Nutrients
To function, the human body must have nutrients. The nutrients known to be essential for human beings are proteins, carbohydrates, fats and oils, minerals, vitamins, and water.
For good health to be maintained, a daily diet of foods must accomplish the previously mentioned three items. Foods that accomplish one or more of the three functions are called nutrients.
Essential of Nutrients for human body
An essential nutrient is a nutrient required for normal body functioning that cannot be synthesized by the body and must be obtained from a dietary source. Some categories of essential nutrient include vitamins, dietary minerals, essential fatty acids, and essential amino acids.
Different species have very different essential nutrients. Most essential nutrients are substances that are metabolically necessary but cannot be synthesized by the organism. Dietary minerals, for example, cannot be synthesized in biological systems,
so (for example) a human must obtain the iron they need to build hemoglobin from their diet. Of course, this iron is recycled, but some is inevitably lost, for example during menstruation.
Many essential nutrients are toxic in large doses .Some can be taken in amounts larger than required in a typical diet, with no apparent ill effects. Linus Pauling said of vitamin B3, (either niacin or niacin amide), "What astonished me was the very low toxicity of a substance that has such very great physiological power. A little pinch, 5 mg, every day, is enough to keep a person from dying of pellagra, but it is so lacking in toxicity that ten thousand times as much can [sometimes] be taken without harm." A similar statement can be made about vitamin C and some other vitamins.
Nature has set us up with all the equipment we need to be perfectly healthy. Health is our natural state, and ill health is unnatural. Every day our systems are exposed to literally millions of bacteria, viruses, allergens, even carcinogens, and yet our immune system has the intelligence and skill to deal with all those invaders and keep us healthy. However, when stress, inadequate nutrition, or just fatigue weaken the immune system, those same invaders may produce disease.
Every second the body is adjusting to countless thousands of changing parameters, keeping us in homeostatic balance. No matter what comes along to upset the balance, the body knows its own nature, knows what ideal temperature it should be and the correct chemistry it needs to maintain, and keeps referring back to that blueprint to maintain proper balance.