Concept explainers
Effects of Dietary Fats on Lipoprotein Levels
Cholesterol that is made by the liver or that enters the body from food cannot dissolve in blood, so it is carried through the bloodstream in clumps called lipoprotein particles. Low-density lipoprotein (LDL) particles carry cholesterol to body tissues such as artery walls, where they can form deposits associated with cardiovascular disease. Thus, LDL is often called “bad” cholesterol. High-density lipoprotein (HDL) particles carry cholesterol away from tissues to the liver for disposal, so HDL is often called “good” cholesterol. In 1990, Ronald Mensink and Martijn Katan published a study that tested the effects of different dietary fats on blood lipoprotein levels. Their results are shown in FIGURE 3.2.
FIGURE 3.2 Effect of diet on lipoprotein levels. Researchers placed 59 men and women on a diet in which 10 percent of their daily energy intake consisted of cis fatty acids, trans fatty acids, or saturated fats.
The amounts of LDL and HDL in the blood were measured after three weeks on the diet; averaged results are shown in mg/dL (milligrams per deciliter of blood). All subjects were tested on each of the diets. The ratio of LDL to HDL is also shown.
In which group was the level of LDL (“bad” cholesterol) highest?
To explain: The group that had the highest level of LDL (“bad” cholesterol).
Concept introduction: Lipoproteins are carriers of hydrophobic molecules in the extracellular matrix and the blood. The lipoproteins are made of phospholipids, cholesterol, and proteins. The proteins are made of amino acids. Low-density lipoprotein (LDL) transports fat, essentially cholesterol molecules in aqueous medium. LDL can get oxidized with arterial walls and forms plaque. Saturated fatty acids have fatty acid chains lacking double bonds between their carbon atoms.
Explanation of Solution
In the experiment, the amount of LDL was checked in three groups of main dietary fats: cis fatty acids, trans fatty acids, and saturated fats. Their optimal levels were also checked. The optimal level of LDL is lesser than 100. The amount of LDL in cis fatty acids is 103, trans fatty acids is 117, and saturated fats is 121.
The saturated fats had the highest level of LDL also known as bad cholesterol among the three groups.
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