Nutrition relates to the ingestion, absorption and assimilation of food in sufficient quantity of sufficient quality. That last sentence describes both what nutrition is about and the many areas in which things can go wrong. Clinical nutrition relates to the therapeutic uses of nutritional substances (whole foods and/or supplements) targeted at specific, assessed needs, to restore and maintain health.
Ingestion means that the food must be able to be consumed. Mostly this happens normally enough, but sometimes, due to marked health deterioration, malformation, trauma or surgery, this isn’t possible. In such cases alternative means must be used to ensure adequate nutrition is taken in. These can include enteral (tube feeding, whether naso-gastric or gastrostomy) and parenteral (intravenous, whether peripheral or central, such as hyperailementation or total parenteral nutrition) methods. Naturally, hydration needs must also be met.
Foods eaten normally must be absorbed. This takes place at least to some limited degree throughout much of the gastrointestinal system, but principally takes place in the small bowel. Clinical and subclinical pathology of the small bowel and/or the liver and pancreas which supply essential enzymes for nutrient absorption, will diminish or prevent absorption of some or all nutrients. Sometimes problems in this area are chronic, or longstanding, and sometimes they are short term in nature.
Assimilation refers to the uptake and use throughout the body at the cellular level of the nutrients that have been absorbed. This is dependent on general health and the effectiveness of the circulatory and eliminative systems.
There is a stage in health decline where any or all three of the above critical stages in deriving benefits from nutrients becomes more difficult, and ultimately impossible. By the time it is becoming difficult, adjunctive therapies will be necessary to restore health with nutrition. That is, if left too late, clinical nutrition is not effective by itself.
The notion of sufficient quantity is important. Not everyone is able to absorb and assimilate at the same rate or level and individuals do vary in their capacity to deal with different nutrients. So enough of each nutrient, allowing for the individual variability, must be consumed. Equally, too much can be harmful. There is the problem of associated energy consumption (calories or kilojoules) which can lead to obesity and the related problem of blocking the absorption (or ingestion) of nutrients due to the excess of less nutrient rich and balanced foods. Aditionally, some nutrients can themselves cause problems if taken to excess, such as vitamin A.
This leads us to quality. Hopefully it is obvious that the nutrient rich foods and supplements consumed must be of sufficient quality to ensure effectiveness when used by the cells. Garbage in, garbage out may be an appropriate phrase when it comes to information technology, but applied to human nutrition, long term garbage in and I’m afraid you’re out.
