Vitamin D: A lifetime achievement award
The Sunshine Vitamin Gets Our Nomination
by nicholina galinsky, RN, BSN, and editorial staff
Vitamin D is known as the sunshine vitamin because our bodies can synthesize vitamin D after our skin is exposed to the sun. The same UVB rays that are believed to cause skin cancer trigger vitamin D synthesis in our skin. Similarly, sunscreens with a sun protection factor (SPF) of 8 or greater will block UV rays that produce vitamin D. While vitamin D may be freely supplied by the sun, there is a long history of vitamin D deficiency in the United States.
Why do we need Vitamin D?
Bone Health - When you think of the role of vitamin D, its importance to bone health is prominent. Vitamin D maintains normal blood levels of calcium and phosphorous and also promotes calcium absorption into bone, giving them strength and mass. Insufficient levels of vitamin D can lead to insufficient levels of calcium absorbed into the body and then into the bones.
Osteoporosis, the most prevalent bone disease in the US, results from a significant loss of calcium and other minerals in bone, which leaves them weak, fragile, and at risk for fractures. Currently, 10 million Americans have osteoporosis and 34 million have low bone mass1. Rickets and osteomalacia are two additional bone diseases related to vitamin D deficiency.
Cancer - Evidence now suggests that vitamin D deficiency is responsible for several thousand premature deaths each year from colon, breast and ovarian cancer, according to Cedric Garland, DrPH, of UC-SD who has been studying the impact of vitamin D on cancer since the 1980’s.
Diabetes - Several large scale studies have shown that vitamin D supplementation during childhood reduces the risk of later type 1 diabetes.
Heart Health - Proper vitamin D levels may also be linked to normalizing blood pressure. There is evidence that vitamin D may play a role in preventing Arteriosclerosis2 (hardening of the arteries).
Lung Health – While getting ample vitamin D doesn’t prevent chronic obstructive pulmonary disease (COPD), it does appear to help people with this lung disease to breathe easier and more deeply. Studies in New Zealand have linked vitamin D to lung health.
Autoimmune Diseases - Vitamin D supplements may protect against developing multiple sclerosis (MS), according to a 2004 issue of Neurology. “Because the number of cases of MS increases the farther you get from the equator, one hypothesis has been that sunlight exposure and high levels of vitamin D may reduce the risk of MS”, claims lead author, Kassandra L. Munger, MSc. She goes on to say, “These results need to be confirmed with additional research, but it’s exciting to think that something as simple as taking a multivitamin could reduce your risk of developing MS”.3
Higher intake of vitamin D may also be associated with a lower risk of rheumatoid arthritis (RA) in older women, according to a 2004 issue of Arthritis and Rheumatism4.
Vitamin D and Pregnancy - A new study suggests that pregnant women with adequate levels of vitamin D could have children who grow stronger bones later in life. A team or researchers in the U.K. found that children of vitamin D deficient mothers (during pregnancy) had weaker bones at nine years old than those from mothers who had adequate vitamin D during pregnancy. Professor Cyrus Cooper said the findings provided evidence that maternal vitamin D status during pregnancy influenced the bone growth of offspring and their risk for osteoporosis later in life. He said that vitamin deficiency of the mother carrying the child, rather than the baby in early life, affected the child’s bone strength later5. Vitamin D is important during pregnancy, but extra amounts should not be taken without first consulting a physician.
How much Vitamin D do we need?
The Institute of Medicine of the National Academy of Sciences developed the Dietary Reference Intakes (DRIs) for vitamin D6.
The Adequate Intake for Vitamin D is as follows:
Birth to 50 years: 200 IU/day
51 to 70 years: 400 IU/day
71+years: 600 IU/day
There has been much written in the past few years that these levels may be too low. This is based on ongoing research that is highlighting the health benefits of higher amounts of this vitamin. Research continues.
A History of Vitamin D Deficiency
There are few natural dietary sources of vitamin D. Oily fish such as salmon, sardines and tuna as well as egg yolk and beef liver are good sources. Cod liver oil is a potent source.
At the turn of the century, vitamin D deficiency led to an epidemic of rickets in U.S. urban centers. We solved the vitamin D deficiency largely through the fortification of foods. But fortification may have gone too far. Peanut butter, hot dogs, soda pop, bread and even beer were fortified with vitamin D. Excessive amounts of Vitamin D also were added to some milk products, causing toxic amounts of Vitamin D to reach infants and young children. The Federal government then restricted the broad inclusion of vitamin D into the American food supply.
Over the last decade, however, evidence is showing a reemergence of vitamin D deficiency in the United States. “We absolutely have a huge problem with vitamin D deficiency”, said Dr. Bess Dawson-Hughes, Director of the Bone Metabolism Laboratory at Tufts University, who argues the point for more recommended dietary vitamin D. Issues potentially related to vitamin D deficiency include:
· Changes in Diet: Milk consumption and breakfast cereals have been a primary source of the fortified foods containing vitamin D. As the American diet has shifted away from these foods, the amount of vitamin D consumed also has declined.
· Infants who are exclusively breastfed: Vitamin D requirements cannot be met by human (breast) milk alone, which usually provides approximately 25 IU vitamin D per liter. Sunlight is a potential source of vitamin D for infants, but the American Academy of Pediatrics (AAP) advises that infants be kept out of direct sunlight and wear protective clothing and sunscreen when exposed to sunlight. The American Academy of Pediatrics (AAP) recommends a daily supplement of 200 IU vitamin D for breastfed infants beginning within the first 2 months of life unless they are weaned to receive at least 500 ml (about 2 cups) per day of vitamin D-fortified formula.
· Children and adolescents: Kids who are not routinely exposed to sunlight and do not consume at least two, 8-fluid ounce servings of vitamin D-fortified milk per day are also at higher risk of vitamin D deficiency and may need a dietary supplement containing 200 IU vitamin D.
· Older adults: A 2004 study by the American Dietetic Association shows that less than 10% of adults aged 51 to 70 are getting an adequate amount of vitamin D from their diets7. As people age, skin cannot synthesize vitamin D as efficiently and the kidney is less able to convert vitamin D to its active hormone form. It is estimated that as many as 30% to 40% of older adults with hip fractures are vitamin D insufficient. Therefore, older adults may benefit from supplemental vitamin D.
· Persons with limited sun exposure: Homebound individuals, people living in northern latitudes such as in New England and Alaska, women who wear robes and head coverings for religious reasons, and individuals working in occupations that prevent sun exposure are unlikely to obtain much vitamin D from sunlight.
· Persons with greater skin melanin content: Melanin is the pigment that gives skin its color. Greater amounts of melanin result in darker skin. The high melanin content in darker skin reduces the skin's ability to produce vitamin D from sunlight. It is very important for people with dark-pigmented skin to consume recommended amounts of vitamin D. Some studies suggest that older adults, especially women, in these groups are at even higher risk of vitamin D deficiency.
· Persons with fat malabsorption: As a fat soluble vitamin, vitamin D requires some dietary fat for absorption. Individuals who have a reduced ability to absorb dietary fat may require vitamin D supplements. Fat malabsorption is associated with a variety of medical conditions including Celiac Disease, Crohn’s Disease and Cystic Fibrosis.
Can you have too much Vitamin D?
Just like anything, too much is also as much of a concern as too little. Too much vitamin D can raise blood levels of calcium causing mental status changes such as confusion. In turn, high blood levels of calcium can cause heart rhythm abnormalities. Vitamin D toxicity can also cause Calcinosis, or the deposition of calcium and phosphate in the body’s soft tissues such as the kidney8. Symptoms of vitamin D toxicity are nausea, vomiting, poor appetite, constipation, weakness, and weight loss.
The dietary upper limits of vitamin D are:
0-12 months: 1,000 IU/day
1 year old +: 2,000 IU/day
Vitamin D on the Red Carpet
Now that you see all of the health benefits of vitamin D, do you think it deserves a red carpet ovation? We obviously need to make sure that we are getting enough Vitamin D to prevent diseases and complications. One of the biggest problems is that the proper amount of Vitamin D is often difficult to get through diet alone. Supplements are an easy and inexpensive way to assure we are getting the proper amount. Getting a little sun can be helpful as well. Of course, if you want that killer tan, you can do what the celebrities do; bring on the spray!
References:
- Bone Health and Osteoporosis: A Report of the Surgeon General, Washington, DC: Office of the Surgeon General, US Department of Health and Human Services; 2004.
- Mosekilde, L, Vitamin D and the Elderly, Clin Endocrinol. 2005; 62 (3): 265-281.
- http://www.medscape.com/viewarticle/466980
- http://www.medscape.com/viewarticle/466881
- http://news.bbc.co.uk/2/hi/health/4584518.stm
- http://ods.od.nih.gov/factsheets/vitamind.asp#h3
- Moore C et al, Vitamin D intake in the United States, J Am Diet Assoc. 2004; 104:980-983.
- http://ods.od.nih.gov/factsheets/vitamind.asp
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