Vitamin D: Health risks from taking too much vitamin D Part 5

[BruceZ]

As discussed yesterday briefly, some patients may feel that if one dose of a vitamin is good then multiple doses could be better. Thus, some of our patients tend to take too much medication thinking that they are doing a good thing. This is especially true with over-the-counter or herbal medications. How many times have you asked a patient how much of an OTC medication they were taking and your eyes widened as they told you the amount. Thus, we must be vigilant in asking our patients about what medications they are taking as well as how much especially OTC or herbal meds. Patients don’t see these as dangerous as prescription medications and thus will often self medicate. That being said, the focus of this last blog of the week on Vitamin D will be what can occur if an individual takes too much vitamin D as a supplement.

?? Reader Question ??

• Can a patient develop vitamin D toxicity from being in the sun too much?

Vitamin D Toxicity

It is highly unlikely that a person would develop vitamin D toxicity by staying in the sun for a long period of time. “Excessive sun exposure does not result in vitamin D toxicity because the sustained heat on the skin is thought to photodegrade previtamin D3 and vitamin D3 as it is formed.” (1) As noted above, the most common cause of vitamin D toxicity is usually from taking too many supplements. (1) Remember, vitamin D toxicity is having a consistently elevated 25(OH)D serum level of > 100 or 200 ng/mL per day (depending on the research findings) as noted in the chart in Part 3 of this series.

The symptoms of vitamin D toxicity (1,2,3,4) could include any of the following:

Acute Toxicity

• Nausea
• Vomiting
• Muscle weakness
• Headache
• Anorexia
• Irritability
• Bone pain
• Apathy
• Conjunctivitis

Chronic Toxicity

• Acute toxicity symptoms listed above
• Constipation
• Hypercalcemia
• Hyperlipidemia
• Abdominal cramps
• Polydipsia
• Polyuria
• Back pain or ache
• Calcinosis
• Hypertension
• Cardiac arrhythmias (shortened refractory period)

NOTE4: Vitamin D increases serum calcium levels. There is mobilization of calcium from the bone as well as increased calcium absorption.

Treatment of Vitamin D Toxicity (4)

• Low calcium diet
• Calcium disodium edentate (removal of calcium through fecal excretion)
• Severe cases: Hydration, diuretics, steroids, calcitonin and/or mitramycin. These individuals need to be hospitalized.

It is imperative that the health care provider evaluate and ask questions about non-prescriptive medications that the patient is taking during their assessment of the patient especially for vitamin usage. Often the public does not realize the dangers that can occur with taking too much of a commonly used substance such as vitamins or multivitamins. Most have been brought up being told the importance of eating the proper foods to get their vitamins. Thus, they may attempt to obtain too much of a good thing. Many of the symptoms noted above are very similar to other differential diagnoses and thus it is important that the health care provider keep vitamin overdose or toxicity in mind when examining a patient with the complaints listed above.

Bruce S. Zitkus, EdD, ARNP, ANP-BC, FNP-BC, CDE

References

1 National Institutes of Health Office of Dietary Supplements. (2010). Vitamin D: Health professional fact sheet. Obtained July 26, 2010 from http://ods.od.nih.gov/factsheets/VitaminD_pf.asp.

2 Hathcock, J.N., Shao, A., Vieth, R., & Heaney, R. (2007). Risk assessment for vitamin D. American Journal of Clinical Nutrition, 85:6-18.

3 Jones, G. (2008). Pharmacokinetics of vitamin D toxicity. American Journal of Clinical Nutrition, 88(suppl):582S-586S.

4 Rosenbloom, M. (2009). Vitamin Toxicity. EMedicine from WebMD. Retrieved from http://emedicine.medscape.com/article/819426-overview