The Science of Nutrition - Essay Example

The Science of Nutrition Assignment 2 Describe the process of fat hydrogenation, and discuss its advantages and disadvantages Hydrogenated fats are oils that are processed through a chemical hardening process to attain higher amount of stiffness of the liquid oils at room temperature. Fully hydrogenated oils have natural saturated fats left intact and all the remaining mono and polyunsaturated fatty acids are converted from their fluid configuration to a full Trans-fat rigid configuration. [7] The hydrogenation process employs three elements. 1. High heat 2. A metal catalyst such as nickel, zinc, copper, or other reactive metals 3. Hydrogen gas. The metals are used to react with the hydrogen gas which is bubbled up through the mixture. The metal catalyst is used to react hydrogen and carbon atoms and convert them into fatty acids by turning over one of the attached hydrogen molecules and rotating it half the diameter of the carbon chain. This creates a new molecular shape resulting in a stiffer and a firmer material changing from a liquid to either a semi-solid or solid substance. [7] Advantages of hydrogenation [10] It produces solid fats which are more stable, more convenient to handle and use and has a better taste and flavor. The hydrogenated oils supply more energy than vegetable oils as such. Disadvantages of hydrogenation [10] It eliminates most of the essential fatty acids as the latter polyunsaturated fatty acids. Excessive use of hydrogenated oils causes obesity which results in many problems such as blood pressure, increased cholesterol etc. List strategies for lowering fat intake with minimal impact in the diet palatability Five different strategies have been developed to lower the intake of fats while keeping normal diet palatability. [14] 1. Replace whole and 2% fat milk with skimmed mild 2. Replace whole milk with low-fat/2% milk 3. Replace higher fat cuts with medium-fat meat 4. Replace higher fat cuts with lean meat 5. Replace full-fat products with fat-modified products Some specific strategies include [6] 1. Consume little or no fried foods (the baked, broiled, or boiled equivalent is OK). 2. Stay away from prepared meats (bologna, salami, bacon, sausage, etc.). 3. Limit the consumption of visible fats (butter, margarine, fat surrounding steak, chicken skin, etc.) Describe the processes involved in cellular protein synthesis. How would synthesis be affected by intake of an otherwise adequate diet that is very low in glycine or low in tryptophan How would synthesis be affected by a diet that is low in energy Proteins are widely used in cells to provide different functions such as providing structural support for cells or to act as enzymes to catalyze certain reactions. Since the beginning of evolution, cells have developed the ability to synthesize proteins. To manufacture proteins, cells follow a very systematic procedure that first transcribes DNA into mRNA and then translates the mRNA into chains of amino acids. The amino acid chain then folds into specific proteins. [11] These two processes are 1. DNA Transcription Protein synthesis initiates in the cell's nucleus when the gene encoding a protein is copied into RNA. Genes, in the form of DNA, are rooted in the cell's chromosomes. The process of transferring the gene's DNA into RNA is called transcription. Transcription helps to increase the amount of DNA by creating many copies of RNA that can act as the template for protein synthesis. The RNA copy of the gene is called the mRNA. After transcription, the mRNA is transported out of the cell's nucleus through nuclear pores to go to the site of translation, the rough endoplasmic reticulum. [4] 2. RNA Translation After the mRNA has been taken to the rough endoplasmic reticulum, it is fed into the ribosomal translation machineries. Ribosomes begin to read the mRNA sequence to convert the mRNA into protein. The mRNA sequence is matched three nucleotides at a time to a complementary set of three nucleotides in the anticodon region of the corresponding tRNA molecule. Opposite the anticodon region of each tRNA, an amino acid is attached and as the mRNA is read off, the amino acids on each tRNA are joined together through peptide bonds thus building the protein. [12] A diet deficient in tryptophan results in a reduction in the synthesis of skin collagen. In addition, it also increases the specific activity in liver proteins subsequent to injecting a higher dose of glycine than on an adequate diet of tryptophan. [9] In the case of taking a diet low on energy the thymus and spleen organ wet weights and DNA content decreases as compared with diets of high protein. [3] List the advantages of a vegetarian diet. What nutrient requirements are more difficult to meet on this diet, and what precautions are needed to prevent insufficient intakes in the child and in the adult A vegetarian diet has been proclaimed as one of the best diets. The reasons why it is declared this way are given below. [1] Longevity - A longer life Less Heart Disease - Because of the low fat, saturated fat and cholesterol content of the vegetarian diet the risk of heart disease is lowered. Less Cancer - Cancer death rates have been associated with obesity and high-fat/low-fiber diets (a low in fruits, grains, and vegetables, but high in animal products). Less Bowel Disease - Diverticular disease and appendicitis appear more frequently with lower fiber intakes. High fiber diets increase the ease with which the food can pass through the system and decrease the transit time from mouth to anus. Less Osteoporosis - Lower protein intake and a higher vitamin D and calcium intake may contribute to higher bone density Less Obesity - The fiber in plant foods dilutes the energy and provides a satisfying meal without all the calories. Less Hypertension Endurance - The best sources of food for endurance exercise are the carbohydrate foods There are some areas of concern regarding the essential elements provided by the vegetarian diet. [1] 1. Calcium: Milk is the real source for calcium and people following a vegetarian diet cannot meet the whole calcium need just from calcium provided by plants. 2. Iron. A vegetarian diet is low on iron than the one that includes meat 3. Minerals and Fiber. Vegetarian diets are usually higher in fiber than non-vegetarian diets. Although there is a positive effect of dietary fiber, sometimes the fiber can bind minerals and stop them from being absorbed into the blood stream. 4. Vitamin B12. Vitamin B12, which is necessary for the development of red blood cells and the brain, may not get it from a vegetarian diet since Vitamin B12 is found only in foods from animals. A total vegetarian diet can be very unwieldy and young children may not be able to eat enough to meet their energy needs. Even for adults certain important elements can not provided just by keeping to a vegetarian diet. Therefore vegetarian diets for young children and adults alike should be carefully planned making sure to include energy dense foods such as nuts, legumes, grains, and dried fruits. [1] Assignment 3 Discuss ways in which the body's metabolism adapts to conditions of fasting/ starvation. How do these adaptations affect the rate of weight loss when dieting Metabolism rate adapts to the conditions of fasting as time increases. During fasting, metabolic rate falls gradually and after a month of total fasting, the metabolic rate is reduced up to 30% leaving fat as the only source of body's fuel. Total energy expenditure falls because of a reduction in spontaneous activity and also the absence of diet induced thermogenesis. The resting metabolic rate falls, due to a reduction not only in the metabolically active cell mass of the body, but also in cellular metabolism. Although a direct relationship can be shown between alterations in thyroid status and resting metabolic rate, it is less clear that the changes in thyroid hormone levels during starvation can explain the observed changes in resting metabolic rate. On the other hand, there may be interactions between the sympatho-ad renal system and thyroid status that potentiate the changes in both. The activity of the sympathetic nervous system, however, is decreased during fasting while re-feeding reverses these changes. [5] In a prolonged starvation the adaptive changes are even more interesting. From the fifth day onwards, adaptation takes place to decrease metabolic rate, not only as a function of the whole body, but per kilogram body weight or per kilogram lean body mass. At the same time, the body levels of ketones increase and the brain adapts to derive a large proportion of its energy supply from ketones, thus sparing glucose from gluconeogenesis. Both these adaptations clearly spare protein, the one by diminishing overall energy requirement, and the other by reducing the rate of production of new glucose from amino acids. Despite the continuing adaptive mechanisms inexorable weight loss and deterioration in body functions occurs. Death usually occurs at 35-45% weight loss, in those who start with a normal body mass index. [5] List the major components that contribute to the body's daily expenditure of energy. Compare and the relative contributions of a sedentary person with marathon runner of the same weight. There are three primary components that make up the body's energy expenditure. These three components are [13] Basal Metabolic Rate (BMR): Most of the body's energy, about 60-70%, goes to supporting the ongoing metabolic work of the body's cells. This includes such activities as heart beat, respiration and maintaining body temperature. Energy Expended During Physical Activity: The second component of the equation depends upon a person's level of physical activity. Physical activity contributes 20-30% to the body's total energy output. One of the most reliable methods in calculating calories burned during physical activity is the Metabolic Energy (MET) Method. Thermic Effect of Food: This last component to calculate has to do with the body's management of food. The increase in energy required to digest food is referred to as the thermic effect of food (TEF). For a person having a weight of 50kgs the contribution can be calculated as For sedentary people: Weight x 14 = estimated cal/day = 700 For active people: Weight x 20 = estimated cal/day = 1000 Under what circumstances can water-soluble vitamins be toxic Cite several examples. Water-soluble vitamins taken in overdose can result in becoming toxic for the body. Some vitamins under certain circumstances can be toxic. These are explained below. FOLATE Folate occurs in various forms in food. The folate in oral vitamin supplements occurs in only one form, however-folic acid. Large doses of folic acid (20 grams/day) can result in eventual kidney damage. [2] VITAMIN B12 Vitamin B12 is important in the treatment of pernicious anemia. Although vitamin B12 toxicity is not an issue for patients being treated for pernicious anemia, treatment of these patients with folic acid may cause problems. Specifically, pernicious anemia is often first detected because the patient feels weak or tired. If the anemia is not treated, the patient may suffer irreversible nerve damage. The problem with folic acid supplements is that the folic acid treatment prevents the anemia from developing, but allows the eventual nerve damage to occur. [2] VITAMIN B6 Vitamin B6 is clearly toxic at doses about 1000 times the RDA. Daily doses of 2-5 grams of one specific form of this vitamin can produce difficulty in walking and tingling sensations in the legs and soles of the feet. Continued mega doses of vitamin B6 can result in further unsteadiness, difficulty in handling small objects and numbness in the hands. [2] VITAMIN C The RDA for vitamin C in adults is 60 mg per day. Large doses of vitamin C are considered to be toxic in persons with a family history of or tendency to form kidney stones or gallbladder stones. [2] NIACIN The RDA for niacin is 15-19 mg per day in adults. Niacin comes in two forms, nicotinic acid and nicotinamide. Either form can satisfy the adult requirement for this vitamin. Nicotinic acid, however, is toxic at levels of 100 times the RDA. It can cause flushing of the skin, nausea, diarrhea, and liver damage. Flushing is an increase in blood passing through the veins in the skin, due to the dilation of arteries passing through deeper parts of the face or other parts of the body. [2] Describe how the body can synthesize active vitamin D with the help of sunlight. The UVB light triggers a modification of a cholesterol-related molecule located in the membrane of skin cells. The vitamin D that is created is then ejected from the membrane into the circulation system reaching the liver. Here it is transformed into 25-hydroxyvitamin D used to assess vitamin-D status. The kidney and some other tissues converts this into 1,25-hydroxyvitamin D also called calcitrol which is the most active vitamin-D metabolite. Calcitrol targets the intestine promoting calcium absorption and targets the bone where it catalyzes calcium release to help restore depleted blood calcium levels. [8] There onwards the circulating Calcitrol enters cells and complexes with the genes in the cell nucleus. This affects DNA expression leading to cell functioning and growth. Since Calcitrol maintains normal cell proliferation, it inhibits cancerous growth. Furthermore Calcitrol influences immune-cell activity by helping to explain vitamin D's seemingly beneficial role in infectious disease such as multiple sclerosis, rheumatoid arthritis, and diabetes. [8] Works Cited 1. "ADVANTAGES OF THE VEGETARIAN DIET" (2002), [Internet], Andrews University Nutrition Department, Available at , Accessed on August 5, 2007 2. Brody, Tom. (2002) "Vitamin toxicity" [Internet], Gale Encyclopedia of Medicine, Available at , Accessed on August 5, 2007 3. DECKEN, ALEXANDRA VON DER; LUND, BERNT and O'TOOLE, CAROL., "Effect of a Low Protein Diet" [Internet], Journal of Nutrition, Available at , Accessed on August 5, 2007 4. "DNA Transcription" [Internet], Think Quest, Available at , Accessed on August 5, 2007 5. "Fasting and starvation" [Internet], Danone Institute, Available at , Accessed on August 5, 2007 6. "Fat" [Internet], Nutrition for Serious Athletes, Available at , Accessed on August 5, 2007 7. "Hydrogenated Fats" [Internet], Cyber Parent, Available at , Accessed on August 5, 2007 8. Michael Holick (2003), "The UV Advantage" [Book], I Books, 224 pages, ISBN-10: 0743486471 9. NIMNI, M. E.; HOM, D; BAVETTA, L.A., "Dietary Composition and Tissue Protein Synthesis", [Internet], Journal of Nutrition, Available at , Accessed on August 5, 2007 10. "Nutrition" [Internet], Vidya Vahini, Available at , Accessed on August 5, 2007 11. "Protein Synthesis" [Internet], Think Quest, Available at , Accessed on August 5, 2007 12. "RNA Translation" [Internet], Think Quest, Available at , Accessed on August 5, 2007 13. Ruth Lahmayer (1989), "How Low Should Calories Go", The Resource For Fitness Instructors, Boston, MA, Reebok University Press 14. "Simple Strategies for Reducing Fat" (1992), [Internet], Food Insight & International Food Information Council, Available at , Accessed on August 5, 2007 Read More