It began as a medical mystery. In the 1920s, cardiovascular disease became the number-one cause of death in the United States. No one understood why. In 1948, the U.S. Public Health Service commissioned the Framingham Heart Study, an ambitious 50-year study involving thousands of people living in Framingham, Massachusetts. A breakthrough discovery happened 13 years into the study, in 1961: Scientists found that an overabundance of cholesterol—a soft, waxy substance that the body produces, which also occurs naturally in many foods—could lead to clogged arteries and, eventually, severe cardiovascular problems.

The results of the Framingham Heart Study led to far-reaching efforts to drop cholesterol levels through diet, exercise, and medication—and they worked. Accord-ing to the Centers for Disease Control and Prevention, the percentage of American adults with hazardously high cholesterol levels dropped from 33 percent in the early 1960s to just 16 percent in the early 2000s. In that same time period, the average adult cholesterol level dropped from 222 mg/dL to 200 mg/dL. Even so, heart disease remains the number-one killer among men and women in the United States, and researchers continue to refine their understanding of why.

Cholesterol isn’t all bad. In fact, the body uses it to waterproof cells, repair wounds, build hormones, and fuel brain function. It’s when low-density lipoprotein (LDL, often called “bad” cholesterol) levels become too high and high-density lipoprotein (HDL, or “good” cholesterol) levels become too low that problems arise.

LDL molecules range in size and density; those that are smaller can penetrate blood vessels and cause vessel damage, explains Jessica Tran, ND, of the Southwest Naturopathic Medical Center in Scottsdale, Arizona. As the body repairs damage from these molecules, plaque builds up, causing decreased blood flow and artery blockages.

One fact on which scientists agree: Maintaining cardiovascular health isn’t as simple as avoiding saturated fats and cholesterol-rich foods—or popping cholesterol-lowering pills. And while it’s still a good idea to keep cholesterol levels in check, other details are equally, if not more, important. Here are a few of the most common myths and truths about your cholesterol.

Myths

Know your LDL number

Doctors have long recommended LDL blood levels of no more than 100 mg/dL. However, research suggests that for many, 100 mg/dL may still be too high. “Over the past 20 years, there has been a general lowering of recommended LDL levels,” says Jorge Plutzky, MD, director of the Vascular Disease Prevention Program at Brigham and Women’s Hospital in Boston. For example, a study of more than 1,000 U.S. Air Force members found that even those who had average LDL levels could significantly reduce their heart-attack risk by further lowering their numbers.

Bottom line

If you have risk factors, aim for an LDL of 100 mg/dL or less, says Plutzky. Risk factors include inactivity, smoking, carrying excess weight, having high blood pressure, a family history of cardiovascular disease, and previous heart attacks or strokes.

Low total cholesterol means you’re in the safe zone

In some cases having low total cholesterol levels also can signal a risk, says Plutzky. Total cholesterol levels include both “good” HDL and “bad” LDL. According to the American Heart Assoc-iation, total levels lower than 200 mg/dL are considered relatively safe and levels above 240 mg/dL are in the certain danger zone. But as Plutzky notes, many heart attacks happen when total cholesterol is lower than 200 mg/dL. A primary reason may be a person’s lack of HDL cholesterol, which can help clear arteries of plaque.

Bottom line

When you get your cholesterol checked, be sure you understand what each part of the total means. HDL levels should be at least 45 mg/dL for men and 55 mg/dL for women.

Cholesterol is the only thing you have to worry about

Cholesterol tests provide only a partial picture of what’s going on in a person’s cardiovascular system, say experts. “Cholesterol is not always the best predictor,” says Donielle Wilson, ND, president of the New York Association of Naturopathic Physicians. Assessing cholesterol levels doesn’t address potential in-flammation in the body—another key factor in cardiovascular disease. In the 1990s, researchers discovered that high levels in the blood of C-reactive protein (CRP), a marker of often hidden inflammation, increased a person’s likelihood of developing heart disease.

Silent, low-grade inflammation due to injuries, illnesses, stress, and environmental factors can lead to the buildup and softening of plaque, the fatty deposits that develop inside arteries. This plaque can break off into the bloodstream, potentially causing clots and eventually a heart attack. (To learn more, check out tame inflammation.)

Bottom line

Aside from a cholesterol test, ask for a highly sensitive C-reactive protein (hs-CRP) assay to detect hidden inflammation. According to the American Heart Association, hs-CRP levels lower than 1.0 mg/L are good; hs-CRP levels higher than 3.0 mg/L are cause for concern.

Truth

For heart health, diet is key

Recent research has shown that cutting out foods rich in dietary cholesterol doesn’t necessarily lower blood cholesterol levels. Many scientists now think that triglycerides, the chemical form of fat found in the body, may hold the key. Formed when calories aren’t used immediately after a meal, triglycerides are the body’s energy reserves. But elevated levels are often associated with low HDL, high LDL, and plaque buildup—in other words, heart disease.

Many experts still recommend eliminating animal-derived saturated fats and trans fats, which the body readily converts into cholesterol. But some question this diet advice, arguing that because the body is prone to keep cholesterol levels steady, it may shift its own cholesterol production. Plant-derived saturated fats found in coconut and palm oil do not pose a danger, and may even promote healthy levels.

Bottom line

To keep triglycerides in check, stay away from all calorie-dense processed foods, says Wilson. Eat small, frequent meals combining protein and nutrient-rich, low-calorie foods such as fruits, vegetables, and whole grains; they’re low in cholesterol, won’t spike triglycerides, and also are good sources of dietary fiber, which reduces blood cholesterol. Eating foods as close to their natural state as possible also can balance energy levels, says Wilson, and help keep harmful stress and inflammation at bay.