But a recent study conducted on the effects of high-dose oral vitamin D and sunburn holds out the hope that if you do mistakenly get sunburned, a mega-dose of vitamin D just might help you dodge its worst effects.
It all started with an experiment in mice to see if high doses of vitamin D could help mitigate the effects of skin injury and assist in wound healing. When vitamin D was indeed found to reduce inflammation, lessen wound damage and bolster the overall health of mice with chemically induced skin injuries, Dr Jeffrey Scott, a dermatologic oncologist who specializes in skin cancer surgery at the University Hospitals Cleveland Medical Center in Ohio and co-author on the original study, decided to see if a high, one-time oral dose of vitamin D could help reduce the effects of sunburn in humans.
In his study, 20 healthy adults were randomized to receive either a placebo or a 50,000 IU, 100,000 IU or 200,000 IU dose of vitamin D3 (cholecalciferol) one hour after an experimental sunburn was induced on one arm by the application of ultraviolet blue (UVB) radiation.
"It definitely reduced the visual redness on the participants' skin," says Dr Scott. "But it didn't completely eliminate the sunburn." And the highest doses of vitamin D were clearly the most effective. Of all the subjects who were given these experimental sunburns, only the subjects who received the highest amounts of vitamin D had less redness.
"We're speculating that vitamin D, because we produce it in our skin, may have some homeostatic regulatory role," says Scott. "Not only are our bodies producing it to generate more vitamin D for bone health, but our bodies may be producing it to help protect us from external insults from the environment. We don't have any data from our paper—our study wasn't designed to ask that question. But... if vitamin D can be anti-inflammatory, could it be that it's acting in this fashion in our skin, as it's being produced on a continual basis?"
The sunshine vitamin
Vitamin D comes in two forms. Vitamin D2 is found in mushrooms exposed to sunlight. Vitamin D3 is created in our epidermis when our skin is exposed to UVB radiation from the sun. UVB light stimulates a chemical in the skin's epidermis called 7-dehydrocholesterol to produce vitamin D. Vitamin D3 is also found in some fatty fishes, such as salmon, herring and mackerel.
Vitamin D from both sources—within our skin and derived from our diet—is actually biologically inert and has to be processed by the liver and then the kidneys in order to create its bioactive form, called calcitriol (1,25-dihydroxyvitamin D3 or 1,25(OH)2D3).2 Calcitriol, while technically derived from a 'vitamin,' is actually a hormone, with critical effects on many organs in the body via the endocrine system.3
For decades, vitamin D was thought to exist simply to promote bone health, because lack of vitamin D was found to be responsible for under-mineralization of the skeletal system leading to the condition known as rickets. Vitamin D deficiency can also cause bone softening, known as osteomalacia. Laboratory experiments have shown that vitamin D strengthens bones by stimulating the intestinal absorption of calcium and phosphate, as well as mobilizing calcium and phosphate stores in the body as they're needed for skeletal growth and bone repair.
Today we know that vitamin D plays an enormous number of roles in maintaining the body's health, as vitamin D receptors are found in most kinds of tissues and cells.
Vitamin D assists transcription—the first step of gene expression where a segment of DNA is copied into RNA, and recently it has been the focus of significant attention for its role in the immune system.
Vitamin D controls genes responsible for the production of antimicrobial agents such as cathelicidin, which the immune system uses to fight off potentially harmful bacteria.4 It has also been suggested to stimulate the immune system to attack certain forms of cancer.5
Vitamin D deficiency is related to the progression of tuberculosis6 as well as the risk of cardiovascular disease7 and chronic kidney disease.8 Vitamin D stimulates the production of insulin, and vitamin D deficiency is also associated with insulin resistance and diabetes.9 Having a low level of vitamin D has been linked to the presence and severity of adult asthma.10 Vitamin D has also been found to have antiproliferative effects, suggesting a possible role in cancer prevention, with vitamin D deficiency particularly linked to a higher risk of colon cancer.11
Vitamin D and inflammation
Scott's study on the effects of vitamin D on sunburn clearly support it having anti-inflammatory properties. And Scott says he and his co-workers have an idea of just how that occurs. "What we think is happening—what our study has data to support—is that it's activating a type of immune cell that helps to resolve inflammation and helps speed up wound healing. Vitamin
D somehow activates that cell that then goes into the skin and helps calm inflammation."
Scott's is not the first experiment to reveal the anti-inflammatory role of vitamin D and its impact on the body. Vitamin D has recently been found to affect the regulation and production of inflammatory cytokines (small proteins secreted by cells in the immune system responsible for intracellular communication and other functions) as well as inhibit the proliferation of pro-inflammatory cells—both of which play important roles in the development of inflammatory diseases.12
Vitamin D protects against inflammatory processes that are involved in atherosclerosis,13 and it has shown promise in the treatment of the inflammatory bowel diseases ulcerative colitis and Crohn's disease.14 Furthermore, vitamin D deficiency has been linked to the progression of multiple sclerosis, a chronic inflammatory disease affecting the central nervous system.15
An interesting question
The question is no longer whether vitamin D mitigates inflammatory processes in the human body or whether vitamin D deficiency is directly responsible for a wide number of disease conditions, inflammatory and otherwise. The interesting question now is whether vitamin D can be used as a prophylactic to help people avoid inflammation in the first place. Dr Scott is clear that his small study is only the starting point for an ongoing clinical investigation into the potential use of vitamin D as a post-sunburn treatment.
While vitamin D appears to have a clear benefit against sunburn, he says, certain ramifications need to be cleared up before vitamin D therapy can be declared a safe and effective treatment for it.
"We know that our immune systems are very important in suppressing the early stages of skin cancer formation," says Scott. "We know that our immune system basically puts the brakes on the events that lead to skin cancer. So, one interesting speculation that you could extrapolate from our data would be that if you are suppressing inflammation in the skin after a sunburn, you are possibly increasing someone's risk of skin cancer because you're shutting down those same processes that would normally help protect you. You may be reducing the sunburn initially. But overall you might be allowing those skin cancer processes to go unchecked."
A pressing issue
It is impossible to underestimate the value of ongoing investigation into the multiple potentials of vitamin D therapy, whether for inflammatory conditions or other health problems.
Studies show that vitamin D insufficiency affects almost 50 percent of the global population. In addition, an estimated one billion people worldwide present with a vitamin D deficiency.16 The reasons for this are many and varied. The first is our increasingly sedentary, indoor lifestyle. Furthermore, in many areas around the globe, air pollution reduces the amount of UVB radiation that can be absorbed through the skin. The widespread use of sunscreens has also radically diminished the amount of vitamin D humans absorb. According to the American Osteopathic Association, using sunscreen with an SPF of 15 or higher can reduce the body's vitamin D3 production by 99 percent. And many traditional food sources of healthy vitamin D are waning. For example, farmed salmon has been found to have vastly lower amounts of vitamin D than wild salmon.17 And factory-farmed eggs from hens kept in indoor cages have up to 400 percent less vitamin D than eggs produced by chickens exposed to sunshine.18
The increasing number of diseases now being correlated with low vitamin D levels are a clear indicator that there is value in keeping the body's vitamin D at acceptable levels. And, in the final analysis, there are many intriguing health links indicating the possibility that vitamin D might indeed one day prove to be a possible protector against sunburn.
Experiments with mice show that the topical application of 1,25-dihydroxyvitamin D3 has photoprotective effects.19 And there are indirect indicators as well. For example, aging has been proven to decrease the ability of our skin to produce vitamin D.20 Not surprisingly, the older we get, the easier it is to get sunburned.
Stress has also been shown to negatively affect the integrity and protective function of the stratum corneum, the tough outer layer of our skin. However, the underlying mechanism is still unclear. Is it possible that insufficient vitamin D is one of the culprits?
Stress hormones have been found to mimic the disturbances in stress systems observed in depression,21 and many studies have shown a relationship between low vitamin D levels and depression. Indeed, one study revealed that vitamin D therapy was more effective at treating depression than phototherapy.22 In addition to depression, low vitamin D levels have also been linked to schizophrenia and alcoholism23 as well as to diminished cognitive function in older adults.24
The story of vitamin D, its many and varied functions in the body and its relationship to human health is a vastly complicated one. But the relationship between vitamin D deficiency, poor skin integrity and an increased vulnerability to sunburn is undeniable, as is its importance in many other inflammatory conditions.
While we unravel its role, whether for helping us avoid the painful consequences of sunburn after a day at the beach or for avoiding more serious conditions, it makes sense to ensure that you're getting enough of this vital hormone from every source.
How much vitamin D is enough?
The recommended daily allowance (RDA) of vitamin D set by the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine in Washington, DC, is 600 international units (IU) daily up to age 70, and 800 IU for people who are older. According to the Institute of Medicine (IOM), 4,000 IU is the safe upper limit for vitamin D supplementation.
Studies show that optimal vitamin D status is achieved with a serum 25-hydroxyvitamin D [25(OH)D] concentration of greater than 75 nmol/L .1
Because everyone's baseline vitamin D serum level is different, it's exceedingly difficult to determine the proper dosage for each individual. The third National Health and Nutrition Examination Survey suggests a dose of 3,800 IU for those above a 25(OH)D threshold of 55 nmol/L and 5,000 IU for those below.1
Opinions vary widely. Dr Michael F. Holick, a professor of medicine, physiology and biophysics at Boston University School of Medicine and a leading spokesperson on vitamin D deficiency, believes just about everybody is lacking in vitamin D. In a 2007 article in The New England Journal of Medicine, he points out that what's now considered to be normal vitamin D levels (between 21 to 29 nanograms per milliliter of blood) have been linked to a large number of health problems, from depression to diabetes to asthma. He suggests a healthier average would be at least 30 nanograms per milliliter.2
The reason for the discrepancy between institutions, says Dr Jeffrey Scott, the dermatologic oncologist involved in the study linking vitamin D to sunburn, is that "no one really understands yet what the ideal dose is."
Scott also points out that an ideal dose might be different for different people, depending on what they're trying to prevent.
The supplemental dose a person might take if they're trying to prevent fractures might be different from the dose they should take to improve their immune health. "But probably anything up to 2,000 IU per day is safe," he says.
What makes you more likely to burn?
Here are some of the things you need to be aware of that can contribute to a decrease in the integrity of the outer protective layer of your skin, thereby increasing the likelihood of sunburn.
Skin care products: Check the labels of your skincare lotions for alpha-hydroxy acids, beta-hydroxy acids and tretinoins such as Retin-A. All of these compounds lower the protective capacity of the skin. Potential irritants and allergens in lotions (including sunscreens) and cosmetics that can affect the protective qualities of the skin include fragrances, parabens, vitamin E, essential oils, benzyl alcohol, propylene glycol, formaldehyde-releasing preservatives, iodopropynyl butylcarbamate, and lanolin.1 Acne products containing the chemical benzoyl peroxide can also cause photosensitivity.
Drugs: Antibiotics including sulfonamides, tetracyclines (doxycycline, tetracycline) and fluoroquinolones (ciprofloxacin, ofloxacin, levofloxacin); antifungals; antihistamines; benzocaine; neuroleptic drugs; nonsteroidal anti-inflammatory drugs such as ibuprofen and naproxen; oral contraceptives; oral diabetes drugs (sulfonylureas); tricyclic antidepressants and traditional herbal remedies including St. John's wort and dong quai can all contribute to phototoxic reactions that reduce your skin's integrity. Older adults should also be careful if they are taking antihypertensives (blood pressure drugs), cholesterol-lowering drugs and diuretics.
Foods: Figs, lime, parsley, wild carrots, celery, dill and fennel can increase sun sensitivity.
How quick are you to burn?
The following scale, developed by Harvard Medical School Professor Thomas Fitzpatrick in 1975 as a way to classify skin pigmentation, rates people's ability to suntan or burn. Vitamin D synthesis occurs more quickly in fairer skin types, although they are also more likely to burn.
Sources of vitamin D
The most efficient way to get your vitamin D is still the old-fashioned way: from the sun. But the amount of sunlight required for photoconversion of 7-dehydrocholesterol to the vitamin D precursor that can be used by the human body varies tremendously based on a person's skin type (see box 63), age, geographic location and the time of year.
Just looking at geography and skin type, for example, in Boston, Massachusetts, from April to October at noon, an individual with type III skin on the Fitzpatrick scale with approximately a quarter of their body surface exposed would need to spend three to eight minutes in the sun to synthesize 400 IU of vitamin D.
Cod liver oil. It tastes better than the stuff your mother used to give you, and it's the go-to supplement for vitamin D in the wintertime. Just one teaspoon delivers a whopping 440 IU of vitamin D. Cod liver oil is also one of the best sources of omega-3 fatty acids on the planet, as well as vitamin A, which works in harmony with vitamin D to keep bones strong. Be sure to buy cod liver oil in dark bottles and store in a cool, dark, dry place to avoid rancidity.
Salmon. Make sure you purchase wild-caught and not farmed salmon, as farmed salmon contains pollutants and has been found to have vastly less vitamin D than fish from the sea. Three ounces gives you 400 IU of vitamin D. It also supplies high levels of all the B vitamins, omega-3 fatty acids, and potassium, and it's loaded with selenium and the powerful antioxidant astaxanthin.
Mackerel. Just three ounces delivers 400 IU of vitamin D as well as omega-3 fatty acids; vitamins A, B6, B12, C, D, E and K; calcium; iron; magnesium; phosphorous; potassium; sodium; and selenium. Mackerel also contains the antioxidant coenzyme Q10.
Tuna. Three ounces contain 228 IU of vitamin D as well as healthy doses of vitamin A; vitamins B1, B2, B3, B6 and B12; phosphorous; potassium; and iodine.
Sardines. They may not be glamorous, but sardines are very healthy, and just three ounces deliver 164 IU of vitamin D. Sardines are also a fantastic source of vitamin B12, selenium, omega-3 fatty
acids, protein, phosphorus
Raw milk, caviar and egg yolks from free-range chickens offer considerably less vitamin D, but are still good sources.