Healthy fats vs. unhealthy fats…how does one tell the difference?
Not all fats and oils are created equal, and there are distinct advantages to including some while excluding others based on myriad factors: biochemistry, nutrient-density, sustainability / ethical sourcing and more. This tutorial explains some basic fat chemistry and give you the tools for selecting high-quality, nourishing fats and oils for your recipes. Look for more posts in this series where I’ll profile individual fats and the pros and cons of each.
First: A Chemistry Lesson
Chemically speaking, fats and oils belong to a category of large molecules (macromolecules) called lipids, and are composed of carbon, hydrogen and oxygen atoms in various patterns and length. (Note: We tend to call lipids that are solid at room temperature “fats”, while lipids that are liquid at room temp are called “oils”. For the purpose of this article, I will call them all fats.)
The backbone of a lipid is called glycerol, and to that, different fatty acids are attached. Think of a Lego block to which 3 other blocks snap into place. When three fatty acids attach to glycerol, you get a triglyceride. Sound familiar? Triglyceride blood levels are often important indicators of health or disease.
Classifying Fats: Length
Fats are classified in a couple ways, and the first is length. Fatty acids range in length depending on the number of carbon atoms they contain, and are classified as short-, medium- and long-chain. The medium-chain triglycerides (MCT) such as capric acid found in coconut oil, for example, are usually either 8 or 10 carbons long. (MCT is well known for its ability to be digested quickly by the body.)
Long-chain triglycerides (LCT) such as stearic, oleic and linoleic acids make up most of the fats we consume. We tend to not be as familiar with these names because fats are usually a mixture of different fatty acids. We call them by common names—such as lard, coconut oil or butter—instead.
Classifying Fats: Saturation
The second way fats are classified is by the relative “saturation” of the fatty acids. Carbon atoms like to be surrounded by four bonds for maximum stability, and many times, hydrogens are on the other side of the bond.
Saturated Fatty Acids (SFA)
When the bonds are all single, the fatty acid stays straight and is very stable. These are called saturated because the molecule contains the maximum number of hydrogens attached to each carbon. Fats with a large percentage of SFA are generally solid at room temperature. Because SFA bonds are all single and stable, they’re less prone to oxidation—or in simpler terms, breakdown.
Unsaturated Fatty Acids (MUFA or PUFA)
Some carbons in a fatty acid chain are attached via double bonds, and this causes the chain to bend and consequently become more fragile. These fatty acids are called unsaturated because fewer (“un—”) than the maximum number of hydrogens are attached.
If there’s one double bond, it’s called a monounsaturated fatty acid (MUFA). More than one? It’s a polyunsaturated fatty acid (PUFA). Fats with a high percentage of MUFA and / or PUFA are generally liquids at room temperature.
What’s all this mean? The more double bonds a fat contains, the more prone to oxidation it is. And, oxidation is not a good thing. Keep reading.
So What Makes a Healthy Fat or Unhealthy Fat?
A few criteria make a fat a good choice for consumption:
- Fats with higher percentages of saturated fatty acids (they’re more stable)
- Fats from animal sources that are grass-fed, pasture-raised and / or organic
- Fats from plant sources that are organic, sustainable and / or minimally processed
- Examples: grass-fed butter, clarified butter or ghee, pastured lard (pork fat), pastured tallow (beef fat), duck fat, coconut oil, palm oil (only sustainable sources are acceptable), extra virgin olive oil (recommended for cold applications because it is a high percentage of MUFA), avocado oil, cold-pressed plant oils, virgin or extra virgin oils
To contrast, here are some criteria that make a fat a less good choice:
- Fats that are a high percentage of polyunsaturated fatty acids
- Fats from “vegetable” oils (these are highly processed, industrial oils)
- Fats that are hydrogenated (these are liquid oils chemically processed to be solid)
- Trans-fatty acids
- Supposedly “good” fats such as coconut oil that are chemically treated or deodorized (sometimes marked as refined)
- Examples: canola, cottonseed, soybean, rapeseed (canola), grapeseed, corn, vegetable, sunflower, safflower, sesame, margarine, buttery spread, other refined oils
Here’s a quick contrast:
Coconut oil = 92% saturated, 6% MUFA, 2% PUFA
Sunflower oil = 6% saturated, 19% MUFA, 63% PUFA
Notice how sunflower oil is mostly composed of unsaturated fatty acids? That poses a problem.
But, Aren’t Some Seed Oils Healthy Fats?
Have you ever noticed how nuts and seeds go rancid, some quite quickly? Walnuts and sunflower seeds come to mind. That’s an example of the MUFA / PUFA oxidizing or breaking down. Fats with a large ratio of MUFA and / or PUFA are more fragile because of their structures. When you see an oil such as flaxseed that’s sold in the refrigerated section of the market in a dark bottle, it’s a huge indication that that oil easily oxidizes. Light, air and heat all speed up oxidation.
Why’s oxidation so bad? Simply put, it creates free radicals in the body that can damage cells. Antioxidants are molecules that intervene and essentially render free radicals neutral, preventing them from further damaging cells. Examples of antioxidants include beta-carotene and Vitamin E. It’s wise to consume foods rich in antioxidants as well as minimize the consumption of easily oxidized fats, a two-pronged approach.
If you’re taking a Paleo or real food approach to your diet, you’re likely to be consuming far fewer “bad” fats because you’ll be avoiding most processed foods. If you use seed or nut oils, it’s wise to use them for cold applications, such as in dressings or drizzling over a finished dish rather than using them for frying or high heat cooking. Rotating the type of fats you use on a regular basis is also recommended. Using less healthy oils once in a while won’t kill you (to be quite blunt), but continued use over time matters. Remember, it’s choices over time that are more consequential than making less-than-ideal ones on an occasional basis. You don’t have to be perfect, but make conscious decisions.
In general, saturated animal fats and coconut oil are stable at room temperature and are my preferred choices for high temperature cooking. Concerned about saturated fat causing heart disease? It doesn’t. Confused? I highly suggest reading Eat the Yolks…it debunks so much conventional wisdom, especially related to sat fat and cardiovascular disease.
Animal fat quality certainly matters, and it’s best to go as high-quality as your budget allows. Certainly, sustainability and the ethical issues surrounding certain fats and oils are also things you may want to consider when you’re narrowing down your choices.
I’ll be covering the benefits (and potential drawbacks) of specific fats and oils in future posts.
- Bias fat and oil choices toward sources with higher percentages of saturated fats. (Click here for an extensive list)
- Limit usage of high concentration MUFA / PUFA nut and seed oils such as sunflower, sesame, walnut, etc.
- Avoid industrial “vegetable” oils such as soybean, cottonseed and canola.
- High concentration MUFA / PUFA oils are more prone to oxidative breakdown.
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