Rachel Spieldoch, MD
We all know Vitamin D is important for ongoing bone health. However, most of us are unaware of the many benefits vitamin D has in our bodies. And many of us are frustrated trying to figure out exactly how much vitamin D is enough and how much is too much.
Vitamin D is produced by the skin in the form of vitamin D3. It can also be ingested in the form of vitamin D3 or vitamin D2. This is further metabolized by the liver into the biologically active form 25-OH vitamin D which can be measured with a simple blood test.
Severe vitamin D deficiency can result in calcium malabsorption, hyperparathyroidism, bone loss, and increased risk for fracture. Muscle pain and bone pain can also occur with severe deficiencies. Interestingly, obesity and women of color are risk factors for vitamin D deficiency. Other risk factors include decreased sun exposure, regular use of sunscreen, low dietary intake of vitamin D, liver disease, anti-seizure medications, and osteoporosis or osteopenia. It is important that women with specific risk factors or a previously low level of vitamin D have their levels tested by a physician. Additionally, blood testing of parathyroid hormone as well as calcium may be helpful in select patients.
Current studies show that at least 30% of U.S. adults age 20 or older have vitamin D deficiency. Additionally, vitamin D supplementation of at least 400 IU /day has been associated with a decreased risk for vertebral, nonvertebral and hip fractures.
Observational studies show that vitamin D deficiency may be linked to cardiovascular disease, cancer, diabetes and autoimmune disorders. Additionally, smaller studies suggest that vitamin D deficiency may be linked to breast cancer and melanoma.
Is it possible to get too much Vitamin D? The answer to this is yes. Surprisingly, too much vitamin D has been associated with a higher risk of fracture! Additionally, observational studies suggest that elevated vitamin D levels may be associated with pancreatic cancer and cardiovascular disease.
According to the Institute of Medicine report from 2010, the recommended dose of vitamin D supplementation for healthy adult women up to age 70 y/o is 600 IU/day. After the age of 70, the recommended dose increases to 800- 1000 IU/day. This is the recommended dose for women not receiving any direct sun exposure. If your vitamin D level is low or you have other risk factors, the medical recommendation may differ.
Achieving optimal benefits from vitamin D involves maintaining a balance. It is important to be mindful that too much vitamin D can carry health risks. However, appropriate supplementation and blood levels appear to have profound impacts on preventing disease and maintaining healthy bones.