The Truth About Vitamin D

Low blood levels of vitamin D have been linked to many diseases including osteoporosis, heart disease, cancer, type 2 diabetes Alzheimer's and autoimmune diseases.

But what about recent headlines declaring that high blood levels of vitamin D can cause heart disease? They were based on a study published in The journal of Clinical Endocrinology & Metabolism, which showed that people with high levels of vitamin D (25- hydroxy-vitamin D) were 30% more likely to die of a heart attack, heart failure or stroke.

As I wrote in a recent paper in the journal Nutrients, citing 49 studies that involved millions of people, vitamin D toxicity is rare. Yes, high levels increase calcium and phosphate, which can damage kidneys and clog arteries. But research shows that daily doses as high as 20,000 international units (IU) of vitamin D-3 (much higher than levels found in most vitamin D-3 supplements, which typically supply 400 IU to 2,000 IU) do not raise blood levels above 100 ng/mL, the level traditionally considered a sign of possible toxicity.

The reality is that many Americans have either an insufficient blood level of vitamin D (21 ng/mL to 29 ng/mL) or an outright deficiency (less than 20 ng/mL). An analysis of 73 studies on vitamin D, involving nearly 900,000 people, shows that low levels raise the risk of dying from heart disease (or any cause) by 35%.

My advice: Blood levels of vitamin D should be at least 30 ng/mL (the preferred range is 40 ng/mL to 60 ng/mL).

To achieve that level, the Endocrine Society recommends that adults take 1,500 IU to 2,000 IU of vitamin D-3 daily, even in the summer when sun exposure gives us more natural vitamin D.