Vitamin D supplements are known for supporting bone health, immunity, and metabolism. Now, new research suggests they might also help lower blood pressure in older adults with obesity. The findings come from a year-long randomized controlled trial and add to growing interest in the cardiovascular effects of vitamin D.

The study, published in the Journal of the Endocrine Society, focused on adults over 65 with a high body mass index and low vitamin D levels. Researchers found that participants who took daily supplements experienced modest reductions in both systolic and diastolic blood pressure. The results indicate that vitamin D may play a role in managing hypertension, but only up to a point.

What the study found about vitamin D and blood pressure

Researchers looked at 221 older adults with overweight or obesity and vitamin D levels between 10 and 30 ng/mL, which is considered low. Everyone in the study also took a small daily dose of calcium. The participants were split into two groups: one received 600 IU of vitamin D per day, the other 3,750 IU.

After one year, both groups showed improvements. On average, systolic blood pressure dropped by 3.5 mm Hg, and diastolic pressure fell by 2.8 mm Hg. The high-dose group saw slightly greater changes, but the difference wasn’t significant enough to show that taking more vitamin D provides extra benefit.

Experts believe vitamin D’s role in regulating the renin-angiotensin system could explain the blood pressure changes. This system helps control fluid balance and blood vessel tension. When vitamin D is low, renin levels may rise, which can increase blood pressure. Calcium may also contribute by helping blood vessels relax and maintain proper tone.

What to know before taking vitamin D supplements

Before adding vitamin D supplements to your routine, it’s important to understand how they work and what to watch out for. The study’s results are promising, but they don’t mean more is better, or that everyone needs a supplement. Here are a few things to consider:

Stick to recommended doses: Most older adults need 600–800 IU per day. Taking more than that doesn’t guarantee better results and may increase health risks over time.
Check your levels first: A blood test can show if you’re deficient in vitamin D. This helps guide whether you need supplements at all, and if so, how much.
Be careful with long-term use: High doses of vitamin D, especially over months or years, can lead to toxicity. This can cause nausea, kidney issues, or calcium buildup in the blood.
Review quality: Choose supplements from reputable brands. Some contain oils that can go rancid if not stored properly.
Take it with food: Vitamin D is fat-soluble, so it’s better absorbed when taken with a meal that includes healthy fats.

While vitamin D may help lower blood pressure in some older adults, particularly those with obesity or low levels, it’s not a definitive solution. Supplements should be used carefully and based on individual needs. Always talk to your doctor before starting a new supplement, especially if you’re on medication or managing a chronic condition.