THE ALIMENTARY SYSTEM
1.0 FOOD AS RIZQ
Food is needed for energy, growth, repair, and maintenance of the body. The Qur'anic term rizq means sustenance. It refers to to food useful to the body. Rizq is from Allah alone and He provides for all. The alimentary canal is a tube outside the body in direct contact with the external environment. Some food ingested at the mouth exits at the anus without entering the body. Digested food is absorbed by the intestines to enter the internal environment. The alimentary canal has a role in balancing the internal and external environments. It takes material from the environment, processes it, and returns it to the environment. Human appetite for food (a requirement for survival) is so strong that prayer is delayed when food is presented. Nutritional habits reflect underlying visions, beliefs, and cultural experiences. The alimentary system can be looked at as the final pathway for human corruption because food security is the underlying but often unstated purpose behind crime, corruption, treachery, amassing of wealth, aggression, and many other transgressions. Believer eat to get energy for ‘ibadat; non-believers may eat for enjoyment or to get energy for evil. A believer is satisfied with less food than a non-believer. The search for food and its ingestion is part of ‘ibadat. The human is rewarded for efforts to feed himself or herself. The ‘ibadat aspect is emphasized by the fact the feeding starts with the basmalah and end with the hamd. Fasting of Ramadhan is one the major acts of obligatory physical ibadat. It serves the functions of cleansing and protecting the body.
2.0 DIGESTION AND ABSORPTION:
Digestion takes place in the mouth, the stomach, and the intestines. The prophet taught measures to prevent oral infections: rinsing the mouth after a meal and use of the tooth-pick. He taught stopping to breathe during drinking because of deglutition apnea. The Qur'anic term batn refers to the whole gastro-intestinal tract or the whole internal cavity and not only the anatomical stomach. Humans have to eat at intervals because of limited internal food storage. The limited storage enables them to engage in ibadat and other activities of human civilization without having to eat continuously. Besides its digestive function, the stomach acts to warn humans of impending starvation by its hunger pangs. The Qur'an mentioned the intestine as being destroyed by bad food.
The alimentary system separates the nutritious food to be absorbed from the non-nutritious one to be eliminated as waste. It protects the environment by detoxifyting ingested toxins or detoxifying metabolic products before elimination into the ecosystem. Feces are considered filth (najasat) largely because of their content of infective and toxic material. Proper disposal of excreta at both the individual and community levels is a mark of civilizational development. Islam started with a revolution in hygiene by teaching proper toilet etiquette and cleaning with water in both wudhu and ghusl. Hygiene is a pre-requisite for many humans to live together (civilized existence) because it prevents infectious and toxic disease.
The complex human food in all its varieties is in the final analysis reduced to a few chemical compounds after digestion (amino acids, glucose, and fatty acids). They are all finally reduced to Acetyl CoA that enters the Krebs cycle. The main purpose of the metabolic processes is to generate energy from food. The liver is the chemical intermediary between the alimentary system and the rest of the body. It is responsible for maintenance of the body's chemical and metabolic homeostasis. It is the great factory involved in both anabolism and catabolism. The liver is also the great protector of the body by detoxifying toxic substances from the alimentary tract.
5.0 GIT and NUTRITIONAL DISORDERS
The diseases of over-nutrition are obesity, diabetes mellitus, ischemic heart disease, and atherosclerosis. The prophet taught the rule of the thirds as a guide for food intake: one third for solid food, one third for water, and one third empty (Musnad Ahmad). He taught that Muslims do not eat until they are hungry and when they eat they do not fill their belly. Ibn al Qayim defined three levels of food: necessary, hajat, sufficient, kifayat, and excess, fadhlat. The necessary is for maintenance of life and health. The sufficient is for psychological satisfaction. The excess is harmful. Obesity is a result of excessive intake without matching physical exercise. In a hadith reported by Aisha, the prophet described obesity as one of the signs of social degradation.