Vitamin D deficiency is concerning as it associated with serious diseases, including bone disease, cancer and multiple sclerosis. Vitamin D is available from two main sources--it is manufactured in the skin and obtained from food. Your skin is able to make vitamin D when it is exposed to sunlight. For people who live in northern climates, it can be especially difficult to get enough vitamin D, because sun exposure is limited in the winter months, and there are a limited number of foods that contain substantial levels of vitamin D. Vitamin D is available in foods such as fish, liver and egg yolks and fortified foods such as breakfast cereals, orange juice and milk.
The current adequate intake, established by the Institute of Medicine in 1997, is 200 international units per day for adults up to 50 years old, 400 IU for adults 51 to 70 years old and 600 IU for adults over 70. According to the Linus Pauling Institute at Oregon State University and other experts, these levels of vitamin D may be inadequate to prevent chronic disease. The Linus Pauling Institute recommends that adults take a 2,000-IU supplement of vitamin D daily.
Bone Disease
According to the Linus Pauling Institute, severe vitamin D deficiency causes rickets in children and osteomalacia in adults. Rickets causes bowing of growing bones as a result of lack of bone mineralization, whereas osteomalacia causes loss of minerals from bone leading to soft bones. Furthermore, while there are many factors that contribute to the development of osteoporosis, insufficient vitamin D appears to play a role in this bone disease as well.
Cancer
According to Kulie et al., in a 2009 article in the "Journal of the American Board of Family Medicine," having higher blood levels of vitamin D appears to be associated with decreased risk for cancer. The Linus Pauling Institute notes that certain studies suggest a decreased risk specifically for colorectal and breast cancer with higher blood levels of vitamin D.
Multiple Sclerosis
Multiple sclerosis is an autoimmune disease in which a person's own immune system attacks the cells that produce the myelin sheath covering nerves. Prevalence of MS increases as you move further from the equator, suggesting a role for vitamin D deficiency in the development of MS. The rationale is that the sun is stronger closer to the equator--thus, people living closer to the equator would be expected to have higher blood levels of vitamin D as opposed to those living further from the equator where the sun is much weaker. According to Kulie et al., multiple studies suggest lower vitamin D levels are associated with increased risk for MS.
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