Does milk thistle help with heart disease? What the research does and doesn't show

The evidence doesn't support milk thistle as a treatment for heart disease broadly. One controlled study, in people already undergoing coronary bypass surgery, found silymarin given beforehand was linked to fewer cases of postoperative atrial fibrillation — a narrow, specific finding, not evidence about heart disease in general. Heart palpitations aren't listed among milk thistle's documented side effects.

What the evidence doesn't support

It doesn't support milk thistle or silymarin as a treatment for heart disease, coronary artery disease, heart failure or any other diagnosed cardiovascular condition, and it doesn't support taking it in place of prescribed heart medication or surgical care. The one study below was run in people already scheduled for heart surgery under close medical supervision, not a general population. Nothing here describes a specific product's dose, and nothing here is a claim about any product.

What the trials found

A 2024 study in the Brazilian Journal of Cardiovascular Surgery followed 160 patients undergoing coronary artery bypass grafting. One group received 400 mg of silymarin by mouth for three days before surgery; the other did not. Postoperative atrial fibrillation, a common and risky complication of this surgery, developed in significantly fewer patients who'd received silymarin (14 versus 30). The silymarin group also had lower C-reactive protein and AST levels measured after surgery. The published report describes this as a "prospective experimental study" but doesn't state that patients were randomly assigned or that the trial was blinded, which matters: without randomization or blinding, it's harder to rule out that the two groups differed in other ways going into surgery. It's a real, single finding in a specific surgical population — not evidence that milk thistle prevents heart disease or heart rhythm problems generally, and not a study anyone should read as license to skip a prescribed heart medication.

Separately, the general safety literature on milk thistle doesn't name heart palpitations or arrhythmia among its reported effects. A 2019 safety review of silymarin, covering trials up to 2,100 mg/day for 24 weeks, lists gastrointestinal upset, headache and skin reactions as the main reported side effects — no mention of heart rhythm changes in either direction.

Questions people ask

Can milk thistle cause heart palpitations?

Palpitations aren't listed among the side effects reported in the human safety research reviewed here. The one heart-related study that exists found the opposite association — less postoperative atrial fibrillation with silymarin, in a specific pre-surgery population, not a report of milk thistle causing an irregular heartbeat.

Is milk thistle good for the heart?

The only direct evidence is one non-randomized study in coronary bypass surgery patients that found fewer cases of a specific rhythm complication with silymarin beforehand. That's not the same as a general heart-health benefit, and no trial has tested milk thistle in people without heart disease or upcoming heart surgery.

When to talk to a doctor

Anyone with diagnosed heart disease, an irregular heartbeat, or an upcoming heart procedure should talk to a doctor; milk thistle is not a treatment for a cardiovascular condition, and the one study above was conducted under medical supervision, not as a self-directed supplement. If you take a heart medication or any other prescription drug, ask a doctor before adding milk thistle — see milk thistle and medications: what to check.

Related reading: milk thistle and blood pressure, milk thistle and cholesterol, and milk thistle side effects.