Vitamin D deficiency is much more common than we think, and can cause serious health issues that may be be erroneously attributed to other causes. Not enough vitamin D can lead to or worsen muscle weakness, osteopenia, osteoporosis, fractures, autoimmune diseases, infectious diseases and cardiovascular diseases. According to the National institutes of Health:

… Americans age 50 and older are at an increased risk of developing vitamin D deficiency. As people age, skin cannot synthesize vitamin D as efficiently and the kidney is less able to convert vitamin D to its active hormone form. As much as 30% to 40% of hip fractures are due to vitamin D insufficiency.

Deficiencies are usually the result of dietary inadequacy, impaired absorption and utilization, increased requirement, or increased excretion (loss). A deficiency of vitamin D can occur when: (a) when usual intake is below recommended levels, (b) when there is limited exposure to sunlight. (c) when the kidney cannot convert vitamin D to its active hormone form, and (d) when someone cannot adequately absorb it from the digestive tract.

“It is estimated that over 25 million people in the United States have, or are at risk of developing, osteoporosis. It is a disease characterized by fragile bones, and it significantly increases the risk of bone fractures. It is most often associated with inadequate calcium intake. However, a deficiency of vitamin D also contributes to osteoporosis by reducing calcium absorption and is an example of a long-term effect of vitamin D insufficiency. Adequate storage levels of vitamin D help keep bones strong and may help prevent osteoporosis in older people, in non-ambulatory individuals (those who have difficulty walking and exercising), in post-menopausal women, and in individuals on chronic steroid therapy. Vitamin D deficiency has been associated with greater incidence of hip fractures. In a review of women with osteoporosis hospitalized for hip fractures, 50 percent were found to have signs of vitamin D deficiency. Daily supplementation with 20 micrograms (800 IU) of vitamin D may reduce the risk of osteoporotic fractures in elderly populations with low levels of vitamin D.”

Muscle strength and avoidance of falls also require adequate vitamin D stores in the body. As vitamin D levels decrease, the chance of falls increases. In fact, vitamin D deficiency is a dangerous cycle, since it increases the risk of falling and reduces the strength of bones to withstand breaking on impact.

Some good food sources of vitamin D: cod liver oil, salmon, mackerel, and sardines.

(Caveat: Cod liver oil is problematic. Just one teaspoon of cod liver oil has 4,500 IU of vitamin A, for instance, and the standard dose is one to three teaspoons a day. Studies have found that as little as 6,000 IU of vitamin A daily can interfere with bone growth and promote fractures. And women of childbearing age should not exceed 10,000 IU of vitamin A because of the risk of birth defects. Cod liver oil is made from livers, so toxins (such as PCBs) get concentrated there. Cod liver oil is more likely to be contaminated than other fish-oil sources.)