Vitamin D is not only a fat-soluble vitamin but a steroid hormone, which means it plays a role in the parathyroid hormones (produced by glands on either side of the thyroid gland) and our mood, as well as bone health. There are pros and cons to taking large doses of vitamin D and it is best to check your levels of vitamin D before going over the recommended daily allowance of 400-600 IU a day.
Recommended Dose
The Food and Drug Administration goes by the recommended daily allowance or intake that was set in 1968. The current RDI for vitamin D is 400-600 IU (International Units). Anything 10 times that amount is called a mega-dose. This level is currently being questioned, since it is known that a single sun exposure of 10-30 minutes can produce up to 10,000 IU before the body stops making vitamin D. A study done by the Department of Medical Oncology in Toronto, Canada in November 2009 found that high doses of vitamin D (10,000 IU) have been helpful for cancer patients, without toxicity. A recent paper by American Family Physician found that supplementation of 1,000 IU a day is safe on a regular basis. Supplementation can be taken in a capsule, tablet or intramuscular muscle injection (IM), but IM is usually only done in a health professional's office.
Therapeutic Effects
The goal of having proper levels of vitamin D is to help regulate calcium and bone health, decrease fall fracture risk and improve the immune system. A 2008 review study of vitamin D research done by the International Journal of Circumpolar Health found that vitamin D deficiency can be linked to diseases like cancer, multiple sclerosis and type I diabetes. This same study also noted that those living in the northernmost areas of the Earth need to supplement vitamin D during the winter since sunlight is not as readily available. By making sure you have appropriate supplementation of vitamin D, there are some protective effects from some of these diseases, much like antioxidants and exercise help decrease risks for other diseases.
Negative Side Effects
Despite all of the research showing the safety of mega-doses of vitamin D, it is still possible to have too much. Signs of too much vitamin D include hypercalcemia, where there are much higher levels of serum calcium in the blood, due to the similar pathways both nutrients share. With the increased calcium in the blood, there can be calcium deposits in soft tissues or areas of hardened tissue. There is also an increased chance of kidney stones, again due to the higher levels of calcium in the blood.
References
- International Journal of Circumpolar Health: Vitamin D and Living in Northern Latitudes---An Endemic Risk Area for Vitamin D Deficiency.; Huotari A, and Herzig KH; June 2008
- Cancer: A Phase 2 Trial Exploring the Effects of High-Dose (10,000 IU/day) Vitamin D(3) in Breast Cancer Patients With Bone Metastases; Department of Medical Oncology Margaret Hospital, Toronto, Ontario, Canada; November 2009
- American Family Physician: Recognition and Management of Vitamin D Deficiency; Bordelon P, et al; October 2009
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