Despite the scientific attention being paid to vitamin D, many experts caution that claims of wide-ranging health benefits are not yet supported by clinical evidence. We’ve been down this garden path before, some researchers say. Hopes for the powers of vitamin E, beta carotene, antioxidant vitamins, selenium and other nutrients have collapsed under the weight of rigorous, randomized clinical trials.
“It’s premature to go out and make a big deal out of vitamin D supplementation when we don’t have the evidence,” said endocrinologist Anastassios Pittas, co-director of the Diabetes Center at Tufts University Medical Center in Boston. “We’ve been burned before on nutrition-based interventions.”
As far as Dr. Joseph Mercola of Chicago is concerned, vitamin D is the magic bullet we’ve all been looking for. “Vitamin D appears to reduce your risk of dying from virtually any disease,” he wrote on his popular website. The excitement stems from a flurry of preliminary studies finding links between vitamin D deficiencies and various illnesses. The federal Institute of Medicine plans to announce revised recommendations regarding dietary intake of vitamin D and calcium that almost certainly will be higher.
Recommended minimum daily requirements, now called intake units (IU), and upper levels of tolerance (UL) will be revised upward and may be officially changed within the next six months, predicted Vicki Koenig, a registered dietitian (the preferred spelling) and nutritionist in New Paltz. Koenig encourages pale-skinned sunbathers to use sun block on their faces, but not to avoid the sun.
What symptoms of D deficiency does she observe? She noted depression similar to that manifested in Seasonal Affective Disorder, also known as SAD syndrome.
The amount of naturally occurring vitamin D in the body has been reduced to dangerous levels by an indoor lifestyle and a fear of sun exposure. Glass blocks ultraviolet B (UVB) light rays, thus preventing skin from producing vitamin D.
The need for vitamin D varies according to weight, skin tone, latitude and season. Dark-skinned individuals need six times as much time in the sun to produce as much D as that produced by light skinned people of the same size. To utilize this vitamin properly, the body also requires magnesium, zinc, vitamin K2, boron and a small amount of vitamin A. Vitamin D has long been recognized as necessary for the absorption of calcium.
More than a vitamin
Perhaps fear of sunlight results from overexposure during past decades, Koenig speculated, when aluminum screens were use to help sunbathers tan faster. Present practice recommends 30 minutes of full-body exposure to the midday sun daily from early spring through early fall. In that half hour, humans make at least 10,000 units of vitamin D, Koenig said, many times more than the current minimum daily requirement.
Your body will naturally store enough vitamin D to get you through the winter. If you haven’t stored enough during the warmer months, however, vitamin D supplement may be needed to fill the gap.
Suntan is an evolutionary device that protects against burning. “Vitamin D production occurs in the skin within minutes and is already maximized before your skin turns pink,” writes John Jacob Cannell, MD, executive director of the Vitamin D Council, a California-based not-for-profit. “We are not saying sunburns are safe. They are not. We are saying that brief full-body exposure may slightly increase your risk of melanoma, but it is a much smarter thing to do than die of vitamin deficiency.”
There’s hardly an organ in the body that isn’t affected by D’s metabolic product, calcitriol, a potent hormone that unlocks more than 2700 binding sites on the human genome, according to Dr. Cannell. Before becoming involved in Vitamin D research Cannell wrote for many years on the unhealthy effects of smoking.
“Those binding sites are near genes involved in virtually every known major disease of humans,” wrote Cannell. “It turns genes on and off at a dizzying rate, genes that are either making proteins that are essential to fighting cancer of genes that are making proteins that are promoting diseases like cancer.”
Calcitriol increases the level of calcium in the blood by increasing the uptake of calcium from the gut into the blood, decreasing the transfer of calcium from blood to the urine by the kidney, and increasing the release of calcium into the blood from bone. Current research implicates vitamin D deficiency as a major factor in the pathology of at least 17 varieties of cancer as well as heart disease, stroke, autoimmune diseases, diabetes, depression, chronic pain, osteoporosis, muscle weakness, birth defects, periodontal disease, and more.
Babies are affected, too
Infants may be adversely affected by a lack of vitamin D, which supports the growth of healthy bones and maintains functions of the brain, heart and muscles. The deficiency can cause rickets, a bone-weakening disorder that becomes apparent during childhood. Regardless of whether an infant is fed breast milk, formula or a combination, consult with your pediatrician about the baby’s vitamin D needs. Mothers are advised to find out whether they or their babies need supplemental vitamin D. Though standard infant formulas include 400 IU of vitamin D in 34 fluid ounces, most babies need to consume less than that. Find a formula that provides 400 IU in fewer fluid ounces. During infancy, mothers have just one chance to get nutrition right, according to the experts. For U.S. babies, vitamin D is often lacking but it is critical for healthy bones and body.
Vitamin D is not only important in bone health, but emerging data support its role in maintaining immunity, according to Dr. Scott Cohen, pediatrician and author of the book, Eat, Sleep, Poop: A Common Sense Guide to your Child’s First Year (Simon & Schuster, 2010). “Unfortunately, many infants are not receiving adequate levels of vitamin D from breast milk, formula, or synthesis from sunlight,” he observes. The mother and/or infant may take supplemental D3, known as cholecalciferol, the natural, most effective form of the vitamin.
Koenig recommends this natural supplemental form for vegans. D3 contains no animal products. The synthetic form of the supplement, D2, is derived from lanolin extracted from shorn sheep’s wool. D3 is produced in the skin when it is exposed to sunlight. Although the synthetic form, ergocalciferol, or D2, may be taken to excess, it’s unlikely a baby could overdose on D3 because it excretes itself as bile (“catabolism”) when it reaches the optimum level in the body. Consult your physician, anyway; certain medical conditions may preclude the use of Vitamin D.
Animals and birds produce cholecalciferol in their fur or feathers. Then they eat the cholecalciferol by licking their fur or rubbing their beaks on their feathers. So when we take cholecalciferol by mouth, we are doing what a number of other animals do, Dr. Cannell of the Vitamin D Council believes.
“Remember,” he explained, “our ancestors lived naked in the sun for several million years. Then some of us migrated to places with less sun. Then we put on clothes, started working inside and living in cities where buildings blocked the sun. Then we started traveling in cars instead of walking or riding horseback, and then only a few years ago, we started actively avoiding the sun...the really significant reductions in sunlight exposure have occurred since the industrial revolution, just the time the diseases of civilization like cardiovascular disease, diabetes, and cancer seem to have greatly increased.”
Is it sound science or hype?
The bottom line for the revised interest in vitamin D is simple. Is it based on sound science, or is it hype? In a recent health column in The New York Times, Tara Parker Pope addresses the two perspectives. Based on the view of the experts she consulted, her conclusion is that more research is needed — and it’s being done.
Dr. JoAnn E. Manson, a Harvard professor and chief of preventive medicine at Brigham and Women’s Hospital in Boston, is leading a major study over the next five years featuring a nationwide clinical trial with 20,000 older adults, including men 60 and older and women 65 and older, to study whether high doses of vitamin D and omega-3 fatty acids from fish-oil supplements will lower risk for heart disease and cancer. (Learn about taking part in the study at www.vitalstudy.org.) Study participants will be divided into four groups. One will take both vitamin D and fish oil pills. Two will take either a vitamin D or a fish-oil supplement and a placebo. The fourth will take two placebo pills.
Although consumers may be tempted to rush out and start taking 2000 I.U.s of vitamin D a day, Pope notes that some doctors warn against it. Several recent studies of nutrients, including vitamins E and B, selenium and beta carotene, have proved disappointing — even suggesting that high doses do more harm than good, increasing risk for heart problems, diabetes and cancer, depending on the supplement.
“My sentiment is that the lesson we have learned form large trials with other vitamin supplements is that there is no proven health or preventative benefit for dietary supplements in nutritionally replete populations, which accounts for most of the people who enter this sort of clinical trial,” concluded Dr. Eric A. Klein, chairman of the Glickman Urological and Kidney Institute at the Cleveland Clinic. “It makes more sense to me to study dietary supplements or vitamins in populations who are deficient.”
Meanwhile, Margaret Eckert-Norton, a family nurse practitioner and diabetes specialist at SUNY Downstate Medical Center, describes fear of sunlight as “paranoia.” She cited a study that the incidence of melanoma has increased dramatically in people who have been avoiding the sun for years.
Home-testing kits for vitamin D levels are available, though analyzing the results may require more knowledge than is readily available to the busy layperson. Cannell advises even healthy people without the diseases of vitamin D deficiency to have their 25(OH)D level measured by a physician. According to him, if your levels are below 50 ng/mL you need to consider more sun, artificial light, oral vitamin D3 supplements or some combination. You want to maintain your 25(OH)D levels between 50 and 80 ng/mL year-round. For more information, go to www.vitamindcouncil.org; www.healthychildren.org; www.fampra.oxfordjournals.org.
According to the lab company Quest Diagnostics, orders for vitamin D tests surged more than half in the fourth quarter of 2009, up from the same quarter a year earlier. And in 2008, consumers bought $235 million worth of vitamin D supplements, up from $40 million in 2001, according to the Nutrition Business Journal. ++