Vitamin D is a fat soluble vitamin that builds and maintains your bones, according to the University of Maryland Medical Center (UMMC). Vitamin D3, also called cholecalciferol, is produced in the skin when exposed to sunlight, and becomes biologically active after undergoing chemical reactions in the liver to make calcidiol, followed in the kidneys to make calcitriol, according to the National Institutes of Health Office of Dietary Supplements. Too much vitamin D3 has health risks.
Toxicity
While the recommended intake of vitamin D is 200 IU per day for adults 50 years and younger, and 400 to 600 IU for adults over 50 years of age, many experts recommend adults of all ages get 1,000 to 2,000 IU of vitamin D per day, according to MayoCllinic.com. Vitamin D toxicity, also called hypervitaminosis D, can result when you take too much vitamin D3 in supplemental form. Vitamin D toxicity can cause serious health problems, particularly if you suffer from heart, liver or kidney conditions. Excessive amounts of vitamin D3 may increase blood levels of calcium, also called hypercalcemia, which in turn can cause symptoms that include nausea, vomiting, weakness, poor appetite, weight loss, constipation, confusion and heart rhythm abnormalities. Research by U. Querfeld published in "Pediatric Nephrology" in 2010 reports that vitamin D toxicity among children and adolescents is associated with cardiovascular complications and chronic kidney disease.
Kidney Stones
Excessive vitamin D3 in postmenopausal women may increase the risk of kidney stones. Research by Rebecca Jackson published in the "New England Journal of Medicine" in 2006 studied the effects of vitamin D3 supplementation and calcium on the risk of hip fractures in postmenopausal women over 7 years and found that supplementation of 400 IU of vitamin D3 and 1000 mg of calcium carbonate did not significantly reduce hip fractures, but did increase the risk of kidney stones by 17 percent.
Pancreatic Cancer
The Cleveland Clinic states that many people do not get sufficient sun exposure and require vitamin D supplementation in amounts ranging from 1,000 to 5,000 IU of vitamin D3 per day. Furthermore, they note that you may need even higher dosages of vitamin D3 if you suffer from celiac disease or are undergoing bariatric surgery. Yet, excess vitamin D3 may increase the risk of cancer. Research by Rachael Stolzenberg-Solomon published in "Cancer Research" in 2006 discovered unexpectedly that higher blood concentrations of vitamin D is associated with a 300 percent increased risk for pancreatic cancer, despite the fact that the pancreas utilizes vitamin D3.
References
- University of Maryland Medical Center: Vitamin D
- Office of Dietary Supplements National Institutes of Health: Dietary Supplement Fact Sheet: Vitamin D
- MayoClinic.com: What Is Vitamin D Toxicity, and Should I Worry About It since I Take Supplements?
- "Pediatric Nephrology"; Vitamin D Deficiency and Toxicity in Chronic Kidney Disease: In Search of the Therapeutic Window; Querfeld, U.; Dec 2010
- "New England Journal of Medicine"; Calcium Plus Vitamin D Supplementation and the Risk of Fractures; Jackson, R.D.; Feb 16 2006



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