Vitamin D deficiency can contribute to the development of osteoporosis. A 2006 multinational study of 2,600 postmenopausal women with osteoporosis found that 64 percent of the participants had insufficient blood levels of vitamin D. Additionally, in a 2003 study published in the American Journal of Clinical Nutrition, researchers followed 72,000 women for 18 years and found that the women who consumed at least 600 IU per day of vitamin D had a 37 percent lower risk of osteoporosis-related hip fracture than women who consumed less than 140 IU per day. Other clinical trials offer additional evidence that vitamin D supplementation reduces bone density loss and osteoporotic fractures in adults who are deficient.
Current evidence suggests that a minimum daily intake of 600 IU of vitamin D can reduce the incidence of bone decalcification and fractures among the elderly. Those who take supplemental vitamin D to promote bone health and avoid fractures should also ensure an adequate dietary intake of calcium (1,000 to 1,200 milligrams per day).
Scientists have found positive links between vitamin D deficiency and several types of cancer, including breast cancer, prostate cancer and colon cancer. A 2007 study of 1,179 postmenopausal women revealed that participants who took supplements containing 1,100 IU of vitamin D and 1,400 mg of calcium over a period of four years had an overall cancer rate that was 60 percent lower than participants who took only placebos. This clinical trial strongly supports the observational studies that have associated sunlight and vitamin D levels with a lower risk of cancer.
Several recent studies offer strong evidence that low vitamin D levels are correlated with the incidence of cardiovascular disease. In a 2008 study published in the Archives of Internal Medicine, researchers compared 454 men (aged 40 to 75) who had a history of heart disease with 900 men who had no history of heart disease. Researchers found that participants with deficient vitamin D levels had a higher risk of heart attack than those with higher vitamin D levels. In another study – one of the most important to date – researchers followed 1,739 members of the Framingham Offspring Study for five years and found that the incidence of cardiovascular disease – including heart attacks, heart failure, and strokes – was from 53 to 80 percent higher in people with low blood levels of vitamin D.
According to the American Heart Association, over half a million Americans have a stroke each year. The most common risk factors for stroke include smoking, high blood pressure, lack of exercise and heart disease. But the results of a study published in2008 in the journal Stroke suggest that the incidence of stroke is higher among people with low vitamin D levels, indicating a correlation between low vitamin D levels and stroke. In another study, a Cambridge University neurologist compared blood vitamin D levels of 34 stroke patients with those of 96 healthy volunteers. Results show that the stroke patients’ blood vitamin D levels were a third lower than those of the healthy volunteers.