Vitamin D and Heart Health: Key Trial Findings

randomized-controlled-trial PMID: 37380191

Vitamin D and Heart Health: Key Trial Findings

Quick Summary: A large Australian study tested if monthly vitamin D supplements could lower the risk of major heart problems like heart attacks and strokes in older adults. The results showed a small possible benefit, with 9% fewer events in the vitamin D group compared to placebo, but the difference wasn't strong enough to be certain. It might help more for people already on heart medications.

What The Research Found

This study looked at whether vitamin D pills could prevent serious heart issues in people over 60. Here's what they discovered in simple terms:

Overall, vitamin D takers had fewer major cardiovascular events (like heart attacks, strokes, or procedures to fix blocked arteries) – 6.0% vs. 6.6% in the placebo group.
The risk dropped by about 9%, but scientists say it's not a sure thing because the results could be due to chance.
Heart attacks were notably lower (19% reduced risk) in the vitamin D group.
Procedures for blocked heart arteries were slightly lower (11% reduced risk), but strokes showed no difference.
Over five years, for every 1,000 people taking vitamin D, about 6 fewer heart events happened compared to placebo. That means you'd need to give the supplement to 172 people to prevent one event.

A bonus finding: People already on heart drugs at the start saw a bigger drop – 16% lower risk – though this needs more proof.

Study Details

Who was studied: Over 21,300 healthy older adults aged 60-84 in Australia. They skipped people with conditions like high calcium levels, kidney stones, or those already taking a lot of vitamin D (more than 500 IU daily).
How long: About five years on average, from 2014 to 2020.
What they took: A monthly dose of 60,000 IU vitamin D (like taking about 2,000 IU a day on average) or a fake pill (placebo). Everyone got the same-looking capsules, and neither participants nor doctors knew who got the real thing.

Doctors tracked heart events using health records to keep it accurate.

What This Means For You

If you're an older adult worried about heart health, this study suggests vitamin D supplements might offer a small edge against major events, especially if you're already on meds for blood pressure or cholesterol. But it's not a game-changer for everyone – the benefit is tiny, and it's not proven enough to start popping pills without advice.

Talk to your doctor: If you have low vitamin D levels (from blood tests) or heart risks, ask about supplements. The monthly high dose worked okay here, but daily lower doses might suit you better.
Don't rely on it alone: Eat vitamin D-rich foods (like fatty fish or fortified milk), get safe sun exposure, and focus on proven habits like exercise and a heart-healthy diet.
Who might benefit most: Folks on heart meds could see more protection, so if that's you, this trial is worth discussing at your next checkup.

Study Limitations

No study is perfect, and this one has some caveats to keep in mind:

The main result wasn't "statistically significant," meaning it might not hold up in every group – the numbers could be a fluke.
They used big monthly doses, which might not work the same as daily ones you're more likely to take.
It only included healthy older Aussies without certain conditions, so results might differ for younger people, those with deficiencies, or different backgrounds.
Heart events were pulled from records, which might miss mild or unreported cases.
The stronger benefit for heart med users was a side finding and needs bigger studies to confirm.

Overall, vitamin D looks promising but not essential for heart protection yet – more research is coming.

Key Findings

The D-Health Trial found that monthly vitamin D supplementation (60,000 IU) reduced the incidence of major cardiovascular events (MCEs: myocardial infarction, stroke, coronary revascularisation) by 9% compared to placebo (HR 0.91, 95% CI 0.81–1.01), though this result was not statistically significant. A subgroup analysis suggested potential benefit in participants already taking cardiovascular medications at baseline, with a significant 16% lower risk of MCEs (HR 0.84, 95% CI 0.74–0.97). Myocardial infarction risk was significantly lower in the vitamin D group (HR 0.81, 95% CI 0.67–0.98), while stroke rates were unchanged (HR 0.99, 95% CI 0.80–1.23). The absolute risk difference at five years was -5.8 events per 1,000 participants, equating to a number needed to treat (NNT) of 172 to prevent one MCE.

Study Design

This was a randomized, double-blind, placebo-controlled trial conducted in Australia from 2014–2020. A total of 21,315 adults aged 60–84 years were enrolled, with 21,302 included in the final analysis. Participants were excluded if they had hypercalcaemia, hyperparathyroidism, kidney stones, osteomalacia, sarcoidosis, or were taking >500 IU/day of vitamin D. The median intervention duration was five years.

Dosage & Administration

Participants received 60,000 IU of vitamin D3 monthly (equivalent to ~2,000 IU/day average) or a placebo. Supplements were administered orally as a single monthly dose in identical capsules. Compliance was monitored via self-report and serum 25-hydroxyvitamin D levels.

Results & Efficacy

Primary Outcome: Vitamin D group had 637 MCEs (6.0%) vs. 699 (6.6%) in placebo (HR 0.91, 95% CI 0.81–1.01; P = 0.07).
Subgroup Analysis: Participants on cardiovascular drugs at baseline (40% of cohort) showed a significant 16% lower MCE risk (HR 0.84, 95% CI 0.74–0.97; interaction P = 0.12).
Secondary Outcomes:
Myocardial infarction: HR 0.81 (95% CI 0.67–0.98).
Coronary revascularisation: HR 0.89 (95% CI 0.78–1.01).
Stroke: HR 0.99 (95% CI 0.80–1.23).
Absolute risk reduction at five years: -5.8 events per 1,000 (95% CI -12.2 to 0.5).

Limitations

The primary outcome’s confidence interval crossed 1.0, indicating uncertainty in the effect size.
Monthly bolus dosing may differ in efficacy from daily regimens.
Exclusion criteria limited generalizability to older adults without pre-existing conditions or high baseline vitamin D intake.
Subgroup findings (e.g., cardiovascular medication users) were exploratory and not statistically significant after adjustment (P for interaction = 0.12).
Reliance on administrative datasets may underestimate asymptomatic events.

Clinical Relevance

For older adults, monthly vitamin D supplementation shows minimal overall cardiovascular benefit, with a small absolute risk reduction (0.58%) over five years. While the subgroup analysis suggests potential value for those on cardiovascular medications, this requires confirmation in targeted trials. Current evidence does not support routine vitamin D use solely for CVD prevention in the general population. However, individuals with deficiency or on CVD therapies might consider supplementation under medical supervision, given the observed trends. The study underscores the need for personalized approaches to vitamin D dosing and cardiovascular risk management.