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.

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, a  point that will become more important later in this chapter and in Chapters 12 and 13.

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 Provide Us with Triglycerides and Cholesterol?

As displayed in Table 5.3, 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 which we will discuss in Chapters 12 and 13.

Why Does Glycemic Index Vary Among Foods?

To understand why different carbohydrate-containing foods have a different glycemic index, we can start with the type of monosaccharide derived from a food. This is important because fructose and galactose do not raise blood glucose to the same extent that glucose does. For instance, the digestible carbohydrate in breads and potatoes is starch, which is made up of glucose. Meanwhile, milk and milk products contain lactose which is made up of glucose and galactose. Based on the difference in glucose content between starch and milk products, it is predictable that milk would have a lower glycemic index than bread.
 

Ripened fruits contain mostly fructose and glucose as well as some sucrose. For example, a medium apple contains about 8 grams of fructose and 3 grams of both glucose and sucrose. Meanwhile a medium banana contains between 5 to 6 grams of both fructose and glucose and 2 grams of sucrose. One tablespoon of honey contains 8 grams of fructose and 7 grams of glucose and less than 1 gram of sucrose, galactose, and maltose combined. So even though fruits and honey are very sweet, they will have a moderate glycemic index and load (see Table 4.4).

Glycemic load is a glycemic index adjusted for a standard serving size.
 

In addition to monosaccharide type, protein, fiber, and fat, as well as the processing of a food can influence its glycemic index. Fiber and 

fat seem to be able to slow the digestion process and thus can lower glycemic index. Certain types of fiber, often referred to as viscous fibers, can thicken the digestive contents in the stomach and small intestine, sort of like thickening up gravy with starch. This slows the digestion of carbohydrate and absorption of monosaccharides, which in turn reduces the rise in glucose.
 

Some amino acids in protein can increase the level of insulin released in response to carbohydrate and thus decrease glycemic index. Meanwhile, pasta has a lower glycemic index than what might be expected of such a high starch food. That’s because starch molecules become trapped within gluten protein networks within the dough. Thus, wheat-based pastas have a relatively lower glycemic index value than expected and relatively lower than pastas made from other grains (for example, rice or corn) which don’t contain gluten.

What Are Oligosaccharides and Starches?

Monosaccharides not only serve as building blocks for disaccharides but also for some larger forms of carbohydrates as well. The most recognizable larger carbohydrate is starch. Starch is found in varying degrees in plants and their products (for example, legumes, vegetables, fruits, and grains). It consists of large, straight and branching chains of the

monosaccharide glucose (Figure 4.1). Some shorter, branching chains of glucose can be found as well, and food manufacturers will also use these in the production of foods. The short, branching chains used by food manufacturers are often called maltodextrins and is typically derived from the partial digestion of corn starch.
 

In the human diet, we can also find a small amount of carbohydrates, called oligosaccharides, constructed from just a few monosaccharides (three to ten) linked together. Since these are found in relatively small amounts, they are not as essential to discuss. However, a few of these carbohydrates (for example, raffinose and stachyose) will require mention later on, not only for their nutritional value but for their effects within the digestive tract.
 

Plants make starch to store energy kind of like mammals store fat. Plant fibers, on the other hand, are not necessarily stored energy but serve more structural roles for plants. Like starch, fiber is also composed of straight and branching chains of monosaccharides, but their monosaccharides building block are not limited only to glucose. Fibers are discussed later in this chapter.

What Are Monosaccharides and What Foods Have Them?

Monosaccharides are as small as carbohydrates get. Said another way, monosaccharides cannot be split into smaller carbohydrates. All other carbohydrates are made up of monosaccharides linked together. For instance, disaccharides are composed of two monosaccharides linked together. The three disaccharides found in our diet, including their monosaccharide building blocks, are listed in Table 4.1. Glucose and fructose can be found in foods either independently or as part of larger carbohydrates. Fructose is what makes honey and many fruits sweet and is used commercially as a sweetener either as fructose or high-fructose corn syrup. On the other hand, while some galactose is found in certain foods, it is mostly found as part of larger carbohydrates.

What Are Nutraceuticals and Functional Foods?

The latter portion of the twentieth century was a time of great strides in modifying the way many nutritionists and health care practitioners viewed nutrition. For decades we made nutritional recommendations based upon what needed to be avoided or limited in our diet choices. The nutritional “bad guys” were fat, which evolved to saturated fat-rich foods, cholesterol, sodium, and arguably sugar. Today it is quite clear that the other side of the nutrition coin, or “what we should eat,” is probably as significant as “what we should not eat.” Nutraceuticals are substances found in natural foods that seem to have the potential to prevent disease or be used in the treatment of various disorders. Meanwhile, functional foods are the foods in which one or more nutraceuticals can be found. Nutraceutical substances include some of the more recognized nutrients such as vitamins C and E and the mineral calcium, but also include such substances as genestein, capsaicin, allium compounds, carotenoids (for example, lutein, lycopene, and zeathanxin) phytosterols, glucosamine, catechins (such as EGCG), fiber (psyllium, oat bran) (see Tables 3.5 through 3.7).
 

Nutraceuticals are nutrients in foods that can promote better health and/or support disease prevention.
 

As you may have already surmised, it is possible for a nutraceutical to be an essential nutrient. However, keep in mind that the nutraceutical

properties of certain essential nutrients may not be why they are essential in the first place. For instance, vitamin C is essential for making important molecules in our body such as collagen, yet its nutraceutical roles may be more related to its antioxidant activities, such as helping to prevent degenerative eye disorders—for example, cataracts and macular degeneration. We will spend more time discussing nutraceutical compounds in the later chapters. We are going to be hearing more and more about nutraceuticals for years to come.

What Is in My Food Besides Natural Components?

Many if not most manufactured foods contain food additives used to improve taste, texture, appearance, shelf life, safety, or nutritional value of the product. Some of the general food additive categories include: antioxidants, antimicrobials, coloring agents, emulsifiers, flavoring agents, sweeteners, pH controllers, leavening agents, texturizers, stabilizers, enzymes, and conditioners. All food additives were tested for safety
and received approval by the Food and Drug Administration (FDA). This process can take years.

How Are Nutrition Recommendations Used on Food Labels?

By law food manufacturers must follow specific guidelines on their food labels with the purpose of informing consumers of the nutritional content of the food and to protect against misleading statements on food labels. Food labels contain the Nutrition Facts (Figure 3.2), which in most cases provide at least the following information:

• a listing of ingredients in descending order by weight
• serving size
• servings per container
• amount of the following per serving: total calories, total protein, calories contributed by fat, total fat, saturated fat, cholesterol, total carbohydrate, sugar, dietary fiber, vitamin A, vitamin C, calcium, iron, sodium

As many individuals try to plan their nutrient intake, the nutrition facts also include the Daily Value (DV). The DV uses reference nutrition standards to indicate how a single serving of a food item relates to nutrition recommendation standards and include:
 

• a maximum of 30 percent total calories from fat, or less than 65 grams total
• a maximum of 10 percent total calories from saturated fat, or less than 20 grams
• a minimum of 60 percent total calories from carbohydrate
• 10 percent of total calories from protein

• 10 grams of fiber per 1,000 calories
• a maximum of 300 milligrams of cholesterol
• a maximum of 2,400 milligrams of sodium

Daily Values on food labels are designed to help people make better informed nutrition choices.
 

Furthermore, the DV for other nutrients, such as vitamins A and C, thiamin, riboflavin, niacin, calcium, and iron, are founded upon RDA-based standards and are presented in Table 3.3. However, these standards are not as specific for gender and age as the RDAs and therefore one quantity will apply to all people.
 

Daily Values are expressed as a percentage and is based on a 2,000 and/or a 2,500 calorie intake, which approximates most American’s recommended energy intake. Therefore a food providing 250 calories per serving will be listed as either 13 percent or 10 percent DV for a 2,000 and 2,500 calorie intake, respectively. Beyond the nutrition facts, food manufacturers must also follow federal guidelines for other statements they choose to make on a food label. Some of the statements are listed in Table 3.4.

What Happens to Food After It Leaves the Stomach?

The mixture of partially digested food drenched in acidic stomach juice is slowly sent into the small intestine. This portion of our digestive tract is the location of the majority of digestive enzyme activity and the absorption of nutrients. The wall of the small intestine presents a very sophisticated pattern of folds and projections. This design allows the small intestine to have an absorptive surface approximating the size of a tennis court. This allows for very efficient absorption.
 

When the food mixture is spurted into the small intestine from the stomach, it hardly resembles what we ate. Yet most of the nutrients still need further digestion to reach their absorbable state. First, bicarbonate produced by the pancreas enters the small intestine and neutralizes the acidic food mixture draining from our stomach. Then digestive enzymes that are also produced by our pancreas and bile from the gallbladder and liver make their way to the small intestine as well. These factors, along with digestive enzymes produced by the cells that line the small intestine, will complete digestion.

What Happens to Food in the Mouth?

Once food is in the mouth it is bathed in saliva. Saliva adds moisture to the food that is being chewed. This will improve the ease of swallowing. Each day we will produce about 1 to 1.5 quarts (liters) of saliva. Furthermore, saliva also contains both a carbohydrate and lipid digestive enzyme that begins the chemical digestive process. Once we swallow, food travels through the esophagus and depots in the stomach.
 

Our digestive tract is over 20 feet long and serves to chemically and physically breakdown food and absorb nutrients

How Does Food Energy Become Our Body’s Energy?

On a daily basis we acquire energy from foods in the form of carbohydrates, protein, fat, and alcohol. However, we cannot use these molecules for energy directly. These substances must first engage in chemical
reaction pathways that break them down and allow for us to capture much of their energy in a form that we can use directly. With the exception of alcohol, these food energy molecules are also stored in our body to
be used as needed.
 

To be more specific, when these energy molecules are broken down some of their energy is captured in so-called “high-energy molecules.” By far the most important high-energy molecule is adenosine triphosphate
or, more commonly, ATP. Figure 1.6 displays a simplified version of ATP. When energy is needed to power an event in our body it is ATP that is used directly. So, the energy in carbohydrate is used to generate ATP, which in turn can directly power an energy-requiring event or operation in our body. As you might expect, the release of the energy from these little molecular powerhouses is controlled. Specific enzymes are employed to couple ATP with an energy-requiring chemical reaction or event and the transfer of energy.
 

Adenosine triphosphate (ATP) is the principal energy molecule to power body activities.
 

Interestingly, not all of the energy released in the breakdown of carbohydrates, protein, fat, and alcohol is incorporated in ATP. It seems that we are able to capture only about 40 to 45 percent of the energy available
in those molecules in the formation of ATP. The remaining 55 to 60 percent of the energy is converted to heat, which helps us maintain our body temperature (Figure 1.7). The final product of the chemical reaction pathways that breakdown carbohydrates, proteins, fat, and alcohol is primarily carbon dioxide (CO2), which we then must exhale, and water (H2O), which helps keep our body hydrated.
 

Looking at the ATP molecule, we notice what looks like a phosphate

tail (see Figure 1.6). Phosphate is made up of phosphorus (P) bonded to oxygen (O) and, as indicated in its name, ATP contains three phosphates. The energy liberated during the breakdown of energy nutrients is used to link phosphates together to make ATP. These phosphate links are thus little storehouses of energy. When energy is needed, special enzymes in our cells are able to break the links between adjacent phosphate groups. This releases the energy stored within that link, which can be harnessed to drive a nearby energy-requiring reaction or process.