Vitamin D levels drop low in the winter months, compromising immunity, cardiovascular health, bone health, metabolism, and most importantly – increasing the risk for early death especially amongst older Americans. A new study shows that adequate vitamin D reduces the risk of all-cause mortality by 29%.

This new data reinforces an emerging scientific consensus regarding the importance of vitamin D. Several studies in the past year reached similar conclusions. Vitamin D deficiency is common around the world. Researchers estimated that correcting this deficiency by doubling the typically low vitamin D levels would result in a 20% mortality reduction. Other data shows that low levels of vitamin D in the elderly more than double their risk of cardiovascular mortality.

Depending on the lab, a “normal” range for vitamin D (25-hydroxyvitamin D or 25(OH)D) can be anywhere from 20 to 100 nanograms per milliliter (ng/mL). The general consensus is that normal is now in the range of 30 to 74 ng/mL. Many scientists now believe that optimal vitamin D levels are important for the reduction of disease, and propose targeting for a level of 50 to 70 ng/mL. Sometimes vitamin D lab tests are reported as nanomoles per liter (nmol/L) or you may read a study with such scoring, making it confusing. To convert ng/mL to nmol/L multiply by 2.5.

In the most recent study, the researchers did a meta-analysis involving 11 studies and 59,231 individuals. Comparing the highest quartile to the lowest quartile, the increased risk of early morality was 29%. As levels dropped below 30 ng/mL the risk for death went up in a linear manner. The researchers did not find that vitamin D levels above 35 ng/mL offered statistically significant mortality reduction, which is interesting because considerable data indicates that vitamin D levels towards the higher end of the normal range prevent many diseases – which is what I would try to achieve.

Fifty-percent of U.S. citizens have vitamin D levels below 30 ng/mL and 40% have major deficiency (below 20 ng/mL). These problems are invariably worse in the winter.

Numerous new studies show the safety of vitamin D supplementation in ranges from 4,000 IU to 10,000 IU per day, with higher levels important in correcting sub-optimal levels of vitamin D. Do not run low of vitamin D, especially in the winter. Get your levels tested every now and then so you know where you stand.