A new study published in JAMA Internal Medicine reveals that vitamin D supplements are ineffective when it comes to lowering blood pressure.

Vitamin D supplements are the second most prescribed vitamin in the country second only to a multi-vitamin.

In the study, researchers gathered blood pressure data from 46 different clinical trials with over 4,541 participants that used vitamin D supplements for a minimum of four weeks. The study, which used a random effects model, found no effect of vitamin D in the systolic and diastolic blood pressure, according to CBS News.

The researchers deemed this trial a logical one seeing that people with higher blood pressure have lower vitamin D. But the results failed and so have many trials failed with vitamin D before.

They said that while there are in fact associations between low levels of vitamin D and heart diseases and cancer, it is not casual.

According to the National Institutes of Health (NIH), there is not enough substantiation to determine how levels of vitamin D could increase risk or protect against cancer.

The NIH also said too much vitamin D in the blood can be harmful, causing nausea, constipation and even damage to the kidneys, among other effects.

Previous studies have shown that people with low levels of vitamin D could be more likely to develop Alzheimer’s disease and die prematurely of cancer or other causes.

The vitamin’s role is unclear.

Seventy-five percent of Caucasians and 97 percent of African Americans are low in vitamin D. Therefore, doctors are reassessing what is normal.

The researchers are urging patients to question their doctors who prescribe them vitamin D, asking for the data that shows it is benefiting.