Eating red meat has long been linked to health problems, including blocked arteries, heart attack and stroke, but new research could allow people to "have their steak and eat it" without risking their health.
Red meat can harm the heart because of the way one of its nutrients is broken down by gut bacteria, research has shown.
By digesting the meat compound, L-carnitine, the bugs generate metabolites that promote hardening and narrowing of the arteries.
Scientists had previously identified one of the danger metabolites, trimethylamine-N-oxide (TMAO).
The latest research has uncovered a second, gamma-butyrobetaine, produced by the microbes at a rate 1,000 times higher than TMAO formation.
Both contribute to atherosclerosis, the build up of hard fat and mineral deposits on the walls of arteries that can lead to heart attacks and strokes.
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However, the mouse studies show that two different types of gut bacteria are responsible for metabolising gamma-butyrobetaine and TMAO from L-carnitine.
The research suggests potential new drug targets for treating atherosclerosis, for example by suppressing bacterial enzymes or affecting the kind of bugs that populate the gut.
Lead scientist Dr Stanley Hazen, from the Cleveland Clinic in Ohio, US, said: "The findings identify the pathways and participants involved more clearly, and help identify targets for therapies for interventions to block or prevent heart disease development.
"While this is into the future, the present studies may help us to develop an intervention that allows one to 'have their steak and eat it too' with less concern for developing heart disease."
Dr Hazen added that people should be wary of taking supplements which contain gamma-butyrobetaine. The compound is used in fat-burning and body-building products.
The research appears in the journal Cell Metabolism.