Vitamin D — I Was Wrong

The TARGET‑D protocol was the active arm of a randomised trial. All patients received standard post‑MI care. Those in the management group had their vitamin D levels drawn; the average was 27 ng/mL, indicating insufficiency. A clinician used a predetermined algorithm to initiate supplementation, frequently at 5,000 IU/day, and scheduled repeat lab draws to adjust the dose, with the explicit goal of pushing 25‑OH‑D above 40 ng/mL. The control group did not undergo structured vitamin D management. The trial demonstrated a 52% reduction in recurrent heart attacks but did not meet its primary composite endpoint. Stanfield explicitly presents this protocol as research‑derived, not as a firm recommendation, and emphasises that blinding deficiencies mean the results may be biased. He is now willing to discuss a similar approach with his own patients, but only after explaining the uncertainty.

Stanfield mentions this regimen in the context of the new TARGET‑D data: because the study piqued his curiosity, he now intends to check his own 25‑OH‑D level. If it comes back low, he would ‘consider boosting my vitamin D intake’. The 1,000 IU is what he already consumes; it is not a protocol derived from the trial but a personal habit. He reiterates that just because he takes a supplement does not mean others should.

The TARGET‑D trial enrolled patients who had just survived a heart attack. All received standard care, but half were randomised to an active vitamin D management arm: their baseline 25‑OH‑D was measured (mean ~27 ng/mL), and a prescriber used an algorithm to start supplementation—often 5,000 IU/day—and titrate the dose based on repeat blood draws to get the level above 40 ng/mL and keep it there. Over roughly 4 years of follow‑up, the primary combined major adverse cardiovascular event (MACE) endpoint showed a 15% lower hazard in the vitamin D group but was not statistically significant (HR 0.85; 95% CI crossed 1). However, the key secondary endpoint—another heart attack—dropped from ~18% in usual care to ~4% in the managed group, which is a 52% relative risk reduction (roughly 4 fewer heart attacks per 100 people). A per‑protocol analysis limited to patients who actually reached the >40 ng/mL target showed even stronger MACE and mortality signals, though these also failed to reach statistical significance in the sensitivity test. Stanfield highlights that the trial was unblinded: patients and clinicians knew who was getting the active protocol, which could introduce placebo effects and differential attention—nurses calling more promptly, doctors being more diligent with other risk factors. He also notes that the forest plot shows non‑significant drift toward higher heart‑failure hospitalisations and strokes in the vitamin D arm, a reminder that “biology is messy.” So while the study doesn’t provide a clean, guideline‑changing answer, it is the first to suggest that achieving a target level in a high‑risk, initially deficient population might yield cardiovascular benefit, challenging the simplistic narrative that vitamin D is useless for heart disease.

Stanfield walks through the plausible story that emerges: if you never correct the underlying deficiency in a trial—because you give everyone the same pill regardless of their starting level, and many participants have adequate vitamin D—you would not expect to see a benefit. TARGET‑D is the first major study to test the opposite approach: identify who is low, treat them aggressively to a pre‑defined threshold, and see if outcomes improve. The fact that they saw a dramatic reduction in recurrent heart attacks in the managed group (albeit with important methodological caveats) lends support to this idea. He warns, however, that the thesis remains unproven until a blinded trial with a true treat‑to‑target design confirms it.

Stanfield describes the conversation he now intends to have with a patient like ‘John’, the archetypal 62‑year‑old heart attack survivor. After covering standard medications and lifestyle, he will lay out the messy state of the evidence: the TARGET‑D trial gives some justification for testing and aiming for a level above 40 ng/mL, but the study is unblinded and the primary MACE endpoint was not significant. If the patient is financially able and comfortable with the uncertainty, testing is a reasonable option; if not, sticking with the current Endocrine Society guidelines—simply taking a moderate daily supplement without testing—is equally acceptable. He emphasises that before the TARGET‑D data he would not have even raised the topic of testing in this setting.