New research published in the Journal of the Endocrine Society has highlighted the potential of vitamin D supplements to help reduce blood pressure in older adults with obesity. However, the study also underscores that exceeding the daily recommended dose does not provide any additional cardiovascular benefits.

The National Institutes of Health (NIH) recommends a daily intake of 600 International Units (IU) or 15 micrograms (mcg) of vitamin D for adults aged 51–70 and 800 IU or 20 mcg for those aged 70 and older. While the study builds on existing evidence of vitamin D’s benefits for circulatory and metabolic health, it reiterates the importance of maintaining appropriate dosage levels.

Study Design and Key Findings

The double-blind, randomized controlled trial involved 221 adults aged 65 and older with body mass indexes (BMIs) over 25, categorizing them as overweight or obese. All participants exhibited “insufficient” or deficient vitamin D levels, with serum 25-hydroxy vitamin D levels between 10 and 30 nanograms per milliliter (ng/mL).

Participants were divided into two groups: one received the recommended daily dose of 600 IU of vitamin D alongside placebo pills, while the other took a high dose of 3,750 IU daily. Both groups also received 250 milligrams of calcium citrate daily. Over a year, researchers observed changes in blood pressure levels.

Results showed that vitamin D supplementation modestly reduced blood pressure. Participants experienced an average drop of 3.5 mm Hg in systolic blood pressure (SBP) and 2.8 mm Hg in diastolic blood pressure (DBP). The reductions were slightly greater in the high-dose group, but the difference between the two groups was not statistically significant. Importantly, individuals with obesity and lower baseline vitamin D levels benefited the most from supplementation.

Vitamin D’s Role in Blood Pressure Regulation

Vitamin D deficiency has been previously linked to hypertension and cardiovascular diseases. According to Michelle Routhenstein, a preventive cardiology dietitian, vitamin D influences the renin-angiotensin system, which regulates blood pressure. Low vitamin D levels may lead to increased renin secretion, activating this system and raising blood pressure.

The inclusion of calcium citrate in the study further supported blood pressure reduction. Calcium helps blood vessels relax and maintain proper tone, contributing to improved circulatory health.

No Added Benefits from High Doses

The study also confirmed that higher-than-recommended doses of vitamin D did not yield additional cardiovascular benefits. Routhenstein cautioned against long-term use of high doses of vitamin D, which can lead to toxicity due to its fat-soluble nature.

“Many people assume more is better, but with nutrients, the goal is balance,” she explained. “Vitamin D toxicity can occur when taken in excessive amounts over time, highlighting the need for regular monitoring of vitamin D levels.”

Routhenstein also advised caution when selecting supplements, noting that many may lose potency due to exposure to heat during storage or transport. She emphasized that consuming vitamin D with a fat-containing meal enhances absorption.

Implications for Older Adults

This research adds to a growing body of evidence supporting the role of vitamin D in cardiovascular health, particularly for older adults with obesity or low vitamin D levels. However, the findings reinforce the importance of personalized supplementation tailored to individual needs, medical history, and laboratory results.

As vitamin D deficiency has also been linked to conditions like autoimmune diseases, falls, and heart disease, regular monitoring and appropriate supplementation can play a pivotal role in promoting overall health in aging populations.