Role of Lipids in Developing Cardiovascular Disease

Instructor: Amanda Robb

Amanda has taught high school Biology & Physics for 8 years. She received her M.Ed. from Simmon's College and M.S. from Tufts in Cellular and Molecular Physiology.

In this lesson we'll be looking into the role of lipids in cardiovascular disease. We'll specifically look at the dangers of hydrogenated fats and trans fatty acids.

Heart Health and Fat

In the 1980's if a patient was to come to a cardiovascular doctor with high blood pressure, atherosclerosis, or post heart surgery, their advice would be unlike what we do today: a diet extremely low in all types of fats.

Later, doctors found that an extremely low fat diet wasn't good at all. Patients got sick more often and lacked energy. Clearly, the body needs some fat.

Through scientific research we found that there are 'good fats' and 'bad fats' based on how they affect our cholesterol. Good fats include natural sources of unsaturated fats, like nuts and avocados which increase our HDL (high density lipoproteins) cholesterol, the type that protects our heart. Bad fats are the delicious animal fats we love, like butter and whole milk and increase our LDL (low density lipoproteins), or bad cholesterol which hurts our heart and clogs our arteries.

Types of cholesterol and fats that increase their content
cholesterol

What Are Lipids?

Fats, or lipids are made of long chains of carbon attached to hydrogen atoms. Saturated fats have all their carbons attached to hydrogens. This makes the molecules straight and they easily pack together, creating solid fat. Unsaturated fats however, have some double bonds in between the carbon, causing kinks in the chains. These fats don't pack tightly together thus and the fat remains liquid.

Structure of saturated and unsaturated fats
saturated and unsaturated fats

Hydrogenated Lipids

Good fats, or unsaturated lipids are liquid at room temperature. They are inexpensive to make and come from a variety of plants like peanuts, corn, olives, rapeseed and more. However, the fats that usually are more tasty and desired for classic American foods come from animals, which are more expensive and worse for our health. Diets high in saturated fat have been linked to heart disease.

So, we have a dilemma. How do we use the healthy, cheap, unsaturated fats in baked goods? Like usual, our scientists had a plan. Their solution was to attach hydrogen atoms to unsaturated fats using a special chemical reaction called hydrogenation to get the desired properties of saturated fats. However, there were some flaws to this strategy.

Like saturated fats, some hydrogenated fats are very bad for your health, even worse than the original saturated fats in some cases. Today, we're going to look at two types of hydrogenated lipids and a more common method today called interesterification.

Partially Hydrogenated Lipids (Trans fats)

During the hydrogenation process of unsaturated fat to saturated fat, there is a middle point at which some hydrogen molecules have attached to the lipid, but not all of them. This molecule is called a partially hydrogenated lipid, or well known in the food industry as trans fats. Trans fats can be found in solid fats, like shortening.

Vegetable shortening contains trans fats
Crisco

Trans fats have no nutritional value for humans and are harmful to our body. They raise the bad cholesterol, or LDL. Increased levels of LDL cause cardiovascular disease, such as atherosclerosis, when plaque builds up in the arteries. With plaque, blood flow is blocked and can even completely clog arteries that carry oxygenated blood to the heart and brain, causing a heart attack or stroke. Trans fats also decrease good cholesterol, or HDL. HDL protects the cardiovascular system against these diseases.

Plaque builds up during atherosclerosis blocking blood flow
atherosclerosis

Trans fats also have been shown to increase inflammation in the body, where the immune system is activated. Although we need inflammation when we get a cut so the body can prevent infection, it's not good to have it happen too much. Unchecked inflammation can cause diseases where the body attacks itself, like arthritis and can also increase the risk for atherosclerosis.

Luckily, trans fats are rare in our food today. In 2003 the Food and Drug Administration (FDA) passed a law that any foods containing more than 0.5 grams of trans fat must present this information on their label. Due to campaigns by the FDA, many people are aware of the dangers of trans fats in their diet and few restaurants use this type of fat.

Fully Hydrogenated Lipids

If you keep adding hydrogen atoms to an unsaturated fat, eventually you get a fully hydrogenated lipid, such as olestra. All the available bonds in this lipid are filled with hydrogen atoms. Fully hydrogenated lipids, although structurally different, have the same properties as saturated fats. They also have a longer shelf life, making them perfect for prepackaged snacks filled with fat, like cookies or baked goods.

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