Vitamin D is a fat soluble vitamin that builds and maintains your bones, according to the University of Maryland Medical Center, or UMMC. Vitamin D-3, 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 D-3 has health risks.
The recommended intake of vitamin D is 200 international units, or IU, per day for adults 50 years and younger, and 400 to 600 IU for adults over 50 years of age. Vitamin D toxicity, also called hypervitaminosis D, can result when you take too much vitamin D-3 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 D-3 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.
Excessive vitamin D-3 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 D-3 supplementation and calcium on the risk of hip fractures in postmenopausal women over 7 years and found that supplementation of 400 IU of vitamin D-3 and 1000 milligrams of calcium carbonate did not significantly reduce hip fractures, but did increase the risk of kidney stones by 17 percent.
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 D-3 per day. Furthermore, they note that you may need even higher dosages of vitamin D-3 if you suffer from celiac disease or are undergoing bariatric surgery. Yet, excess vitamin D-3 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 D-3.