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Nutrition
Nutrition science studies the relationship between diet and states
of health and disease. Dieticians are Health professionals who are
specialized in this area of expertise, highly trained to provide
safe, evidence-based dietary advice and interventions.
Between the extremes of optimal health and death from starvation or
malnutrition, there is an array of disease states that can be caused
or alleviated by changes in diet. Deficiencies, excesses and
imbalances in diet can produce negative impacts on health, which may
lead to diseases such as scurvy, obesity or osteoporosis, as well as
psychological and behavioral problems. Moreover, excessive ingestion
of elements that have no apparent role in health, (e.g. lead,
mercury, PCBs, dioxins), may incur toxic and potentially lethal
effects, depending on the dose. The science of nutrition attempts to
understand how and why specific dietary aspects influence health.
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Overview
Nutrition science seeks to explain
metabolic and physiological responses of the body to diet. With
advances in molecular biology, biochemistry, and genetics, nutrition
science is additionally developing into the study of integrative
metabolism, which seeks to connect diet and health through the lens
of biochemical processes.
The human body is made up of chemical compounds such as water, amino
acids (proteins), fatty acids (lipids), nucleic acids (DNA/RNA), and
carbohydrates (e.g. sugars and fiber). These compounds in turn
consist of elements such as carbon, hydrogen, oxygen, nitrogen, and
phosphorus, and may or may not contain minerals such as calcium,
iron, or zinc. Minerals ubiquitously occur in the form of salts and
electrolytes. 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
organisms (e.g. plants, animals) that humans eat.
The human body necessarily comprises the elements that it eats and
absorbs into the bloodstream. The digestive system, except in the
unborn fetus, participates in the first step which makes the
different chemical compounds and elements in food available for the
trillions of cells of the body. In the digestive process of an
average adult, about seven litres of liquid, known as digestive
juices, exit the internal body and enter the lumen of the digestive
tract. The digestive juices help break chemical bonds between
ingested compounds as well as modulate the conformation and/or
energetic state of the compounds/elements. However, many
compounds/elements are absorbed into the bloodstream unchanged,
though the digestive process helps to release them from the matrix
of the foods where they occur. Any unabsorbed matter is excreted in
the feces. But only a minimal amount of digestive juice is
eliminated by this process; the intestines reabsorb most of it;
otherwise the body would rapidly dehydrate; (hence the devastating
effects of persistent diarrhea).
Study in this field must take carefully into account the state of
the body before ingestion and after digestion as well as the
chemical composition of the food and the waste. Comparing the waste
to the food can determine the specific types of compounds and
elements absorbed by the body. The effect that the absorbed matter
has on the body can be determined by finding the difference between
the pre-ingestion state and the post-digestion state. The effect may
only be discernible after an extended period of time in which all
food and ingestion must be exactly regulated and all waste must be
analyzed. The number of variables (e.g. 'confounding factors')
involved in this type of experimentation is very high. This makes
scientifically valid nutritional study very time-consuming and
expensive, and explains why a proper science of human nutrition is
rather new.
In general, eating a variety of fresh, whole (unprocessed) plant
foods has proven hormonally and metabolically favourable compared to
eating a monotonous diet based on processed foods. In particular,
consumption of whole plant foods slows digestion and provides higher
amounts and a more favourable balance of essential and vital
nutrients per unit of energy; resulting in better management of cell
growth, maintenance, and mitosis (cell division) as well as
regulation of blood glucose and appetite. A generally more regular
eating pattern (e.g. eating medium-sized meals every 3 to 4 hours)
has also proven more hormonally and metabolically favourable than
infrequent, haphazard food intake. |
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