Tuesday, 23 December 2008

More about food and digestion

The natural and processed food Hong Kong has a lot of ready-to-eat processed food, some of the food additives is being added. Natural food contains no food additives and keep their nutrient. Conversely, the processed food lost most of their nutrients. The 4 major additives are: 1) Preservatives prevent food going bad, example are slat, sugar, vinegar and nitrites. 2) Falvouring gives a better flavour. MSG (monosodium glutamate) is commonly used. 3) Colourings makes food more attractive, some of them are man-made while some are made from natural sources. 4) Sweeteners give food sweetness. Meanwhile, some food additives may harm our health. Generally the food additives allowed by law are safe for most people, but some may have allergic on certain food substances, for example, some people may have diarrhea, vomiting, abdommal cramps after taking MSG. In conventional farming, pesticides and chemical fertilizers are added to their crops. If the product isn’t washed through, they’re harmful to our body. Organic farming avoids the use of pesticides and chemical fertilizers. They use organic fertilizers (e.g. animal manure), use crop rotation, to avoid pests and diseases and control pests biologically by introducing pest-eater in the field. Food produced by organic farming is called organic food, free from toxic chemicals, and safer to eat. GM food -- the nuclei of body contains genes, if we change some part which holding a characteristics by some virus, it becomes genetically modified organisms(GMO). The food or ingredients of GMO are GM food, and they’re available in whole or processed food in the market. They’re supposed to be safe to eat, there’s no scientific evidence showing that they aren’t safe. However, people are still worrying these years.GM foods should be labeled. Health foods are popular in these years. However, we should consider it’s function and effect, and a balanced diet, enough exercise and rest and far more important than eating those food. Our digestive system The digestion take place in our digestion system which consist alimentary canal and also some organs that secrete digestive juice. Alimentary canal -- In order, the major parts are mouth cavity, oesophagus, stomach, small intestines, large intestine, and anus. Glands including pancreas, liver, gall bladder. There’s also an appendix-- useless in digestion. In our mouth cavity (which is for chewing/ingestion, tearing the food into smaller pieces), we have 4 kind of teeth, incisors, canines, premolars and molars. Generally an adult has 32 teeth. Incisors are in chisel-shape and sharp, used for biting and cutting food, canine are pointed and used for tearing food. Premolar and molars are board top(but not flat-topped) and molars are bigger. Used for grinding food. The inside of teeth divide into several parts, enamel -- white, shiny, hard, non-living substance, protecting our teeth; dentine, under enamel, bone-like living tissue; and pulp cavity which contains nerve (temperture &pain) and blood vessel. Tooth decay -- the food debris and bacteria in the mouth forma a layer of plaque and it’s sticky and invisible. The bacteria act on sugar in the debris and produce acid, dissolving the enamel and make a hole on the teeth. The acid then destroy dentine, and pulp cavity, finally to the gum and forms a abscess for the most serious case. Periodontal disease -- There’s a layer periodontal membrane. Toxins from the plaque destroy those membrane and form a periodontal pockets. At Last the teeth become loose and swollen gum appeared, bleeding is also easy to occur.

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