The big Debate
Vitamin D is now a nutritional super hero boasting an array of healing powers reaching far beyond the bones.
Long a silent sidekick to calcium, vitamin D is now a nutritional super hero boasting an array of healing powers reaching far beyond the bones. A deluge of recent studies suggests tantalizing connections between vitamin D and a bevy of conditions. While many in the medical community embrace the emerging benefits of the vitamin, some remain cautious, if not skeptical. So why all the hype and what do you need to know?
Your doctor can determine your vitamin D level through a simple blood test.
Vitamin D levels:
Low: < 10 – 15 ng/mL or < 25 – 37.5 nmol/L
Normal: 30 ng/mL or 75 nmol/L
Possible toxic: > 200 ng/mL or > 500 nmol/ L
Vitamin D levels: reported in both nanograms/milliliter (ng/mL) and nanomoles/liter (nmol/L)
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Vitamin D, Calcium and Your Bones
Vitamin D and calcium are crucial for the development and maintenance of strong bones. In children, a deficiency of vitamin D causes rickets, a crippling bone disease rarely seen in the United States since the addition of vitamin D to milk.
Adults may develop osteopenia or osteoporosis, a thinning of the bones resulting from too little calcium and vitamin D, but are you aware that a lack of vitamin D also causes osteomalacia? This little known, but painful bone condition is often overlooked by physicians and is sometimes confused with fibromyalgia. Although osteomalacia doesn’t show up on x-ray studies, it is easy to diagnosis on physical exam and it responds to treatment with vitamin D.
The Sunshine Vitamin
When exposed to ultraviolet B (UVB) radiation in sunlight, your skin produces vitamin D, which is then converted into a usable form in a two step process occurring first in the liver and then the kidneys. The activated vitamin D travels through your blood to target areas such as the intestines where it aids in the absorption of calcium.
Sunshine is the major source of vitamin D that is found naturally in only a few foods such as salmon, mackerel, tuna, cod liver oil, egg yolks, and fortified milk and cereals. Unfortunately, research indicates that there is a worldwide epidemic of vitamin D deficiency just as we are discovering exciting and unexpected benefits of the sunshine vitamin.
Vitamin D and Cancer
As early as 1941, scientists observed that people who lived in northern states such as Massachusetts or Vermont were more likely to die of cancer than those who lived in the south. Four decades later, studies confirmed these findings regarding colon cancer and since then, numerous studies have shown that if you live at higher latitude, you have a greater risk of developing and dying of breast, prostate, ovarian esophageal, or colon cancers due to an increased risk of vitamin D deficiency.
We are learning that vitamin D, in addition to its role in calcium regulation; also helps control the growth and maturation of cells throughout the body. Scientists think that vitamin D plays a key role in preventing cells from multiplying out of control – thus preventing cancer.
In the past few years, researchers such as Michael F. Holick, M. D. of Boston University School of Medicine and Cedric F. Garland, M. D. of Moores Cancer Center at the University of California, San Diego have presented compelling evidence that vitamin D is crucial in the prevention of cancer. Dr. Garland, in an August 2007 news release, stated that almost 150,000 cases of breast and colorectal cancer could be prevented in this country by maintaining an adequate level of vitamin D.
A study conducted at the German Cancer Research Center and released in April 2008 revealed supporting evidence regarding breast cancer: the lower your vitamin D level, the greater your risk of developing breast cancer. More recently, Dr. Garland analyzed the results of three studies with similar findings and he has recommended that physicians consider measuring vitamin D levels in women at risk for breast cancer.
Vitamin D and Heart Disease
Men low in vitamin D had an increased risk of heart attack.
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Adding muscle to its super hero status, vitamin D may be a key nutrient in preventing heart disease. A study published in the June 9, 2008 issue of Archives of Internal Medicine, concluded that men low in vitamin D had an increased risk of heart attack and a second study published later that month revealed that those low in vitamin D had twice the risk of dying from any cause.
So strong is the growing evidence concerning low levels of vitamin D that Erin Michos, M.D., M.H.S. of Johns Hopkins considers it a risk factor for heart disease along with high blood pressure, smoking, high cholesterol, and other proven risks. In fact, Dr. Michos and her colleagues released a study in August 2008 revealing that folks with vitamin D deficiency have a stunning, twenty-six percent increased risk of death.
Does Vitamin D Do More?
In addition to these findings, vitamin D is suspected to yield further benefits. Low levels are linked to peripheral artery disease (PAD), a blockage of blood flow in the arteries of the legs, and with increased osteoarthritis pain of the knees, muscle weakness, and an increase in falls and fractures in the elderly.
Ongoing research is investigating the relationship between vitamin D and type I diabetes, multiple sclerosis, hypertension, and rheumatoid arthritis. But some physicians and researchers remain cautious, if not skeptical, about the current nutritional darling, citing the need for more research.
Sunshine in a Bottle
Currently, the Food and Nutrition Board (FNB) recommends a daily dose of 200 International Units (IU) to 600 IU depending on age to insure an adequate intake, but this year the American Academy of Pediatrics (AAP) recommended a higher dose for children. While the FNB says 200 IU of vitamin D each day is sufficient from birth to age 13, the AAP is advising that children and adolescents receive 400 IU. Breast milk contains very little vitamin D so breastfed infants in particular need supplementation.
However, because low levels of vitamin D are associated with cancers and heart disease, physicians such as Dr. Holick are advising their adult patients to take 800 IU per day or more depending on how much time they spend in the sun. Many gynecologists are advocating 800 IU per day for women at risk for bone loss, but again, talk with your doctor concerning your own unique circumstances before adding vitamin D to your daily regimen.
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The Debate about D
Right now, researchers tend to agree that vitamin D deficiency is linked to colon, breast, prostate, ovarian, esophageal, and non-Hodgkin’s lymphoma for those who live in the north while those with low vitamin D living anywhere are at increased risk for colon and breast cancers. But not everyone is convinced.
Some physicians caution that just because a low level of vitamin D is associated with cancer or heart disease, it doesn’t necessarily follow that normal levels prevent them. Others, such as Drs. Holick and Garland, are firm believers in the powers of D, screening their own patients for a deficiency. However, even if physicians agreed on the benefits, there is no consensus on a daily requirement or how to prescribe it and the sun itself presents some challenges.
Sunshine: Friend or Foe?
While sun exposure supplies adequate vitamin D, not all sunshine is created equal. The farther you are from the equator, the less UVB is absorbed by the skin due to the angle of the sun – an effect accentuated during the winter when many areas of the United States receive inadequate sunlight for vitamin D production. In fact, only those living south of a line from Columbia, South Carolina to Los Angeles (latitude 34 degrees north) receive sufficient sunlight to maintain adequate levels of vitamin D all year.
Depending on where you live, you may develop vitamin D deficiency for three to six months of the year but there are other factors that affect the production of this nutrient. Dark skin absorbs less UVB than lighter skin and the ubiquitous use of sunscreen, while protecting us from skin cancers, prevents us from making the vitamin.
While no one has ever developed vitamin D toxicity from too much sun, skin cancers are a real risk. Some physicians are recommending 15 minutes of sun exposure at least twice a week before applying sunscreen but this advice makes other physicians nervous. If you have ever had a skin cancer, have a family history of skin cancer, or are at risk for developing it, you should discuss sun exposure with your doctor who may advise that you take a vitamin D supplement instead.
Vitamin D, we are learning, is much more than a staunch defender of bones and regulator of calcium. It appears that this quiet nutrient plays a key role in preventing cancers and low levels of it are linked to heart disease and death. Other intriguing studies hint that vitamin D is associated with type I diabetes, multiple sclerosis, hypertension, arthritis, and other chronic diseases. No matter what more we may learn, it is clear that we need the healing powers of vitamin D – perhaps more than we ever knew.
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"The big Debate"
authored by:
Dr. Thomas has been board certified by the American Academy of Family Physicians since 1990. She is a member of the American Medical Association and the North Carolina Medical Society. She is a columnist for the Washington Daily News in Washington, N...
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