In that study, girls had twice the risk of deficiency compared with boys, and overweight teens were at greater risk than normal-weight adolescents.
Now, new research shows that judging even by conservative standards, many children are vitamin D deficient.
Dr. Jonathan Mansbach of Children's Hospital Boston led a team that analyzed blood samples taken from 5,000 children under the age of 12, who'd participated in the 2001-2006 Nation Health and Nutrition Examination Survey (NHANES).
As Mansbach said in a press release, “There are a lot of studies demonstrating associations between low levels of vitamin D and a laundry list of poor health outcomes” (CHB 2009).
His team's analysis—funded by the National Institutes of Health—shows that nearly one in five of children in the U.S. have undesirably low blood levels of less than 50 nmol/L (nanomoles per liter).
And they found that two-thirds of U.S. children (24 million) have vitamin D levels below 75 nanomoles per liter… 80 percent of Hispanic children, 92 percent of black children, and 59 percent of white children (Mansbach JM et al. 2009).
The American Academy of Pediatrics recommends blood levels of vitamin D in children of at least 50 nanomoles per liter, and studies have shown that adults should maintain blood levels of 75 to 100 nmol/L.
According to Dr. Mansbach, “If 75 nmol/L or higher is eventually demonstrated to be the healthy normal level of vitamin D, then there is much more vitamin D deficiency in the U.S. than people realize” (CHB 2009).
The problems with D deficiency
Vitamin D deficiencies have been associated with an increased occurrence of childhood and adult diabetes (types I and II), inflammatory diseases, high blood pressure, cardiovascular disease, cancer and increased vulnerability to infections.
In contrast, high levels of vitamin D are associated with lower risk of these health problems, and substantially reduced rates of several common cancers… malignancies that seriously injure and kill many more Americans than skin cancer does.
Most skin cancers are not life-threatening, and while over exposure to sun may promote dangerous skin melanoma tumors, other factors are at play, since they often occur in people with little or no sun exposure.
Extreme vitamin D deficiencies in growing children causes rickets, a softening of the bones and that bows the legs … but the body is weakened in many ways by D deficiency, at blood levels that would not produce obvious symptoms like rickets or extreme muscle weakness.
Vitamin D is a key part of the body's antimicrobial defense system, so a lack leaves one more vulnerable to myriad infections.
As the press release from Children's Hospital Boston noted, “…recent studies suggest that it [vitamin D] also may prevent a host of common childhood illnesses, including respiratory infections, childhood wheezing, and winter-related eczema” (CHB 2009).
Vitamin D Sources
The human body naturally produces vitamin D through exposure to sunlight, but indoor-dwelling, sun-avoiding Americans often make insufficient amounts.
It takes about 30 minutes of exposure to strong (summer-strength) sunlight to avoid deficiency, and darker skinned people need more exposure than the lighter skinned do. This explains why African-Americans, people of Middle-Eastern descent, some Hispanics, and other dark skinned people suffer higher rates of vitamin D deficiency.
Most people who live in northern states don't get enough strong sunlight during the winter months… even those in southern climes may not make sufficient vitamin D during the summer if they over-avoid sun or overuse sunscreen.
And most Americans lead indoor lives, with little exposure to strong sunlight for the 20 (lighter skinned people) to 40 minutes a day or more (darker skinned people) needed to produce adequate blood levels.
Few foods contain much vitamin D, and the best sources by far are tuna and wildsalmon (400-700 IU per 3 oz), followed by other fatty fish such as sardines and mackerel (15-250 IU per 3 oz), trailed by egg yolks, milk, and some cheeses and meats.
But very few American children consume enough of these to match the vitamin D that could be provided by summer sun or vitamin D supplements.
For most people, dietary supplements provide the easiest way to ensure adequate vitamin D levels.
Authors and experts urge more vitamin D for kids and teens
Mansbach and his co-authors suggest that all children take vitamin D supplements, because of the generally low levels they found and the potential health benefits of boosting vitamin D levels.
Although sun exposure generates healthy doses of vitamin D, it can also cause skin cancer. Dermatologists and the AAP recommend wearing sun block, but this actually blocks our skin's ability to make vitamin D.
In the study, children taking multi-vitamins that included vitamin D had higher levels overall, but this accounted for less than half of all children. Mansbach recommends that all children take vitamin D supplements, especially those living in high latitudes, where the sun is scarce in the wintertime.
As Dr. Mansbach said, “…we believe many U.S. children would likely benefit from more vitamin D.”
In response to the new study, leading vitamin D researcher Michael F. Holick, M.D., put it plainly, saying, “…we estimate that vitamin D deficiency is the most common medical condition in the world… children should take vitamin D supplements and be less afraid of sensible sun exposure” (HealthDay 2009).
“At a minimum, from the time a child is born, they should be on 400 IU of vitamin D a day,” Holick suggested. “After the age of one, they should be up to 1,000 IU a day, and teenagers should definitely be on 2,000 IU a day” (HealthDay 2009).
(Dr. Holick, whom we've heard lecture and have spoken with, is professor of medicine, physiology, and biophysics and director of the Vitamin D, Skin, and Bone Research Laboratory at the Boston University School of Medicine.)
Minorities at higher risk
The racial/ethnic disparity found in the study relates to the amount of skin pigmentation… kids with more produce less vitamin D than those with fairer skin.
However, the disparity also suggests that children in these minority groups do not enjoy healthy diets.
A growing concern is the poor diets found in many urban neighborhoods, which tend to have higher minority populations.
Another recent study showed that nearly half of all black teens are vitamin D deficient and nearly twenty times more likely to be vitamin D deficient than white teens (Saintonge S et al. 2009).
- Children's Hospital Boston (CHB). October 26, 2009. Latest analysis confirms suboptimal vitamin D levels in millions of US children. Accessed athttp://www.eurekalert.org/pub_releases/2009-10/chb-lac102209.php
Dowshen S. Half of Black Teens May Be Lacking Vitamin D. March, 2006.Accessed at http://kidshealth.org/research/more_vitamind.html
HealthDay. 6 Million U.S. Kids Lack Enough Vitamin D. Monday, October 26, 2009. Accessed at http://www.nlm.nih.gov/medlineplus/news/fullstory_91055.html
Mansbach JM, Ginde AA, Camargo CA, Jr. Serum 25-Hydroxyvitamin D Levels Among US Children Aged 1 to 11 Years: Do Children Need More Vitamin D? Pediatrics Vol. 124 No. 5 November 2009, pp. 1404-1410 (doi:10.1542/peds.2008-2041)
Saintonge S, Bang H, Gerber LM. Implications of a new definition of vitamin D deficiency in a multiracial us adolescent population: the National Health and Nutrition Examination Survey III. Pediatrics. 2009 Mar;123(3):797-803.