By John C. Pittman, MD, and Mark N. Mead, MSc
If you’re like millions of Americans who regularly tune into the news, you probably heard about the vitamin D report issued in November 2010 by the Institute of Medicine’s Food & Nutrition Board (FNB), a committee of 14 medical scientists appointed to assess current data of health outcomes associated with these two nutrients. The FNB report concluded that most North Americans get enough of this “sunshine vitamin” through their diets, and moreover that consuming extra vitamin D is unlikely to help protect the public from cancer, heart disease, diabetes, or other chronic diseases. Among the report’s other conclusions:
• Raise the recommended daily amount of vitamin D to 600 international units (IU), up from the 200 IU level that had been recommended in 1997. People over age 70 are advised to get 800 IU daily. Our response: Most experts agree that it is virtually impossible to significantly raise your vitamin D levels when supplementing at only 600 to 800 IU/day. Michael Holick, MD, PhD, director of the General Clinical Research Center at Boston University Medical Center and author of numerous scientific reports on vitamin D, has recommended that all adults supplement with 2000 IU daily. Holick himself takes 3000 IU per day and has many patients taking at least that much. Robert Heaney, a professor of medicine at Creighton University in Omaha who has long studied vitamin D’s health benefits, says people should consider taking up to 4,000 IUs a day.
• The risk of harm increases at daily vitamin D intake levels greater than 4000 IU. Our response: This would suggest that a daily intake of 10,000 IU/day would cause toxicity in humans; however, the FNB report provided no evidence to support this position, citing only one poorly conducted study indicating 20,000 IU/day may cause mild elevations in serum calcium but not clinical toxicity. Several leading vitamin D researchers have proposed that the new upper tolerable limit should be 10,000 IU, based on extensive observations of adults taking this dose or higher.
• Regarding the serum 25-hydroxyvitamin-D level—the primary indicator of vitamin D status—the FNB report deemed that a level of 20 ng/mL is sufficient for all persons. Our response: The most widely used benchmark for sufficiency has been 32 ng/mL, and many experts suggest that higher levels may be needed for specific health outcomes.
The FNB report made headlines across the country, and prompted many people to either cut back on their vitamin D dose or stop supplementing altogether. However, we see several serious limitations in the FNB’s approach and conclusions. First, the guidelines are based on the minimum amount of vitamin D needed to ensure bone health and do not address the amount that may affect other health outcomes, such as the prevention of cancer and heart disease, or improvement in muscle and joint health. Ostensibly, the FNB committee believed that evidence was insufficient to determine the role of vitamin D in the prevention of these other chronic diseases and health outcomes. However, many leading vitamin D authorities throughout the world would take issue with this perspective.
For example, a comprehensive evidence-based review, published in the November-December 2009 Journal of the American Board of Family Medicine, concluded that, “Low vitamin D levels are associated with increased overall and cardiovascular mortality, cancer incidence and mortality, and autoimmune diseases such as multiple sclerosis.” Even more recently, an international committee of 25 experts from various medical disciplines proposed clinical guidelines for vitamin D intake. Their focus was on the vitamin D needs of adult patients with or at risk for fractures, falls, cardiovascular or autoimmune diseases, and cancer. The expert panel reached strong agreement about the need for vitamin D supplementation in these specific groups of patients and the need for assessing their 25(OH)D serum levels “for optimal clinical care.” A target range of “at least 30 to 40 ng/mL” was recommended—about twice the level proposed by the FNB report. These recommendations were published in the September 2010 issue of Autoimmunity Reviews.
Against this backdrop, it’s also important to realize that the FNB’s guidelines have nothing to do with the requirements for optimal functioning and overall health. Physicians who carefully observe what happens with their individual patients are better able to discern the effects of different doses of vitamin D in the context of specific health situations. For someone with low blood levels of vitamin D, an initially high supplemental dose—on the order of 5000 to 10,000 IU per day—may result in better mood, increased muscle strength, relief of joint aches, and other clinical benefits. But one size does not fit all; the same dose of vitamin D is not appropriate for everyone. This is why individual testing and expert supervision are so important when trying to pinpoint the optimal dose for you personally.
The Sunshine Deficiency
Vitamin D has emerged in recent years as a nutrient with astounding potential for promoting human health. The vitamin’s most recognized function is the enhancement of calcium absorption and bone mineral metabolism. In 2007, the Dietary Supplement Education Alliance estimated that appropriate use of calcium with vitamin D by older adults for five years could lead to the elimination of approximately 776,000 hospitalizations and nursing stays linked to hip fractures, resulting in an annual savings of $16.1 billion. In other words, supplements such as calcium and vitamin D serve as a potent form of “biological insurance” that can help keep the human frame intact. As we explain in a moment, however, the benefits of improving your vitamin D status extend far beyond healthy bones.
Vitamin D is classified as a vitamin, but it’s really a hormone your body generates in response to sunlight. Fair-skinned people can generate 20,000 IU of vitamin D through 20-30 minutes of mid-day sun exposure; in contrast, dark-skinned individuals may require at least four times this level of exposure to attain the same output. (Note that these levels far surpass any amount obtainable through diet alone, which helps explain why the US recommended dietary allowance of vitamin D is set at a mere 200-400 IU for people aged 1-70 years.)
Your body’s production of vitamin D depends on the amount of skin surface exposed and the quality of sunlight. Direct-overhead sun exposure provides the strongest stimulus for the skin’s synthesis of vitamin D. In temperate regions, almost all of this “human photosynthesis” occurs in summertime, because the angle of sunlight largely determines the intensity of ultraviolet radiation, hence the rate of vitamin D production.
Given these facts, it comes as no surprise that most cases of vitamin D deficiency are due to a sunlight deficit, not a dietary one. If you were to totally avoid the sun and regularly took two standard multivitamins every day for several years, each containing 400 IU of vitamin D as your sole source of vitamin D, you would eventually become vitamin D deficient. (Remember, most people meet 90% of their vitamin D needs from very casual sun exposure, like the sunlight that strikes your face, arms and hands when stepping outside for a few minutes in the middle of the day.)
These days, due to fears of developing skin cancer, many people get too little sunshine. This results in a low or suboptimal blood level of 25-hydroxyvitamin D—the sole measure of one’s vitamin D status. If this level is low—say, below 50 nanomoles per liter (nmol/L) — research indicates that you may be more prone to developing a host of health problems. The classical disorder linked with vitamin D deficiency is known as osteomalacia, a painful softening of the bones. In children, the deficiency causes the shafts of leg bones to irreversibly bow or bend, resulting in the grotesque disfigurement known as rickets. Sunbathing or taking cod liver oil (which contains vitamin D) were eventually found to prevent rickets, which is now extremely rare, thanks mainly to the practice of fortifying dairy products with vitamin D.
But lack of vitamin D can also lead to various other health problems, including osteoporosis, osteopenia, heart disease, hypertension, diabetes, osteoarthritis, joint problems, muscle weakness, chronic muscle pain, fibromyalgia, multiple sclerosis, Type 1 diabetes, depression, mental illness and yes, many types of cancer as well. Let’s take a quick look at what science is telling us about the connections between vitamin D and these various disorders.
Osteoporosis and Osteopenia. When you’re lacking in vitamin D, you’re more prone to developing osteoporosis, osteopenia, and osteomalacia (as mentioned above), and your risk of experiencing a fracture increases. Achievement of optimal blood vitamin D levels is essential for boosting bone mineral density and maximizing bone strength, which is why elderly people with osteoporosis—particularly those being treated with bisphosphonates—are advised to boost their intake to at a range of 800 to 2000 IU, along with calcium. Again, however, if your vitamin D status is poor initially, it’s important to supplement at a higher dosage level in order to truly improve the blood levels of 25(OH)D. Daily supplementation at the right level—again, relative to the blood test result—is especially important for older adults because aging is linked with a reduced capacity to synthesize vitamin D in the skin upon sun exposure.
Cardiovascular Disease and High Blood Pressure. Vitamin D deficiency has been linked with a greater risk of cardiovascular disease and high blood pressure. For example, a meta-analysis of 18 studies found that the lower the serum vitamin D level, the higher the risk of high blood pressure, as reported in the 28 December 2010 Journal of Hypertension. In addition, we know that vitamin D can impact several key mechanisms involved in heart disease, such as inhibiting inflammation as well as vascular muscle proliferation and vascular calcification. To date, however, studies evaluating vitamin D supplementation have not consistently shown a benefit, possibly due to suboptimal levels of vitamin D (no studies have yet looked at doses higher than 2000 IU, even in deficient individuals) or a lack of consideration for other factors that impact cardiovascular health.
Cancer. People living in colder climates not only experience more bone thinning with age but also have higher rates of various cancers. These individuals tend to spend more time indoors, so they get less sun exposure. It’s also interesting to note that cancer mortality rates tend to be lowest in the summer, when vitamin D levels are highest. Laboratory studies indicate that high-dose vitamin D may help block the growth of cancers of the breast, colon, rectum, prostate, lung and head/neck region, as well as lymphoma, leukemia and multiple myeloma. Generally, the lower one’s overall sun exposure and vitamin D intake, the greater the risk of developing and dying from cancer. In a five-year clinical trial conducted out of Creighton University in Nebraska, women who regularly took 2000 IU of vitamin D3 showed a 77% reduction in overall cancer rates compared to women taking a placebo pill, as reported in the June 2007 issue of the American Journal of Clinical Nutrition. This 2000 IU level of vitamin D3 has also been shown to reduce PSA levels in men with prostate cancer.
One other key application concerns cancer treatment. Vitamin D has a synergistic effect against malignant disease when combined with several kinds of anti-cancer drugs, including the taxanes (Taxol and Taxotere), platinum compounds (e.g., cisplatin), dexamethasone, tamoxifen, and mitoxantrone. Soy isoflavones, too, seem to synergize with vitamin D in combating cancer. Finally, there’s good evidence that vitamin D can be very effective in slowing down the breakdown of bone and lessening bone pain in patients with advanced cancers.
Obesity and Metabolic Syndrome. Vitamin D is fat-soluble and therefore stored in fatty tissue. This explains why obese people have a greater capacity to store the vitamin; however, obese people have been shown to produce about half the vitamin D produced by people of a normal weight when exposed to the same amount of sunshine. Moreover, the vitamin D in those who are lean is more available for the body's metabolic needs than in those who are obese. In a 2007 report for Clinical Nutrition, about half of all morbidly obese individuals were found to be vitamin D deficient. Those with the lowest levels of vitamin D had the greatest risk for the so-called metabolic syndrome. (The latter condition includes the presence or more of the following factors: excess abdominal fat, elevated triglyceride levels, low HDL cholesterol, elevated blood pressure, and elevated fasting glucose and insulin levels.)
Autoimmune Diseases. Lack of vitamin D has been linked with multiple sclerosis, rheumatoid arthritis, type I diabetes, lupus, and Crohn’s disease. For example, babies deficient in vitamin D may have a greatly increased risk of developing type I diabetes by age 30 compared to those who are not deficient. Animal studies suggest that a vitamin D supplement will greatly impede the development of type I diabetes in susceptible individuals. A 2009 report in Arthritis Research & Therapy concluded that vitamin D deficiency is highly prevalent in patients with lupus and rheumatoid arthritis. However, whether supplementation can help patients with these disorders remains to be proven.
Colds and Flus. Sharply reduced levels of vitamin D, due to the low intensity of solar UV radiation, may have some connection to the increased occurrence of colds and the flu in winter. Scientists have found that people with low vitamin D levels are less capable of fighting off infections, and that supplementing with vitamin D boosts resistance to colds and the flu. In a randomized controlled trial conducted in Japan, researchers gave 1,200 IU/day of vitamin D3 for six months to Japanese 10 year-olds and compared them to children receiving a placebo. As reported in the May 2010 American Journal of Clinical Nutrition, there was a 42% reduction in the incidence of influenza A, along with an 83% reduction in asthma attacks in the vitamin D group compared to the placebo group. Had those researchers followed the new FNB recommendations and used 400 IU instead of 1,200 IU, it is unlikely that the children would have experienced any benefit at all.
The problems just mentioned are only the tip of the proverbial iceberg. Low levels of vitamin D also have been linked with mood disorders (e.g., depression), mental illness, autism, muscle weakness, periodontal disease, unexplained bone and muscle pain, infertility, preeclampsia, cystic fibrosis, psoriasis, and age-related cognitive decline. In some cases, clinical benefits have been seen following vitamin D supplementation—for example, reductions in depressive moods in adults, and improvements in muscle strength and function in children with autism.
How Much Is Needed?
These days, most of us just don’t get out in the sun as much as our ancestors did. We spend far more time indoors, and yet the sunshine that comes through glass windows will not stimulate vitamin D synthesis. Even if we did get outdoors on a regular basis, we’d then have to reckon with problems associated with getting too much sun—problems such as sunburn, premature aging of the skin, and a heightened risk of skin cancer, especially in fair-skinned people. Older individuals and obese people have more difficulty synthesizing vitamin D, so they would need to be out in the sun longer, thus further increasing the skin cancer risk.
Aside from sunshine, we can get additional vitamin D from foods like fatty fish and fortified milk. Unfortunately, most fortified dairy products contain synthetic vitamin D, which confers fewer biological benefits than vitamin D3. Moreover, relying on fatty fish may not be a suitable way to get your vitamin D, because you’d have to eat a large amount of fish every day. For many people, vitamin D-rich cod liver oil is a great source, one that has been used in northern regions for well over a century.
This brings us back to vitamin D supplements. Vitamin D in its natural form is called vitamin D3 or cholecalciferol. This form of vitamin D generally has more drawn-out effects and need not be taken daily; in contrast, synthetic forms such as calcitriol need to be taken daily for optimal effectiveness. Also whereas vitamin D is relatively cheap, calcitriol can be quite expensive – and your insurance company may or may not provide coverage.
So how much do we really need? Many of the leading vitamin D authorities say that, if you rarely if ever get any mid-day summertime sun exposure, most adults can benefit by supplementing in the range of 2,000 and 5,000 IU per day. A recent clinical trial by Dr. Reinhold Vieth confirmed that the 5000 IU amount was safe even for elderly people. For people who do get exposed to 15 or 20 minutes of mid-day sunshine in the spring, summer and fall, the recommended amount is about 2,000 IU per day. You can also take your week’s worth of vitamin D (say 15,000 to 20,000 IU) all on the same day, once a week. This makes it much easier to take the vitamin, but there are those individuals who may still have problems absorbing this much Vitamin D at one time, in which case daily dosing is still better.
The only caveat of taking higher doses of vitamin D is that some individuals may be prone to a condition known as hypercalcemia (excessive calcium in the blood). Symptoms of hypercalcemia include weakness, fatigue, somnolence, headache, anorexia, dry mouth, metallic taste, nausea, vomiting, cramps, diarrhea, muscle pain, bone pain and irritability. If you have cancer and certain other conditions, your physician should monitor you for hypercalcemia in order to safeguard against this problem. If you do happen to become hypercalcemic, your physician will have you discontinue the vitamin D and then check your blood calcium level daily until it has normalized, and then twice weekly on a lower dose of vitamin D.
John Cannell, MD, founding director of the Vitamin D Council, notes that thousands of individuals reading the Council’s newsletter routinely have taken 5,000 IU/day for up to eight years. “Not only have they reported no significant side effects, indeed, they have reported greatly improved health in multiple organ systems,” Dr. Cannell states. “My advice: especially for pregnant women, continue taking 5,000 IU/day until your 25(OH)D is between 50 ng/ml and 80 ng/ml—the vitamin D blood levels obtained by humans who live and work in the sun and the mid-point of the current reference ranges at all American laboratories.” The FNB recommendations are a major disappointment to Cannell and many other proponents of higher vitamin D intake. Given the low cost of vitamin D, as well as the large body of evidence for safety and benefit at intakes well above these recommendations, why not take a chance of achieving those benefits?
John C. Pittman, MD, is the Medical Director of the Carolina Center for Integrative Medicine in Raleigh, NC, and is certified by the American Board of Clinical Metal Toxicology. Mark N. Mead, MSc, serves as the Center’s Nutrition Educator and Integrative Medicine Research Consultant.
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