Vitamin D is a fat-soluble vitamin you need to build strong bones, grow cells, stimulate your immune system, reduce inflammation and increase absorption of calcium. Very few foods naturally contain vitamin D. You can obtain the nutrient by consuming foods fortified with the vitamin, taking supplements and by exposing your skin to ultraviolet rays of the sun each day. Consuming excess amounts of vitamin D is toxic, however, and can cause health problems.
Dose
The recommended daily intake of vitamin D is 600 IU per day for adults 70 years of age and under, and 800 IU per day for adults over 70 years of age. Vitamin D toxicity usually occurs from taking excessive amounts in supplements, rather than from food or exposure to sunlight. Vitamin D toxicity is a serious condition that can increase your calcium levels and cause nausea, confusion and heart rhythm abnormalities.
Pregnancy and Breast-feeding
Taking too much vitamin D when you are pregnant or breastfeeding can increase the risk of birth defects and abnormalities in growth and development of your newborn. Pregnant women and breast-feeding mothers who are vulnerable to vitamin D deficiencies often take supplements to improve nutritional health and reduce the risk of asthma and wheezing in their children. Research by scientists at Massachusetts General Hospital and Harvard Medical School, Boston, and published in the "American Journal of Clinical Nutrition" in 2007 discovered that a higher maternal intake of vitamin D through diet and supplements during pregnancy may decrease the risk of a recurrent wheeze in early childhood. Consult your doctor about the proper dosage of vitamin D supplements to take when you are pregnant or breastfeeding to avoid excessive amounts, potential toxicity and adverse effects on your children.
Kidney Disease
If you have kidney disease, taking too much vitamin D from supplements may augment the amount of calcium you absorb into your body, elevate your blood levels of the mineral and increase your risk of atherosclerosis, hardening of the arteries. You may need to take less vitamin D, but not so low that it would increase your risk of osteodystrophy, a bone disease characterized by kidney failure and improper blood levels of calcium and phosphorous. An excessive intake of vitamin D may also increase your risk of kidney stones. Research by scientists at The Ohio State University in Columbus and published in the "New England Journal of Medicine" in 2006 found that postmenopausal women who take supplements containing vitamin D with calcium to improve bone health increase their risk of kidney stones.
Cancer
Excessive intake of vitamin D may increase your risk of cancer. Research by scientists at the National Cancer Institute in Rockville, Maryland, and published in "Cancer Research" in 2006 discovered that high blood concentrations of vitamin D are associated with a threefold increased risk for pancreatic cancer. Consult your doctor before taking vitamin D supplements to determine the benefits and risks.
References
- Office of Dietary Supplements National Institutes of Health; Dietary Supplement Fact Sheet: Vitamin D; 2009
- MayoClinic.com; What Is Vitamin D Toxicity, and Should I Worry About It since I Take Supplements?; Zeratsky, K.; Dec 11 2009
- MedlinePlus; Vitamin D; 2010
- "American Journal of Clinical Nutrition"; Maternal Intake of Vitamin D During Pregnancy and Risk of Recurrent Wheeze in Children at 3 Y of Age; Carlos Camargo, et al.; Mar 2007
- "New England Journal of Medicine"; Calcium Plus Vitamin D Supplementation and the Risk of Fractures; Rebecca Jackson, et al.; Feb 16 2006
- "Cancer Research"; A Prospective Nested Case-Control Study of Vitamin D Status and Pancreatic Cancer Risk in Male Smokers; Rachael Stolzenberg-Solomon, et al.; Oct 15 2006
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