Fats in food

Nutrition labels can be very confusing, especially the part that lists all the different types of fats. Why so many? What do they mean? Why does it matter? Let’s dig in and find out.

Fats

Fats are great ways to store energy. They pack more calories per gram (9 calories per gram) than proteins or carbohydrates (4 calories per gram).

Fats are basically a chain of carbon atoms (C). Each carbon atom is attached to one or more hydrogen atoms (H), except the one on the very end. That one is attached to two oxygen atoms (O).

Saturated Fats

In simplest terms, a saturated fat has every carbon atom “saturated” with as many hydrogen atoms it can hold. Each carbon atom is held to the next carbon in the chain by a single bond (the single dashes in the illustration). Every carbon atom must always have 4 bonds.

Saturated fats are mainly found in animal products like cheese, whole milk, butter, and high-fat cuts of meat. Palm and coconut oils are also high in saturated fats. Saturated fats are usually solids at room temperature (although palm and coconut oils are exceptions).

Unsaturated Fats

While saturated fats are usually solids at room temperature, unsaturated fats are liquids at room temperature. These are considered your “heart healthy” fats. Unsaturated fats have at least one carbon atom that is not “saturated” with hydrogen atoms. This is a MONOunsaturated fat – there are two carbon atoms that only have one hydrogen atom (instead of two), and they are held together by a double bond (the equal sign in the illustration). It’s called a “mono” unsaturated fat because there is only one double bond in the fat molecule.

Monounsaturated fats are found in plant-based oils like olive oil, canola oil, and soybean oil. They are also in foods like fish, nuts, seeds, and some vegetables (like avocados).

POLYunsaturated fats have multiple carbon atoms with only one hydrogen atom, and more than one double bond between carbons in the molecule.

There are two types of polyunsaturated fats, and you’ve probably heard of them – omega-6 and omega-3. Vegetable-based oils like soybean, corn, and safflower oil are high in omega-6 polyunsaturated fats. Places to get omega-3 polyunsaturated fats include soybean oil, canola oil, walnuts, flaxseed, and fish like salmon, trout, and herring.

These double bonds between carbon atoms force the fat molecule to have a bent shape. This is called the cis configuration of a fat. That’s only important so you can understand what comes next – the trans fats.

Trans fats

Here’s our new friend, the monounsaturated fat, in a little different diagram. See how that double bond between the carbon atoms makes the molecule bend? That’s because both of the hydrogen atoms are on the same side of the molecule (the yellow hydrogen atoms) This is the natural form (the cis form) of unsaturated fats.

Remember that we said that unsaturated fats are liquids at room temperature? That’s because of this bend in the molecule. These bends mean the fats can’t pack together very tightly, and they stay in a liquid form.

Some trans fats are naturally occurring in some meat and dairy products. But most of the trans fats we see in food are made by chemical processing (called hydrogenation). In hydrogenation, a bunch of extra hydrogen atoms are added to polyunsaturated fats. These extra hydrogen atoms break the double bonds between some of the carbons, and then attach to the “unsaturated” carbon atoms. Technically, a trans fat is still an unsaturated fat. But, see how the yellow hydrogen atoms are on different sides of the molecule? This makes the trans fat molecule have more of a straight shape.

That straight shape means that trans fats are solids at room temperature. In fact, this is exactly why trans fats were developed – to make products like margarine and spreads from vegetable-based oils that will stay solid at room temperature. They are also commonly used in baked goods and frozen foods.

How do you know if your favorite cookie dough has trans fats? First, check the nutrition label. If there is more than 0.5 gram of trans fats per serving, it is declared in the nutrition facts panel.

Second, check the ingredients list. Anything that is called a “partially hydrogenated oil” is a trans fat. If there is less than 0.5 gram in a serving size, it does not need to be included on the nutrition facts panel, but it still needs to be listed in the ingredients.

Clear as mud? Right. Next time we’ll talk about how these fats might affect your health.

In the meantime… You most definitely need to Meet the Fats! Check out this great series of articles from the American Heart Association for more information about all the fats we’ve talked about here.