Human digestive system is distinctively different from herbivores and carnivores. Herbivores normally have longer digestive system compared to human and herbivores have digestive anatomy and bacteria symbiosis that allow them to digest cellulose from plant materials. Cellulose digestion in herbivores is assisted by bacteria in the rumen (partitioned stomach) or in the cecum (hindgut fermentation) in the case of cows and horses respectively. Carnivores have shorter digestive system compared to human, as carnivore’s nutrition comes from meat that can readily be broken down by enzymes into protein and amino acids.
Human is categorized as omnivore, and human digestive system starts in the mouth cavity as an entry point of food intake into subsequent parts of the digestive system. Digestion takes place in the form of mechanical (chewing) and chemical (enzymatic) digestion process. Absorption follows the digestion process, and this is where nutrients from food are absorbed for energy generation. Nutrients consisting of sugar, protein, and lipid are used as raw materials for energy production through Krebs’s cycle in cells mitochondria.
Energy generated from Krebs’s cycle is used to fuel metabolism. Metabolism in resting state is known as basal metabolism, or minimum energy cost for living (Hulbert and Else 869). Most of higher living organisms (including human) do not stay resting all the time, so basal metabolism is always adjusted based on various conditions. Basal metabolic rate may be reduced in the case of starvation (Dulloo and Jacquet 599) and metabolic rate may increase in the case of exercise (Tunstall, Mehan and Wadley E66). Nutrition also plays significant role for growth through production of Human Growth Hormone (Rudman, Feller and Nagraj 1).
Last week’s diet consisted of milk, muffins, white bread and omelet for breakfast; rice, stir fried vegetables, and occasional double cheeseburger from a fast food restaurant for lunch; and pasta bolognaise, salad (vegetable or fruit with mayonnaise dressing), and orange juice for dinner. Occasionally, there were chocolate bars for afternoon snack. This list shows that last week’s diet contained carbohydrate from rice, bread, pasta, and potatoes (in salad); fat from milk, cheese, salad dressings and frying oil in fried food; protein from milk, egg, vegetables, beef patty, and bacon; and fiber from bread, fruits, and vegetables. There was also significant intake of sugar from the sweetened orange juice and chocolate bars. Sodium was present from the use of salt in various food items, and sodium helps glucose absorption by opening a glucose transport protein in the intestine (Mace, Affleck and Patel 379).
Last week’s diet shows that it was clearly not a vegetarian diet, as it still contains meat. Compared with USDA guidelines of healthy food (US Department of Agriculture; US Department of Health and Human Services 52), last week’s diet consists of vegetables, fruits, dairy products, and protein food groups. Last week’s diet shows that grain food group is not included in last week’s diet. Although most of last week’s diet is aligned with the healthy living pattern listed in the guideline, there are still rooms for improvements. Diet improvements may include switching the white bread to the whole grain bread or adding cereals to include grain food group representation in the diet.
Healthy eating recommendation includes maintaining calorie level at 2,000 calorie per day. Last week’s diet shows that there is a large calorie intake from sugar in chocolate bar and in sweetened orange juice. Large calorie intake also comes from cheeseburgers, as fast food often contributes to the high calorie intake (Gerend 84). Adjustments to meet the 2,000-calorie level can be made by eliminating (or reducing) fast food items, selecting non-sweetened juice, and opting to low-fat or non-fat dairy products. US Department of Agriculture; US Department of Health and Human Services show that frying fat has a major contribution to the calorie level (47), so reducing intake of fried food can also lower the daily calorie intake.
Today’s eating habit will have behavioural and physiological consequences depending on genetics, age, and physyical fitness (Ravussin and Borgadus 968). Behavioral consequences (coupled with physiological factors) may eventually manifest into obesity. Fast food eating habit formed in the adolesent age will likely to stay on to the later stage in life (Gerend 84). This will cause a build up of calorie that is used for basal metabolism and fueling various activties. Excess calorie is unused and is stored as fat for future use, but when the calorie intake is consistenly greater than the metabolic needs, the fat builds up and form a condition known as obesity. Obesity is a medical problem than can lead to other medical problems such as respiratory and cardio-vascular disease (Kopelman 641).
Physiological consequences of eating habit may include the building up of free radicals. Free radicals are naturally produced from aerobic metabolism (Fang, Yang and Wu 874), and these free radicals cause cell damages. In addition to the metabolism, free radicals can also form as a result of environmental factors such as radiation (Fang, Yang and Wu 874) and pollution. Nutrition can provide solution to neutralize these free radicals by consuming plenty of anti-oxidants. Anti-oxidants will pair with free radicals, remove free radicals and reduces the potential of cell damages. Free radical removal can be done by nutrients such as protein, vitamins, lipids, phytochemicals, and minerals (Fang, Yang and Wu 877).
This example shows that nutrients from our diet shape our health status by maintaining metabolims needs (basal or elevated); maintaining homeostasis; providing building blocks and catalysts for growth; and preventing cell damages. Therefore, maintaining quality of our food will ensure the quality of nutrient intake which will eventually improve our health status.
Works Cited
Dulloo, A G and J Jacquet. "Adaptive reduction in basal metabolic rate in response to food deprivation in humans: a role for feedback signals from fat stores." Am J Clin Nutr 68 (1998): 599-606. Print.
Fang, Y Z, S Yang and G Wu. "Free radicals, antioxidants, and nutrition." Nutrition 18 (2002): 872– 879. Print.
Gerend, M A. "Does calorie information promote lower calorie fast food choices among college students?" Journal of Adolescent Health 44 (2009): 84-86. Print.
Hulbert, A J and P L Else. "Basal metabolic rate: History, composition, regulation, and usefulness." Physiological and Biochemical Zoology 77(6) (2004): 869–876. Print.
Kopelman, P G. "Obesity as a medical problem." Nature Vol 404 6 April 2000: 635-643. Print.
Mace, O J, et al. "Sweet taste receptors in rat small intestine stimulate glucose absorption through apical GLUT2." J Physiol 582(1) (2007): 379-392. Print.
Ravussin, E and C Borgadus. "Relationship of genetics, age, and physical fitness to daily expenditures and fuel utilization ." Am J Clin Nutr 75 (1989): 968-975. Print.
Rudman, D, et al. "Effects of Humang Growth Hormone in men over 60 years old." the New England Journal of Medicine 323(1) (1990): 1-6. Online document.
Tunstall, R J, et al. "Exercise training increases lipid metabolism gene expression in human skeletal muscle." Am J Physiol Endocrinol Metab 283 (2002): E66–E72. Print.
US Department of Agriculture; US Department of Health and Human Services. Dietary guidelines for Americans 2010. Washington DC: USDA & HHS, 2010. Print.
