- Vitamin D supplements are linked to many health benefits, including decreasing the chance of heart disease, supporting immune function, and aiding weight loss.
- New research suggests that calcium and vitamin D supplements may have a high blood pressure-lowering effect, particularly for older adults with overweight or obesity.
- However, the study indicates that taking more than recommended and exceeding the daily dose of vitamin D does not create any additional benefits.
New research published in the Journal of the Endocrine Society suggests that vitamin D supplements may help lower blood pressure in older adults with obesity, and taking more than the daily recommended dose does not provide any additional health benefits.
According to the NIH Office of Dietary Supplements, older adults ages 51–70 years are recommended 600 International Units (IU) or 15 mcg of vitamin D dailyTrusted Source, while those ages 70 years and older are advised an intake of 800 IU or 20 mcg.
This study adds to the growing evidence of vitamin D’s many health benefits, particularly circulatory and metabolic health.
The study received financial support from the Fogarty International Center and Office of Dietary Supplements of the National Institutes of Health (NIH), the American University of Beirut, Saint Joseph University, the Lebanese Council for National Scientific Research, the Mayo Clinic, and the Odense University Hospital.
Effects of low dose vs. high dose vitamin D
In this double-blind, randomized controlled trial (RCT), researchers examined 221 adults ages 65 years or older who had BMIs over 25 and were considered overweight or obese.
They also had a serum 25-hydroxy vitamin D level between 10 and 30 ng/mL, which indicates either “insufficient” vitamin D levels (below 30/mL) or vitamin D deficiency (below 20 ng/mL).
All participants were given 250mg of calcium citrate daily. For their vitamin D intake, they were divided into two groups: the “low dose group” took 600 IU/day along with placebo pills, and the “high dose group” took 3,750 IU/day. Researchers observed the participants for a year.
At the end of the study, the researchers found that vitamin D supplementation helped lower blood pressure.
Although there was no statistically significant difference between both groups, on average, the participants experienced a 3.5 mm Hg reduction in systolic blood pressure (SBP), and a modest 2.8 mm Hg reduction in diastolic blood pressure (DBP) after one year. Those in the high-dose vitamin D group experienced a slightly greater reduction than those in the low-dose vitamin D group.
The researchers also saw no extra benefit in participants taking a higher dose of vitamin D.
Out of all the participants, the researchers observed that the people with obesity and those with low vitamin D levels benefited the most from supplemental vitamin D.
Low vitamin D levels linked to hypertension
Previous research has linked vitamin D deficiency to an increased risk of falls in older adults, as well as some autoimmune diseases, such as multiple sclerosis and type 1 diabetes.
Some studies have also found an association between vitamin D deficiency and an increased risk of cardiovascular diseasesTrusted Source, including hypertension and heart disease.
A low vitamin D intake has also been linked to high blood pressure later in life.
Michelle Routhenstein, MS, RD, CDCES, CDN, Preventive Cardiology Dietitian and Heart Health Expert at EntirelyNourished.com, who was not involved in the study, said the study results weren’t surprising, given the roles of calcium and vitamin D in blood pressure regulation.
Routhenstein explained how vitamin D may affect blood pressure:
“Vitamin D is involved in regulating the renin-angiotensin system, which plays a key role in controlling blood pressure. When vitamin D levels are low, renin secretion tends to increase, which can raise blood pressure by activating this system.”
“Calcium was also provided, and it is known to support blood pressure regulation due to its effect on blood vessel function. By helping blood vessels relax and maintain proper tone, calcium can contribute to lower blood pressure,” she told Medical News Today.
Why more vitamin D isn’t always better
One important finding from the study is that taking higher than recommended doses of vitamin D does not have any additional benefits in terms of cardiovascular health.
Commenting on this, Routhenstein said:
“Many people assume that more is always better, but when it comes to nutrients, it’s about finding the right balance for your body, taking into account factors like your lab results, diet, and medical history. The goal is to get enough to meet your needs—not too little, but also not too much.”
She also cautioned against using vitamin D supplements for long periods and higher than necessary doses.
“For vitamin D, which is fat-soluble, taking high doses for long periods can lead to toxicity. That’s why it’s important to have your vitamin D levels checked to make sure you’re getting the right amount for your health,” she told MNT.
On the topic of choosing the right vitamin D supplements, Routhenstein underscored that not all supplements are created equal.
“[M]any contain oils that can become rancid when exposed to heat during storage or transport,” she said.
“Since vitamin D is fat-soluble, taking it with a meal that contains fat can enhance absorption and ensure it works more effectively,” she added.
Study limitations
The study has several limitations, particularly regarding its sample size, diversity, and baseline comorbidities.
The participants were primarily older adults (mean age of 71.1 years) with a high body mass index (mean BMI of 30.2). Moreover, only nine participants engaged in regular physical activity.
These may limit the generalizability of this study’s findings to other populations or age groups. The same can be said about the racial or ethnic diversity of the study participants, which may mean the findings do not apply to larger, more diverse populations.
The participants also had a high prevalence of comorbidities, such as hypertension, with 48% of the participants being treated with anti-hypertensive medication. In addition, some started treatment after they entered the study. However, sensitive analyses showed that starting blood pressure medication did not change the study’s overall results. This may also impact the generalizability of these results to individuals without high blood pressure.
