Vitamin D

The one health benefit that sunlight has on human skin is the production of vitamin D. Unfortunately, the ultraviolet rays that stimulate vitamin D production (UVB rays) are the same ones that cause skin cancer and premature aging.

There isn't very much vitamin D in the typical American's diet.  Some is present in oily fish (e.g., salmon, mackerel, sardines) milk, and fortified cereal or orange juice, but dietary sources alone are usually not sufficient for a healthy blood level without the addition of substantial sun exposure or a vitamin supplement.

Vitamin D deficiency can cause rickets in children, and osteoporosis in adults.  An increased risk of other ills, such as cancer of the colon, breast, or prostate, as well as multiple sclerosis and type 1 diabetes might be linked to vitamin D deficiency.  More research is needed before all of these associations can be considered certain but in the meantime it seems reasonable for everyone to take prudent measures to maintain an adequate blood level of vitamin D.

During summer months, particularly in the southern latitudes, some individuals acquire enough sun exposure to achieve an adequate vitamin D level.  However, while sun exposure is an effective source of vitamin D, it can simultaneously increase the risk of skin cancer.  When sunscreen is applied to the skin, it not only reduces sun damage, but unfortunately it also blocks vitamin D production. 

Darkly pigmented skin, advanced age, and low UV index (e.g., winter months in northern latitudes) are some of the factors that decrease the amount of vitamin D produced by the skin in response to sun exposure.  Because of the dual impact of the sun's UV rays (skin cancer induction and vitamin D production) those with the lightest skin pigment are at the highest risk of sun damage resulting in skin cancer, while people with darker skin pigment are at lower risk of skin cancer but higher risk for vitamin D deficiency.

Some authorities recommend routine limited or "sensible" sun exposure for vitamin D. However, too many variables affect the amount of exposure time needed (e.g., season, time of day, weather conditions, skin color, age) making it impossible to give a simple recommendation such as "[X] minutes of sun per day" that would be assured to provide sufficient vitamin D for all people. This introduces the risk that people will unintentionally over-expose (fall asleep while sunning) and increase their risk of skin cancer in the process. Sun Safety for Kids agrees with the American Academy of Dermatology: “Vitamin D from food and dietary supplements offers the same benefits — without the danger of UV exposure — as vitamin D obtained from the sun¹.”

The amount of Vitamin D in food or in a supplement is commonly listed in International Units (IU). Evidence is still emerging to determine the ideal safe and effective amount of vitamin D that people should get. At present, the National Institutes of Health² maintains that, unlike other vitamins, there is insufficient scientific information to establish a Recommended Dietary Allowance (RDA) for vitamin D. However, they list Adequate Intake (AI) amounts as follows:  200 IU from birth to age 50, 400 IU for ages 51-70, and 600 IU beyond age 70. Based on recent research, many experts now believe that the average healthy adult should ingest a total of 800 to 1,000 IU daily to maintain an adequate level of vitamin D. In June, 2007, the Canadian Cancer Society³ recommended that adults who do not get much sun should take a daily 1,000 IU vitamin D supplement.

Vitamin D supplements are most effective if taken with food. But, Beware! Vitamin D can be toxic in high doses. The NIH lists 2,000 IU per day as the upper limit for safety.

The directors of Sun Safety for Kids believe that optimum health will be achieved if people practice careful sun protection year round and compensate by ingesting a sufficient daily amount of vitamin D. Until more evidence is available, a total daily intake in the range of 800 to 1,000 IU is reasonable for healthy sun-safe adults. 

Vitamin D for Children

A 2008 report⁴ from the American Academy of Pediatrics (AAP)states, "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."  This is the same amount of vitamin D that is contained in one teaspoon of cod liver oil, a treatment that was proven safe and effective at preventing rickets by routine use in children over a period of several decades.

The recommendation applies to all children except those who consume at least one quart of vitamin D-fortified formula or milk per day.  The AAP recognizes that, "Given the dietary practices of many children and adolescents, a dietary intake of 400 IU of vitamin D is difficult to achieve.  Thus, for older children and adolescents, a daily multivitamin or vitamin D-only preparation containing 400 IU of vitamin D would be warranted."

Regarding sun exposure, the report states, "Although the AAP encourages physical activity and time spent outdoors, children's activities that minimize sunlight exposure are preferred, and when outdoors, protective clothing as well as sunscreens should be used.  In following these guidelines, vitamin D supplements during infancy, childhood, and adolescence are necessary."

"Children and adolescents at increased risk of developing rickets and vitamin D deficiency, including those with... ...decreased sunlight exposure... ...may require even higher doses than 400 IU/day of vitamin D," according to the AAP.  However, because vitamin D can be toxic in high doses parents should consult their child's pediatrician before increasing the amount of supplementation above 400 IU per day.  The doctor can assess the child's vitamin D status with a simple blood test and then could advise an appropriate adjustment to the daily supplement amount if indicated.

The AAP's recommendations are aimed primarily at preventing rickets or poor bone mineralization.  Further refinement of the AAP's recommendation might be forthcoming as additional benefits of vitamin D are discovered and confirmed.  Perhaps it will be revealed that a different amount is necessary to provide optimum health for not only the bones but other systems as well.  However, more study is needed before that can be determined.

Ask to Be Tested

A simple blood test called "25-hydroxy vitamin D" measures circulating vitamin D and provides a fair assessment of one's level. Periodically checking this test helps to assure that vitamin D sufficiency is being maintained. Leading experts suggest that blood levels in the range of 30 to 60 ng/ml are preferred. Levels tend to fluctuate with the seasons (lower in winter/higher in summer) due to incidental sun exposure. Bearing this in mind, blood test results will aid your doctor in determining the amount of vitamin D supplementation that is indicated (in winter or year-round) in order to maintain an optimum level.

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¹ http://www.aad.org/ (type “vitamin D” into the search site dialog box)
² http://ods.od.nih.gov/factsheets/vitamind.asp
³ http://www.cancer.ca/ccs/internet/mediareleaselist/
0,3208,3172_1613121606_1997621989_langId-en,00.html
⁴ http://www.aap.org/new/VitaminDreport.pdf