Components
and role of nutrition
Nutrition is the selection of foods and preparation
of foods, and their ingestion to be assimilated by the body. By practicing a healthy diet, many of the known health issues can be avoided. The diet of an organism is what it eats, which is
largely determined by the perceived deliciousness of foods.
A poor diet may have an injurious impact on health,
causing deficiency diseases such as scurvy and kwashiorkor; health-threatening
conditions like obesity and metabolic syndrome; and such common
chronic systemic diseases as cardiovascular
disease, diabetes, and osteoporosis
Nutrients
There are six major classes of nutrients: carbohydrates, fats, minerals, protein, vitamins, and water. These nutrient classes can be categorized
as either macro-nutrients (needed
in relatively large amounts) or micronutrients (needed
in smaller quantities). The macronutrients include carbohydrates
(including fiber),
fats, protein, and water. The micronutrients are minerals and vitamins.
The macronutrients (excluding fiber and water)
provide structural material (amino acids from which proteins are built, and
lipids from which cell membranes and some signaling molecules are built)
and energy.
- Carbohydrate
In food science and in
many informal contexts, the term carbohydrate often means any food that is particularly rich in the
complex carbohydrate starch (such
as cereals, bread, and pasta) or simple carbohydrates, such as sugar (found in candy, jams, and desserts).
Foods with high carbohydrate are often highly
processed or refined foods made from plants; including sweets, cookies and
candy, table sugar, honey, soft drinks, breads and crackers, jams and fruit
products, pastas and breakfast cereals. Unrefined foods usually contain lower
amounts of carbohydrate; including beans, tubers, rice, and unrefined fruit.[16] Foods from
animal carcass have the lowest carbohydrate but milk does contain lactose.
All carbohydrates, when it is metabolized it can
produce four Calories (kilocalories) of energy per gram.
- Fats
Despite the belief that fats are bad for you, they
are required for general health.
A molecule of dietary fat typically consists of
several fatty
acids (containing long chains of carbon and hydrogen atoms),
bonded to a glycerol.
Fats may be classified as saturated or unsaturated depending
on the detailed structure of the fatty acids involved. Saturated fats have all
of the carbon atoms in their fatty acid chains bonded to hydrogen atoms,
whereas unsaturated fats have some of these carbon atoms double-bonded, so their
molecules have relatively fewer hydrogen atoms than a saturated fatty acid of
the same length.
There are nine kilocalories in each gram of fat.
Saturated fats (typically from animal sources) have
been a staple in many world cultures for millennia. Unsaturated fats (e. g.,
vegetable oil) are considered healthier, while trans fats are to be avoided.
Saturated and some trans fats are typically solid at room temperature (such
as butter or lard), while unsaturated fats are typically
liquids (such as olive
oil or flaxseed
oil).
3. Protein
Each protein molecule
is composed of amino
acids, which are characterized by inclusion of nitrogen and sometimes
sulphur (these components are responsible for the distinctive smell of burning
protein, such as the keratin in hair). The body requires amino acids to produce
new proteins (protein retention) and to replace damaged proteins (maintenance).
As there is no protein or amino acid storage provision, amino acids must be
present in the diet. Excess amino acids are discarded, typically in the urine.
A diet that contains
adequate amounts of amino acids (especially those that are essential) is
particularly important in some situations: during early development and
maturation, pregnancy, lactation, or injury (a burn, for instance).
Sources of dietary
protein include meats, tofu and other soy-products, eggs, legumes, and dairy products such as milk and cheese. Excess amino acids from protein can be
converted into glucose and used for fuel through a process called gluconeogenesis.
4. Minerals
Dietary minerals are
the chemical
elements required by living organisms, other than the four
elements carbon, hydrogen, nitrogen, and oxygen that are present in nearly all organic molecules.
Some dietitians
recommend that these be supplied from foods in which they occur naturally, or
at least as complex compounds, or sometimes even from natural inorganic sources
(such as calcium
carbonate from ground oyster shells). Some minerals are absorbed
much more readily in the ionic forms found in such sources. On the other hand,
minerals are often artificially added to the diet as supplements; the most
famous is likely iodine in iodized salt which
prevents goiter.
a. Macrominerals
Many elements are
essential in relative quantity; they are usually called "bulk
minerals". Some are structural, but many play a role as electrolytes. Elements
with recommended dietary allowance (RDA)
greater than 200 mg/day are, in alphabetical order (with informal or
folk-medicine perspectives in parentheses):
- Calcium, a common electrolyte, but also needed structurally (for muscle and digestive system health, bone strength, some forms neutralize acidity, may help clear toxins, provides signaling ions for nerve and membrane functions)
- Chlorine as chloride ions; very common electrolyte; see sodium, below
- Magnesium, required for processing ATP and related reactions (builds bone, causes strong peristalsis, increases flexibility, increases alkalinity)
- Phosphorus, required component of bones; essential for energy processing
- Potassium, a very common electrolyte (heart and nerve health)
- Sodium, a very common electrolyte; in general not found in dietary supplements, despite being needed in large quantities, because the ion is very common in food: typically as sodium chloride, or common salt. Excessive sodium consumption can deplete calcium and magnesium,[verification needed] leading to high blood pressure and osteoporosis.
- Sulfur, for three essential amino acids and therefore many proteins (skin, hair, nails, liver, and pancreas). Sulfur is not consumed alone, but in the form of sulfur-containing amino acids
b. Trace minerals
Many elements are
required in trace amounts, usually because they play a catalytic role in enzymes. Some trace mineral elements
(RDA < 200 mg/day) are, in alphabetical order:
- Cobalt required for biosynthesis of vitamin B12 family of coenzymes. Animals cannot biosynthesize B12, and must obtain this cobalt-containing vitamin in the diet
- Copper required component of many redox enzymes, including cytochrome c oxidase
- Chromium required for sugar metabolism
- Iodine required not only for the biosynthesis of thyroxine but also - it is presumed - for other important organs as breast, stomach, salivary glands, thymus, etc. (see Extrathyroidal iodine); for this reason iodine is needed in larger quantities than others in this list, and sometimes classified with the macrominerals
- Iron required for many enzymes, and for hemoglobin and some other proteins
- Manganese (processing of oxygen)
- Molybdenum required for xanthine oxidase and related oxidases
- Nickel present in urease
- Selenium required for peroxidase (antioxidant proteins)
- Vanadium (Speculative: there is no established RDA for vanadium. No specific biochemical function has been identified for it in humans, although vanadium is required for some lower organisms.)
- Zinc required for several enzymes such as carboxypeptidase, liver alcohol dehydrogenase, and carbonic anhydrase
5. Vitamins
Some vitamins are
recognized as essential nutrients, necessary in the diet for good health. (Vitamin D is the
exception: it can be synthesized in the skin, in the presence of UVB radiation.)
Vitamin deficiencies
may result in disease conditions, including goitre, scurvy, osteoporosis, impaired immune system, disorders of
cell metabolism, certain forms of
cancer, symptoms of premature aging,
and poorpsychological health (including eating disorders), among
many others.[58] Excess
levels of some vitamins are also dangerous to health (notably vitamin A), and for at least
one vitamin, B6, toxicity begins at levels not far above the required amount.
Deficient or excess levels of minerals can also have serious health
consequences.
6. Water
The human body is
composed of 60 percent water and your brain is composed of 70 percent
water.
Water is excreted from
the body in multiple forms; including urine andfeces, sweating, and by water vapour in the
exhaled breath. Therefore it is necessary to adequately rehydrate to replace
lost fluids. Early
recommendations for the quantity of water required for maintenance of good
health suggested that 6–8 glasses of water daily is the minimum to maintain
proper hydration For
healthful hydration, the current EFSA guidelines recommend total water intakes
of 2.0 L/day for adult females and 2.5 L/day for adult males.
Malnutrition
Malnutrition refers to
insufficient, excessive, or imbalanced consumption of nutrients by an organism.
In developed countries, the diseases of malnutrition are most often associated
with nutritional imbalances or excessive consumption.
|
Nutrients
|
Deficiency
|
Excess
|
|
Low energy levels.
|
||
|
Micronutrient
deficiency
|
Obesity, cardiovascular disease (high glycemic
index foods)
|
|
|
Rabbit
starvation, ketoacidosis (in
diabetics)
|
||
|
Low testosterone
levels, vitamin deficiencies.
|
||
|
None
|
||
|
Fat-soluble vitamin
deficiency
|
||
|
Hypervitaminosis
A (cirrhosis, hair loss)
|
||
|
?
|
||
|
Skin and
corneal lesions
|
?
|
|
|
Dyspepsia, cardiac
arrhythmias, birth defects
|
||
|
?
|
||
|
Diarrhea causing dehydration
|
||
|
Hypervitaminosis
D (dehydration, vomiting, constipation)
|
||
|
Neurological disease
|
Hypervitaminosis
E (anticoagulant: excessive bleeding)
|
|
|
Liver damage
|
||
|
Bleeding,
Hemorrhages, Hemorrhagic
stroke, reduced glycemic control among diabetics
|
||
|
None
|
||
|
None
|
||
|
Weakness, nausea,
vomiting, impaired breathing, andhypotension
|
||
|
Iodine toxicity (goiter,
hypothyroidism)
|
||
List of vitamins
Each vitamin is
typically used in multiple reactions, and, therefore, most have multiple
functions.[6]
|
Vitamin
generic
descriptor name |
Recommended dietary allowances
(male, age 19–70) |
Deficiency
disease
|
Overdose
disease
|
Food sources
|
|
|
Fat
|
900 µg
|
Liver, orange,
ripe yellow fruits, leafy vegetables, carrots, pumpkin, squash, spinach, soy
milk, milk
|
|||
|
Water
|
1.2 mg
|
Drowsiness or
muscle relaxation with large doses.
|
Pork, oatmeal,
brown rice, vegetables, potatoes, liver, eggs
|
||
|
Water
|
1.3 mg
|
Dairy
products, bananas, popcorn, green beans, asparagus
|
|||
|
Water
|
16.0 mg
|
Liver damage (doses > 2g/day) and other problems
|
Meat, fish,
eggs, many vegetables, mushrooms, tree nuts
|
||
|
Water
|
5.0 mg
|
Diarrhea;
possibly nausea and heartburn.
|
Meat,
broccoli, avocados
|
||
|
Water
|
1.3–1.7 mg
|
Impairment ofproprioception, nerve
damage (doses > 100 mg/day)
|
Meat,
vegetables, tree nuts, bananas
|
||
|
Water
|
30.0 µg
|
Raw egg yolk,
liver, peanuts, certain vegetables
|
|||
|
Water
|
400 µg
|
Megaloblastic anemia and Deficiency during
pregnancy is associated withbirth defects, such
as neural tube defects
|
May mask
symptoms of vitamin B12deficiency; other
effects.
|
Leafy
vegetables, pasta, bread, cereal, liver
|
|
|
Water
|
2.4 µg
|
Acne-like rash
[causality is not conclusively established].
|
Meat and other
animal products
|
||
|
Water
|
90.0 mg
|
Many fruits
and vegetables, liver
|
|||
|
Fat
|
10 µg
|
Fish, eggs,
liver, mushrooms
|
|||
|
Fat
|
15.0 mg
|
Deficiency is
very rare;sterility in males
and abortions in females,
mildhemolytic
anemia in newborn infants.
|
Increased
congestive heart failure seen in one large randomized study.
|
Many fruits
and vegetables, nuts and seeds
|
|
|
Fat
|
120 µg
|
Increases
coagulation in patients takingwarfarin.
|
Leafy green
vegetables such as spinach, egg yolks, liver
|
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