What Is Vitamin D Deficiency ?
Vitamin D deficiency is considered by many to be an epidemic seriously impacting the health of our nation.
A new study finds that over the past 20 years American’s vitamin D levels are dramatically declining. The report was published in the March 23 issue of the Archives of Internal Medicine. Dr. Adit Ginde, an assistant professor of surgery at the University of Colorado Denver School of Medicine and the lead researcher on the study found a marked increase in vitamin D deficiency over the past two decades.
“Over three out of every four Americans now have vitamin D levels below what we believe is necessary for optimal health. African-Americans and Hispanics are at particularly high risk ? nearly all have suboptimal levels.”
Data was collected from 18,883 people between 1988 and 1994, and 13,369 people collected between 2001 and 2004 and examined their vitamin D levels. All the data came from the Third National Health and Nutrition Examination Survey.
According to findings of the Archives of Internal Medicine, and of the people studied 45 percent of people had 30 nanograms per milliliter or more of vitamin D, the blood level a growing number of doctors consider sufficient for overall health; a decade later, just 23 percent of 13,369 of those surveyed had at least that amount.
The greatest drops in vitamin D levels were seen among African Americans, where levels of vitamin D of less than 10 nanograms per milliliter rose from 9 percent to 29 percent, and levels of more than 30 nanograms per milliliter or higher dropped from 12 percent to 3 percent, the researchers found.
Increased Vitamin D Deficiency in Population on the Rise
“Increases in vitamin D deficiency in the population may have reduced the overall health of the population,” Ginde said. “Since sunlight is the body’s major source of vitamin D, increases in sunscreen, sun avoidance, and overall decreased outdoor activity, while successful in reducing skin cancers, has probably reduced vitamin D levels in the population.”
Ten minutes of sunlight on exposed arms and legs two to three times per week would significantly improve vitamin D production, but must be weighed against the risk for skin cancer, Ginde noted. Vitamin D supplementation is another way to increase levels. However, current recommended doses of vitamin D supplements are outdated and inadequate, he added.
Right now, recommended levels of vitamin D supplements are 200 international units per day from birth to age 50, 400 international units (IU) per day from age 51 to 70, and 600 international units per day for adults aged 71 and older. These recommendations are primarily for improving bone health.
Vitamin D the Under Appreciated Public Health Issue
“Vitamin D is an important and under appreciated public health issue and may be responsible for some racial differences in health outcomes,” Ginde said. “Most Americans could use more vitamin D. Higher doses of vitamin D supplementation than currently recommended, at least 1,000 to 2,000 IU daily, are likely needed to raise vitamin D levels for many people.”
Dr. Michael F. Holick, director of the Vitamin D Laboratory at Boston University, and world renown vitamin D expert noted that the recommended levels of vitamin D are under review and likely to be increased.
Holick believes that by mid-2010 the Institute of Medicine will offer new recommendations. “It’s pretty clear that you need a minimum of 1,400 and up to 2,000 IU a day, and if you are obese, you probably need at least one and a half to two times as much, because the fat sequesters the vitamin D,” he said.
The fact is people are staying out of the sun and drinking less milk, which are the main reasons for the decreasing vitamin D levels in the population.
Holick believes one way to combat the problem is to increase vitamin D supplementation in foods. New recommendations that increase vitamin D levels will let the food industry increase vitamin D levels in foods and add vitamin D to more foods, he said.
“We are in desperate need to have a marked increase in the adequate intake recommendation, and hopefully, that will be 1,000 to 2,000 Ius per day and raise the safe upper limit to at least 10,000 IUs a day,”
Holick said. “The plan would be to increase the amount per serving and increase the number of foods fortified with vitamin D.”
Groups at Risk of Vitamin D Inadequacy
Obtaining sufficient vitamin D from natural food sources alone can be difficult. For many people, consuming vitamin D-fortified foods and being exposed to sunlight are essential for maintaining a healthy vitamin D status. In many groups, dietary supplements might be required to meet the daily need for vitamin D.
Breast Fed Infants
Vitamin D requirements cannot be met by human milk alone, which provides only about 25 IU/L. A recent review of reports of nutritional rickets found that a majority of cases occurred among young, breastfed African Americans. The sun is a potential source of vitamin D, but AAP advises keeping infants out of direct sunlight and having them wear protective clothing and sunscreen.
As noted earlier, AAP recommends that exclusively and partially breastfed infants be supplemented with 400 IU of vitamin D per day.
Americans aged 50 and older are at increased risk of developing vitamin D insufficiency. 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. As many as half of older adults in the United States with hip fractures could have serum 25(OH)D levels <12 ng/mL (<30 nmol/L). People With Limited Sun Exposure Homebound individuals, people living in northern latitudes (such as New England and Alaska), women who wear long robes and head coverings for religious reasons, and people with occupations that prevent sun exposure are unlikely to obtain adequate vitamin D from sunlight. People With Dark Skin Greater amounts of the pigment melanin result in darker skin and reduce the skin's ability to produce vitamin D from exposure to sunlight. Some studies suggest that older adults, especially women, with darker skin are at high risk of developing vitamin D insufficiency. However, one group with dark skin, African Americans, generally has lower levels of 25(OH)D yet develops fewer osteoporotic fractures than Caucasians. People With Fat Malabsorption As a fat-soluble vitamin, vitamin D requires some dietary fat in the gut for absorption. Individuals who have a reduced ability to absorb dietary fat might require vitamin D supplements. Fat malabsorption is associated with a variety of medical conditions including pancreatic enzyme deficiency, Crohn's disease, cystic fibrosis, celiac disease, surgical removal of part of the stomach or intestines, and some forms of liver disease. People Who Are Obese Individuals with a body mass index (BMI) =30 typically have a low plasma concentration of 25(OH)D; this level decreases as obesity and body fat increase. Obesity does not affect skin's capacity to synthesize vitamin D, but greater amounts of subcutaneous fat sequester more of the vitamin and alter its release into the circulation. Even with orally administered vitamin D, BMI is inversely correlated with peak serum concentrations, probably because some vitamin D is sequestered in the larger pools of body fat. Learn How Much Vitamin D You Should Have - Click Here!
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