Vitamin D Toxicity: How Much Vitamin D is Too Much?

As a Registered Dietitian, one of the questions I hear often is concerning Vitamin D. How much Vitamin D is too much? Where do I get it? Why is it important? Vitamin D, also known as the “sunshine vitamin” is a fat-soluble vitamin that comes in several forms. One of the largest roles Vitamin D plays in the human body is in calcium metabolism. Maintenance of blood calcium is vital for normal functioning of the nervous system, as well as for bone growth and density. The body converts sunlight into to Vitamin D, however, a large percentage of the population is deficient in the vitamin that is vital for bone density, immune health, treating psoriasis, and may be effective for weight loss, cancer prevention, and reducing risk of rheumatoid arthritis. Vitamin D is also available is some foods, as well as in supplement form.

How much Vitamin D to take?

The latest recommendations for Vitamin D are higher then previous recommendations due to the positive links between Vitamin D status and disease/condition prevention, As of 2010, the daily reference intake or DRI for people ages 1-70 years of age, as well as pregnant or lactating women, has increased to 600 IU daily. People over the age of seventy should receive 800 IU daily. People who are currently deficient in the vitamin will need larger doses to get their levels within a normal range and should consult a doctor.

How do I get Vitamin D?

The sunshine vitamin is just that- available to our bodies through ultravoilet light in sunlight. Since it is available through sunlight, Vitamin D is considered “conditionally essential.” However, factors such as less hours of sun in the winter months, wearing lotions or makeup with SPF, and hours of working indoors prevents many from receiving the Vitamin D they need daily from the sun. Wearing sunscreen with an SPF as little as eight will reduce the production of Vitamin D by 95%. That said, sunscreen is essential for reducing risk of skin cancer and I wear it daily!

Vitamin D is available in some foods. Refer to the list below to find food sources of Vitamin D.

1 Tbsp cod liver oil, 1360 IU
3 ounces herring, 765 IU
3 ounces salmon, 425 IU
3 ounces canned sardine, 255 IU
1 C fortified milk, 100 IU
3 ounces shrimp, 90 IU
1 C fortified cereal, approximately 40-50 IU
1 medium egg yolk, 25 IU

From this list, you can see why many people find it hard to fit in enough Vitamin D each day from diet alone. This is why I usually recommend my clients, and practice what I preach myself, to take a multivitamin or Vitamin D3 supplement daily. Remember to take this supplement with a source of dietary fat, since it is a fat-soluble vitamin.

When deciding to supplement Vitamin D, too large of doses can be toxic. Hypervitaminosis D (Vitamin D toxicity) can result from Vitamin D supplementation of 10,000-50,000 IU/day over several years. Consult with your doctor before making decisions about large doses of Vitamin D.

Sources:

“Vitamin D.” Eatright.org. The American Dietetic Association, Web. 21 Nov. 2011. <http://www.eatright.org/Public/content.aspx?id=6795>.
“Vitamin D: Dosing – MayoClinic.com.” Mayo Clinic. Web. 21 Nov. 2011. <http://www.mayoclinic.com/health/vitamin-d/NS_patient-vitamind/DSECTION=dosing>.
“Vitamin D: MedlinePlus Supplements.” National Library of Medicine – National Institutes of Health. Web. 21 Nov. 2011. <http://www.nlm.nih.gov/medlineplus/druginfo/natural/929.html>.
Higdon, Jane. An Evidence-based Approach to Vitamins and Minerals: Health Implications and Intake Recommendations. New York: Thieme, 2003. Print.