Saturated, Monounsaturated & Polyunsaturated Fat: Dietary Needs

Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

The fat found in foods comes in many forms, and has both positive and negative effects when eaten. Learn about the human body's dietary needs, and explore saturated, unsaturated, monounsaturated, and polyunsaturated fats. Review good vs. bad fats, lipids, triglycerides, trans-fatty acids, omega fatty acids, and sources and amounts of fat to understand the impact of fat on health. Updated: 10/02/2021

Good and Bad Fat

Fat is often demonized for leading to many conditions that are detrimental to our health, ranging from obesity to cancer to heart disease to arthritis. This is no doubt true when the wrong kind of fat or too much fat, in general, is consumed. But the right kind of fat is important in our diet for many different things, and this lesson will point out which things those are, which fat is bad, and which is good.

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  • 0:01 Good and Bad Fat
  • 0:27 Lipids and Triglycerides
  • 1:05 Saturated and Unsaturated Fat
  • 2:45 Trans-Fatty Acids and…
  • 3:46 Impact on Health
  • 5:47 Sources and Amounts of Fat
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Lipids and Triglycerides

Fats, more technically called lipids, come in a wide variety of shapes and flavors. Most of the different fats that we eat are called triglycerides, which are compounds that contain an alcohol called glycerol and three fatty acids. By the definition, you should see where the term 'tri'-'glycer'ides came from as there are three ('tri') fatty acids attached to a 'glycer'ol.

But that's enough of the overtly complicated stuff. Let's talk about the more commonly used terms when we describe the different kinds of fat.

Saturated and Unsaturated Fat

You've undoubtedly heard of one type of fat, called saturated fat. Saturated fat is a type of fat that doesn't have double bonds in its structure. A double bond gives fat a little kink, twist, or turn in its structure. This means that a saturated fat is like a straight line.

This is in contrast to unsaturated fat, a type of fat that contains one or more double bonds in its structure. When there's only one double bond, it's termed a monounsaturated fat. When there's more than one twist or kink, then it's a polyunsaturated fat. In either case, owing to these chemical double bonds, the fat is kinked and twisted and turns every which way. Polyunsaturated fats just have a lot more twists and turns than a monounsaturated fat. It's like a line that zigzags all over the place nonstop.

Ok, knowing all of this, think about the time you left some animal fat out in a pan you were frying bacon in. Can you recall what happened when the plate cooled down to room temperature? The fat solidified into this white thing. But if you were to go right now to your pantry and find some vegetable oil you'll see that it's still liquid at room temperature.

Which fat do you think is the unsaturated fat? It's the vegetable oil. That's because the kinks and twists in unsaturated fat prevent those fat molecules from neatly sticking to one another into a neat, orderly, and therefore solid structure.

Trans-Fatty Acids and Omega Fatty Acids

When unsaturated fats have hydrogen added to them, through a process called hydrogenation, a trans-fatty acid, aka trans-fat, is formed. Namely, the oil that is hydrogenated is vegetable oil, and hydrogenation makes the resulting fat less likely to spoil but more solid in composition than it was before.

Other than what I've mentioned already, other types of fats you may have heard of are omega-3 fatty acids and omega-6 fatty acids. These guys are unsaturated fats. They're important to know because two polyunsaturated fats, alpha-linolenic acid, a type of omega-3 fatty acid, and linoleic acid, a type of omega-6 fatty acid, are essential fatty acids. Meaning, they must be obtained from the diet because our body cannot make them.

Impact on Health

Fat, in general, plays important roles in our body. Fat helps insulate the body, cushions internal organs, and helps us absorb important vitamins such as vitamins A, D, E, K. But not all fats are equal, and many, especially when ingested in high quantities, may result in weight gain or even more serious health problems. Other than obesity, too much intake of fat can result in things such as arthritis by way of damaging your joints as a result of having to carry around excess weight.

Further still, improper fat intake increases the levels of cholesterol, a fat-like substance that helps to keep your body functioning properly but too much of which can lead to heart disease. Bad cholesterol is known as low-density lipoprotein or LDL. Good cholesterol is known as high-density lipoprotein or HDL. Since the word 'low' usually has a negative or bad connotation, then it's easy to remember which type of cholesterol is bad - it's the LDL.

Eating solid fats, that is to say saturated and trans-fats, increases the amount of this bad cholesterol. This causes the formation of things called plaques in the arteries of the body, resulting in a condition called atherosclerosis. Atherosclerosis causes the arteries, critically in the heart, to narrow and harden. This can lead to a heart attack and death.

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