Nutrition: The Proteins and Amino Acids

Describe the consequences of consuming too much or too little protein.

Let's first look at too little protein. If you consume too little protein, you can become malnourished, If you consume too little protein, that can lead to slow growth because protein is used in growth and maintenance. Too little protein—the immune system can become impaired because the body doesn't have enough protein to make antibodies or other immune compounds that are needed for the immune system to function correctly. You can get impaired nutrient absorption because the body can't make the transport proteins. Think about lipoproteins that are used to transport lipids or the protein that I talked about in another video hemoglobin, used to transport oxygen or the proteins themselves that move nutrients in and out of cells. So if you don't have a sufficient intake of protein, part of the malnutrition is you get poor absorption of other nutrients as well. And then you can also have brain and kidney function can become impaired. Decreased growth Decreased disease resistance and increased susceptibility to infections Loss of muscle tissue - > weakness Edema Kidney & heart problems Apathetic, listless Too much: when you eat excess protein, that protein is broken down in the body, so protein—the body takes the protein, it clips off the amino acids, and remember that through the process of deamination it removes the nitrogen group from the amino acid. And once that nitrogen group is removed, you can't use the component parts to build proteins anymore. You need that nitrogen group. I often joke with people that drink a lot of high-protein beverages that they're just creating very expensive urine, because that excess protein is going out in the urine. When we eat excess protein, and we remove that nitrogen group, remember that the amino acid—the side chains of the amino acids can be converted to glycogen or fat for storage. Now high intake of protein has been studied in various conditions. Studies looking at heart disease showed that excess protein does not cause heart disease, but some high-protein foods may lead to heart disease. Think about a really fatty meat. We know that the saturated fat can lead to heart disease. The kidney is an important organ in the breakdown of excess protein. It's used in the production of urea from the amine groups. And in humans, increased protein leads to an increased kidney workload, but it doesn't damage or cause kidney disease. But if a person has kidney disease, high protein diets can speed up the decline of the kidneys. Now in subjects—in studies where subjects consumed high amounts of purified proteins, people would lose calcium in the urine, so this we had researchers wonder if too much protein was related to bone loss. However, unlike purified protein, which is a protein given in a research condition—the protein from food, from milk, meat, legumes, et cetera—that does not increase the calcium loss from bones, and we do know that inadequate protein is known to weakened bones. You need a sufficient amount of protein to have healthy bones. Protein intake has also been studied for any relationship to cancer. And protein as a whole has no link to cancer, but some high-protein foods have been linked to cancer, such as red meats and processed meats like hot dogs, sausage, lunch meats, et cetera. Just remember that most Americans get plenty of protein, but if you follow the USDA protein—the USDA Eating Plan, you'll get just the right amount of protein. Get a variety, lean meats, seafood, lean poultry, eggs, legumes (peas and beans), nuts, seeds, and soy products.

Characterize foods in terms of protein amount and quality and also identify proteins that are complementary.

high quality proteins provide essential amino acids and the amounts needed by the body to make the proteins that you need. And low quality protein foods are limited in one or another essential amino acid. Animal products, or animal proteins, are the highest quality proteins. Legumes—such as black beans, pinto beans, kidney beans, soy—are moderate quality proteins, and your plant foods including your grains and vegetables are lower quality protein. high-quality protein from animal foods or a complete protein will give you that complete amino acid profile. legumes and wheatgrain or a nut with a legume. For example, tortillas—could be a corn tortilla, that's a grain, or it could be a wheat tortilla, made from wheat is a grain—you eat that with beans, and you've combined a grain and a legume. Or rice, which is a grain, and lentils, which is a legume, or pita bread, which is generally made from wheat, and hummus. Hummus is made from the legume chickpeas, or garbanzo beans, or bread which is often made from wheat or you could have it made from other grain products, and peanut butter. Did you know that peanuts are actually a legume? They're not a nut. They grow in the ground like other legumes. Nuts are tree nuts such as walnuts, almonds, or pecans, so just remember that peanuts are a legume not a nut. high quality proteins because they contain all the essential amino acids and they are easily digested. Notice that complete proteins all come from animals. Meat Fish Poultry Cheese Eggs Milk low quality proteins: Legumes: Legumes are dried beans such as kidney, navy, red, white beans, etc. Peanuts are legumes, so peanut butter is also in this class. Soybeans are a legume—their amino acid composition is better than the amino acid pattern of other dried beans, but not quite as good as the animal proteins' quality. Vegetables: Vegetables have less protein than either legumes or grains, but their amino acid pattern is similar to that of legumes. Green beans, whose seeds are immature, are classified with the vegetables, not with the legumes. Grains: Wheat, rice, corn, oats, barley, and rye are the most common examples in the North American food pattern.

List and describe the roles of protein in the body and explain nitrogen balance.

Amino acids must be continuously available to build the proteins of new tissue. ess obvious is the protein that helps to replace worn-out cells and internal cell structures. Each of your millions of red blood cells lives for only 3 or 4 months. Then it must be replaced by a new cell produced by the bone marrow.Amino acids conserved from these processes provide a great deal of the required raw material from which new structures are built. The entire process of breakdown, recovery, and synthesis is called protein turnover.regulation of gene expression great deal of the body's protein (about 40 percent) exists in muscle tissue. Specialized muscle protein structures allow the body to move. In addition, muscle proteins can release some of their amino acids, should the need for energy become dire, as in starvation.Among proteins formed by living cells, enzymes are metabolic workhorses. An enzyme acts as a catalyst: it speeds up a reaction that would happen anyway, but much more slowly. Acid-base balance. Proteins help maintain the acid-base balance of various body fluids by acting as buffers. Antibodies. Proteins form the immune system molecules that fight diseases. Blood clotting. Proteins provide the netting on which blood clots are built. Energy and glucose. Proteins provide some fuel for the body's energy needs. Enzymes. Proteins facilitate needed chemical reactions. Fluid and electrolyte balance. Proteins help to maintain the water and mineral composition of various body fluids. Gene expression. Proteins associate and interact with DNA, regulating gene expression. Hormones. Proteins regulate body processes. Some hormones are proteins or are made from amino acids. Structure and movement. Proteins form integral parts of most body tissues and confer shape and strength on bones, skin, tendons, and other tissues. Structural proteins of muscles allow body movement. Transport system. Proteins help transport needed substances, such as lipids, minerals, and oxygen, around the body. Under normal circumstances, healthy adults are in nitrogen equilibrium, or zero balance; that is, they have the same amount of total protein in their bodies at all times. When nitrogen-in exceeds nitrogen-out, people are said to be in positive nitrogen balance; somewhere in their bodies more proteins are being built than are being broken down and lost. When nitrogen-in is less than nitrogen-out, people are said to be in negative nitrogen balance; they are losing protein.

Describe celiac disease, including what happens in the digestive tract, the consequences, how it is diagnosed, and what foods need to be avoided.

Celiac disease is an autoimmune disease in which people are intolerant to a protein called gluten. It's an autoimmune response to the protein gluten found in wheat, rye, barley, and sometimes in contaminated oats. When people with celiac disease eat gluten, it damages the villi in their small intestine. The villi in the small intestine are flattened and destroyed as you can see on the picture on the right. This damage affects the ability to absorb nutrients properly. Persons with celiac disease can become malnourished because of the nutrient malabsorption. Remember that celiac disease is an autoimmune disease not an allergy. And celiac disease can develop at any point in life: infancy to adulthood. Some symptoms in the GI tract include abdominal pain, constipation, diarrhea, nausea and vomiting, and foul-smelling stools. Persons with celiac disease can also get a secondary lactose intolerance. If you recall from our discussions in the carbohydrate section, lactose intolerance happens when you are missing or don't have enough of the enzyme lactate. In celiac disease, because the enzyme that breaks down lactose is produced in the villi, when the villi are damaged, they can't make that enzyme lactase anymore. The lactose intolerance goes away when the person with celiac disease stops eating gluten and the villi improve. The skin is often involved in the autoimmune response related to celiac disease. People with celiac disease can get an itchy skin condition and a rash called dermatitis hepataphormis. Systemically, people can have weight loss due to poor absorption of nutrients. They can have fatigue due to a lack of energy absorption from food. They can get hair loss because protein and other nutrients aren't available due to malabsorption. And some people actually have depression. Diagnosis of celiac disease is done by a blood test and a biopsy. The blood test looks at different antibodies: one is called tissue transglutaminase antibodies, and then other antibodies are called IGG and IGA antigliadin antibodies. You do not need to know the names of these antibodies. Positive results on these blood tests are positive, but negative results in the blood tests can be false. The gold standard for diagnosing celiac disease is a small bowel biopsy. When a biopsy is done, tiny pieces of the small intestine are clipped out and removed and then sent to a lab to check for damage to the villi. The treatment for celiac disease is following a gluten-free diet. That means no wheat, rye, or barley. Oats do not contain gluten. However, they are commonly contaminated. So people with celiac disease would want to check that their oats are labelled as gluten-free. There are grains derived from wheat, rye, and barley that people with celiac disease should be aware of. Some names include triticale, durum, graham (like a graham cracker), kamut, semolina, which you see often in pasta and spelt among some. Also malt and malt flavorings are made from barley. People with celiac disease need to be very careful about contamination. There are complications if somebody with celiac disease does not follow the diet. The first we listed here are related to the malabsorption of nutrients. So people with celiac disease could get bone disease, anemia, or low blood sugar because they're malabsorbing calcium, iron, or even glucose. Because celiac damages the villi, if it goes untreated, people with untreated celiac disease have a higher risk of developing certain types of intestinal cancers. And then we've also seen higher incidents of infertility and miscarriage and liver disease for people who have celiac disease and it goes untreated. Celiac disease is an autoimmune response to the protein "gluten" found in wheat, barley, and rye. As a result of this, the villi in the small intestine are flattened and destroyed, thus negatively affecting nutrient absorption. Symptoms of celiac disease can include nausea, vomiting, diarrhea, and reduced growth in children. Celiac disease can only be definitely diagnosed through blood test (they look for specific types of immune factors) and an intestinal biopsy that reveals the damaged villi. Treatment is life-long avoidance of gluten-containing foods and any products made from them. You will be given a chance to identify foods someone with celiac disease could safely eat in the Celiac Menu Activity.

Describe protein digestion, absorption, and metabolism.

During the digestion of a food protein, the stomach acid opens up the protein's structure, permitting digestive enzymes to make contact with the peptide bonds and cleave them. Denaturation also occurs during the cooking of foods. Each protein performs a special task in a particular tissue of a specific kind of animal or plant. When a person eats food proteins, whether from cereals, vegetables, beef, fish, or cheese, the body must first alter them by breaking them down into amino acids; only then can it rearrange them into specific human body proteins.Other than being crushed and torn by chewing and moistened with saliva in the mouth, nothing happens to protein until it reaches the stomach. Then the action begins. In the Stomach Strong hydrochloric acid produced by the stomach denatures proteins in food. This acid helps to uncoil the protein's tangled strands so that molecules of the stomach's protein-digesting enzyme can attack the peptide bonds. You might expect that the stomach enzyme, being a protein itself, would be denatured by the stomach's acid. Unlike most enzymes, though, the stomach enzyme functions best in an acid environment. Its job is to break other protein strands into smaller pieces. The stomach lining, which is also made partly of protein, is protected against attack by acid and enzymes by its coat of mucus, secreted by its cells.By the time most proteins slip from the stomach into the small intestine, they are denatured and cleaved into smaller pieces. A few are single amino acids, but the majority remain in large strands—polypeptides. In the small intestine, alkaline juice from the pancreas neutralizes the acid delivered by the stomach. The pH rises to about 7 (neutral), enabling the next enzyme team to accomplish the final breakdown of the strands. Protein-digesting enzymes from the pancreas and intestine continue working until almost all pieces of protein are broken into single amino acids or into strands of two or three amino acids, dipeptides and tripeptides, respectively (see Figure 6-7). Figure 6-8 summarizes the whole process of protein digestion.The cells of the small intestine complete digestion, absorb amino acids and some larger peptides, and release them into the bloodstream for use by the body's cells.

State the AMDR for protein. Calculate an individual's recommended protein intake (DRI).

For adults of healthy body weight, the DRI recommended intake is set at 0.8 grams for each kilogram (or 2.2 pounds) of body weight (see Dietary Reference Intakes (DRI)). The minimum amount is set at 10 percent of total calories, although some evidence suggests that certain groups of people, such as the elderly, may need more than this minimum for optimal health.Footnote Athletes may need slightly more protein—1.2-1.7 grams per kilogram per day—but even this amount is provided by a well-chosen eating pattern with enough energy for an athlete (see Chapter 10). 10-35 percent of calories The RDA for protein is just 0.8 grams of protein per kilogram per day. And the AMDR for protein, which you already learned, so the Acceptable Macronutrient Distribution Range, is that 10 to 35 percent of your calories should be coming from protein. The upper range of this is really how many calories you would have from protein if you ate the lowest percent of calories from carbohydrate and fat. And so the bottom range is your minimum. You don't need to go up to the upper range. In fact, the World Health Organization recommends that 10 to 15 percent of your calories should come from protein. The RDA of 0.8 is considered a minimum where the—while the AMDR is a range with a minimum and an upper amount. The average American probably consumes about 17% of their calories from protein. That equates to about 95 grams of protein for men and about 65 grams of protein for women.https://byu.instructure.com/courses/1424/files/248108/download?wrap=1

Describe the structure of proteins and explain why adequate amounts of all the essential amino acids are required for protein synthesis.

The structure of proteins enables them to perform many vital functions. One key difference from carbohydrates and fats is that proteins contain nitrogen atoms in addition to the carbon, hydrogen, and oxygen atoms that all three energy-yielding nutrients contain. These nitrogen atoms give the name amino (which means "nitrogen containing") to the amino acids, the building blocks of proteins. Another key difference is that in contrast to the carbohydrates—whose repeating units, glucose molecules, are identical—the amino acids in a strand of protein are different from one another. A strand of amino acids that makes up a protein may contain 20 different kinds of amino acids.

Identify the strengths and limitations of vegetarian and meat-containing diets.

When we look at a vegetarian diet versus a meat-containing diet, both of these diets can be healthy and both of these diets can be unhealthy, depending on the foods the person chooses. So if a meat-eater chooses high-fat meat, which you see on that top left corner, they can lack nutrients if they're not having vegetables and fruits and grains along with that, and get a lot of fat. But, if they choose to eat the proportions of meat recommended in the USDA guide along with vegetables, fruits, and grains, the diet can be healthy. The same is true for vegetarian eating. If a person chooses high fat vegetarian foods such as french fries or fried vegetables, or if they're a vegetarian that eats dairy products, then they put a lot of melted cheese over things, that's not healthy. But, if they eat a variety of food, including vegetables, grains, fruits, and non-animal protein foods like beans or legumes, the diet can be healthy. Some benefits of vegetarian eating that have been shown in research show a reduced risk for heart disease, cancer, and high blood pressure. We also see these same benefits in meat-containing diets when people follow the eating pattern guidelines. Meaning they choose lean meats, they have small portions, and they contain a sufficient amount of fruits and vegetables and whole grains. If you recall the 2015 dietary guidelines that you learned about back in Lesson 2, there is a USDA eating pattern for vegetarians. It does include dairy, and then it includes protein foods from eggs, legumes, nuts, and soy. There are few nutrients of concern when people follow a vegetarian diet. The first is protein, but vegetarians can easily get a sufficient amount of protein by including non-meat containing protein foods, such as beans and legumes and nuts, and then also include a variety of vegetables and grains. Another concern is getting a sufficient amount of omega-3 fats. So if you remember in the lipids section, we learned that the best source of omega-3 fats is fatty fish. However, you can get omega-3 fats from plant sources such as canola oil or flax seeds. The body just needs to do some conversion. So vegetarians should make sure they include good plant sources of omega-3 fats in their diets. Vitamin B12 is a vitamin that's only present in animal products and in small amounts in soy products. So vegetarians can get vitamin B12 in fortified products; soy milk, breakfast cereals, and supplements are probably the best sources. Although soy beans have a little bit of vitamin B12, it's very poorly used. And so it doesn't provide sufficient amount unless that soy milk or other soy products are fortified. Vitamin D—the main source of vitamin D is milk. So for those people who don't drink milk as part of their vegetarian diet, they should probably pay attention to vitamin D. The body can actually create vitamin D from sun exposure. Most people can meet their vitamin D needs with about 20 minutes of sun exposure each day. However, if you live in a northern area, which includes most of the US and Canada or any countries that are above those lines as well, you can't get enough sun exposure during fall and winter due to the angle of the sun. So vegetarians may need to choose fortified foods, meaning foods that are fortified with vitamin D. You can often find that in soy milk or cereals; cold cereals often are fortified with vitamin D. They can also take a supplement. Calcium is another nutrient of concern because the best source of calcium is dairy products. There are plant sources of calcium, including kale, broccoli, dried beans, and almond. However, the calcium in plant sources is poorly absorbed. So vegetarians should choose plant sources of calcium, but because it's hard to get enough calcium from plants, they should also consider some calcium-fortified foods, such as a calcium-fortified orange juice, or even a calcium-fortified soy milk. The best source of zinc is red meats, but plants such as whole grains, nuts, dried beans, and fortified cereal can provide zinc for vegetarians. There are a couple of other nutrient concerns for vegetarian diets. Pregnant women have a higher need for many vitamins and minerals, and so pregnant women who follow a vegetarian diet will probably need a supplement. And children on a vegetarian diet can have a concern with getting enough calories. If the vegetarian or vegan diet that the child is following is really high in fiber, a lot of little kids will fill up from the fiber before getting sufficient calories. So their diets should be carefully planned to assure that they are getting a sufficient amount of calories. Here are some tips for vegetarian meal planning. First is to choose a variety of foods. Second is to choose calcium-rich foods, such as almonds, fortified-soy juice, fortified soy milk or fortified juice, or cereals. If a vegetarian is a lacto-vegetarian, they could include cow's milk or other cow's milk and dairy products. And also vegetables such as bok choy, broccoli, and kale. They also need to choose foods that are high in omega-3 fats. That includes some oils such as canola oil; some nuts and seeds will also help provide some omega-3 fats. Should be aware of getting an adequate amount of vitamin D and fortified foods, or eggs or milk if they're a lactoovo vegetarian. And they need to choose sources of vitamin B12 each day, such as fortified cereals, supplements, or there's even something called a nutritional yeast that they use. And remember that you can always check the 2015 USDA dietary guidelines for a meal-planning guide for vegetarian diets. Vegetarian and Vegan diets have been shown to be high in fiber, fruits, and vegetables and low in saturated fats, and to have lower risk of obesity and chronic diseases. However, because of limiting meat products in the diet (especially among those consuming a vegan diet), intakes of calcium, iron, zinc, vitamins B12 and D may be low. As a side note, omnivore diets can also have the same health benefits of decreased risk of obesity and chronic diseases if they consume a diet that meets MyPlate recommendations.