For years, so-called "bad" and "good" cholesterol have been the yin and yang of heart health, the two lipids around which so much advice revolves.

Bad cholesterol (low-density lipo­protein, or LDL) deposits excess cholesterol in your arteries, where it can build up into plaques, increasing the likelihood of heart disease and blood clots. Good cholesterol (high-density lipo­protein, or HDL) carries surplus cholesterol back to your liver so that it can be excreted.

To prevent heart disease, we’ve been told to keep our bad cholesterol level down and our good cholesterol level up—with 45 milligrams per deciliter usually offered as a good target.

Sounds pretty straightforward, right? Doctors thought so, too.

But according to several recent studies, good cholesterol alone has little ability to lower heart disease risks, and more is not necessarily better.

Here’s what you need to know about the current thinking, along with some healthy-heart guidelines that are unlikely to change, even if our understanding of cholesterol does. 

The New Evidence on HDL

The first clue that the role of good cholesterol was more complicated than previously thought emerged when scientists tried to develop medications to raise HDL levels.

The drugs they tested—niacin and cholesteryl ester transfer protein inhibitors—boosted HDL in the blood but failed to reduce cardiovascular-disease risk.

Those results surprised doctors. We know that certain lifestyle changes, such as exercising more and quitting smoking, drive HDL levels up and heart-disease risk down.

But increasing HDL levels arti­fi­cially, without behavioral changes, doesn’t reduce risk at all. “It turns out that HDL is not a very good therapeutic target,” says Dennis Ko, M.D., a cardiologist and senior scientist at the Institute for Clinical Evaluative Sciences in Ontario, Canada.

What’s more, Ko’s own research suggests that above a certain threshold, more HDL could increase health risks.

His team looked at 631,762 people and found that those with an HDL level greater than 70 mg/dL (in men) or 90 mg/dL (in women) were more likely to die—for reasons ­unrelated to cardiovascular disease. 

Getting Good Cholesterol Up

As researchers work to figure out what these findings mean in the quest to keep hearts healthy, your doctors might still use your HDL level (in conjunction with measurements of LDL and total cholesterol) to help predict your cardiovascular-disease risk.

Our experts say that a very low HDL level can be a sign of trouble, but that the only meaningful way to raise it is through lifestyle changes. 

"There is no evidence for a benefit from any HDL-raising drug," says Steven Nissen, M.D., a cardiologist with the Cleveland Clinic. "It's still important to pay attention to the numbers, but the main focus should be on making healthy choices." 

In other words, whether your HDL is low, high, or somewhere in the middle, the prescription for a healthy heart will be the same: Don't smoke, drink alcohol only in moderation, exercise regularly, and stay away from trans fats, which are found in fried foods, baked goods, and other items made with partially hydrogenated oils. 

As Marvin M. Lipman, M.D., Consumer Reports' chief medical adviser, notes, "Everyone agrees with the pursuit of a healthy lifestyle." 

Bringing Bad Cholesterol Down

Last year the U.S. Preventive Services Task Force recommended that a vastly larger group think about taking statin medications, which lower LDL cholesterol.

If you’re 40 to 75 and have diabetes, high cholesterol, or blood pressure, or you smoke, you’re now advised to have a doctor estimate your chance of a major cardiovascular event within 10 years. If chances are 10 percent or greater, the task force suggests a statin. For a risk of 7.5 to 10 percent, it suggests that you consider one.

While our Best Buy Drugs analysis of these recommendations is underway, our current advice is that for those whose 10-year risk is lower than 10 percent, diet and lifestyle changes should be the first steps. They could lower your risk enough that you are no longer a candidate for a statin, which has well-­established adverse effects.

Editor's Note: This article also appeared in the March 2017 issue of Consumer Reports on Health.