Nutritional science investigates the metabolic and physiological responses of the body to diet. With advances in the fields of molecular biology, biochemistry, nutritional immunology, molecular medicine and genetics, the study of nutrition is increasingly concerned with metabolism and metabolic pathways: the sequences of biochemical steps through which substances in living things change from one form to another.
The human body contains chemical compounds, such as water, carbohydrates (sugar, starch, and fiber), amino acids (in proteins), fatty acids (in lipids), and nucleic acids (DNA and RNA). These compounds in turn consist of elements such as carbon, hydrogen, oxygen, nitrogen, phosphorus, calcium, iron, zinc, magnesium, manganese, and so on. All of these chemical compounds and elements occur in various forms and combinations (e.g. hormones, vitamins,phospholipids, hydroxyapatite), both in the human body and in the plant and animal organisms that humans eat.
The human body consists of elements and compounds ingested, digested, absorbed, and circulated through the bloodstream to feed the cells of the body. Except in the unborn fetus, the digestive system is the first system involved. In a typical adult, about seven liters of digestive juices enter the lumen of the digestive tract. These digestive juices break chemical bonds in ingested molecules, and modify theirconformations and energy states. Though some molecules are absorbed into the bloodstream unchanged, digestive processes release them from the matrix of foods. Unabsorbed matter, along with some waste products of metabolism, is eliminated from the body in the feces.
In general, eating a wide variety of fresh, whole (unprocessed), foods has proven favorable for one’s health compared to monotonous diets based on processed foods. In particular, the consumption of whole-plant foods slows digestion and allows better absorption, and a more favorable balance of essential nutrients per Calorie, resulting in better management of cell growth, maintenance, and mitosis (cell division), as well as better regulation of appetite and blood sugar. Regularly scheduled meals (every few hours) have also proven more wholesome than infrequent or haphazard ones, although a recent study has also linked more frequent meals with a higher risk of colon cancer in men.
WHAT TO LEARN IN THIS UNIT?
The meaning of nutrition in living beings: nutrition as an exchange of matter and energy. Humans as heterotrophs.
Overview of the nutrition in humans; organ systems involved (digestive system, respiratory system, circulatory system and excretory system).
The digestive system anatomy: alimentary canal and accessory glands.
Stages of the digestive system work: ingestion, digestion (types, stages, enzymes), absorption and elimination.
Ventilation and respiration as contributing processes to human nutrition.
The respiratory system anatomy: respiratory pathways, lungs, ribcage.
The respiratory system physiology: breathing movements, gas exchange, breathing rhythm control.
Components of the blood: plasma and blood cells (types and functions).
The cardiovascular system: blood vessels (types and roles); the heart (structure and function); cardiovascular circuits.
Overview of the lymphatic system.
The urinary system: its role in homeostasis and waste disposal; structure and function of the kidney; structure and function of the nephrons; composition of the urine as compared to the blood.
The sweat glands: their role in homeostasis and waste disposal; composition of the sweat as compared to the blood.
Types of nutrients.
Types of foods.
Balanced diets; basal metabolic rates.
Specific diets: for weight management, for sports, for longevity.
Food conservation, manipulation and marketing.
Food production enhancement methods and their consequences: fertilisers, pesticides, herbicides, intensive farming, GM foods.