Introduction to diet and nutrition

Nutrition can be defined as the supply of food materials needed by an organism and the cells in order to sustain life. Human medicine experts and nutritionists define nutrition as the science of consuming and utilizing food. People have different tastes and preferences for food depending on their nutrient, energy and enjoyment needs. Diet, on the other hand, can be defined as the sum of food consumed by an individual. There are different factors which determine food selection in a family setup. For instance, one needs to consider cultural and environmental considerations and an individual’s beliefs. A healthy diet helps children to be jovial, grow well and perform well in class. It also helps adults to perform well in their jobs and occupations. The human body requiresessential nutrients for growth since such nutrients are not manufactured in the body. Examples of such nutrients include; vitamins, minerals, certain amino acids, and certain fatty acids. Food is also rich in fiber and other components. The human body requires seven major nutrients. However, some nutrients such as water and fiber do not provide the body with energy, though they are important. Micronutrients are required by the body in small quantities. This paper will focus on the topic of nutrition particularly; calories, macro, and micronutrients, nutrient timing and supplements.

Total calories

Calorie refers to a unit of energy. There are two ways in which calorie is defined depending on the SI unit. Small calorie denoted as (cal) is the amount of energy required to raise the amount of one gram of water by one degree Celsius at a pressure of one atmosphere. Notably, one small calorie is equivalent to 4.2 joules. Large calorie denoted as (Cal or kcal) refers to the amount of heat energy needed to heat one kilogram of water by one degree Celsius at a pressure of one atmosphere. Large calorie is also known as food calorie and is equivalent to 1000 small calorie. One large calorie is equal to 4.2 kilojoules.

In a nutritional perspective, calorie refers to the total amount of energy an individual obtain from the meals and drinks they consume in addition to the energy they use during activities such as playing, walking or working. Calorie intake of an individual is determined by various factors such as; sex, weight, height, health status of an individual, physical activities and body shape.

For human bodies to survive, they require calories. Without energy, the heart and the lungs would cease functioning;the cells in the body would die, the essential organs would also stop functioning. Therefore energy is paramount in the body of an organism. having too high or too low-calorie intake would lead to poor health; thus an individual should consume the appropriate amount of calorie to remain healthy and strong.

Active calories refer to the calories burnt during an exercise such as jogging, jumping, working or any other activity. Resting calories, on the other hand, refers to the number of calories that an individual burns while at rest. Generally, total calories will include the sum of both resting and active calories. Dietitians recommend that an adult should obtain about 45-65% of the calories from carbohydrates; 20-25% should be achieved from fats while 10-35 should be acquired from proteins. Remarkably this would be a balanced diet. Children require a higher proportion of fats. Hence, 25-40% of the calories should be obtained from fats and less than 25% gained from added sugars. The following are high-calorie foods; avocado; 227 calories each, olive oil; 119 calories per tablespoon, nuts; 828 calories per cup of peanuts dark chocolate and whole grains; 648 per bar. Low-calorie foods include; vegetables such as spinach; 16 calories per cup of shredded romaine, oranges; 70 calories, broccoli;15 calories per cup, etc.


Nutrients refer to ecologicalconstituents used for development, energy and bodily activities by anycreature. Macronutrients can be defined as chemical substances which provide energy to an organism in large amounts. Lipids, proteins, and carbohydrates are the three major macronutrients.Each of the outlined macronutrients provides energy to the human body in terms of calories. Fats produce 9 calories, protein 4 and carbohydrates 4 per gram. Therefore, given a food label with; 5 grams of protein, 10 grams of carbohydrates and 0 grams of fats, then the food contains 60 grams of calories.


Carbohydrates are required by the human body in large quantities. According to the United State Department of Agriculture (USDA), adults ought toingest 45-65% of their daily caloric consumption from carbohydrates. Carbohydrates are essential in the human bodies for several reasons; first, they are chemically broken down to release metabolic energy. The energy released support cell growth, functioning of the organs etc.They are helpful in the amino acid synthesis and also aid in proper metabolizes of fats. Indigestible carbohydrates such as fiber are crucial for intestinal health.

Commonly, starch is found in starchy foods such as potatoes, fruits, grains, and milk. Their traces can also be found in food components such as nuts, vegetables, beans etc. Carbohydrates are either simple or complex. Simple carbohydrates are very sweet, for example, fruit sugar while complex carbohydrates are salty such as in potatoes. Indigestible carbohydrates are not broken down in the human digestive system. They, therefore, pass through with other wastes thus preventing constipation and hemorrhoids.  They also reduce high obesity, heart diseases, and high cholesterol. High fibers are found in fruit, whole grains, and vegetables.


The USDA recommends that an adult should consume 10-35% calories and day which can be obtained from proteins. Proteins are helpful in the human body since it is the primary component of most cells. The body is generally made of proteins and therefore, it defines the behavior and shape of an organism. Protein forms 50% of an organism’s dry weight. These macronutrients are useful in new tissue production and growth. Enzymes which are critical in digestion, immunity, and protection of the body are protein in nature.They are also used to regulate body functions. They serve as a source of energy in case carbohydrates are not available. They are obtained from, poultry, meat substitute, fish, legumes, cheese, milk etc. their traces are also found in vegetables and starchy foods.Proteins are broken down in the body into amino acids. There are more than 500 different types of amino acids. 21 amino acids needed in the human body. Of all the 21 amino acids 9 are essential since they cannot be manufactured in the body thus, has to be eaten.Proteins containing the 9 essentialamino are referred to as high-quality proteins and are obtained from animal sources. Low-quality proteins do not include the 9 essential amino acids and are obtained from plant sources.


The ASDA recommends adults to consume 20-35% calories derived fromfats and oils. The fats are useful in the supply of the fatty acids needed by the body and the body is not able to make from within. They also help in the absorption of fat-soluble vitamins such as carotenoid, A, D, E, and K. Fats are vital in the human body. They are used as storage of vitamins, energy, and production of hormones. Fats also used to protect body organs such as the heart where they serve as shock absorbers. They are either saturated or unsaturated fats. Saturated fats if taken in large quantities would be harmful to heart health.Less than 10 % of an individual’s daily caloric consumption should be obtained from saturated fats.They are found in butter, meat fats, peanut, cotton seeds, coconuts and occasional foods such as cakes, chips, and biscuits. Unsaturated fats are healthy and more should be included in the diet. They are beneficial to the health of the heart. They are found in fish, avocados, vegetable oils and nuts.


Micronutrients are substances that are required by the body in small quantities to facilitate physiological processes.Suchsubstances are vital in hormone and enzyme production. Micronutrients also play critical roles in the body such as treatment and prevention of various diseases. They also help in the optimization of both mental and physical functions. The common micronutrients are minerals and vitamins. They are needed in small quantities in the body but carries important roles in human well-being and development. Lack of micronutrients in children leads to stunted growth. Micronutrient deficiency in adults leads to diseases such as scurvy; lack of vitamin C, lack of vitamin D leads to rickets and osteoporosis resulting from lack of calcium. Micronutrients are found in foods. Meals containing a high level of micronutrients are referred to as nutrient dense foods. The number of nutrients in food can be determined by comparing the ratio of micronutrients to the number of calories. Calcium is found in foods such as yogurt, spinach, and milk.  Potassium in bananas, potatoes, and spinach, Vitamin B12 is found in cheese, fish, beef, and eggs.


There are two forms of vitamins that are, fat-soluble and water-soluble vitamins. The water-soluble minerals need to bereplaced on a daily basis since they are easily lost through body fluids.Examples of water-soluble vitamins are vitamin C and vitamin B-complex. Vitamin B12 and B6 are the major components of B-complex since they are not easily lost from the body like other water-soluble vitamins. Fat-soluble vitamins accumulate in the body and therefore, they are not replaced daily. Examples of fat-soluble vitamins are K, E, D, and A.

Different vitamins play different roles in the body. For instance, vitamin D helps to maintain normal bones. Vitamins A and B6 help to maintain normal skin and normal physiological functioning respectively. Biotin helps in hair maintenance. Vitamin C helps to maintain normal collagenformation and proper function of gumsand teeth while Vitamin B12 is responsible for normal functioning of the nervous system, structure of healthy red blood cells and normal energy-yielding digestion. Vitamin K is responsible for blood clotting while B1 contributes to normal energy-yielding metabolism.


They occur in two forms; micro minerals and macro minerals. The macro minerals are needed by the body in large quantities. They include magnesium, calcium, potassium, sodium and phosphorous. The, on the other hand, are needed in small amounts in the body. They include copper, zinc, iron, iodine, and fluoride.

Macrominerals play the following roles in the body; Calcium helps in normal functioning of the muscles, neurotransmission, and normal energy-yielding metabolism. Magnesium assists in protein synthesis, the normal function of the nervous system and normal muscle functions. Phosphorouscontributes to the maintenance of normal bones and teeth. They also help with muscle functions. Potassium, on the other hand, helps to maintain healthy blood pressure, the normal function of the nervous system and muscles. Chlorides contribute to normal digestion.

Micro minerals are also important for body functioning. For instance, iron is responsible for normal hemoglobin and red blood cell formation. They also help in the transportation of oxygen in the body. Fluorides contribute development of strong teeth and tooth mineralization. Selenium and chromium are responsible for cell protection from oxidative stress and maintenance of normal blood sugar level respectively.

Generally, micronutrients can be depleted due to various conditions such as infections. For example consumption of alcoholleads to depletion of vitamins B and C, minerals and antioxidants. Infections and allergies have been found to drain vitamins A and C and zinc. Antioxidants in the body can also be depleted due to exposure to toxic substances as well as air pollutants within the environment. They can also be drained by smoking. Research has indicated that stress can deplete all nutrients particularly both vitamins B and C.

The nutrient requirement by depending on an individual. There are people who require more nutrients in relation to the general public. The elderly, children and pregnant women require more nutrients compared to normal healthy adults. Athletes and other people undertaking vigorous exercises require more nutrients compared to those who spend more hours resting.


Nutrient timing

Nutrient timing refers to eating specific nutrients in quantified amounts at given times.  It can also be described as a planned alteration of macronutrient intake with the aim of promoting health and work performance.  The strategies of nutrient timing are set based on how the body handles various types of foods at different times. It is recommendable to take non-fruit and veggie carbohydrates immediately before and after an exercise. Different authors have defined nutrient timing as the application of knowing what and when to eat before during and after an exercise.

Nutrient timing has various objectives which include; health improvement, nutrient partitioning, improve athletic performance, improve the composition of the body etc. nutrient timing are aimed to help recreational contestants to realize their beneficial exercise performance and recovery. Nutrient timing system involves three distinct phases which are determined by the muscles, their nutrient necessity and retrieval demand for best outcomes and strengthconsequences.Notably, these phases include; energy phase, anabolic phase and growth phase.

Nutrient timing phases

Energy phase

The primary fuel used in this phase is muscle glycogen. Low accumulation of muscle glycogen results in muscle fatigue thus the body is unable to complete high-intensity exercises. Depletion of muscle glycogen also results in acute muscle weakness which may lead to poor force production. Both aerobic and anaerobic exercises reduce glycogen stores. Hence, carbohydrates are needed in large quantities during the energy phase. The phase is also characterized by physiological and hormonal responses. The level of insulin decreases, cortisol level increases while muscle glycogen stores are exhausted; thus the energy phase is catabolic.

The aim of energy phase is to increase nutrients supply to the muscles particularly some proteins and carbohydrates. It is also aimed at limiting protein and glycogen loss, limit the damage of tissuesand reduce suppression of the immune system. Researchers have found that consumption of proteins with carbohydrate supplements before aerobic exercise stimulates protein production after the workout. Ingestion of the protein-carbohydrate mix also helps in strong recovery after an exercise.

Anabolic phase

The phase occurs within 45 minutes of post-exercise. During this phase, the muscle cells are highly sensitive to insulin. Therefore, it is essential to consume proper nutrients at this point hence promoting muscle strength and endurance. Drinking the same nutrient after two or more hours would not be beneficial enough. During this phase, the anabolic hormones are actively involved in the repair of the muscles to lessen their inflammation. Immediate consumption of carbohydrates is recommendable since insulin sensitivity causes the cell membrane of the muscle cells to be more permeable to glucose. Outstandingly, this will help the body to store more glycogen which will provide sufficient glucose for muscle recovery. Consumption of carbohydrates an hour later after the exercise helps in protein synthesis.

Growth phase

This phase comprises of 18-20 hours of post-exercise. During this phase, muscles are repaired, growth and strength occur at this phase. The primary objective of this stage is to sustain insulin sensitivity so as to continue replenishing glycogen store and to retain the anabolic condition. It is recommendable to consume proteins and carbohydrates during this phase. Certainly, this will help in protein synthesis. Carbohydrates with sufficient glycemic indexes are suitable since they assist in fueling the post-exercise.




Dietary supplements are manufactured products which are aimed at complementing the diet. They are taken as capsules, pills, liquid or tablets.  Supplements can offer nutrients which are extracted from food sources or artificial. Dietary complements may contain compounds such as minerals, fiber, vitamins, amino acids, and fatty acids.

It should be noted that supplements are not meant to substitute food since they cannot offer all the nutrients contained in whole grains. Whole grain has three major benefits over supplements. First, whole foods are more nutritious in relation to supplements. The greater nutrient is associated with the complexity of the food thus containing some micronutrients needed in the body. Secondly, they are rich in fiber; for instance fruits, vegetables and whole grains. Fiber diet helps in prevention of diseases such as heart diseases and diabetes type 2. Lastly, whole food contains protective substances.  Whole foods are rich in antioxidants whichhelp to slow down processeswhich may harm the cells, organs, and tissues.

Supplements should not be taken by healthy individuals and who take a balanced diet. A balanced diet may contain; fruits, vegetables, low-fat dairy products, whole grain, lean meat and fish and legumes.  However, in some situations supplements are recommendable. For example, expectant mothers should consume 400 micrograms of folic acid a day which can be obtained from supplements in addition to eating foods that are naturally rich in folate. They are also recommended to take prenatal vitamins rich in iron or iron supplements.  The elderly should consume supplements rich in vitamin B12.

Dietary supplementary is also recommendable to people who do not eat well or consume fewer calories. Vegetarians who eat fewer varieties of foods are also recommended to consume supplements. Ladies with heavy blood flow during menstrual cycles may ingest supplements in order to regain lost nutrients.They are also recommendable for individuals who are allergic to milk. The choice of supplements may result in a severe harmful effect on an individual’s health. Therefore, one is advised to seek medical guidance.


In conclusion, a balanced diet is essential for human growth and development. A balanced diet helps to avoid diseases such as rickets, night blindness, anemia etc. healthy individuals are more active and yields to high performance in their daily occupations. Children are also able to do well in class. High level of nutrition is beneficial not only to the family but also to the entire nation. Healthy people are more productive and therefore creating job opportunities as well as generating national wealth throughexports earnings.

Nutrition intake is determined by the preferences and tastes of given individuals. It is important to understand the family health background in order to provide a healthy diet. For instance, a family with obesity record would significantly reduce the consumption of fats.Nutrients are categorized into two that is, macronutrients and micro nutrients. The macronutrients are taken in large quantities while micronutrients are taken in small quantities.The macronutrients comprise of fats, proteins, and carbohydrates. The carbohydrates are energy giving food; proteins are energy building while fats help in protecting body organs.

Carbohydrates are classified into either simple or complex carbohydrates. The simple carbohydrates are very sweet eg sweet fruit juice while complex carbohydrates are savored.Fats are classified as saturated and unsaturated fats.The high amount of saturated fats are harmful and therefore should not be consumed in large quantities. Examples of saturated fats are cotton seeds and meat fats. Unsaturated fats are healthy and should be consumed in large quantities. The help in the reduction of heart diseases;an example of such fats include fish and avocado fats. Proteins are classified as high-quality proteins and low protein quality. Notably, this is determined by the presence of the 9 essential amino acids which are rare.

Vitamins and minerals are the critical components of micronutrients.Vitamins are classified into water-soluble and fat-soluble proteins. The water-soluble proteins are easily lost through body fluids and therefore need to be replaced regularly on a daily basis. Fat-soluble vitamins are not easily forgotten and therefore, do not need to be replaced on regular basis. Examples of water-soluble vitamins arevitamin C and B complex while fat-soluble vitamins include vitamin A, D, E and K. Minerals are categorized as macro minerals and micro minerals depending on the quantities consumed. Minerals demanded in large numbers are known as macro minerals and include; calcium, magnesium, potassium,phosphorous and sodium.  Microminerals, on the other hand, are required in small quantities and include; fluoride, copper, zinc, iron, andiodine.

Nutrient timing is the science of understanding what and when to eat before, during and after exercises. The process involves three phases which include; energy phase, anabolic phase and growth phase. Supplements are taken orally in form of capsules, tablets, pills or liquids. Before taking supplementary it is important to consult medical practitioners in order to avoid complex effects which may arise.


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