FATS AND CHOLESTEROL ARE NOT ALL BAD

Over the past couple of decades fat and cholesterol have taken a beating in the press, being labeled as the nutritional “bad boys.” Often we are told to avoid them as much as possible. However, today we are told that we do indeed need fat, especially certain types of fat that might support cardiovascular and joint health as well as help support the maintenance of memory and cognition later in life. Cholesterol from food, on the other hand, might not be as potent a blood-cholesterol raiser as we once thought. So which types of fat are better for you and which are more expendable from the diet? Furthermore, how much cholesterol is okay and are some sources healthier than others? In this chapter we will answer basic questions related to fat and cholesterol, and continue to set up later chapters related to metabolism, weight loss, joint health, heart disease, and more.

The Basics of Fats and Cholesterol

What Are Lipids?

Fats and cholesterol belong to a special group of molecules called lipids. The members of this club have something pretty significant in common: they are relatively insoluble in water. This might not seem like a big deal, but keep in mind that most of our planet’s surface is water and, more important to our topic, most of our body is water as well. Because of their inability to dissolve into water, we must make special concessions to accommodate lipids both during digestion and also inside of the body.

Fat and cholesterol are lipids, which are a group of molecules that don’t dissolve well into water.

During digestion, an emulsifying substance called bile is called to action to facilitate lipid digestion and absorption. As for fat and cholesterol inside of the body, they require special transport shuttles to circulate. Fat also has its own cell type specifically designed for storage. These cells are called adipocytes, or more commonly “fat cells,” and large collections of adipocytes are called adipose tissue. Adipose tissue is found under the skin (subcutaneous fat) and in deeper deposits (visceral fat) such as in the abdomen, around vital organs, and throughout skeletal muscle.

What Is the Difference Between Fat, Oils, and Triglycerides?

Fats and oils are terms commonly used to refer to food sources of triglycerides. Often fat and oil are considered to be different based on appearance: fat is solid at room temperature and oil is liquid. However, they are really two of the same thing, generally speaking. They are both collections of triglycerides. For simplicity, we will use “fat” to include all sources of triglycerides.

A triglyceride molecule is a combination of three fatty acids linked to a glycerol molecule backbone. Although a triglyceride molecule will always have this general design, there can be great variability in the type and combinations of fatty acids that link to glycerol. Only one glycerol molecule exists, but like monosaccharides there are numerous different types of fatty acids in nature. Furthermore, if a triglyceride involves three fatty acids then monoglycerides and diglycerides will have one and two fatty acids attached to glycerol, respectively. Technically, they can be considered fat as well.

What Is Cholesterol and Can We Make It in Our Body?

Cholesterol has received its share of negative press over the years, however it is important to realize that cholesterol is absolutely vital to our existence. Cholesterol can be made in many cells, and under normal situations we seem to make all that we need. In fact, we will make about 1 gram of cholesterol each day depending on how much cholesterol is in the diet. The liver is by far the most productive organ when it comes to making cholesterol and one of its jobs is to share with the rest of the body. Cholesterol is a necessary component of cell membranes and many vital substances in the body are made from cholesterol. These substances include bile components, vitamin D, testosterone, estrogens, aldosterone, progesterone, and cortisol.

Cholesterol is needed for cell membranes and to make certain hormones, digestive factors, and vitamin D.

Fatty Acids: A Closer Look

Can Fatty Acids Vary in Length?

For the most part, the length of fatty acids can vary by as much as twenty carbon atoms or so. If a fatty acid has four carbon atoms or fewer, it is referred to as a short-chain fatty acid. On the other hand, if a fatty acid chain has six to twelve or greater than twelve carbon atoms, it would be referred to as a medium-chain fatty acid or a long-chain fatty acid, respectively. Often, fatty acids with twenty or more carbon atoms are referred to as very-long-chain fatty acids. Most fatty acids in nature have an even number of carbons, yet some fatty acids do indeed have an odd number of carbons.

What Are Saturated and Unsaturated Fatty Acids?


Fatty acids can differ in their degree of saturation. Saturation refers to whether all of the carbon atoms between the end carbons are linked to two atoms of hydrogen. If this is the case, then the carbons are saturated with hydrogen and that particular fatty acid would be called a saturated fatty acid (SFA). However, if, at one or more points, adjacent carbon atoms are bonded to only a single hydrogen atom each, the fatty acid would then be an unsaturated fatty acid.

By nature, when two adjacent carbon atoms in a fatty acid are linked to only one hydrogen atom each, the carbon atoms must bond to each other twice. Chemists call this a double bond and if a fatty acid has only one double bond, it is referred to as a monounsaturated fatty acid (MUFA). Meanwhile, if there is more than one double bond, then it is a polyunsaturated fatty acid (PUFA).

What Does “Omega” Mean with Regards to Fatty Acids?


Because fatty acids can vary greatly, scientists will indicate the number of carbons and double bonds in a fatty acid. For instance a 18:3 fatty acid will be 18 carbons long and have three double bonds. Scientists also use omega system to indicate where double bonds are in a fatty acid. It works like this. If a fatty acid is linked to glycerol, the second carbon closest to the link is referred to as the alpha (α) carbon. Meanwhile, the carbon furthest from the linkage with glycerol is called the omega (ω) carbon.

The omega system is based on the Greek alphabet. Alpha is the first letter of the alphabet and omega is the last. No matter how many carbons are in your fatty acid chain, these carbon atoms will always be addressed in this manner. Looking at a fatty acid not linked to glycerol, the alpha carbon would be the first carbon atom adjacent to the carbon bonded to two atoms of oxygen.

To indicate position of the first double bond we count the number of carbons to the first carbon of the first double bond from the omega end. For instance, if the first double bond starts at the third carbon atom in, it is an omega-3 (ω-3) fatty acid. Likewise, if the first double bond appears at the sixth or the ninth carbon atom in, these would be ω-6 and ω-9 fatty acids, respectively. For the most part, when addressing polyunsaturated fatty acids, we indicate only the position of the first double bond because subsequent double bonds seem to occur in series after one saturated carbon atom.

What Are “Trans” Fatty Acids?

 If the hydrogen atoms attached to the carbon atoms of a double bond are positioned on the same side of the double bond, it is a cis bond that is the predominant way they are found in nature. If the hydrogen atoms bonded to the carbon atoms are on opposite sides of the double bond, it is referred to as a trans fatty acid.

Interest has been growing regarding the presence of trans fatty acids in our diet and their potential impact upon health. Although cis versus trans may seem like a very minor point in regard to fatty acid design, these contrasting forms can impart different properties to a fatty acid. Cis double bonds cause a kinking or bending of the fatty acid, while trans double bonds do not. This makes unsaturated fatty acids with trans double bonds similar to saturated fatty acids in that they do not bend or kink.

Trans fats are like saturated fats in that they don’t bend, and increase the risk of cardiovascular disease.

What Do We Mean by Saturated and Unsaturated Fats?

Regardless of the origin of a triglyceride source (plant or animal), the triglycerides will contain a mixture of fatty acids. When we say that a fat source is saturated, we are indicating that the majority of the fatty acids within the source are saturated. For instance, we often refer to butter and beef fat as saturated fats. This is because the majority of their fatty acids are saturated.

Why Are Oils Liquid at Room Temperature While Fats Are Solid?

In general, if the majority of fatty acids in a triglyceride source are saturated, then it most likely will be solid at room temperature. Contrarily, if a triglyceride source contains a greater percentage of unsaturated fatty acids, especially PUFA, then this source will most likely be liquid at room temperature. Saturated fatty acids are straighter than unsaturated fatty acid. This allows them to pack closer together and to be more solid. Notice that the oils have a higher percentage of unsaturated fatty acids while the more solid fats (lard, tallow, etc.) have a high percentage of saturated fatty acids. Despite their names, palm oil and palm kernel oil are more solid at room temperature.

Can Different Kinds of Fatty Acids Be Part of the Same Triglyceride Molecule?

There are probably no definite rules as to the selection of fatty acids that make up a triglyceride molecule. One triglyceride molecule may be composed of one saturated, one monounsaturated, and one polyunsaturated fatty acid, all of the same or varying lengths. However, the types of fatty acids found within triglyceride molecules will depend on the plant or the animal source. For instance, the triglycerides in olive oil largely contain the MUFA oleic acid (18:1 ω-9) (about 82 percent), while about two-thirds of the fatty acids in butter are SFAs of varying length.

The presence of certain types of fatty acids in either a plant or an animal largely depends upon the nature of the plant or animal and the purpose of the fat for that life-form. For instance, fish that live in deeper water tend to be better sources of ω-3 PUFA because these fatty acids are found in the cell membranes of these fish and play a protective role against the increased pressure and decreased temperatures at greater depths as well as help regulate their buoyancy. Land animals create storage fat that is largely composed of saturated fatty acid. Since these fat molecules can pack tightly in fat cells it minimizes the necessary space.

Fat and Cholesterol Requirements and Food Sources

What Foods Provide Us with Triglycerides and Cholesterol?

Fats and oils, and thus triglycerides, are present in both animals and plants. Oil is a natural component of many plant tissues including leaves, stem, roots, kernels, nuts, and seeds. Common edible oils include sunflower, safflower, corn, olive, coconut, canola, and palm oil. Contrarily, butter is made from the fat in milk, while lard is hog fat, and tallow is the fat of cattle or sheep. Other animal flesh will contain fat, including poultry and their eggs.

Cholesterol is not a necessary substance for plants; therefore they do not need to make it. Contrarily, mammals will make cholesterol to help meet their body needs. As a result, cholesterol intake in the diet is attributed only to consumption of animal foods or foods that have animal products in their recipe. It should be mentioned though that plants do create molecules that are similar to cholesterol called phytosterols.

How Are Vegetable Oils Produced?

Vegetable oils are the edible oils extracted from seeds, nuts, kernels and other plant tissue. Edible vegetable oils are extracted from plants using solvents such a hexane and/or through mechanical processes such as cold pressing and expelling. Mechanical processing does not involve solvents and the major difference is the temperature of the extraction processes. Cold pressing involves a hydraulic press between two plates and the temperature tends to stay below 120°F. Meanwhile, expelling involves a screwing mechanism which results in more frictional heat allowing the temperature to reach as high as 185°F.

How Much Fat Do We Need in Our Diet?

At this time there is not a Recommended Dietary Allowance (RDA) (or Adequate Intake (AI)) for total fat. Meanwhile an Acceptable Macronutrient Distribution Range (AMDR) has been declared as 20 to 35 percent of energy, which would be practical for most people based on today’s food supply. It is important to realize that the AMDR is not a requirement level and many nutrition scientists believe that the absolute lowest requirement for fat in our diet could be as little as 5 percent of calories (for weight maintenance) as long as it is derived from healthier sources including seeds, plant oils, as well as fish and other marine life.

Some fat is needed in the diet to provide essential fatty acids, which are important regulatory factors.

Are There Essential Fatty Acids?

The need for dietary fat is not necessarily for energy purposes. Fat is needed in our diet as a means of providing two essential fatty acids, linoleic acid, an ω-6 PUFA, and α-linolenic acid, an ω-3 PUFA. Since the amount of these fatty acids in fat storage (adipose tissue) is limited, this suggests that their role in our body isn’t really to provide calories, although they will be used for energy. Linoleic and α-linolenic acid are used to make longer, more complex fatty acids that have special functions.

Linoleic acid is used to make a longer ω-6 fatty acid called arachidonic acid (ARA) while α-linolenic acid is used to produce longer ω-3 fatty acids, namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Both ARA and DHA are found in higher concentration in the brain and are vital for the development of the central nervous system and eyes. Meanwhile, EPA and ARA can be used to make factors called eicosanoids (for example, prostaglandins, thromboxanes, and leukotrienes) that help regulate many bodily functions.

What Foods Are Good Sources of Essential Fatty Acids?

Good sources of linoleic acid are safflower oil, sunflower seeds (oil roasted), pine nuts, sunflower oil, corn oil, soybean oil, pecans (oil roasted), Brazil nuts, cottonseed oil, and sesame seed oil. Dietary surveys in the United States suggest that the intake of linoleic acid is about 12 to 17 grams for men and 9 to 11 grams for women.

Good plant sources of α-linolenic acid are flaxseed and walnuts—their oils are among the best sources of α-linolenic acid—as are soybean, canola, and linseed oil as well as some leafy vegetables. Diet surveys in the United States suggest that typical intakes of α-linolenic acid are about 1.2 to 1.6 grams daily for men and 0.9 to 1.1 grams daily for women. Therefore the ratio of linoleic acid to α-linolenic acid is about 10 to 1.

Marine mammals (for example, whale, seal, and walrus) and the oil derived from cold-water fish (cod liver, herring, menhaden, and salmon oils) provide eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA are fatty acids that are made from linolenic acid in marine animals. A lot of interest in the ω-3 PUFA was created when researchers reported that there is a lower incidence of heart disease in some populations, such as Greenlanders. Diet patterns showed high fish consumption in these people, which leads to greater ω-3 PUFA intake and a reduced incidence of heart disease. In addition, there are links between the consumption of fish and cognitive development as well as reducing age-related losses in memory and cognition.

Fish and fish oil supplements are good sources of the omega-3 fatty acids DHA and EPA.

What Foods Contain Trans Fatty Acids?

Trans fatty acids can be found in many fat sources although its prevalence is very low. Bovine (cows, steer, oxen, etc) food sources are probably the greatest natural contributors of trans fatty acids to the human diet. For instance, beef, butter, and milk triglycerides may contain 2 to 8 percent of their fatty acids as trans fatty acids. Interestingly, cattle are not solely responsible for generating this trans fatty acid content. It is actually the bacteria in their unique stomachs that produce the trans fatty acid. These fatty acids are then absorbed by the cow and make their way into the tissues and milk of these animals.

In addition, trans fatty acids can be created during the processing of oils (that is, margarine and other hydrogenated oils), which will be described later, and when cooking oils are re-used over long periods, such as in fast-food restaurants and diners. In more recent decades, more than half of the trans fatty acids in the human diet were derived from processed oils either consumed plain or used in recipes (for example, fried foods, baked snack foods). Cookies, crackers, and other snack foods that utilize hydrogenated vegetable oil may contain up to 9 to 10 percent of their fatty acids as trans fatty acids.

Because the consumption of higher amounts of trans fatty acids is linked to increased risk of heart disease and stroke, the American Heart Association, and the most recent Dietary Reference Intakes (DRIs) in the United States and Canada, recommend limiting the trans fat level of the diet. In addition, food manufacturers in many countries, including the United States and Canada, are required to list the trans fat levels in the Nutrition Facts on food labels. Because of this, snack-food manufacturers are choosing hydrogenated oils with lower trans fat content to produce snack foods. Furthermore, in 2006 New York City placed a ban on trans fat in restaurants, a public health initiative that is being followed by other cities.

By Dr Robert E. C. Wildman PhD , RD in "The Nutritionist - Food, Nutrition, and Optimal Health", Routledge, New York & London, 2009, excerpts p.96-107. Adapted and illustrated to be posted by Leopoldo Costa.

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