The Truth About Fats: Saturated Fats

moo cow

There is something strange that has been going on for a while in the food world–I remember it as a child of the nineties, and I know it has been going on much longer than that. It is the Fear of Fats and it needs to stop now.

This is the first in a three-part series on fats that will focus on saturated fats, unsaturated fats, and trans fats. I’m starting with saturated fats because who doesn’t love controversy (as I found out with the attention this post got)? And saturated fats have caused nothing if not controversy. Well, that and a significant amount of stress for parents trying to protect their children from poor health. But fats need not frighten– in some (unexpected) cases, they are even helpful.

So, what is a saturated fat?

Let’s start with some basic biology direct from Campbell’s Biology: a fatty acid has a carbon skeleton (with varying numbers of carbons), a carboxyl group at one end (a carbon with a double-bonded oxygen and a single-bonded hydroxyl group) and the rest of the carbons bound to each other and hydrogen atoms. It is the carboxyl group that makes this molecule an acid. Now there are different types of fatty acid: saturated, unsaturated, and trans. All these names are based on the amount and arrangement of the hydrogens. If fatty acid has all single bonds between carbons and thus as many hydrogens as possible bind to the carbons, the acid is said to be saturated with hydrogens.

saturated and unsaturated fat molecule

The carboxyl group for each of these fatty acids is on the right hand side. Looking left, you will see the carbon skeleton–containing 12 carbons in each fat. On the saturated fat, there are 24 total hydrogen atoms and on the unsaturated fat there are only 18 total hydrogen atoms.

Then we get to unsaturated fats and interesting things happen. In an unsaturated fat, the two or more carbons share a double bond, and thus, there are fewer hydrogens. In a standard saturated fat, the hydrogens bonded to the carbons are on the same side (hence the cis-fat molecule). This results in a bend in the molecule. The bend is essential in biology because it adds fluidity to cell membranes, especially at low temperatures, while straight saturated fats add stability even at high temperatures.

Now, what happens if we want to make these unsaturated fats straight? We can do that–we just make a trans-fat. It is called a trans-fat because those two carbons attached to the double bonded carbons are on opposite sides. This effectively takes the bend out of the molecule and is most often used to make…dun, dun, DUN…margarine. But more on unsaturated and trans fats in the next posts.

trans and cis fats molecules

Notice the bend in the cis-fat molecule–this bend is what makes mostly unsaturated olive oil liquid at room temperature and butter (saturated and without bends) solid. Notice that the trans-fat is straight–by chemically modifying the saturated fats in olive oil, we can take the bend out, allowing the molecules to pack more efficiently, and resulting in a solid at room temperature. Can anyone say olive oil margarine?

Okay, so saturated fats are lots of carbon and hydrogen. Why are they evil?

Short answer: No.

Long answer: Among others, The Seven Countries Study, headed up by Ancel Keys, would eventually put saturated fats on the radar of every health-conscious man, woman, and child, but it was wrong. Really, no one has put more research into this than this girl, and I suggest that everyone reads this article (and really, pretty much the rest of her blog right after).

The article is quite long though, so here is the condensed version: Ancel Keys really studied 22 countries, but he threw out all of the data that didn’t perfectly match his perfect graph, but there was still a positive correlation between saturated fat and heart disease with the data from all 22 countries. That can be explained away by two things: the countries self-reported all these death statistics (some didn’t properly identify heart attacks back in the day) and the study wasn’t based on actual food intake, but food available per capita (which doesn’t account at all for scraps and discarded food). Basically, more developed nations were more likely to correctly identify a heart attack as the cause of death and they had more animal foods available, so there appeared to be a correlation between saturated fat and heart disease. Except that this is not an experiment but an observational study and you can’t determine association from an observational study (Stats students: commit that one to memory–it will be on the test).

Now that we look at it like that, it must seem silly to hate saturated fats so much since the research was flawed. We aren’t all that silly–there must have been other research! There has been, of course, but in the name of brevity, I will gloss: there was more research (some solid, some not so much) and it supported this idea that came to be called the lipid hypothesis–broadly, that as cholesterol levels increase, so too does the risk of cardiovascular disease, and since saturated fat is connected to increasing dietary cholesterol, it is Evil with a capital E and we must protect our children from it  should be avoided. There was also other research that didn’t fit the saturated fat narrative and thus wasn’t taken seriously by authorities making nutritional guidelines.

Recently, however, there has been disagreement in the medical world as more and more research is showing that there is little scientific evidence to support the lipid hypothesis. Among the most recent of these articles is “Saturated fat is not the major issue.” Published in the BMJ, the author  goes so far as to claim that saturated fats are good for you (as does Nina Planck in Real Food). According to the research cited, saturated fats can be protective. Additionally, they provide a way for the body to use vitamin A and D, and higher amounts of vitamin D are though to be protective against heart disease (little aside: this is why whole milk–for those who can drink it–isn’t so bad: it provides calcium and vitamin D along with the fats necessary to metabolize them). The article is very short and I recommend reading it.

In 2010, the Dietary Guidelines Advisory Committee stated that stearic acid (18 carbons) lowers cholesterol and went so far as to propose reclassifying fats into “cholesterol-raising fats” (trans-fats and saturated fats, minus stearic acid and short chained saturated fatty acids with 4 to 10 carbons–but long chain saturated fats were still on the naughty list) since the “all saturated fats are bad” mantra just doesn’t seem to hold up to scientific scrutiny. Those other long chain fats turn out not to be so bad either. Lauric acid (a 12 carbon chain), myristic acid (14 carbons), and palmitic acid (16 carbons) all increase the so-called bad cholesterol, but increase the good cholesterol, too, resulting in a neutral effect and don’t negatively affect the ratio between HDL and LDL cholesterol (good and bad, respectively). In some studies, the ratio was even improved, but the discussion about cholesterol will have to wait for another day and another post.

So, I can eat saturated fats?

Yep! But don’t just run out and buy all the bacon, full-fat yogurt, and eggs you can carry (yes, I was tempted when the door  to a world where saturated fats were not demonized was opened to me–oh, so tempted). Eggs from free-range chickens are healthier for you, and provide more nutritional bang for your buck. Dairy products and beef are better for you when they come from grass-fed cows–stearic acid is found in greater quantities in these cows. Other dairy add meat depends on what that particular animal is made to eat.

There is so much to say about the health of the animal that any animal based foods come from, but if you made it to the end of this post, you know that it is a topic for another day. Thanks for reading! Next time it will be about unsaturated fats.

Read the rest of the series, The Truth about Fats

Unsaturated Fats and Trans-Fat and Hydrogenation


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