If you've had heart problems before, aiming to get your 'bad' cholesterol really low—below 55—cuts your risk of another heart issue by about a third compared to keeping it just under 70.

For people who already have heart disease, aiming to get their 'bad' cholesterol (LDL) below 55 mg/dL cuts their risk of serious heart problems by about one-third over three years compared to aiming for below 70 mg/dL — and it doesn’t seem to cause more side effects.

If you have heart disease from clogged arteries, getting your bad cholesterol down to around 56 mg/dL instead of 66 mg/dL can cut your risk of heart attacks or strokes by about a third over three years. For every 32 people treated this way, one person avoids a major heart problem.

For people with heart disease from clogged arteries, getting their bad cholesterol down to around 56 doesn’t cause more serious side effects than staying at 66, and it’s safe to keep it that low for at least three years.

Lowering 'bad' cholesterol below 55 might sound like the best thing to do to avoid heart attacks or death, but studies don’t consistently show that people live longer or have fewer heart problems at that ultra-low level compared to slightly higher levels—so maybe doctors don’t need to push everyone that low.

When people lower their 'bad' cholesterol to very low levels using strong medications, they have fewer heart attacks and strokes than those with higher cholesterol levels.