In 2010 the Institute of Medicine updated the recommended daily allowance (RDA) of vitamin D from 400 IU to 600 IU per day for adults up to age 70, and 800 IU per day for adults 71 years and older. While this update was a (tiny) step in the right direction, many experts think it comes up far too short. The recommendations are based on the ability of 600 IU vitamin D daily to raise blood levels of vitamin D to 20 ng/mL, which the IOM thinks of as “sufficient.”

To the contrary, many health experts consider at least 50 ng/mL to be an optimal level of vitamin D, and it takes more than 600 IU daily to reach that level. A recent study published in the American Journal of Cardiology brings this issue to light. “Many previous studies on vitamin D supplementation have used doses of 400 to 800 IU, which might not be adequate to ensure optimal serum [blood] levels, with more appropriate daily supplement doses suggested as 1,000 to 2,000 IU,” stated the authors of the study.

They tested vitamin D levels in the blood of over 10,000 participants, average age 58. Participants were classified as deficient if their levels were 30 ng/mL or lower. (You can already see the discrepancy between experts—IOM states levels over 20 ng/mL as sufficient.) The average vitamin D level of participants was 24 ng/mL. In other words, 70 percent were considered deficient.

The most important finding of their study, however, was that the risk of all-cause mortality (that is, the risk of death by any cause) was 164 percent higher in those people with vitamin D deficiency. Remember, that’s 70 percent of them. Vitamin D supplementation was associated with better survival, especially in patients with precious deficiency. “Our study suggests a significant association of vitamin D supplement use and improved survival in deficient subjects, supporting the potential benefit of this intervention.” Vitamin D deficiency was also associated with increased risk of cardiovascular-related conditions such as high blood pressure, heart disease, and diabetes.

If you haven’t had your vitamin D level tested, ask your doctor about it. Vitamin D deficiency, or insufficiency, is associated with a wide range of chronic health conditions.