By establishing more stringent recommendations, the new guidelines, which were first established by the National Institutes of Health more than two decades ago, actually challenge Americans to work harder.

"These guidelines have become a little more rigorous than the previous guidelines mainly because researchers were discovering that some people with cholesterol levels considered "borderline" under the old criteria actually were developing heart disease later on," says Dr. Robert Keith, an Alabama Cooperative Extension System nutritionist. "Based on this new information, the National Institutes of Health decided that the new guidelines needed to be a little more stringent."

Under the new recommendations, for example, Americans are advised to keep their HDL, or so-called good or "protective," cholesterol levels above 40 milligrams. Under the old recommendations, anything above 35 milligrams was considered good.

Some recommendations have remained the same under the new guidelines. For example, the desired cholesterol level for healthy adults remains at 200 milligrams or below. Even so, the new guidelines, in a few respects, depart significantly from the old recommendations. For example, a new sliding scale has been developed with respect to LDL, or "bad," cholesterol levels.

"Following this sliding scale, individuals who don’t have other heart disease factors would want to keep their LDL cholesterol levels below 160 milligrams," Keith says. "If another heart disease risk factor is present, LDL cholesterol levels should be below 130 milligrams."

However, Keith stresses people with multiple risk factors or who suffer from conditions such as diabetes should reduce their LDL cholesterol levels to below 100 milligrams.

The advice would apply even in cases where the individual’s LDL levels were at or near the 130-milligram level otherwise considered healthy, he says.

The guidelines also place a greater emphasis on a factor known as "metabolic syndrome," which is now considered as big a risk for heart diseases as smoking and, therefore, as important to treat. Metabolic syndrome comprises a host of factors, including obesity, high blood sugar levels, high blood pressure, low HDL cholesterol and a tendency to form blood clots.

The simplest way to determine one’s chances of having metabolic syndrome is by taking a waist measurement, Keith says.

"Men with waist measurements of 40 inches or more will need to go to a doctor to determine their risk for heart disease," Keith says. "The same goes for women with measurements of 35 inches or more."

In the most significant change outlined in the new regulations, experts now recommend earlier cholesterol-lowering drug intervention for people with moderate or high cholesterol levels.

"Under the old guidelines, the approach tended to be, ‘let’s recommend lifestyle changes first and then go the drug route,’" Keith says. "Now, the approach is, ‘we’ll put you on the drugs now and try and get you to follow through with lifestyle changes in the meantime.’"

Statins, the class of drugs most often prescribed to reduce cholesterol, are generally considered safe, he says.

Even so, doctors still prefer that people choose serious lifestyle changes instead, and, despite the changes outlined in the new guidelines, the old advice is still valid: reduce saturated fats, eat plenty of fruits and vegetables, and exercise.

"Saturated fat is a major driver behind total serum and LDL cholesterol," Keith says. "The bulk of this comes from animal products such as whole-milk dairy products and red meats."

As an alternative to these types of foods, he recommends switching to skim milk and consuming more poultry products, such as chicken without the skin.

Obesity, which often stems from consuming too many calories of whatever type, is also a major risk factor.

"We would like you to lose some of that weight by adopting two lifestyle changes: first, reduce your caloric intake and, second, increase your levels of exercise," Keith says.

While any type of aerobic exercise, such as walking, will improve health and reduce one’s heart disease risk, Keith says the most effective approach involves performing about one hour a day of vigorous exercise, such as jogging, aerobics, cycling or swimming.

Despite the best efforts of Keith and other nutritional experts, nearly 61 million Americans – about 1 in every 5 men and women – have some sort of heart disease that claims more than 500,000 lives a year. The new guidelines are part of a wider effort to identify and treat those at highest risk of developing the disease.

(Source: Dr. Robert Keith, Alabama Cooperative Extension System nutritionist and Auburn University professor of nutrition and foods.)