid to travel on an airplane because I would always hurt my ears and usually get a bad cold. Since I started with UV light, I've been getting steadily better. For those in good health, there is no easy decision. There are obvious risks from both UV light and vitamin D supplements. Cannell passionately believes that high doses of vitamin D will prevent a majority of cancer cases. If he's right, my risk of cancer is now much lower - a huge extra benefit on top of my improved immunity to colds and improved dental health. If I didn't have the bad teeth and poor immunity to colds, would I risk vitamin D side effects to prevent a cancer that I might not get in the first place? I don't know.
Any comments from readers? Can anyone point me to data about how the maximum amount of vitamin D that can be made by sun and UV light exposure? Please help if you can.