Last time I wrote about saturated fat, typically considered a bad egg in the fats family. In that respect, unsaturated fat is treated as the golden child. The American Heart Association recommends getting most dietary fat from sources of unsaturated fats, rather than saturated or trans-fats. The Mayo Clinic more or less recommends the same. So, let’s see what makes these fats so much more desirable.
A Little Biology
So, recall last time what a fatty acid is: a carbon chain with a carboxly group, with lots of hydrogens attached. And an unsaturated fat has at least 1 double bond between carbon atoms. This is where the first differentiation comes in: monounsaturated fatty acids (often abbreviated as MUFAs) have one double bond and polyunsaturated fatty acids (even funnier: PUFAs) have multiple double bonds.
An unsaturated fat is always in the cis-configuration. If it is not (and thus, in the trans-configuration), it is a trans-fat. Now, remember that the unsaturated fat has a bend in it where the two carbons form a double bond. This bond is essential to one of the physical properties of an unsaturated fat: it’s liquid at room temperature because the bend results in less efficient packing.
So, are unsaturated fats good for me or not?
The standard narrative is that MUFAs and PUFAs are great for you (in moderation, of course!) because they improve your cholesterol ratio, decrease the amount of bad cholesterol floating around in your blood, and may be helpful in controlling Type II Diabetes. They are a central part of the Mediterranean diet (in moderation!). And, they come from plants–plants are awesome and contain antioxidants, making plant-fat that much more nutritionally valuable than animal fat.
Of course, I like to offer counterarguments, and I would say that animal protein offers some fantastic benefits that plants don’t. Like the long-chain omega-3s (EPA and DHA) in wild-caught salmon. But I am getting ahead of myself: more on that in a second! First: unsaturated fat nomenclature.
To begin with, there are different classifications of unsaturated fats beyond mono- and polyunsaturated. For instance, within polyunsaturated fats there are omega-3, omega-6, omega-7, and omega-9 fatty acids. In a fatty acid, the last carbon in the chain (a methyl group with three hydrogens) is called the omega carbon. These particular fatty acids are named for how many carbons away from the omega carbon the double bond it. I am going to start by discussing these polyunsaturated fats–focusing omega-3 and omega-6 fats–which are a mixed bag of good and bad news.
Omega-3 Fatty Acids
You have heard about omega-3 fats before, I am sure. All good things, too. Some of these fatty acids are essential for good health and these include: alpha-linolic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA cannot be made by the body and EPA and DHA are not made efficiently, so eating them is a dietary requirement (cough*eat your fish*cough) .
What makes these omega-3 fats so cool, though? For starters, they act as anti-inflammatory agents in two ways: first, they decrease inflammation by inhibiting enzymes that create inflammatory particles and inhibit transcription factors for genes that lead to inflammation so that the inflammatory genes aren’t expressed in the first place. Second, omega-3 fats produce anti-inflammatory molecules. That is a case of double win. inflammation is now thought to be a component of any diseases–including metabolic syndrome, type 2 Diabetes, and Cardiovascular disease–as well as diseases long-known to involve inflammation, like rheumatoid arthritis . Since all of these diseases are pretty common where ever the Western Diet* is eaten, it is especially important to eat healthful foods as a preventative measure.
Additionally, omega-3 fatty acids are involved in breast cancer prevention. One study found a negative relationship between development of breast cancer and intake of ALA. This study focused on food sources and found that fruits, vegetables, and some oils where the healthiest sources of ALA–at least in terms of breast cancer .
In another study, omega-3 fatty acid was found to effect E2, an essential gene in the proliferation of cancer. E2 is a proto-oncogene: it typically is part of the cellular pathway that leads to growth and proliferation. For those of us who have not yet forgotten the minutiae our teachers crammed into our heads this semester, you may remember the gateways between different parts of the cell cycle; the gateway between the G1 and S phases is controlled in part by E2.
If E2 is mutated to become a cancer-causing oncogene, we run into the beginnings of cancer. Omega-3 fatty acids were shown to activate a second function of E2, which causes apoptosis–stopping the growth and proliferation of dangerous cells. The authors of the study think that an omega-3 treatment can act as a preventative treatment, without the risks of estrogen treatments .
The best sources of omega-3 fatty acids are flaxseed oil and fish or fish oils–for instance cod liver oil or salmon. However, wild plants (for those of you who are quite adventurous or how have a farmer’s market selling foraged foods) are also high in omega-3 fats, especially ALA . Normal plants also offer some omega-3 fats, however, omega-3s make the food less stable, so it rots faster. Because of this, omega-3s have been bred out of industrial plant foods, so I suggest organic or heirloom or whatever the trendy people are calling traditionally grown produce in your area.
Omega-6 Fatty Acids
Now, there are the omega-6 fats, and those are a little messier. See, some are essential–linolenic acid (LA), gamma-linolenic acid (GLA), and dihomo-gamma-linolenic acid (DGLA–thank God for acronyms, right?)–but eating too much in relation to the omega-3 fats in your diet can be harmful. The first issue is eating too much LA, which can be a precursor to arachidonic acid (AA, which in turn is a precursor to many different inflammatory molecules .
The ratio between omega-6 and omega-3 fats is important to overall health and in the Western Diet, that ratio is way out of whack. The recommended ratio of omega-6 to omega-3 is between about 1:1 or equal parts (though, there are some recommendations for 1:2), though some recommendations go as high as 4:1 [5, 6]. In the Western Diet, our ratio is somewhere between 17 and 30 to 1. No good. This means that we are getting way too much of the precursor to the inflammatory response I wrote about earlier and nowhere near enough of the precursor to the anti-inflammatory response [1, 6].
You might be thinking that this supersaturation of dietary omega-6 fat is a new thing, and you would be correct. Remember last time when I wrote about everyone thinking saturated fats were evil? Well, we still had to fry our french fries in something! Enter the USDA food pyramid. Does it strike anyone else as weird that the agency meant to take care of farmers and industrialized food is in charge of our food recommendations? Why not the FDA, which is supposed to be the consumer advocate? I hadn’t thought about this until I read Foodist, but there it sits–and it explains in part our omega-6 overload.
What are good sources of omega-6 fats? Soy bean oil, corn oil, safflower oil. Who grows a lot of soy beans and corn? Us! It is basically our patriotic duty to eat french fries (fried in soybean oil) and hamburgers (patties made from corn-fed cow meat), since with corn and soy subsidies, we have too much corn and soy. So, how was that for a conspiracy?
Monounsaturated Fatty Acids
monounsaturated fats are truly central to the Mediterranean diet–especially as studied by Ancel Keys in the Seven Countries Study (*cough*22 country study*cough*). Really, though, they are not so bad for you (in moderation! If you notice that I keep writing that, it is because I worry that I have been too open-handed about fats in past posts. Yes, they are not evil, but still, it is not a free pass to eat it without worry). And they are universally accepted as a healthy fat among nutrition and health experts .
The 18-carbon sister of polyunsaturated LA and ALA is oleic acid. It is an omega-9 fat, and its name derives from olive, and is the predominant fat in olive oil. We know olive oil is some good stuff, but it honestly deserves its own post. Anyway, MUFAs are found in most nuts and seeds, in avocados, olive oil, and in dark chocolate**.
So, it’s okay?
Yeah, these fats aren’t so bad: try to increase the amount of omega-3 fats in your diet, limit your omega-6s (Based on that 17:1 or even 30:1 ratio we talked about above, I am not very worried that omega-6 intake will get too low), and don’t worry too much about MUFAs–they aren’t so bad either. Just as long as the food comes from good sources and you eat in moderation, these fats are part of a healthy diet.
*I used Western Diet because I felt that it is more inclusive of cultures eating poorly (due in some cases to the McDonaldization of the world, in some cases), though I would have used Standard American Diet since the acronym is SAD and that is a fantastic descriptor for the nutritional quality of the Western Diet.
**Chocolate is just sounding better and better, right? First stearic acid, now oleic acid–both known to be heart-healthy and delicious.