the science that explains the interactivity of nutrients and other
substances in food in relation to maintenance, growth, reproduction,
health and disease of an individual. It includes food intake,
assimilation, biosynthesis, catabolism and excretion.
The diet of
an individual is what he/she eats, which is largely determined by the
availability and palatability of food stuff. A healthy diet includes
the integration of food stuff enriched in nutrients required for the well-being
of humans; food preparation and storage methods that preserve nutrients from
oxidation, heat or leaching, and that reduces risk of foodborne diseases and
Unhealthy diet can cause deficiency-related
diseases, life threatening complications and chronic systemic diseases and
illnesses; this includes anemia, blindness, scurvy, stillbirth, preterm birth,
obesity and metabolic syndrome, common
chronic systemic diseases such as cardiovascular disease, diabetes, and
Undernutrition can lead to body wasting during
the acute phase but eventually to malnutrition in chronic phase for example in
case of marasmus.
According to the best research evidence, the food we
eat has a significant impact on our health. Healthy dietary helps prevent or
control many health problems, including obesity, diabetes and certain risk
factors for cancer and heart disease, pre and post-natal complications as well as help prevent or control a varied
number of musculoskeletal conditions in infants and adults.
studies suggest there are two types of nutrients required by the human body:
macro-nutrients which are needed in relatively large quantities, and
micronutrients which are needed in smaller quantities. Dietary fiber,a type of
carbohydrate, i.e. non-digestible material such as cellulose, is required for
both mechanical and biochemical reasons.Some nutrients can be stored, for
example the fat-soluble vitamins,while others are required more or less
Poor health can be caused by a lack of required nutrients, or for some minerals and vitamins, too much of a required nutrient is also a problem to your body.
macronutrients are Carbohydrates, fiber, protein, fats and water
The macronutrients (excluding water and fiber) provide structural material (amino acids from which proteins are built, and lipids from which cell membranes and some signaling molecules are built) and energy. Some of the structural material can be used to generate energy internally, and in either case it is measured in Joules or kilocalories. Carbohydrates and proteins provide 17 kJ approximately (4 kcal) of energy per gram, while fats provide 37 kJ (9 kcal) per gram, although the net energy from either depends on factors such as absorption and digestive effort, which may vary occasionally. Vitamins, minerals, fiber, and water do not provide energy, but are required for other reasons.
may be classified as monosaccharides, disaccharides and polysaccharides depending
on the number of monomer (sugar) units they contain. They constitute a large
part of foods such as rice, bread, noodles and other grain-based products,
such as maize, millet sorghum also potatoes, yams, beans, fruits, fruit juices
Monosaccharides, disaccharides, and polysaccharides contain one, two, and three or more sugar units, respectively. Polysaccharides (starch) are often referred to as complex carbohydrates because they are typically long, multiple branched chains of sugar units.
fiber is a carbohydrate that is incompletely absorbed in humans and in some
animals. Like all carbohydrates, when it is metabolized it can produce four
Calories (kilocalories) of energy per gram. However, in most circumstances it
accounts for less than that because of its limited absorption and
digestibility. Dietary fiber consists mainly of cellulose, a large carbohydrate
polymer which is indigestible as humans do not have the required enzymes to
are two fiber subcategories: soluble and insoluble fiber.
Soluble fiber is found in whole grains, fruits (especially prunes, plums and figs), and vegetables are good sources of dietary fiber. There are many health benefits of a high-fiber diet. Dietary fiber helps reduce the chance of gastrointestinal problems such as constipation and diarrhea by increasing the weight and size of stool and softening it. Insoluble fiber, found in whole wheat flour, nuts and vegetables, especially stimulates peristalsis. The involuntary rhythmic muscular contractions of the intestines which move, digest along the digestive tract. Soluble fiber, found in oats, peas, beans, and many fruits, dissolves in water in the intestinal tract to produce a gel that slows the movement of food through the intestines. This may help lower blood glucose levels because it can slow the absorption of sugar. Additionally, fiber, perhaps especially that from whole grains, is thought to possibly help lessen insulin spikes, and therefore reduce the risk of type 2 diabetes.
are structural materials in much of the animal body (e.g. muscles, skin, and
hair). They also form the enzymes that control chemical reactions throughout
the body. Each protein molecule is composed of amino acids, which are distinguished 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. For all
animals, some amino acids are essential (an
animal cannot produce them internally) and some are non-essential (the animal can produce them from other
nitrogen-containing compounds). About twenty amino acids are found in the human
body, and about ten of these are essential and, therefore, must be included in
A diet that contains adequate amounts of amino acids (especially those that are essential) is particularly important in situations like; during early development and maturation, pregnancy, lactation, or injury (a burn, for instance). A complete protein source contains all the essential amino acids while an incomplete protein source lacks one or more of the essential amino acids.
It is possible to combine two incomplete protein sources e.g., rice and beans, to make a complete protein source. Characteristic combinations are the basis of definite and different cultural cooking traditions. Complementary sources of protein do not need to be eaten in the same meal as they are used together with the body excess amino acids from protein and can be converted into glucose and used for fuel through a process called gluconeogenesis .
molecule of dietary fat typically consists of several fatty acids (containing long chains of carbon and hydrogen atoms),
bonded to a glycerol. They are typically found as triglycerides (three
fatty acids attached to one glycerol backbone).
may be classified as saturated or unsaturated basing 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, their molecules have
relatively fewer hydrogen atoms than a saturated fatty acid of the same length.
Unsaturated fats may be further classified as monounsaturated (one double-bond)
or polyunsaturated (many double-bonds). Furthermore, depending on the location
of the double-bond in the fatty acid chain, unsaturated fatty acids are
classified as omega-3 or omega-6 fatty acids. The trans fats are a type of
unsaturated fat with trans-isomer bonds; these are rare in nature
and in foods from natural sources; they are typically created in an industrial
process called hydrogenation There
are nine kilocalories in each gram of fat. Fatty acids such as conjugated
linoleic acid, eleostearic acid, catalpic acid, and punicc acid, other than
providing energy, represent potent immune modulatory molecules.
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),
unsaturated fats are typically liquids (such as olive oil or flaxseed
oil).Trans fats are very rare in nature, and have been shown to be highly
detrimental to human health, but have properties useful in the food processing industry,
such as rancidity resistance.
is essential for chemical processes to partake in human body and it constitutes
the highest percentage in body cells, tissues and even blood which plays a key
role in nourishment of the entire body systems
recommendations for the amount of water required for maintenance of good health
suggested that 6–8 glasses of water daily is the minimum to maintain the proper
state of body hydration. However, the notion that a person should consume eight
glasses of water per day cannot be traced to a credible scientific source.
Water is rid off from the body in multiple forms; including water vapour in exhaled breath, sweating, urine and feces. It is therefore, necessary and most importantly to adequately rehydrate to replace lost fluids from the body systems as water plays a vital role for the well-being and systems operation.
Pure ethanol provides calories per
gram. Wine and beer contain a similar range of ethanol for servings of 5 ounces
and 12 ounces, respectively, but these beverages also contain non-ethanol
calories. A 5 ounce serving of wine contains 100 to 130 calories. A 12 ounce
serving of beer contains 95 to 200 calories. Alcoholic beverages are
considered empty calories foods
because other than calories, these contribute no essential nutrients.
The micronutrients include: -
Vitamins and Minerals (macro-minerals and trace minerals)
Dietary minerals are inorganic chemical elements required by living organisms, the four elements which includes oxygen, carbon, hydrogen and nitrogen, are present in nearly all organic molecules. The term "mineral" is archaic, since the intent is to describe simply the less common elements in the diet. Some are heavier than the four just mentioned, including several metals, which often occur as ions in the body. 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. Also, minerals are often artificially added to the diet as supplements; the most famous is likely iodine in iodized salt which helps to prevents goiter
Many elements are essential
nutrients known as dietary minerals.
Some have cofactors roles while
others are electrolytes. Below are Elements
with recommended dietary allowance greater than 150 mg/day.
Calcium, a common
electrolyte, and needed structurally (for muscle and digestive system health,
bone strength, in some forms neutralize acidity, provides signaling ions for
nerve and membrane functions)
Phosphorus, required component
for building of bones; essential for energy processing
Magnesium, required for
processing ATP and related
reactions. Builds bone, and facilitates peristalsis.
Potassium, an electrolyte (essential
for heart and nerve functions)
· Sodium, an electrolyte; common in food and manufactured beverages, as sodium chloride. Excessive intake of sodium chloride can deplete calcium and magnesium which might lead to high blood pressure.
Many elements are required in trace
amounts; generally, because they play a catalytic role
in enzyme activities. Some trace mineral elements are with recommended
dietary allowances of < 200 mg/day are listed below.
Cobalt required for
biosynthesis of vitamin B12 family
of coenzymes. Animals cannot
biosynthesize B12, and must obtain this cobalt-containing vitamin in their
component of many redox enzymes, including cytochrome c oxidase Chromium
for sugar metabolism
Iodine required not
only for the biosynthesis of thyroxine but it is used for other important
organs as breast, stomach, salivary glands, thymus, etc. for this reason iodine
is needed in larger quantities than others in this list.
Iron is required for many enzymes, and for hemoglobin and
some other proteins in the body
Manganese is needed for
processing of oxygen
Molybdenum is required for xanthine oxidase and related
· Selenium is required for peroxidase (antioxidant proteins)
Vitamins are essential nutrients for
the human body necessary in the diet for good health. Vitamin deficiencies may
result in disease conditions, such as scurvy osteoporosis goiter, impaired
immune system, disorders of cell metabolism, certain forms of cancer, and
symptoms of premature aging, mental health problems, and many
others. Excess levels of some vitamins are also risky to health. The Food
and Nutrition Board of the Institute of Medicine has established Tolerable
Upper Intake Levels for seven vitamins.
Phytochemicals for example polyphenols are compounds produced
naturally in plants (in Greek phyto means "plant"). Generally, the
term associates compounds that are prevalent in plant foods, but are not proven
to be essential for human nutrition, as of 2018. There is no conclusive
evidence in humans that polyphenols or other non-nutrient compounds from plants
confabulate health benefits, mainly because these compounds have indigent
bioavailability i.e., following ingestion, they are digested into smaller
metabolites with unknown functions, then are quickly eliminated from the body
The initial studies sought to reveal if dietary supplements might promote health, one meta-analysis concluded that supplementation with antioxidant vitamins A and E and beta-carotene did not convey any benefits, and may increase risk of death. Vitamin C and selenium supplements did not impact mortality rate. Health effects of non-nutrient phytochemicals such as polyphenols were not assessed in this review.
In humans, there four
dominant phyla, this includes
Firmicutes, Bacteroidetes, Actinobacteria and Proteobacteria. They are
essential to digestion and are also affected by food that is consumed.
Bacteria in the large intestine perform many important functions for humans,
including breaking down and aiding in the absorption of fermentable fiber,
stimulating cell growth, repressing the growth of harmful bacteria, training
the immune system to respond only to pathogens, producing vitamin B12 and
defending against some infectious diseases. Probiotics refers to the idea of deliberately consuming live
bacteria in an attempt to change the bacterial population in the large
intestine, to the health benefit of the host human or animal. Prebiotic refers to the idea that
consuming a bacterial energy source such as soluble fiber could support the
population of health-beneficial bacteria in the large intestine. There is not
yet a scientific consensus as to health benefits accruing from probiotics or