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Vitamin D isn't just for healthy bones any more.
Although scientists have known for over 80 years that the body uses vitamin D to make the hormones needed for transporting calcium into bones, a growing body of evidence has found that vitamin D is also essential for immune regulation and for the prevention and amelioration of diabetes, cancer, and heart disease.
Vitamin D and Diabetes
The insulin-producing beta cells of the pancreas are activated by an inflow of calcium which is made possible by a form of vitamin D known as D3, which makes the membranes of the beta cells more permeable to the calcium needed to trigger the release of insulin. A study of involving 55 diabetics conducted by Swiss researchers found that correcting vitamin D deficiencies also improved insulin sensitivity all over the body, lowering blood sugar levels by making insulin more efficient.
Vitamin D and Cancer
As early as the 1908, medical investigators noticed that cancer deaths were more common in people who lived in northerly climates. Even among people who spent most of their time outdoors in the sun, farmers for instance, cancer deaths were more common in the cool, cloudy northern New England states of the USA than in the sunny South.
In 2014, scientists at Harvard, Oxford, and other universities collaborated in a study of vitamin D status and health outcomes in over 1 million people worldwide.
Other studies have found that low vitamin D levels are associated with more aggressive breast cancer in women and more advanced prostate cancer in men, and that there the more sun you get, the less likely you are to develop bladder cancer, colon cancer, gastric, or colorectal cancer. Sunshine exposure also reduces the risk of cervical and endometrial cancer in women.
Vitamin D and Heart Disease
Vitamin D is essential for making the hormones that transport calcium into bones, but it is also essential for making the hormones that transport calcium out of cholesterol-laden plaques in the linings of arteries. Low vitamin D levels are associated with greater risks of atherosclerosis, dysfunctions of heart valves, and, since calcium is needed to power the muscles, poor contractile function, or "pumping power," of the heart. And because low vitamin D levels are linked to insulin resistance, they also are related to high levels of cholesterol and triglycerides, accelerating the process of atherogenesis, or hardening of the arteries.
It's an open question of whether these disease processes are caused by vitamin D deficiency, or they cause vitamin D deficiency. But due the fact that an increasing number of long-term clinical trials are finding that taking supplemental vitamin D prevents these diseases, it seems that deficiency causes disease rather than the other way around. And vitamin D deficiency isn't hard to remedy.