You already know the bad news about eating too much fat: it can wreak havoc on your cardiovascular system, increase the risk of certain cancers, and make you, well, fat. But somewhere in all of this discussion, it seems like one simple fact has gotten lost: A certain amount of fat, about 30 percent of your daily calories, is always going to be part of a healthy diet.

Some research suggests that it’s not so much the amount of fat, but the type of fat that causes health problems. So rather than laboring in vain to reduce your dietary fat to ascetic levels — and dooming yourself to a grim array of unappealing, unsatisfying meals that aren’t all that healthy anyway — maybe it’s best to learn which fats are best for you (and the planet) and enjoy them in moderation.

All fats have the same calorie count — 120 per tablespoon — but they each offer a different set of pros and cons. Trans fats have recently trumped lard as the big heart-disease baddie, while vegetable oils are cholesterol-free, says Marisa Moore, a spokesperson for the American Dietetic Association. And just as with produce, some fats and oils are produced in more eco-friendly ways than others. For help maneuvering the supermarket shelves, here’s the lowdown on the most common fats you’ll find for preparing food. Just remember: always read the label.

Olive oil
Olive oil is a superstar vegetable oil. It’s high in unsaturated fats (the most heart-healthy type), highest in the monounsaturated fats which help lower LDL cholesterol (the “bad” kind that gums up your arteries), and it helps raise HDL (the “good” kind which helps clear them). Plus, it tastes great. The most flavorful — and eco-friendly — varieties are extra-virgin, organic, boutique oils from “single-estate” operations that are labeled as “cold-pressed” or “expeller-pressed.” These are produced without chemical solvents like hexane, a petroleum product often used to refine cooking oil. (Only a trace amount of hexane makes its way into the oil, but it can leak into the air and water supply during the production process.) These fancier oils are meant to be used for drizzling over pasta or salads, since cooking destroys their delicate flavor. Cheaper varieties (those labeled either “virgin” or just “olive oil”) have less flavor and are meant for sautéing. It’s best not to cook with olive oil at high temperatures, though, since it can smoke.

Canola oil

Created in Canada in the ’70s from a type of rapeseed (a mustard-green relative), canola actually stands for “Canadian oil, low acid.”  This is another healthy choice. After olive oil, canola contains the lowest level of saturated fats and the second-highest percentage of monounsaturated fats. (The remaining is polyunsaturated, which is almost as healthy as mono — it also raises the good cholesterol and lowers the bad, just not quite as much.) Canola oil is neutral-flavored and can be used at higher temperatures; it’s often cheaper, too. One potential drawback is that a large percentage of rapeseeds are genetically modified. While genetic modification has not been linked to human or environmental harm, critics worry about its effects on insects and cross-pollination with organic crops, as well as its potential to add allergens to foods. You can avoid both genetically modified seeds and chemical solvents if you buy organic, expeller-pressed varieties.

Soy, safflower, peanut and corn oils

Low in saturated fats and relatively inexpensive, these oils can be used to fry at high temperatures or sauté without adding a strong flavor. Look for pure oils or blends that have more monounsaturated fats than polyunsaturated fats on the labels. (Peanut oil is especially high in monounsaturated fat.) These oils are also often processed with hexane unless labeled otherwise, and it can be difficult to find cold- or expeller-pressed versions of them than of olive or canola oils. However, they are generally available in organic varieties.

Grapeseed, sesame, walnut and other flavorful oils

These days, plenty of flavorful oils are available for adventurous cooks. Like olive oil, many are appreciated for their unique tastes, whether it’s the fruitiness of grapeseed for a salad or the smoky tang of sesame for a marinade or stir-fry. Others, like flaxseed oil, offer health benefits like omega-3s, the essential acids found in salmon and other fatty fish. (Fish oil, often recommended as a dietary supplement, is not suitable for use as a cooking oil or as an ingredient in recipes.) These specialty oils tend to be two to three times as expensive as other vegetable oils, but they’re not really meant to be used as everyday cooking oils. They’re best for drizzling, salad dressings, and special recipes. Organic varieties from small estates abound on grocery-store shelves.

Butter and lard

It’s true that animal fats should be a rare treat since they consist mostly of saturated fat. Butter actually has the most saturated fat of the two; both are high in LDL cholesterol. Still, experts now agree that these products are not as bad for you as margarine and partially hydrogenated oils, which are so unhealthy that a few U.S. cities are considering banning their use in restaurants. It’s okay for people in good health to use a little bit of butter or lard every once in a while in cooking, especially in place of trans-fat-laden margarine or shortening. Tastier and more sustainably produced varieties of beef tallow and lard (the key to a stellar pie crust), as well as better butter, can be found at farmers markets, where sellers tend to offer organic goods or maintain small farms with happier animals and more earth-friendly practices. (Buying local also cuts down on “food miles,” the amount of refrigerated shipping required to get food around the country.)

Margarine and shortening

Created as substitutes for butter and lard, margarine and shortening are usually blends of vegetable oils, flavorings and additives. While they don’t have butter’s cholesterol (or flavor), they do have saturated fat and trans fats, thanks to hydrogenation, a process that adds hydrogen to unsaturated fats (usually soybean oil) to make them act like saturated fats so they’ll stay fresher longer and have a smoother texture. Trans fats appear to increase your risk of heart disease even more than saturated fats. They also raise bad cholesterol and lower good cholesterol (saturated fat raises both). Since trans fats are also abundant in processed foods and fast food, check labels or ask restaurants about the oils they’re using. Anything with partially hydrogenated oil has trans fats, and nutrition labels must now list trans fats as well. While manufacturers have recently created trans fat–free varieties of many products, many are highly processed and some have unhealthy palm oil (see below).

Tropical oils

Tropical oils like palm, palm kernel and coconut oil are higher in saturated fats than many animal fats. In addition, palm oil production on plantations typically harms the tropical rainforest, due to harvesting techniques that destroy plants and animal habitats. The Center for Science in the Public Interest discourages the use of palm oil for both health and environmental reasons. While few Americans cook with these oils, they’re increasingly being used in place of partially hydrogenated fats to fill out processed foods or margarines, so check labels carefully and ask about the oil being used to deep-fry food at restaurants.

Story by Rachel Wharton. This article originally appeared in Plenty in December 2006. This story was added to in June 2009.

Copyright Environ Press 2006

MNN homepage photo: bhamsandwich/Flickr

The lowdown on lipids
Some fats are better for you — and the Earth — than others. Here's an explanation of the most common fats for preparing food.