New Study Suggests Recommended Vitamin D Doses May Be Inadequate

Dr. Heidi May Research Team Clinical Trial Results

A new study suggests that the typically recommended dosage of vitamin D supplements may be too low to achieve optimal blood levels of vitamin D.

 

The non-profit medical system in the United States, Intermountain Health, conducted a clinical trial (TARGET-D) led by cardiovascular epidemiologist Dr. Heidi May. The results, reported by Medical News Today on the 22nd, revealed this fact.

The research team randomly divided 632 participants into two groups. A clinician advised one group to take the typical vitamin D dosage while another group received targeted vitamin D therapy.

The goal was to achieve a blood vitamin D level of at least 40ng/mL.

Both groups adjusted their dosages every three months according to a medication algorithm until their blood levels of vitamin D reached 40ng/mL.

Once the blood level of vitamin D reached this level, the participants no longer increased their dosage and measured their blood levels of vitamin D once a year.

51% of the clinical trial participants needed 5,000 to 8,000 vitamin D supplements to reach this level, and 14.6% required 10,000 IU.

This far exceeds the recommended intake of vitamin D supplements, which is 600 to 800 IU.

65% achieved a blood vitamin D level of 40ng/mL within three months and 25% within six months.

In the target treatment group, 58.5% of people with blood levels of vitamin D below 40ng/mL started with 5,000 IU of vitamin D supplements.

The research team pointed out that the previously published vitamin D studies might have given participants too low a dosage, which likely failed to increase their blood levels properly.

Vitamin D and Cardiovascular Health

Among them, 104 had experienced cardiovascular events such as non-fatal myocardial infarction and stroke within 30 days before participating in the study.

Their average blood level of vitamin D before participating in the clinical trial was 25ng/mL. Experts consider blood levels of vitamin D below 20ng/mL as “deficient” and levels between 20 and 30ng/mL as “insufficient.”

The research team will monitor whether these participants experience recurrent cardiovascular events or die from cardiovascular disease.

Research results suggest a lack of vitamin D is not good for cardiovascular health. However, these associations have not been confirmed in clinical trials.

The research team explained that the dosage of the vitamin supplement given to participants in the clinical trials might have been too low, which prevented the achievement of the expected results.

Dr. Mary Green of Manhattan Heart Hospital in New York said there are several mechanisms by which vitamin D could help cardiovascular health.

She explained that healthy blood levels of vitamin D can promote glucose metabolism and insulin sensitivity, improve endothelial function, regulate blood pressure, maintain blood flow homeostasis, and suppress inflammation.

The results of this study were presented at the annual conference of the American Heart Association (AHA) in Philadelphia.