Research » D-ficient Kids Review
D-ficient Kids Review
A study from Harvard Medical School found that more than six million children in the United States are vitamin D deficient. The researchers analyzed blood samples for vitamin D using data on about 5,000 children under age 12 years from the National Health and Nutrition Examination Survey (2001-2006). Results showed that one in five children had blood vitamin D levels below acceptable levels. According to the data, two-thirds of children (24million) have blood levels below 75nmol/L, a level considered closer to optimal. (1)
Background:
Vitamin D, a steroid hormone produced in the skin, has specific regulatory or functional effects on other parts of the body. Vitamin D is hydroxylated in the liver to 25-hydroxyvitamin D (25[OH]D) and further hydroxylated in the kidney to 1,25-dihydroxyvitamin D. Hydroxylation in the kidney is regulated closely by parathyroid hormone (PTH), hypocalcemia, and hypophosphatemia and is inhibited by 1,25- dihydroxyvitamin D. As well, 1,25- dihydroxyvitamin D (produced locally within
cells) regulates gene transcription through nuclear high-affinity VTD receptors. These receptors are found in the classic target organs: gut, bone, kidney, and parathyroid and many other tissues as well, such as brain, breast, colon, heart, pancreas, prostate, skin, and immune system. Vitamin D regulates cell growth and maturation, inhibits renin production, stimulates insulin secretion, and modulates the function of activated T- and B-lymphocytes and macrophages. (2)
Many individual and environmental factors interfere with the ability to have sufficient sun exposure to produce vitamin D endogenously. Over the past 4 decades, increasing scientific evidence has linked vitamin D deficiency to many chronic diseases including hypertension, immune dysfunction, cancer, diabetes, and cardiovascular disease. In adolescents, these relationships have only begun to be explored. It is reasonable to infer that because many of the potential consequences of vitamin D deficiency develop over time, prevention should begin in childhood. (3)
Why are our kids D-ficient?
Newborn infants have a unique source of vitamin D: the mother; cholecalciferol (the parent compound of vitamin D) does cross the placenta, maternal and fetal cholecalciferol blood concentrations are low and placental transfer contributes minimally to the vitamin D status of the fetus or newborn infant because 1,25-Dihydroxyvitamin D [1,25(OH)2D], the physiologically active metabolite, does not cross the placenta. However, the placenta can synthesize 1,25(OH)2D directly, and this might contribute to the infant's circulating level of 1,25(OH)2D. (4) The prenatal nutritional status of the mother directly affects the nutritional status of the fetus and neonate. Prenatal vitamin D deficiency may increase maternal risk of preeclampsia and gestational diabetes and may be associated with reduced bone mineralization in the offspring. (3)
The skin naturally produces vitamin D from the reaction of sunlight (ultraviolet B irradiation) with 7-dehydrocholesterol; however because of the relation of sun exposure to skin cancer, the Centers for Disease Control and Prevention, with the support of many organizations (including the AAP, the American Academy of Dermatology, and the American Cancer Society), recommend that infants younger than 6 months not be exposed to the sun and that all children and adolescents use sunscreens and clothing to protect them from ultraviolet B radiation exposure and to prevent skin cancer. (4)
Good evidence exists that many breastfed infants not supplemented with vitamin D during the first 6 months of life have serum vitamin D concentrations <50 nmol/L and are therefore at increased risk of rickets. This is especially true for infants who have high skin pigmentation and little sun exposure. (4)
Recommended Intake:
The new recommended daily intake of vitamin D is 400 IU/day for all infants, children, and adolescents beginning in the first few days of life - by the American Academy of Pediatrics (AAP): (5)
- AAP recommends that exclusively and partially breastfed infants receive supplements of 400 IU/day of vitamin D shortly after birth and continue to receive these supplements until they are weaned and consume >1,000 mL/day of vitamin D-fortified formula or whole milk.
- All non-breastfed infants ingesting <1,000 mL/day of vitamin D-fortified formula or milk should receive a vitamin D supplement of 400 IU/day.
- AAP also recommends that older children and adolescents who do not obtain 400 IU/day through vitamin D-fortified milk and foods should take a 400 IU vitamin D supplement daily. (6)
Conclusion:
Because numerous factors contribute to deficiency, routine supplementation should be considered along with monitoring of serum levels to document the attainment of adequate vitamin D. These measures can determine future dosing and dietary guidelines. (3)
Along with adequate vitamin D intake, dietary calcium intake to achieve optimal bone formation and modelling must be ensured. A dietary history is essential in assessing the adequacy of dietary intake for various vitamins, minerals, and nutrients, including vitamin D and calcium. (5)
| Additional Facts to consider:
Good evidence also shows that supplements of 400 IU vitamin D/d keep 25(OH)D concentrations higher than 70 nmol/L prevent rickets in white infants. (4) Rickets is an example of extreme vitamin D deficiency, with a peak incidence between 3 and 18 months of age. A state of deficiency occurs months before rickets is obvious on physical examination, and the deficiency state may also present with hypocalcemic seizures, growth failure, lethargy, irritability, and a predisposition to respiratory infections during infancy. (5) |
References:
1 Mansbach J, Ginde A, Camargo C: Serum 25-hydroxyvitamin D levels among US children aged 1 to 11 years. Pediatrics 2009;124:1404-1410
2 Schwalfenberg G: Not enough vitamin D- Health Consequences for Canadians-Clinical Review. Canadian Family Physician 2007;53:841-854
3 Saintonge S, Bang H and Gerber L: 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;123;797-803
4 Greer F: 25-Hidroxyvitamin D: functional outcomes in infants and young children. American Journal of Clinical Nutrition 2008:88
5 Wagner C, Greer F and the Section on Breastfeeding and Committee on Nutrition: Prevention of Rickets and Vitamin D Deficiency in Infants, Children, and Adolescents. Pediatrics 2008;122;1142-1152
6 National Institute of Health- Office of Dietary Supplements -Dietary Supplement Fact Sheet: Vitamin D Health Professional Fact Sheet
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