Due to fear of melanoma, a deadly disease that has been erroneously attributed to sunlight exposure, the people are leaving the sunlight and becoming more like cave dwellers. For those of you who believe in evolution, can you imagine that after millions of years under the sun, human beings have been frightened away from their heritage?
There is an inconvenient truth about melanoma that the Powers of Darkness (those who would take away our sunlight) would prefer you not know: people who work regularly outdoors have a lower risk of melanoma than those who work indoors.
Godar, et al. present evidence that outdoor workers, while receiving 3-9 times the UVR exposure as indoor workers,  have had no increase in melanoma since before 1940, whereas melanoma incidence in indoor workers has increased steadily and exponentially. Other research corroborates the idea that outdoor workers have fewer melanomas than indoor workers. Vagero, et al. showed that melanomas were less common among indoor office workers and other indoor workers than among outdoor workers, and Kennedy, et al. showed that a lifetime of sunlight exposure correlated to a reduced risk of melanoma. Garland, et al. showed that those who worked indoors had a 50% greater risk of melanoma than those who worked both indoors and outdoors, and Kaskel, et al. demonstrated that children who engage in outdoor activities are less likely to develop melanoma than those who do not. Many other papers in the scientific literature show that both incidence and death rate from melanoma are reduced with increasing exposure to sunlight.          
This is not to say that sunburn does not contribute to melanoma, but it certainly shows that habitual, non-burning sun exposure correlates to a reduced risk of this deadly disease. In addition, there are approximately 105 additional diseases that are reduced among those who have higher sunlight exposure and therefore have higher levels of vitamin D (see my book for a discussion on each disease). We cannot live without vitamin D, which is not a vitamin at all, but in its most active form is a potent steroid hormone that controls at least 1,000 genes. It is also important to understand that 90% of all vitamin D is produced in the skin by the action of sunlight on skin.
However, blood levels of this important hormone are dropping precipitously in the American population, with a near doubling of the prevalence of vitamin D insufficiency that existed 10 years ago, and with 90% of Blacks, Hispanics and Asians, and 75% of the white population now suffering from the disorder.
So what does this mean to the health of US citizens? I have calculated in a manuscript currently in preparation, that the diseases that correlate to sunlight deprivation/vitamin D deficiency kill approximately 1.42 million people per year in the US. Diseases that correlate to sunlight exposure kill approximately 1,500 people per year. That produces a ratio of about 948:1. I will continue with my mid-day sunbathing, thank you!
Remember that no one is advising the injudicious use of sunlight; baking in the sun for hours is neither necessary nor desirable, but regular sunlight exposure is a sine qua non for vibrant health. To say that we should avoid sunlight is like saying we should avoid water. Water correlates to drowning, but no one asks us to avoid water; if we did the results would be catastrophic, as are the results of vitamin D deficiency due to sunlight deprivation.
Of course, there are some extremely rare conditions that may preclude sunlight exposure. Check with your (enlightened) physician.
Is it time to return to reasonable, habitual, non-burning sunlight exposure? It could save your life!
 Godar DE, Landry RJ, Lucas AD. Increased UVA exposures and decreased cutaneous Vitamin D3 levels may be responsible for the increasing incidence of melanoma. Med hypothesis (2009), doi:10.1016/j.mehy.2008.09.056
 Godar D. UV doses worldwide. Photochem Photobiol 2005;81:736–49.
 Thieden E, Philipsen PA, Sandby-Møller J, Wulf HC. UV radiation exposure related to age, sex, occupation, and sun behavior based on time-stamped personal dosimeter readings. Arch Dermatol 2004;140:197–203.
 Lee J. Melanoma and exposure to sunlight. Epidemiol Rev 1982;4:110–36.
 Vågero D, Ringbäck G, Kiviranta H. Melanoma and other tumors of the skin among office, other indoor and outdoor workers in Sweden 1961–1979 Brit J Cancer 1986;53:507–12.
 Kennedy C, Bajdik CD, Willemze R, De Gruijl FR, Bouwes Bavinck JN; Leiden Skin Cancer Study. The influence of painful sunburns and lifetime sun exposure on the risk of actinic keratoses, seborrheic warts, melanocytic nevi, atypical nevi, and skin cancer. Invest Dermatol 2003;120:1087–93.
 Garland FC, White MR, Garland CF, Shaw E, Gorham ED. Occupational sunlight exposure and melanoma in the USA Navy. Arch Environ Health 1990; 45:261-67.
 Kaskel P, Sander S, Kron M, Kind P, Peter RU, Krähn G. Outdoor activities in childhood: a protective factor for cutaneous melanoma? Results of a case-control study in 271 matched pairs. Br J Dermatol 2001;145:602-09.
 Garsaud P, Boisseau-Garsaud AM, Ossondo M, Azaloux H, Escanmant P, Le Mab G. Epidemiology of cutaneous melanoma in the French West Indies (Martinique). Am J Epidemiol 1998;147:66-8.
 Le Marchand l, Saltzman S, Hankin JH, Wilkens LR, Franke SJM, Kolonel N. Sun exposure, diet and melanoma in Hawaii Caucasians. Am J Epidemiol 2006;164:232-45.
 Armstong K, Kricker A. The epidemiology of UV induced skin cancer. J Photochem Biol 2001;63:8-18
 Crombie IK. Distribution of malignant melanoma on the body surface. Br J Cancer 1981;43:842-9.
 Crombie IK. Variation of melanoma incidence with latitude in North America and Europe. Br J Cancer 1979;40:774-81.
Weinstock MA, Colditz,BA, Willett WC, Stampfer MJ. Bronstein, BR, Speizer FE. Nonfamilial cutaneous melanoma incidence in women associated with sun exposure before 20 years of age. Pediatrics 1989;84:199-204.
 Tucker MA, Goldstein AM. Melanoma etiology: where are we? Oncogene 20f03;22:3042-52.
 Berwick M, Armstrong BK, Ben-Porat L, Fine J, Kricker A, Eberle C. Sun exposure and mortality from melanoma. J Nat Cancer Inst 2005;97:95-199.
 Veierød MB, Weiderpass E, Thörn M, Hansson J, Lund E, Armstrong B. A prospective study of pigmentation, sun exposure, and risk of cutaneous malignant melanoma in women. J Natl Cancer Inst 2003;95:1530-8.
 Oliveria SA, Saraiya M, Geller AC, Heneghan MK, Jorgensen C. Sun exposure and risk of melanoma. Arch Dis Child 2006;91:131-8.
 Elwood JM, Gallagher RP, Hill GB, Pearson JCG. Cutaneous melanoma in relation to intermittent and constant sun exposure—the western Canada melanoma study. Int J Cancer 2006;35:427-33
 Luz E. Tavera-Mendoza and John H. White. Cell Defenses and the Sunshine Vitamin. Scientific American 2007;November, p.42.
 Reichrath J. The challenge resulting from positive and negative effects of sunlight: how much solar UV exposure is appropriate to balance between risks of vitamin D deficiency and skin cancer? Prog Biophys Mol Biol 2006;92(1):9-16.
 Adams, J and Hewison, M. Update in Vitamin D. J Clin Endocrinol Metab 2010;95: 471–478.
By Graham Pembrey
Summer is on the horizon and it is only natural that many of us will be reaching for the sun cream, in an attempt to keep our pale British skin from burning in the heat. One thing that many of us will not realise as we do so, however, is that while sun lotion blocks out harmful rays from the sun, it also prevents our bodies from absorbing an important vitamin that helps us to fight off obesity.
You see, while excessive sunshine might burn us, sunshine is also an important source of what is known as the ‘sunshine vitamin’ – vitamin D. Vitamin D has many benefits. It helps bone growth, prevents depression, and aids weight loss. When we lack in this vitamin, our bodies can suffer. As can our emotions – which is one of the major reasons why seasonal affective disorder, commonly known as SAD, affects many people in the cold season, giving them the ‘winter blues’.
There is some good news for people who want to tan without burning, but also want to avoid obesity; vitamin D can be found in certain foods including oily fish, eggs and dairy products. The vitamin can also be found in margarines, and in cod and liver oil. By eating plenty of these foods, it may be possible to make up for some lack of exposure to sunlight. Still, you should try to get at least 10 to 20 minutes of sunlight most days.
40% of Children Have Vitamin D Deficiency How to Make Sure Your Kid Isn’t One of Them
By Dan Shapley April 6, 2010
At least 40% of infants and toddlers, and 42% of teens, aren’t getting enough vitamin D, the “sunshine vitamin,” according to new research.
Vitamin D is produced when the body reacts to sunlight, and helps the body absorb calcium. Without it, people are prone to bone disease, autoimmune diseases like diabetes, multiple sclerosis and certain cancers, as the Washington Post put it — as well as increased risk for heart attacks (learn more here).
The new Boston Children’s Hospital research, on infants and toddlers, suggests that nursing mothers should be giving their children Vitamin D supplements, since human breast milk lacks the fortification given to store-bought milk.
Teens may also need supplements, researchers told the Post.
Another solution we humbly suggest? Go outside. While it is important to be careful to avoid overexposure to the sun, there’s no reason people can’t get more Vitamin D the natural way.
In our hyperconnected, hyperfearful times, we’re more apt to stay indoors plugged into a computer, video game, television or PDA than to take a walk outside, play sports, fish or otherwise get some sun. Parents are increasingly concerned about the threat of pedophiles and the like, so children are less apt to just take off for the great outdoors unsupervised.
There were already good reasons to make sure – via whatever extra effort is necessary – that children aren’t suffering from so-called nature deficit disorder. There’s the food for the soul argument, the inspiration for creativity argument, the exercise for health argument, and now there’s another: good nutrition.
It’s a poignant commentary about a society when its children lack the sunshine vitamin.
By Jane E. Brody
The so-called sunshine vitamin is poised to become the nutrient of the decade, if a host of recent findings are to be believed. Vitamin D, an essential nutrient found in a limited number of foods, has long been renowned for its role in creating strong bones, which is why it is added to milk.
Now a growing legion of medical researchers have raised strong doubts about the adequacy of currently recommended levels of intake, from birth through the sunset years. The researchers maintain, based on a plethora of studies, that vitamin D levels considered adequate to prevent bone malformations like rickets in children are not optimal to counter a host of serious ailments that are now linked to low vitamin D levels.
To be sure, not all medical experts are convinced of the need for or the desirability of raising the amount of vitamin D people should receive, either through sunlight, foods, supplements or all three. The federal committee that establishes daily recommended levels of nutrients has resisted all efforts to increase vitamin D intake significantly, partly because the members are not convinced of assertions for its health-promoting potential and partly because of time-worn fears of toxicity.
This column will present the facts as currently known, but be forewarned. In the end, you will have to decide for yourself how much of this vital nutrient to consume each and every day and how to obtain it.
Where to Obtain It
Through most of human history, sunlight was the primary source of vitamin D, which is formed in skin exposed to ultraviolet B radiation (the UV light that causes sunburns). Thus, to determine how much vitamin D is needed from food and supplements, take into account factors like skin color, where you live, time of year, time spent out of doors, use of sunscreens and coverups and age.
Sun avoiders and dark-skinned people absorb less UV radiation. People in the northern two-thirds of the country make little or no vitamin D in winter, and older people make less vitamin D in their skin and are less able to convert it into the hormone that the body uses. In addition, babies fed just breast milk consume little vitamin D unless given a supplement.
In addition to fortified drinks like milk, soy milk and some juices, the limited number of vitamin D food sources include oily fish like salmon, mackerel, bluefish, catfish, sardines and tuna, as well as cod liver oil and fish oils. The amount of vitamin D in breakfast cereals is minimal at best. As for supplements, vitamin D is found in prenatal vitamins, multivitamins, calcium-vitamin D combinations and plain vitamin D. Check the label, and select brands that contain vitamin D3, or cholecalciferol. D2, or ergocalciferol, is 25 percent less effective.
Vitamin D content is listed on labels in international units (I.U.). An eight-ounce glass of milk or fortified orange juice is supposed to contain 100 I.U. Most brands of multivitamins provide 400 a day. Half a cup of canned red salmon has about 940, and three ounces of cooked catfish about 570.
Myriad Links to Health
Let’s start with the least controversial role of vitamin D — strong bones. Last year, a 15-member team of nutrition experts noted in The American Journal of Clinical Nutrition that “randomized trials using the currently recommended intakes of 400 I.U. vitamin D a day have shown no appreciable reduction in fracture risk.”
A Swiss study of women in their 80s found greater leg strength and half as many falls among those who took 800 I.U. of vitamin D a day for three months along with 1,200 milligrams of calcium, compared with women who took just calcium. Greater strength and better balance have been found in older people with high blood levels of vitamin D.
In animal studies, vitamin D has strikingly reduced tumor growth, and a large number of observational studies in people have linked low vitamin D levels to an increased risk of cancer, including cancers of the breast, rectum, ovary, prostate, stomach, bladder, esophagus, kidney, lung, pancreas and uterus, as well as Hodgkin’s lymphoma and multiple myeloma.
Researchers at Creighton University in Omaha conducted a double-blind, randomized, placebo-controlled trial (the most reliable form of clinical research) among 1,179 community-living, healthy postmenopausal women. They reported last year in The American Journal of Clinical Nutrition that over the course of four years, those taking calcium and 1,100 I.U. of vitamin D3 each day developed about 80 percent fewer cancers than those who took just calcium or a placebo.
Vitamin D seems to dampen an overactive immune system. The incidence of autoimmune diseases like Type 1 diabetes and multiple sclerosis has been linked to low levels of vitamin D. A study published on Dec. 20, 2006, in The Journal of the American Medical Association examined the risk of developing multiple sclerosis among more than seven million military recruits followed for up to 12 years. Among whites, but not blacks or Hispanics, the risk of developing M.S. increased with ever lower levels of vitamin D in their blood serum before age 20.
A study published in Neurology in 2004 found a 40 percent lower risk of M.S. in women who took at least 400 I.U. of vitamin D a day.
Likewise, a study of a national sample of non-Hispanic whites found a 75 percent lower risk of diabetes among those with the highest blood levels of vitamin D.
Vitamin D is a fat-soluble vitamin that when consumed or made in the skin can be stored in body fat. In summer, as little as five minutes of sun a day on unprotected hands and face can replete the body’s supply. Any excess can be stored for later use. But for most people during the rest of the year, the body needs dietary help.
Furthermore, the general increase in obesity has introduced a worrisome factor, the tendency for body fat to hold on to vitamin D, thus reducing its overall availability.
As for a maximum safe dose, researchers like Bruce W. Hollis, a pediatric nutritionist at the Medical University of South Carolina in Charleston, maintain that the current top level of 2,000 I.U. is based on shaky evidence indeed — a study of six patients in India. Dr. Hollis has been giving pregnant women 4,000 I.U. a day, and nursing women 6,000, with no adverse effects. Other experts, however, are concerned that high vitamin D levels (above 800 I.U.) with calcium can raise the risk of kidney stones in susceptible people.
If this vitamin isn’t in your medicine cabinet, it probably should be.
By Linda B. White, M.D.
What do the following conditions have in common: osteoporosis, multiple sclerosis, high blood pressure, diabetes and cancer? Give up? Experts suspect that insufficient levels of vitamin D raise your risk of getting these diseases. Unfortunately, most of us probably are vitamin D deficient.
About all I was taught in medical school is that vitamin D keeps bones strong. Recently however, this area of study has exploded as scientists uncover the vitamin’s far-reaching effects. Because it increases calcium levels, vitamin D indirectly fortifies bones and teeth. It also regulates cells all over the body, which explains vitamin D’s disparate roles, such as influencing insulin production and immune function, as well as helping prevent inflammation and cancer.
The scary thing is that vitamin D deficiency appears to be quite common. A recent British study found that 87 percent of volunteers had low blood levels of the vitamin in winter and spring, and 61 percent had low levels in summer and fall. Why the seasonal variation? Our chief source of vitamin D is sunshine.
Why We’re D-ficient
In response to ultraviolet B (UVB) rays in sunlight, our skin transforms a derivative of cholesterol normally found in the skin into vitamin D3 (cholecaliferol). The liver, kidneys and other tissues further activate this molecule. Given that the skin is a veritable vitamin D factory, why is deficiency so rampant? History — ancient and recent — holds the answers.
Humans evolved near the equator and spent days outdoors, allowing the skin to generate ample amounts of this vitamin. About 50,000 years ago, some of our ancestors migrated toward the poles, where winter sunlight isn’t intense enough for vitamin D production. However, their diet of vitamin D-rich fish compensated for the deficit.
But rickets became prevalent in the 18th century during the Industrial Revolution, when people shifted to indoor labor and the skies darkened with pollution. This manifestation of severe vitamin D deficiency causes skeletal deformities, such as bowed or knocked knees and bony knobs along the ribs, known as rachitic rosary. During the 1930s, the decision to add vitamin D to milk nearly eradicated rickets in the United States. But nowadays, kids and adults drink less milk and more juice and sodas, and sadly, rickets is making a comeback in American children according to a study released last year.
Starting about 30 years ago, another cultural shift deepened our vitamin D deficit: public health campaigns to avoid the midday sun, cover up and apply sunscreen. They were justified attempts to save our skins from sun-induced aging and cancer, but now we’re not making enough vitamin D. These days, vitamin D deficiency has become commonplace, even in the tropics. For instance, a sampling of adults in sunny Honolulu showed that half were low in D.
Of course, we can take supplements, but current government recommendations are cautious — 200 IU a day for young adults, 400 for people 51 to 70, and 600 for those over 70. Vitamin D expert Bruce W. Hollis, M.D., of the Medical University of South Carolina, says such doses might be enough to prevent rickets, but aren’t sufficient to fulfill other important functions.
Most of us don’t even meet these inadequate guidelines. A German study found that 80 percent of sampled adults didn’t get recommended amounts, and nearly 60 percent had low blood levels of vitamin D, a statistic that rose to 75 percent in women over 65 years old. Furthermore, those women with low blood levels of vitamin D were more likely to have high blood pressure, cardiovascular disease and type 2 diabetes.
Results of D-ficiency
So what are the dangers of too little vitamin D in your system? A whole host of chronic conditions.
Weak bones and muscles. Rickets was the first disease tied to vitamin D depletion. This severe deficiency during childhood can prevent kids from reaching their potential for full height and peak bone mass. (Bone mass peaks in early adulthood; after that it slowly declines.)
In adults, vitamin D deficiency can lead to osteoporosis (thin, brittle bones) and osteomalacia (rubbery, demineralized bones). The latter causes bone pain, and both elevate the risk of broken bones.
Additionally, vitamin D deficiency causes muscle weakness and discomfort. One study found that patients with aches and weakness were often severely vitamin D deficient. Hollis says he’s hearing from doctors that vitamin D supplementation often resolves these aches and pains, adding, “A lot of ‘fibromyalgia’ is probably D deficiency.”
Weakened muscles increase the risk of falls and fractures — a dangerous combination for the elderly. The research shows that, although the recommended dose of 600 IU a day doesn’t prevent falls and fractures in older adults, doses over 800 IU do. In fact, consuming 700 to 800 IU of vitamin D a day (plus or minus calcium) could prevent a quarter of hip fractures in older people, according to a study published in the Journal of the American Medical Association.
Cancer. Vitamin D deficiency has been linked to several types of cancer, including breast, prostate, colon and melanoma. In fact, for more than 60 years, research has found that people living at higher latitudes with less exposure to sunlight showed an increased risk of cancer mortality. Adequate vitamin D levels seem to protect against some cancers. In a recent study, researchers followed healthy postmenopausal women whom they assigned to take either 1,400 to 1,500 milligrams a day of supplemental calcium plus 1,100 IU a day of vitamin D3, or a placebo for four years. After the first year, vitamin D supplementation led to a 57 percent reduction in cancer.
Cardiovascular disease. In addition to cancer and bone disease, vitamin D may also be healthy for your heart. Vitamin D levels are inversely associated with the risk of high blood pressure and congestive heart failure. Exposing people with high blood pressure to ultraviolet light has been shown to improve the condition.
Asthma. Preliminary studies show that vitamin D also may help alleviate respiratory problems, such as asthma. According to one study published in the American Journal of Clinical Nutrition, children of mothers with lower intakes of vitamin D during pregnancy are more likely to develop asthma.
Autoimmune disorders. Vitamin D reduces inflammation and plays a role in the maturation of the immune system. Deficiency is common in autoimmune diseases where the immune system attacks normal cells, such as type 1 diabetes, rheumatoid arthritis and multiple sclerosis (MS). Emerging research shows that vitamin D may have a preventive effect. One study examined two large groups of women for 10 years and found a reduced risk of MS was associated with vitamin D supplementation. A study of Finnish children taking 2,000 IU a day (10 times the current recommendation) showed they had a decreased risk of developing type l diabetes. In an analysis of the Iowa Women’s Health Study, women consuming higher levels of vitamin D showed a reduced risk for rheumatoid arthritis.
Mental health. Psychiatrist John Cannell, M.D., founder of the nonprofit Vitamin D Council, says that vitamin D may contribute to several emotional disorders. In a study of elderly people, mood and cognitive skills deteriorated with lower levels of D. Cannell points out that seasonal affective disorder (SAD) is a type of depression whose onset follows the waning daylight of autumn and winter. An Australian study found that vitamin D supplements lifted the mood of people with SAD.
How to Get Enough D
Expose yourself. Your skin can tackle much of your vitamin D needs. If you’re young, fair, scantily clad and near the equator, 10 to 15 minutes of peak sunshine produces 20,000 IUs.
However, Hollis says a dark-skinned person requires 10 times that exposure to make an equivalent amount of D. And a 70-year-old person makes only a quarter of the vitamin D that a 20-year-old can produce. During the fall and winter in higher latitudes (above 37 degrees latitude — San Francisco is just above 37 degrees), the levels of UVB fall below the threshold needed for even a fair-skinned person to produce enough vitamin D. Additionally, complete cloud coverage cuts UV energy in half, and shade reduces it by 60 percent.
Sunscreens also block UVB waves, the wavelength that stimulates the skin’s vitamin D production. According to Michael F. Holick, M.D., Ph.D., of the Boston University School of Medicine, a sunblock with SPF 8 reduces the skin’s vitamin D production by 95 percent. “If you wear sunscreen ‘properly,’ you’ll become vitamin D deficient,” he says.
But what about skin cancer? Despite increased sunscreen usage, skin cancer rates have risen. One reason is that, until recently, sunscreens didn’t impede deeply penetrating UVA light, and presumably, our false sense of security led to more time in the sun and an increase in skin cancer.
What should you do? “Be sensible,” Holick advises. “Know your own skin sensitivity.” For instance, if you turn pink after 30 minutes in the summer sun, thenspending five to 10 minutes (in a bathing suit) in the sun should generate plenty of vitamin D. After that, apply sunscreen, cover up and seek shade.
Eat D-licious foods. Only a few foods contain much vitamin D. Sources of vitamin D include cod liver oil (1,360 IU per tablespoon); oily fish such as salmon, sardines and mackerel (about 350 IU per 3.5 ounces); eggs (about 20 IU per yolk); and fortified milk, soy milk and orange juice (98 IU per 8-ounce serving). (We’re testing pasture-raised chicken eggs for vitamin D as part of our 2007 egg testing project. See October/November 2007 for the initial results. — Mother)
Shiitake mushrooms can be an exceptional source of vitamin D, as noted in research published in Paul Stamets’ book, Mycelium Running. Shiitake mushrooms grown and dried indoors have only 110 IU of vitamin D per 100 grams. But when the shiitakes were dried in the sun, the vitamin D content rose to 21,400 IUs per 100 grams. Even more surprising, when the mushrooms were dried with their gills facing up toward the sun, their content rose to 46,000 IU!
Take supplemental D. Most North Americans can’t maintain healthy blood levels of D from sunlight and good diet. Therefore, many experts recommend 800 to 1,000 IU a day — several times the government guidelines of 200 to 600 IU.
The exact amount depends upon several things. If you’re dark-skinned or spend little time outdoors, you’ll obviously need more than a Caucasian lifeguard. And if you’re already deficient in vitamin D, you’ll need hefty doses just to get your blood levels up to normal.
If you’re pregnant or nursing, you’ll also need more. Hollis and colleagues are currently researching the effects of different vitamin D doses in pregnant women of various races. Until the results of that trial are finalized, he can’t recommend more than 2,000 IU per day.
When asked how much vitamin D they normally take, Hollis says he takes 4,000 IU a day, while Holick says each member of his family takes 1,000 IU of D3 a day. Holick also spends reasonable amounts of time outdoors.
Be aware that many supplements provide vitamin D as ergocalciferol (vitamin D2), rather than cholecalciferol (vitamin D3). D3 is the form naturally occurring in our bodies and is more effective.
No one really knows how much vitamin D might be too much; however, toxicity is exceedingly rare. The Food and Nutrition Board sets the upper level for daily dietary intake at 2,000 IU, though Hollis thinks that’s not enough to maintain health at northern latitudes. Accumulated research demonstrates 10,000 IU of vitamin D3 to be a more realistic upper limit.
Who’s at Risk?
The only way to measure vitamin D blood levels is to check a form of vitamin D called 25-hydroxyvitamin D. Doctors don’t routinely perform this test, and Holick thinks universal screening would be too expensive. If you’re at risk for, or already have symptoms of, deficiency, then you might want the blood test.
Just who’s at risk? Research shows the following populations face greater risk of vitamin D deficiency:
Dark-skinned people. Melanin darkens skin and absorbs UV light, which protects against sun damage and limits vitamin D production. Holick’s research shows that 80 percent of African-Americans studied in Boston over age 65 were vitamin D deficient — at the end of summer!
Northerners. People who live at higher latitudes where winters are long and dark run a higher risk of vitamin D deficiency. Holick notes that even fair-skinned people living above 37 degrees latitude make little vitamin D during the winter.
Older adults. The skin production of vitamin D and its activation in the kidneys declines with age. Further, the elderly typically spend more time indoors. Vitamin D deficiency in this age group contributes to osteoporosis and falls.
Breast-fed infants. Research in Iowa by Hollis and colleagues found that vitamin D deficiency, including severe deficiency, was common among breast-fed infants without vitamin D supplementation. Vitamin D deficiency in nursing mothers is the reason breast milk is D deficient. Unfortunately, early deficiency can have lifelong consequences.
People with intestinal disorders. Disorders that interfere with fat absorption include celiac disease, Crohn’s disease, pancreatic insufficiency, liver disease or cystic fibrosis. Fat-soluble vitamins such as D are absorbed from the intestine with dietary fat, so people with low ability to absorb fat may need vitamin D supplements.
Sun avoiders. People who cover up for religious, cultural or health reasons also run the risk of deficiency. Clothing blocks UVB waves, interfering with or preventing the skin’s formation of vitamin D.
The obese. In a British study, obese people were twice as likely as those of normal weight to be low in vitamin D. Hollis explains it’s because fat sponges up vitamin D and stores it, but doesn’t release it.