Good fats vs. bad: Nutrition experts weigh in

Are all saturated fats bad? What about coconut oil? Is it dangerous to heat olive oil? Which is better: polyunsaturated or monounsaturated fat? We asked a few nutrition experts, and here are their answers.

Is it true that you should not heat olive oil?

According to Dr. David L. Katz, a professor at the Yale School of Public Health, "Unsaturated oils are less tolerant of heat than saturated oils. When unsaturated oils are heated, some trans fat can form. This is the basis for claims that unsaturated oils such as olive oil are unsafe to cook with." But the claims are unfounded. "The degradation of oils occurs mostly at the 'smoke point,' the temperature above which the oil gives off smoke. This temperature is reached in deep fryers but is rarely reached with home cooking."

Bottom line: It's safe, but don't deep fry in it.

Are all saturated fats unhealthy?

There is clear evidence that not all saturated fatty acids are created equal. "Stearic acid, for instance, appears innocuous; it does not raise serum cholesterol or increase the risk of heart disease. This is one of the reasons why dark chocolate is as heart-healthy as it is," says Katz.

So why has saturated fat been vilified?

"Most of the demonization of saturated fat is based on the belief that it always raises cholesterol, an argument that has two huge holes in it," says Jonny Bowden, author of "The Healthiest Meals on Earth "(Fair Winds Press, July 2008).

Saturated fat doesn't always raise cholesterol, though it sometimes does. "There are many more types of cholesterol than just the commonly understood 'LDL-bad' and 'HDL-good,' " Bowden says. "LDL alone has at least five different subtypes, and some of them (LDL-A) are absolutely harmless while others (like LDL-B) are not. Saturated fat tends to raise LDL, but it sometimes raises the harmless subtype, not the 'bad' subtype. It also raises HDL, frequently more than it does LDL, leaving an overall better blood-lipid profile than before, even though the total cholesterol number may have gone up."

Additionally, "Cholesterol is turning out to be a very poor predictor of cardiovascular disease and death, as we saw in those trials of the cholesterol drug that lowered cholesterol more than any before but did nothing for heart disease, plaque or mortality. If you take the fear of cholesterol-raising out of the equation, what's the problem with saturated fat? Not too much," adds Bowden.

However, that doesn't mean you should start doubling up on the prime ribs. "Some saturated fatty acids, says Katz, "are still very much implicated. So red meat is still a concern; choosing meats that are lean, with relatively low saturated fat content, is the way to go."

Pritikin Nutrition Research Director James J. Kenney is strongly opposed to any saturated fat. "There are no naturally occurring fats that are high in saturated fats that do not raise LDL-C (low-density lipoprotein cholesterol)," he says "because they contain palmitic, myristic and lauric acids — the three saturated fatty acids proven to raise LDL-C and promote atherosclerosis." He goes on to argue that the only difference among the LDLs is that in some people, some LDL patterns may be less harmful than in others — but they are still dangerous.

Bottom line: While no one is suggesting a diet high in saturated fat, limited amounts of whole-food sources such as "eggs, butter, grass-fed meat and the like may not be as bad as we once thought," Bowden says, "especially when intake is balanced with plenty of anti-inflammatory omega-3s and phytonutrients from vegetables and fruits."

Can coconut oil be healthy with all that saturated fat?

"There is evidence that the mix of saturated fatty acids in coconut oil may not be as harmful as once believed," says Katz, "but there is evidence to the contrary, too. It is likely that coconut oil will prove to be less harmful than once believed, but very unlikely that it will emerge as competition for olive oil or canola oil as one of the most healthful options. It may, however, make a good alternative to trans fat in commercial foods."

Kenney, however, believes the mere suggestion that coconut oil is safe is naive. "Coconut oil," he says, "is extremely high in the three saturated fatty acids proven to raise LDL-C and promote atherosclerosis."

Bowden is optimistic. "Coconut oil — provided it's 100 percent organic and extra virgin — is a superfood. It suffered from a bad rap due to two concerns: One, it's high in saturated fat, and two, the early coconut oil sold in the '70s was an inferior product, high in trans fats."

"The fat in coconut oil is largely lauric acid, a particularly healthy fatty acid that has antiviral and antimicrobial properties and is helpful for the immune system. It also contains the fatty acid caprylic acid, which is well-known as a 'yeast' fighter," says Bowden.

Bottom line: Probably not as bad as once thought, but many experts are still adamant that it will raise bad cholesterol and lead to heart disease. Also, like any oil, it's high in calories: One tablespoon is about 120 calories.

Which is better, polyunsaturated or monounsaturated fat?

Both do good things for the body, but monounsaturated fatty acids might win by a nose in the race for heart health. According to Lona Sandon, a professor of nutrition at the University of Texas Southwestern Medical Center at Dallas, "Monounsaturated fats [such as in olive oil and tree nuts] help lower total and LDL cholesterol levels while increasing the artery-protective HDL cholesterol. Monounsaturated fats may also help lower levels of inflammation in the body."

Polyunsaturated fats include the much-talked-about essential fats known as omega-3s and omega-6s. In general, polyunsaturated fats lower total and LDL "bad" cholesterol, but they can also lower heart-healthy HDL cholesterol — which is not good.

Bottom line: Both are good in moderation.

Charles Stuart Platkin is a nutrition and public-health advocate, and founder and editor of DietDetective.com, an online source for nutrition, fitness, food, diet and wellness information.