Another aspect of the Nurses' Health Study looked at the percenta...

Question

Another aspect of the Nurses' Health Study looked at the percentage of change in the risk of coronary heart disease associated with substituting one dietary component for another. These results estimated that replacement of 5% of energy from saturated fat in the diet with unsaturated fats would reduce the risk of heart disease by 42%, and that the replacement of 2% of energy from trans fat with unsaturated fats would reduce the risk by 53%. Explain what these numbers mean.

Accepted Answer

Hi everyone. Let's look here at our next problem. It says which fatty acid among the following lowers the risk of coronary artery disease. And our choices are saturated fatty acids, unsaturated fatty acids, trans fatty acids or all of the above. So, there is a possibility there's more than one correct answer. So to think about this, we need to recall from our content videos what the structure is of these different types of fatty acids. So let's just recall a saturated fatty acid, the saturated meaning that of course all the carbons have a single bonds because every bonding spot on the carbon that isn't part of the chain is filled with hydrogen and as a result, the chain of that fatty acid, little hydro filic head look something like this. And when you have multiple fatty acid chains like this, they can pack very close together and that gives it the tendency to remain solid. As a result, when these are consumed, they can leave fatty deposits in the blood vessels leading to atherosclerosis or the hardening of arteries. Then let's look at unsaturated fatty acids. These have at least one double bond in our carbon chain. So we get to that there double bond here and as a result at least this chain having a kink or bend in it where the double bond is when these chains are bent like this, they can't pack tightly together the way the saturated fatty acids do and therefore an unsaturated fatty acid has a tendency to remain liquid and therefore doesn't leave those deposits in the blood vessels the way saturated fatty acid does. Then finally, we have trans fatty acid. Now, this also does have some double bonds in the chain. However, due to a different structure of the double bonds, it does not have this bend or kink in the chain. And that's because And you see with the name trans fatty acid, it's the difference between a cyst and a trans double bond illustration over here, assist double bond. As we've seen, the unsaturated fatty acid has the hydrogen on the same side of that double bond with the side chains. In this case the fatty acid chain on the same sides. So you see here the side chains double bond side chain with the hydrogen, both on the same side here. That's what gives it that structure. But in a trans double bond, the hydrogen czar on opposite sides of the double bond. And as a result, when we look at the fatty acid chain here, instead of seeing that bend. When you get to the double bond, we see here's our double bond. But because the side chain is on the opposite side, it continues on like that. Again, we see the two side chains on opposite sides of the double bonds. That means that that chain still has the ability the fatty acid chains have the ability to pack tightly, just like the saturated fatty acid and can therefore remain solid, tends to remain solid and can leave those fatty deposits in the arteries. Trans fatty acids are created synthetically because the unsaturated fatty acids have a tendency to react with oxygen over time, giving foods with them bad taste a bad smell. So food manufacturers tend to convert the unsaturated fatty acids to trans fatty acids um through a chemical process because the trans fatty acids are more stable at room temperature for a long period of time to make the food last longer on the shelf. But trans fatty acids just like saturated fatty acids, both raise the risk of coronary artery disease because of that tendency to remain solid and build up plaques fatty deposits in the arteries. So, back to our question, which lowers the risk of coronary artery disease. That's going to be choice be unsaturated fatty acids, since they do not build up those plaques in the blood vessels. As we saw the saturated fatty acids and trans fatty acids actually raise the risk of coronary artery disease. And of course, choice D all of the above is incorrect. So again, which fatty acid lowers the risk coronary artery disease? Choice B unsaturated fatty acids. See you in the next video

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