Harvard Heart Letter

Can LDL be too low?

Ask the doctor

Q. After a year of taking a statin, my LDL cholesterol measurement is 50 mg/dL, which seems awfully low. Is there any downside to a very low LDL?

A. Based on what we currently know, a low-density lipoprotein (LDL) level of 50 mg/dL appears to be reasonably safe, especially when attained naturally. Studies of people who've already had a heart attack suggest that lowering LDL to about 50 mg/dL provides further protection against recurrent cardiovascular events versus reaching a level of around 70 mg/dL. In studies lasting up to seven years or so, these lower LDL levels appeared to be well tolerated.

Several ongoing trials are now testing a new class of cholesterol-lowering drugs known as PCSK9 inhibitors to see if LDL levels lower than 40 mg/dL provide even greater protection against heart attacks and dying from cardiovascular disease. These studies will also examine the safety of having a very low cholesterol level, including a careful evaluation of any subtle effects on brain function.

Although the Internet is full of claims that cholesterol-lowering drugs cause memory problems, there is no good scientific evidence to date that supports a link between cholesterol-reducing drugs and memory loss or other cognitive problems.

-- Dr. Deepak Bhatt
Editor in Cheif, Harvard Heart Letter