Quick, name the good fats (and their sources) from the following: monounsaturated, saturated, polyunsaturated, trans.

If you can't answer right away, don't worry. You have a lot of company.

According to recent polls, many Americans are dropping low-fat diets for "healthy fat" diets, but only about a third of us can correctly differentiate between so-called good and bad fats.

(By the way, the answers: Polyunsaturated and monounsaturated are good fats, and sources include olive oil, avocados and oily fish.)

Though science may have more surprises in store, today's mainstream nutritional advice largely places heart-healthy monounsaturated fatty acids and polyunsaturated fatty acids on the good team and saturated fatty acids and trans fatty acids on the bad. Basically, eat your sardines and olive oil but ditch your burgers and snacks made with partially hydrogenated oils.

New research, however, is challenging this simple formula and indicating that some types of saturated fats may actually be neutral to beneficial. Another important finding, according to Harvard University scientist Dariush Mozaffarian: The recent trend in Western diets of replacing saturated fats with refined carbohydrates (such as sugar and white bread) actually makes health worse. They should be replaced, instead, with polyunsaturates (as found in soybean oil and corn oil).

Still, reports from the National Institutes of Health suggest that we need to be choosy about our polyunsaturates, based on their ratio of omega-6 to omega-3. Researcher Joseph Hibbeln says most seed oils (soy, corn, etc.) deliver unhealthy levels of omega-6.

Studies also show "bad" foods can develop healthier fat profiles depending on what animals are fed and how the fats are processed. Some advocate the healthful consumption of certain animal fats and dairy from pastured animals.

So how can a consumer sort through all of this? The following list reflects the most current thinking about dietary fat and cholesterol. (Your best choices will depend on your cardiovascular health, metabolism, genetics and consultations with your doctor.)

> Good fats, bad fats

Polyunsaturated fat:

Sources: Corn, soybean and flaxseed oils, as well as walnuts, flaxseeds and fish. Best sources of omega-3 polyunsaturates are oily fish; plant sources offer smaller levels.

What they do: Lower cholesterol levels and reduce inflammation among other benefits.

The debate: Some scientists caution that seed oils contain too much omega-6 fat at the expense of omega-3 benefits. Others argue that both omega-3 and 6 are beneficial.

Daily recommendation: 8 percent to 10 percent of calories

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Monounsaturated fats:

Sources: Peanuts, canola, olive oil, avocados, almonds, hazelnuts, pecans and pumpkin seeds

What they do: Improve blood cholesterol levels among other health benefits.

The debate: Their effects when substituted for saturated fats are still being studied.

Daily recommendation: 10 percent to 25 percent of calories

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Saturated fats:

Sources: Meat and whole milk dairy as well as coconuts and palm

What they do: Raise bad cholesterol levels but also good cholesterol.

The debate: Reductions in saturated fats have not produced better cardiovascular health but have coincided with a rise in obesity. Since many have swapped saturated fats for refined carbohydrates, experts are debating the wisdom of continued reduction recommendations.

Daily recommendations: 10 percent of calories or less

* * *

Trans fats:

Sources: This plant oil injected with hydrogen is found in stick margarine, some shortening and some processed snacks.

What they do: Lower good cholesterol levels while raising bad.

The debate: None

Daily recommendation: None