Where's the Sunshine?
Vitamin D deficiency playing greater role in health concerns
By Catherine Spader, RN
Monday September 22, 2008
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Vitamin D has become a celebrity. The media is touting it as the latest wonder vitamin and was even endorsed by Oprah when she threw her head back and choked down a shot of slimy cod liver oil in front of millions of TV viewers.
"People might think that the vitamin D craze is just a bunch of hype, but the case for vitamin D really has substance," says Joan M. Lappe, RN, PhD, FAAN, a vitamin D researcher and the Criss/Beirne Endowed Chair in Nursing and professor of medicine at Creighton University in Omaha, Neb.
New research is finding a deficiency in vitamin D may play a role in more conditions than rickets, osteomalacia, and osteoporosis. According to the National Institute of Health (NIH) Office of Dietary Supplements, early studies are pointing to the possibility vitamin D may help prevent and/or treat conditions such as –
• Muscle weakness and falls
• Type I and type II diabetes
• Hypertension
• Multiple sclerosis
• Rheumatoid arthritis and other forms of chronic pain
• Coronary artery calcification and heart disease
• Some cancers, including breast, colon, ovary, kidney, lung, and uterus
Nurse-led research about vitamin D's link to cancer is particularly notable. Lappe was the lead investigator in one randomized study, in which participants took 1,100 IU of vitamin D3 (nearly three times the U.S. government's current Recommended Daily Allowance for middle-age adults) along with calcium.
Results included a 60% or greater reduction in cancer risk than women who did not get the vitamin. The study followed 1,179 healthy, postmenopausal women from rural eastern Nebraska from 2002-2005 and was published in the June 8, 2007, online edition of the American Journal of Clinical Nutrition.
More Than it Appears
Fat-soluble vitamin D is more than it appears to be and has a wide range of effects, including functioning as a hormone, says Lappe. "Many types of cells in the body have vitamin D receptors, and it has many different mechanisms of action depending on what type of cell it connects with," she says.
Vitamin D plays a vital role in processes, such as –
• Calcium absorption and maintenance of adequate serum calcium and phosphate concentrations
• Bone growth and bone remodeling
• Modulation of neuromuscular and immune function
• Reduction of inflammation
• Modulating many genes encoding proteins that regulate cell proliferation, differentiation, and cell death
A Contemporary Issue
Unfortunately, vitamin D deficiency has become an issue in the modern age. Throughout history, most people were able to meet their vitamin D needs from nature's primary source – the sun's ultraviolet rays, which triggers the body's endogenous vitamin D synthesis.
In the past, people living in northern latitudes often supplemented the sun, especially during the short days of winter, with a daily dose of vitamin D-packed cod liver oil, which no longer is a common staple in the American diet.
"Many people from childhood through old age are vitamin D deficient as compared to 50 or more years ago when we were a more rural society and more people worked out in the sun," says Lappe.
Many elements decrease the amount of vitamin D people synthesize from the sun's rays, including:
• Use of sunscreen with a sun protection factor (SPF) of 8 or more can block vitamin D-producing UV rays.
• Obesity and large amounts of subcutaneous fat trap vitamin D and alter its release into circulation.
• Smog and cloud cover reduce the intensity of the sun's UV rays.
• In the U.S., only areas south of a line that runs from Los Angeles to Columbia, S.C., receive UV rays strong enough to produce adequate vitamin D year round.
• Many Americans work indoors and are not outside from 10 a.m. to 3 p.m., when the sun's rays can most effectively produce vitamin D.
• Darker skin tones have greater amounts of the pigment melatonin, which reduce the body's ability to synthesize vitamin D.
• Older people do not synthesize vitamin D as efficiently as younger people.
Fortified foods including milk, some cereals, selected brands of orange juice, yogurt, and margarine, provide the primary source for vitamin D for most Americans today. The best natural food sources include salmon, tuna, mackerel, and fish liver oils. Smaller amounts are found in beef liver, cheese, and egg yolks.
However, it's pretty hard to get enough vitamin D in milk and in your diet," says Lappe.
Tanning Not Necessary
Because sun exposure in itself carries a risk of skin cancer, Lappe believes the best and most reliable source of vitamin D is supplementation.
"You don't need a suntan to get adequate vitamin D," she says.
Medical groups vary in their recommendations of supplemental dosing, but a daily intake in the range of 800-1,000 IU of vitamin D3 would probably be beneficial to most adults, according to the July 2008 Mayo Clinic Women's HealthSource. Although more research is needed, vitamin D3 could be more than three times as effective as vitamin D2, according to the NIH.
Lappe recommends adults take 2,000 IU per day in the form of a vitamin D3 supplement. At this time, a dose of 2,000 IU has been established as the tolerable upper intake level for healthy adults that does not increase the risk of adverse effects, such as GI upset, kidney stones, confusion, and heart arrhythmias. However, higher limits of safety and increased recommended dosages may be coming down the pipe as more research is collected, says Lappe.
The best way to determine a person's vitamin D status is to use the serum 25(OH)D test. Although it has not yet been determined what the optimal level of vitamin D is yet in healthy people, a concentration of
Catherine Spader, RN, is a contributing writer for Nursing Spectrum and NurseWeek. To comment, e-mail editorDC@nursingspectrum.com.
