I recently had the opportunity to cook for a small group of relatives. Like you, I’ve got all kinds of relatives. This night, some were strictly avoiding meat, dairy, and refined carbs; others, not so much. So I tried to make everyone happy with a sort of a hash – carrots, red bell pepper, chick peas, onions and garlic, fresh parsley and thyme, all browned and softened in a cast-iron skillet with plenty of olive oil.

As I brought it to the table, I could not imagine a possible objection. 

“Wait – you cooked that in olive oil?” asked one young man, incredulously. “Didn’t you know it’s unhealthy? It’s okay to eat, but not to cook with.”

“Actually,” said his girlfriend, “all oil is bad for you. It doesn’t matter if you cook in it. Even nuts are unhealthy, because they contain oil. I read this in a book.” 

And that is when my head exploded.

To be fair, the fat and oil situation is complicated.  It’s complicated to begin with, and then it gets worse when people try to oversimplify it (i.e. saturated fats are always bad). And it’s not just a matter of oversimplification: some of the things we hear are just plain wrong. For example, margarine is not better than butter. Coconut oil will not raise your cholesterol. It’s enough to make your head spin.

Hence, this article. It will be a three-parter. Part one this month will cover the basics. Part 2 in October will be the fun part: oils to use in your kitchen. November will talk about omega-3 and omega-6 fats, plus therapeutic oils.

So, where do we start? How about with some generalizations of our own.

The Biggest Generalization #1: oils from fruits, nuts, and edible seeds[1] are healthy. By which I mean to say, they’re not just “neutral,” they’re actually good.

• Fruits: avocado, olive, palm fruit…
• Nuts: coconut, macadamia, walnut, pistachio, hazelnut…
• Seeds: hemp seed, flax seed, sesame, sunflower; and yes, grape seed…

The Biggest Generalization #1½: almost no fats are inherently unhealthy (although many are merely neutral: empty calories). Trans-fats are unhealthy, of course. Some oils become unhealthy because of how they’re processed and stored…

The Biggest Generalization #2: not all healthy oils are healthy in all situations. Some of the best are also the easiest to damage with heat, oxygen and time.

What’s the difference between saturated fats and unsaturated fats? Chemistry is the difference! Long story short: molecules of saturated fat are more stable – they have a tendency to just “sit there” and not interact. So on one hand, they’re less likely to do anything, exert “vitamin-like” effects in the body. On the other hand, they don’t go rancid as easily, and stand up better to high-heat cooking. You can recognize saturated fats because they’re solid at or around room temperature: think butter, coconut oil, palm oil.

Polyunsaturated fats, on the other hand, are highly reactive. There’s a better chance they’ll do something good for you. Also, a better chance they’ll get damaged by heat, light, air, and time. So you want to keep them in the fridge, away from light, and airtight; use them fairly quickly, and don’t heat them too much. All too often – unless they’re packed in dark glass, pressed fresh, and stored under refrigeration – they’re already damaged by the time they get to you. You can tell polyunsaturated fats because they stay liquid even in the fridge: think canola, flax, fish oil.

Monounsaturated fats like olive and grapeseed oils are in between. They can stand up to cooking, but you probably don’t want to get them too hot. They’re fine for 10-15 minutes of heat, as long as they don’t start smoking.  Monounsaturates tend to solidify or “cloud” a little bit in the fridge: think olive oil.

Of course I’m guilty of oversimplification as well. No oil is just one kind of fat or another. For example, olive oil is predominantly monounsaturated, not entirely so. Nature is rarely “pure”!

What’s the deal with cold-pressed oils? Cold-pressed (or expeller-pressed, or virgin) oils are extracted using pressure to squeeze the seed. Even with newfangled machines, this is still an old-fashioned technology. It’s clean and safe. But it leaves behind about 10-25% of the oil.

Heating the seeds can speed the process, but may damage the oils. And then there’s hexane. Hexane is a powerful solvent, which can get those last drops out. However, hexane is also potentially hazardous, more so to the environment than to the consumer of the finished product.

You should assume that any oil that isn’t described as “cold-pressed,” isn’t. 

What are unrefined vs. refined oils? Just like we can make white flour from whole wheat, by removing the fiber-rich bran and nutrient-rich germ, so edible oils can also be refined. Processes like degumming, bleaching, neutralizations, and deodorization[2] seek to remove naturally occurring “impurities” like phospholipids, chlorophyll, carotenoids, sterols, lignans, and volatile compounds responsible for an oil’s unique color, flavor, and aroma. Bear in mind that almost all these “impurities” are substance we sell you, in pill form, to improve your health!

The upside of a highly processed oil is its versatility: it won’t taste or look or smell like anything in particular, so you can use it in anything. Refined oils also stand up better to high heats. So, for frying, or when other oils start to smoke[3]. The downsides are loss of nutrition, loss of shelf life, and loss of flavor.