December 2012 Issue
Vitamin D Deficiency in Children
By Maura Keller
Vol. 14 No. 12 P. 26
Kids can play outdoors in the sunshine this winter and eat foods fortified with this crucial nutrient to boost daily intake.
Now that the winter season is in full swing, the days are noticeably shorter and the nights are longer. That means children and teens are spending a lot more time indoors away from the natural sunlight that produces vitamin D in the body.
Much discussion has surfaced lately about this important vitamin and its role in preventing various chronic diseases, such as cardiovascular disease, diabetes, and hypertension, and different types of cancers. Studies show that millions of children and teens suffer from vitamin D deficiency and insufficiency, and dietitians and other healthcare practitioners are evaluating the best ways to increase their intake.
As you know, vitamin D plays an important role in bone health. It promotes the absorption of calcium and phosphorus and helps deposit these minerals in bones and teeth, making them stronger and healthier. It also strengthens the immune system and helps regulate cell growth.
RDs interviewed by Today’s Dietitian discuss the role of vitamin D in preventing chronic disease, how sunlight produces the nutrient in the body, symptoms of deficiency, who’s at risk, and strategies for counseling children and teens to help them boost their intake.
“Vitamin D has various roles in the body, including modulation of cell growth, neuromuscular and immune function, and reduction of inflammation,” says Emilia Baczek, RD, LDN, an outpatient dietitian at La Rabida Children’s Hospital in Chicago. “Many studies also have linked vitamin D [deficiency] to cardiovascular disease, many cancers, gene expression, seasonal affective disorder, multiple sclerosis, autoimmune disorders, and insulin resistance in adults.”
Vitamin D is a fat-soluble vitamin naturally occurring in animal products and irradiated plant products, Baczek explains. It also can be obtained from sunlight exposure through synthesis in the skin. “Vitamin D comes in many forms, but the two major ones are vitamin D2 [ergocalciferol] that originates from the yeast and plant sterol called ergosterol, and vitamin D3 that originates from 7-dehydrocholesterol, a precursor of cholesterol synthesized in the skin. Vitamin D is produced endogenously when ultraviolet rays from sunlight shine on the skin and trigger vitamin D metabolism,” Baczek says.
Tammi Timmler, MS, RD, CD, CDE, a clinical dietitian in nutrition and diabetes services at Marshfield Clinic in Wisconsin, says it’s often difficult to get enough vitamin D through diet, and even though sunlight is the best source, most people now limit sun exposure due to the increased risk of skin cancer.
Some research on vitamin D suggests that approximately five to 30 minutes of sun exposure on the face, arms, legs, or back without sunscreen between 10 am and 3 pm at least twice per week usually leads to sufficient vitamin D synthesis. However, Baczek notes that the skin synthesis of vitamin D is affected by many factors, including degree of skin pigmentation, latitude, time of day, season of the year, weather conditions, and the amount of body surface covered with clothing or sunscreen. “Thus, it’s difficult to control for all those variables and to quantify one’s daily sun exposure and make specific recommendations based on that,” she says. “Sunscreen application also blocks skin synthesis of vitamin D.”
Where people live plays a key role in their levels of vitamin D absorption through sunlight exposure. “In the northern hemisphere, the UVB rays are more intense during the summer months and less intense during the winter months,” Timmler says. “Picture a map of the United States with a line drawn from Boston, Massachusetts, to California; anyone north of that line likely will need additional vitamin D, either from food or supplements, in the winter months. The intensity of UVB rays also is reduced by clouds and pollution, and they won’t pass through glass, so sitting next to a window won’t provide enough sunlight exposure to make vitamin D.”
As mentioned, vitamin D deficiency is prevalent among children and adolescents. A 2009 study published in Pediatrics found that “overall, 9% of the pediatric population, representing 7.6 million US children and adolescents, were 25(OH)D deficient, and 61%, representing 50.8 million US children and adolescents, were 25(OH)D insufficient.” According to the National Institutes of Health, this means that 7.6 million US children and teens have serum 25-hydroxyvitamin D [25(OH)D] levels of 12 ng/mL or lower, rendering them deficient; and 50.8 million have 25(OH)D levels of 12 to 20 ng/mL, classifying them as insufficient or having inadequate vitamin D levels for bone and overall health.
In children and adults, symptoms of vitamin D deficiency include bone pain or tenderness, dental deformities, impaired growth, increased bone fractures, muscle cramps, short stature, and skeletal deformities such as rickets.
“The American Academy of Pediatrics has reported rickets to be on the rise,” Timmler says. “Rickets is a medical condition tied to low vitamin D levels. The low vitamin D causes bones to weaken, specifically the legs bow out under the weight of the child’s upper body.”
Suboptimal vitamin D status is common among otherwise healthy young children, and indicators of vitamin D status vary in infants and toddlers. “Skeletal deformities, such as bow legs and thick wrists and ankles, are symptoms and signs of vitamin D deficiency in children,” Timmler says. “Curvature of their spines, a pigeon chest, skull malformations, and pelvic deformities also are signs of rickets in children. The bones of these children tend to be very soft and brittle, resulting in fractures. Pain, tenderness, and muscle weakness may accompany the bone deformities.”
Due to the prevalence of vitamin D deficiency and insufficiency in children and teens, it’s important to determine the best time to test their vitamin D levels. Experts say vitamin D levels are checked if calcium status is low or if patients are experiencing bone malformation (rickets), bone weakness and softness, or fractures that occur without real injury. “Vitamin D levels also may be used to help diagnose or monitor problems with parathyroid gland functioning since PTH [parathyroid hormone] is essential for vitamin D activation,” Baczek says. “In cases where vitamin D, calcium, phosphorus, or magnesium supplementation is necessary, vitamin D levels may be measured to monitor treatment effectiveness.”
According to Letitia Warren, RD, CSP, a pediatric clinical dietitian at DMC Children’s Hospital of Michigan, children at risk of vitamin D deficiency include those who have reduced exposure to sunlight; are on certain medications, such as anticonvulsants that interfere with metabolism; and are overweight or obese since vitamin D is held in adipose tissue and isn’t bioavailable. Others at risk include those experiencing fat malabsorption due to cystic fibrosis, Crohn’s disease, or Roux-en-Y gastric bypass surgery. Some children may not be drinking enough milk by choice or because they have a milk allergy, are lactose intolerant, or follow a vegan diet.
Moreover, children who have limited sun exposure, darker skin tones, excess body fat, and are living at higher latitudes are at higher risk of vitamin D deficiency and may benefit from getting tested.
Vitamin D supplements should be considered when the recommended dietary intake isn’t met by food alone. Children younger than 1 should receive 400 IU/day (10 mcg); kids older than 1 year should take 600 IU/day (15 mcg). “However, many believe nutrients should be obtained through food and fear that recommending supplements may lead to treating vitamin D like it’s less of a nutrient and more like a drug,” Baczek says.
Maria Hanna, MS, RD, LDN, an advanced practice dietitian in the department of clinical nutrition at Children’s Hospital of Philadelphia agrees: “It’s important to encourage foods that contain vitamin D naturally or via fortification. But because there are so few foods that are naturally excellent sources of vitamin D, it’s safe and acceptable to include supplementation to meet the recommended amount for age through a daily multivitamin or a reliable over-the-counter vitamin D supplement containing 400 to 600 IU of vitamin D per dose. Children at high risk of vitamin D deficiency likely will need higher levels of supplementation and would benefit from checking and monitoring their vitamin D status via the accepted standard.”
Dietary sources of vitamin D are limited. They include some fish liver oils; fatty fish such as salmon, tuna, and mackerel; eggs from hens that have been fed vitamin D; fortified milk products; and other fortified foods such as breakfast cereals. “Most of the vitamin D in the American diet comes from fortified foods such as milk, breakfast cereals, and some brands of juice, yogurt, or margarine,” Baczek says.
Cod liver oil is a rich source of vitamin D; however, it also has a high vitamin A content, Hanna says. “In order to avoid vitamin A toxicity, cod liver oil is no longer recommended,” she says. “Some foods are fortified with vitamin D, but the content isn’t as high. In the United States, milk is fortified with vitamin D so that every 8-oz serving contains approximately 100 IU. Other foods include vitamin D fortified milk substitutes, such as soy, almond, or coconut milk and yogurt; fortified orange juice; and fortified cereals. It’s important to read the label to verify the amount of fortification.”
Timmler agrees that obtaining sufficient levels of vitamin D from natural food sources alone is difficult. “For many people—much less kids—consuming vitamin D-fortified foods and being exposed to some sunlight are essential for maintaining a healthful vitamin D status,” she says. “Since the risks of low vitamin D are well-known, parents should try and reverse the trend by getting their kids to drink their milk—or eat their fortified yogurt—and decrease the time spent watching television, playing games on the computer or handheld devices, and spend some time outside in the sun.”
— Maura Keller is a Minneapolis-based freelance writer and editor.
• National Institutes of Health Office of Dietary Supplements Dietary Supplement Fact Sheet, Vitamin D: http://ods.od.nih.gov/factsheets/VitaminD_pf.asp
• The Hormone Foundation’s Patient Guide to Vitamin D Deficiency: www.hormone.org/Resources/upload/PG-VitaminD-v2-Web-Corrected.pdf
What’s on the Menu?
Children and teens can boost their daily vitamin D intake if they choose their meal and snack selections wisely, says Tammi Timmler, MS, RD, CD, CDE, a clinical dietitian in nutrition and diabetes services at Marshfield Clinic in Wisconsin. “Many of the traditional foods high in vitamin D aren’t always a fan favorite with kids, so you may need to be creative,” Timmler says.
Here are some healthful vitamin D breakfast, lunch, dinner, and snack options that meet almost 50% of the daily requirements.
• 3 oz sockeye salmon, cooked: 447 IU
• 1 cup fortified orange juice: 137 IU
• 1 cup 2% milk: 120 IU
• 1 cup TOTAL Raisin Bran cereal: 104 IU
• 1 cup fat-free milk: 115 IU
• 6 oz Dannon Light & Fit Vanilla yogurt: 80 IU
Vitamin D Meal Options
• canned (or smoked) salmon and Swiss cheese quiche;
• fried tuna and mushroom frittatas;
• chilled salmon pasta salad with hard-cooked egg slices, cheese, and tuna;
• mushroom quesadillas; and
• sandwiches such as tuna melts, egg salad, and salmon burgers.
Recommended Dietary Allowances
According to Emilia Baczek, RD, LDN, an outpatient dietitian at La Rabida Children’s Hospital in Chicago, the Food and Nutrition Board established Recommended Dietary Allowances (RDAs) for vitamin D representing a daily intake that’s sufficient to maintain bone health and normal calcium metabolism in healthy people. The reference values, collectively called Dietary Reference Intakes (DRIs), include the Estimated Average Requirement, RDA, Adequate Intake, and Tolerable Upper Intake Level. The RDA is the average daily dietary intake level that’s sufficient to meet the nutrient requirements of 97% to 98% of healthy individuals in a specific life stage and gender group to maintain a defined nutritional state, such as normal growth, maintenance of normal circulating nutrient values, or other aspects of nutritional well-being or general health.