Nutrient Guide: Vitamin D

Vitamin D enables bones and teeth to grow properly and helps a child’s body absorb calcium and phosphorous – the building blocks for strong, healthy bones. Vitamin D is also known as the “sunshine vitamin” because the body manufactures it after being exposed to natural light. But studies suggest many children are vitamin D deficient1,16, 17, and that even children living in sunny climates may not produce vitamin D in amounts sufficient for their growing bodies and bones. Current Reference Daily Intake (RDI)* for Vitamin D is 600 IU for adults and 400 IU for children. 

  • Vitamin D is stored in the skin, brain, spleen, and bones and promotes a child’s neuromuscular development10 and a healthy immune system function, including the ability to ward off colds and influenza2.
  • Vitamin D is instrumental in preventing rickets (soft bones) and may help prevent certain infections, and may help reduce deficiency related depression7.
  • At least one in five American children between the ages one and 11 may be at risk for a variety of health issues as a result of not getting a sufficient amount of vitamin D4,17
  • Children with dark skin, which is more resistant to the sun’s radiation, or who live in areas with limited exposure to sunlight may be particularly susceptible to vitamin D deficiency.

NOTE: Excessive intake of any nutrient, including vitamin D, can cause toxic effects5. Because vitamin D is fat-soluble– meaning it is stored in the body–ingesting abnormally high doses over sustained periods of time could lead to calcium deposits in soft tissue. The upper limit of vitamin D for adult is 10,000 IU per day.  Excessive sun exposure does not cause vitamin D toxicity.

Sources of Vitamin D

  • Vitamin D is found in dairy products like cheese, butter, fortified milk (all milk in the United States is vitamin D-fortified), and fortified cereals.
  • D3, or “natural” vitamin D, is found in fish liver, which is the traditional source of vitamins A and D. Egg yolks, butter, and liver have some vitamin D, as do oily fish like mackerel, salmon, sardines, and herring.
  • Plant foods are fairly low in vitamin D, which means that strict vegetarians who do not get adequate exposure to sunlight often may not get adequate amounts of vitamin D.
  • Breast milk6 alone is not considered to have sufficient levels of vitamin D for a nursing baby.

VITAMIN D OVERVIEW

Vitamin D is technically not a vitamin at all but rather an ingredient in hormones manufactured in the skin after exposure to sunlight. Like vitamins A and E, vitamin D is retained in the body’s fat tissue, and not quickly excreted like most water-soluble vitamins are. Fat-soluble vitamins like D are necessary for the function or structural integrity of specific body tissues and membranes.*

Most plants and animals exposed to sunlight have the capacity to make vitamin D, and it is considered critically important for the development, growth, and maintenance of a healthy body from birth and throughout life.

But vitamin D deficiency remains common in children and adults7. In fact, in utero and during childhood, vitamin D deficiency can cause growth retardation and skeletal deformities and may increase the risk of hip fracture later in life.7

Despite its natural availability and essential benefits, vitamin D intake is found to be insufficient in six of 10 American children1 and seriously deficient in another 10 percent, according to data collected by the National Health and Nutrition Examination Survey8. The deficiencies are thought to be part of an increasing decline in vitamin D levels in children nationwide17, as changes to their and their families’ lifestyles and work patters afford children less active daylight time outdoors.

Previous studies12 have also shown that children lacking sufficient levels of vitamin D had increased levels of blood pressure and cholesterol and had a greater likelihood of being overweight. In addition, scientific evidence13 suggests that getting enough vitamin D may help children ward off colds and influenza14.

Overall, children considered at higher risk for a vitamin D deficiency were older, female, obese, drank milk less than once a week and spent more than four hours a day watching TV, playing video games or sitting at a computer1. A 2009 study15 also found significant differences in vitamin D levels among white, black, and non-black Hispanic children.

NOTE: Always seek the advice of your pediatrician or nutritionist before making changes to you or your children’s diet or nutrient intake.

* The Reference Daily Intake (RDI) is the value of established by the Food and Drug Administration (FDA) for use in nutrition labels. It was based initially on the highest 1968 Recommended Dietary Allowance (RDA) for each nutrient, to assure that needs were met for all age groups. To see more recent recommendations, please see the Dietary Reference Intakes (DRI). These are the most recent set of dietary recommendations established by the Food and Nutrition Board of the Institute of Medicine, 1997-2001. They replace previous RDAs and may be the basis for eventually updating the RDI’s. See here for a comparison of RDIs and DRIs: http://en.wikipedia.org/wiki/Reference_Daily_Intake

REFERENCES

  1. CNN, “Vitamin D deficiency common in U.S. children,” Aug. 3, 2009.http://www.cnn.com/2009/HEALTH/08/03/vitamin.d.children/index.html
  2. eNotAlone, “Vitamin D Prevents Cold And Flu,” Feb. 25, 2009.http://www.enotalone.com/article/19368.html
  3. Pediatrics, Vol. 122, No. 5, pp. 1142-1152, November 2008.http://pediatrics.aappublications.org/cgi/content/abstract/122/5/1142
  4. MayoClinic.com, “What is vitamin D toxicity?” Aug. 22, 2009.http://www.mayoclinic.com/health/vitamin-d-toxicity/AN02008
  5. DoctorsNatural.com, “RDA of vitamin D to double for children,” Oct. 23, 2008.http://www.doctorsnatural.co.uk/news/54/RDA-of-vitamin-D-to-double-for-children.html
  6. LiveScience.com, “Lack of Vitamin D in Children ‘Shocking’,” Aug. 3, 2009.http://www.livescience.com/health/090803-vitamin-d-children.html
  7. MedIndia.net, “Vitamin D Boosts Immunity, Prevents Colds, Flu: Study,” Feb. 24, 2009.http://www.medindia.net/news/Vitamin-D-Boosts-Immunity-Prevents-Colds-Flu-Study-47873-1.htm
  8. Science Daily, “New Guidelines Double Amount Of Recommended Vitamin D For Young,” Oct. 14, 2008. http://www.sciencedaily.com/releases/2008/10/081013141737.htm
  9. Science Daily, “Low Vitamin D Levels Appear Common In Healthy Children,” Jun 6, 2008.http://www.sciencedaily.com/releases/2008/06/080602160835.htm

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