Every action we perform, from each breath to walking and talking consumes energy. We get this energy from the food we eat. Food also provides the building blocks we require for our bodies to grow and repair any wear and tear that occurs from our daily activities. Food is therefore extremely important for all living beings and without food and the nutrition it provides us we would not survive.
What is food?
Food is any nutritious substance that people or animals eat or drink or that plants absorb in order to maintain life and growth.
What is Nutrition?
Nutrition is the process of obtaining the nutrients the body needs for life and growth.
Plants are the primary producers of food on our planet. Through a process called photosynthesis, plants can produce carbohydrates.
What is Photosynthesis?
Photosynthesis is the process used by green plants, algae and certain bacteria to convert carbon dioxide and water into carbohydrates in the presence of sunlight. The carbon dioxide is absorbed from the atmosphere while the water is absorbed from soil by the roots.
Green plants, algae, etc are the only living organisms capable of synthesising their own carbohydrates and they do this with the help of a pigment called chlorophyll which gives them their green colour.
By this process plants are able to convert the heat energy from the sun into chemical energy making it available for animal and human consumption.
The main source of food for humans is plant and animal products. Fruit, grain, vegetables and herbs are plant products that are consumed as food while meat, fish, eggs and milk are animal products. Through consumption of these foods we provided our bodies with the proteins, carbohydrates, fats, vitamins, minerals and water that are required for our health and growth.
Each of these food groups plays an important role:
There are three macronutrients: carbohydrates, protein and fats. Macronutrients are essential for proper body functioning, and the body requires large amounts of them. All macronutrients must be obtained through diet; the body cannot produce macronutrients on its own.
Carbohydrates are the sugars, starches and fibres found in fruits, grains, vegetables and milk products. Carbohydrates are the body’s main source of energy. They are called carbohydrates because, at the chemical level, they contain carbon, hydrogen and oxygen.
Carbohydrates are divided into simple carbohydrates like glucose, sucrose, lactose and fructose which are made up of just one or two sugar molecules and complex carbohydrates like starch and cellulose which are long chains of sugars.
Digestion of carbohydrates starts in the mouth with the help of an enzyme called amylase which is present in saliva. Further, carbohydrates are completely broken down in the small intestines with the help of intestinal amylase. During digestion most carbohydrates, except for cellulose, get broken down into glucose which is our main source of energy. The hormone insulin is responsible for helping the cells in our body to absorb glucose and use it as fuel for all the cell’s functions. Unused glucose is converted to glycogen and stored in our liver for use later. When there is a scarcity of food, our bodies use up all our stored glycogen and we can therefore survive for a few days even if we do not eat.
The simple carbohydrates are useful for providing instant energy and are preferably consumed by athletes and people whose lives include a lot of high intensity activity. However on a daily basis for regular individuals excessive intake of simple carbohydrates can be unhealthy.
Complex carbohydrates serve as storage for energy and because they take longer to break down and release small amounts of glucose into the bloodstream at a time are more useful as a source of energy.
Carbohydrates also have structural functions; cellulose is the main component in plant cell wall. Ribose and deoxyribose are simple carbohydrates which help to build up RNA and DNA respectively.
The fibre we get from eating vegetables is made up of cellulose and helps to maintain a healthy digestion.
Complex carbohydrates are therefore important for survival and can be obtained for vegetables, fruits and whole grains.
Proteins are one of the most important components of the human body, nearly every single bodily function and structure requires proteins. Proteins are made up of chains of molecules called amino acids. Humans require twenty amino acids to make up all the proteins in the body. Out of these twenty amino acids, nine cannot be made by our bodies and therefore have to be obtained from our diet. This is why it is essential to include lots of protein rich foods in our diet.
Proteins are essential in repairing cells and making new ones, they are important in building muscle mass and extremely necessary for growth in children. Proteins make up our hair, skin and nails. Proteins are also important in the formation of enzymes which regulate body functions like digestion. Haemoglobin, the molecule in red blood cells that transports oxygen throughout the body, is a protein. The blood clots that form over a wound to stop further bleeding and allow the broken skin to heal are made up of proteins. The heart is the most important muscle in the body and is made up of proteins. Proteins can also be used as a backup source of energy when there is a shortage of carbohydrates.
The proteins we consume in our food are digested in our stomach and small intestines. In the stomach the enzyme pepsin breaks down the long protein chains into smaller chains of amino acids called polypeptides. These polypeptides pass into our small intestine where they are further broken down into single amino acids with the help of enzymes like trypsin, chymotrypsin and carboxypeptidase. The single amino acids are then absorbed by the blood and transported to all our cells to be used as the building blocks for all the proteins that the body requires.
Proteins are most commonly found in animal products like fish, meat, eggs and milk but can also be obtained from other sources such as nuts, vegetables like peas, seeds and dhals.
A lack of sufficient proteins in our diet can lead to a lot of health problems like weight loss, muscle breakdown, aching joints, hair loss, skin rashes, weakness, headaches and even heart problems. When there is a severe lack of proteins in the diet like in conditions of drought and famine then the body starts breaking down its own muscle to provide the amino acids to build other proteins that are required for survival.
Fats are also known as lipids. Fats serve many important functions in our body. The main function of fat is as an energy reserve. The adipose tissue in our bodies stores fat and also helps to regulate our body temperature. Our cave dwelling ancestors would start “getting fat” just before the cold winter started so that their bodies could keep warm and even in times when food was scarce they would have the stored fat to provide energy to their bodies.
Phospholipids which are a fat compound are the main structural component in cell membranes of all animal cells. This cell membrane protects the cell from its environment and selectively allows certain ions and organic molecules into the cells. The cell membrane controls the movement of substances in and out of the cell.
Fats also help in the digestion of certain vitamins which are fat soluble or dissolve only in fats. The human brain contains nearly 60% fat and fats are extremely important in growing children for the development of the brain and nervous system.
The myelin sheath which surrounds the axons of nerve cells is made up of fats. This sheath forms an electrically insulating layer and is important for the proper functioning of nerve cells.
Fats are present in foods like meat, fish, milk and milk products like butter and cheese. Vegetables like avocado and olives are a good source of fats in our diet. Nuts are also a very good source of fats.
Fats get digested in our small intestines with the help of bile which is secreted by the liver. Once the bile has broken down the fat into smaller droplets an enzyme called lipase secreted by the pancreas, further breaks down the fat into free fatty acids and monoglycerides. The cells of the small intestines then absorb these small particles of fat and convert them into triglycerides which are the main form of stored fat in our body. From here the triglycerides are transported with the help of proteins through the blood stream to the various cells of the body for different functions.
A deficiency of essential fats in our diet can lead to increased risk of cancer, heart disease and brain function. A deficiency in fats can also lead to a deficiency in many of the important vitamins which fats helps to digest.
Some fats called trans fats are not good for health and should be avoided in high quantities. Junk food contains trans fats.
Unlike macronutrients, micronutrients are required in much smaller quantities by the body. These micronutrients include vitamins and minerals. Micronutrients aid in the production and function of enzymes and hormones.
Vitamins: Vitamins are organic compounds which are needed in small quantities to sustain life. We get vitamins from food, because the human body either does not produce enough of them or none at all. There are currently 13 recognized vitamins. Insufficient amounts in the diet may cause deficiency diseases. Vitamins fall into two categories: fat soluble and water soluble. The fat-soluble vitamins; A, D, E, and K dissolve in fat and can be stored in your body. The water-soluble vitamins; C and the B-complex vitamins (such as vitamins B6, B12, niacin, riboflavin, and folic acid), need to dissolve in water before your body can absorb them.
Some functions of vitamins include:
- Vitamin A helps maintain healthy teeth, bones and skin
- Vitamin B1 is important for nerve function
- Vitamin B2 is important for normal vision and skin health
- Vitamin B6 helps form red blood cells and maintain brain function
- Folic acid is important in making DNA and new cells
- Vitamin C helps in protein metabolism, important for the immune system and helps in the absorption of iron
- Vitamin D is important for the proper absorption of calcium
- Vitamin E protects cells
- Vitamin K is required for proper blood clotting.
There are more vitamins in the vitamin B complex with several other functions important for the normal functions of the body.
Green leafy vegetables and colourful fruits and vegetables are rich in vitamins. A deficiency in vitamins in our diet can lead to a host of health problems including:
- Shortness of breath
- Pale or yellowish skin
- Irregular heartbeats
- Weight loss
- Numbness or tingling in your hands and feet
- Muscle weakness
- Personality changes
- Unsteady movements
- Mental confusion or forgetfulness
A deficiency of vitamin D in babies can cause rickets, a disease where the bones do not get enough of calcium and become soft and deformed. Night blindness is caused by vitamin A deficiency and a deficiency in vitamin C can cause a disease called scurvy which results in weakened bones and blood vessels, resulting in internal bleeding.
Minerals: Like vitamins, minerals are substances found in food that your body needs for growth and health. Minerals are inorganic elements that come from the soil and water. Plants absorb minerals from the soil and water and we in turn can get our minerals directly from plants or from meat sources that have consumed plants. There are two kinds of minerals: macrominerals and trace minerals. Macrominerals are minerals your body needs in larger amounts; they include calcium, phosphorus, magnesium, sodium, potassium, and chloride. Other minerals like chromium, copper, iodine, iron, selenium, and zinc are called trace minerals because you only need very small amounts of them each day.
Sodium, chloride and potassium help to maintain a proper balance of water in the body. Minerals like calcium, phosphorus and magnesium are important for healthy bones. Sulphur is important in maintaining the structure of proteins, especially those found in skin, hair and nails.
Iron is an important component of haemoglobin which carries oxygen to all the cells in the body. Fluoride strengthens bones and teeth. Zinc helps in clotting of blood and is an important part of the immune system. Copper is required for the proper function of several enzymes.
These are just a few of the functions of minerals in our bodies. A deficiency in one or more of these minerals leads to several health issues due to the inability of the body to function properly without them. Iron deficiency cases anaemia, calcium deficiency can lead to osteoporosis and a deficiency in zinc can cause loss of appetite, decreased immune function and less effective clotting of blood.
Different minerals are obtained for different types of foods, therefore it is important to have a diet with a variety of foods.
Water is one of the most essential elements for good health. Two thirds of the human body comprises of water. Some of the functions of water in our body are as follows:
- Water regulates body temperature
- Keeps tissues like eyes, mouth and nose moist
- Lubricates joints for smooth movement
- Protects organs and tissues
- Is a main component of blood
- Is a main component of cell cytoplasm
- Helps to breakdown nutrients
- Helps carry glucose to cells
- Helps to carry water soluble vitamins to cells
- Helps dissolve minerals and make them accessible to cells
- Helps prevent constipation
- Helps transport waste products out of cells
- Helps to carry waste products out of the body through urine and flushes the kidneys and liver
Because water is so important for so many of our bodily functions, no one can survive without water for more than three days. If we do not consume enough water every day we suffer from dehydration. Some of the symptoms of dehydration include:
- Dry mouth and lips
- Sleepiness or tiredness
- Decreased urine
- Dry skin
It is therefore important to keep ourselves well hydrated and drink sufficient quantities of clean, good quality water every day. It is recommended that children up to thirteen years drink 1.5 litres of water in a day while 2 to 3 litres of water are recommended for children above thirteen years and adults, daily.
Junk food is a term used to refer to processed, packaged food which is high in salt, sugar, fat and calories but with little to no nutritional value. Junk food is easily available almost everywhere and can be very addictive.
Fast foods are the most common junk food. These pre-prepared foods are loaded with chemical additives to improve flavour and taste and to keep the food from going bad. By the end of all these processes the natural nutrients present in the meat or vegetables used to prepare the fast food has been completely destroyed and is no longer available in a form which our bodies can absorb during digestion.
Junk food is addictive because it is made to trigger a chemical reaction in our brains which makes us feel happy. Soon we associate the taste of the junk food with the nice feeling we get and actually long for more. While junk food makes us feel full and satisfied for a short period of time are bodies are still starving for the nutrition it requires for survival and soon we feel hungry again.
Junk food occasionally will not cause much harm but when consumed in large quantities and on a regular basis can lead to a host of illnesses including; indigestion, obesity, cardiovascular disease, diabetes, etc.
Burgers, pizzas, chips, chocolates and carbonated beverages like cola are just some of the junk foods that a consumed regularly by thousands of children around the world.
Malnutrition is the lack of proper nutrition, caused by not getting enough food to eat, not getting the right type of food or by not being able to assimilate nutrients from the food that is eaten.
A person who is malnourished becomes weak and the body is unable to grow, repair itself and resist disease. A malnourished person becomes tired easily and also finds thinking difficult. Malnutrition is the largest single contributor to disease in the world, according to the UN’s Standing Committee on Nutrition (SCN).
Malnutrition in very young children affects both physical and mental development. If a child suffers from malnutrition in the first two years, then their growth will be affected for the rest of their lives. Extreme malnutrition will eventually lead to death.
It is estimated that about one in every nine people and one in every six children suffer from malnutrition worldwide.
Cooking and storing of food:
We eat a lot of uncooked food like fruits, nuts and some vegetables, however we need to cook most vegetables and all meats. While we might put a lot of thought into how we are going to prepare our food on a particular day we hardly ever put any thought into why we cook our food.
Cooking serves a triple function:
- The heat used for cooking our food kills off any bacteria and other pathogens that could cause us to fall ill if we consumed them through our food
- Cooking helps break down some of the proteins and other fibrous substances like cellulose found in vegetables making them easier for our body to digest
- Cooked food stay fresh longer
It is advisable to store leftover food in the refrigerator because the cool temperature keeps bacterial activity down to the minimal preventing the food from spoiling. It is best to consume food within a few hours of cooking and within 48 hours if refrigerated. Even cooked and refrigerated food will go bad when kept for too long and can then become harmful for consumption.
If it is required to store food for longer periods of time then the food should be frozen in a freezer and kept frozen until it is required. Once food has been frozen and thawed it should all be used up and cannot be frozen again.
Preserving and pickling of food
Before the invention of the refrigerator food could not be stored for long period of times. In several countries around the world no food would be available during the long cold winters, so people had to find ways of preserving food so that they would not spoil and could be used during the cold months when nothing would grow.
Some of these methods included drying and salting of meat, pickling of vegetables and making fruits preserves and dried fruit.
It was found that if meats and fish were dried and salted then they would not spoil for a long period of time. The process of removing all the moisture and rubbing the meat or fish with salt would help to kill off germs and prevent the food from going bad.
Pickling of vegetables requires vegetables to be completely immersed in either a solution of brine (very salty solution) or vinegar. Both these liquids prevent bacterial activity and allow the vegetables to keep for a long time.
Fruits contain a lot of acid which acts as a natural preservative. When fruits are placed in air tight jars and then placed in a pot of boiling water, all the bacteria in the jars get killed off and the fruit can remain unspoiled for up to a few months. Once the seal of a jar is broken bacteria can re-enter it so the fruit must then be consumed within a few days.
Another method of preserving fruit is by drying it. In the hot desert countries of the Middle East it was found that fruits like dates and figs could last for a long time if they were dried. The local tribes would dry the fruit and then carry it with them on their long journeys across the desert. A very common fruit that we consume often in its dried form in the grape which when dried is called a raisin.
Spoiling of food and Food borne diseases:
Food is biodegradable, which mean that it can be broken down by the effects of microorganisms to its simplest form. The breakdown of food is a normal process and part of the cycle of life. As food breaks down its chemical structure changes and also the microorganisms (germs) breaking down the food, multiply in numbers. Spoilt food starts to lose its colour and texture and starts to emit a bad smell. Spoilt food can no longer be consumed and has to be discarded.
Cooking kills the germs in food but if we keep food for too long after cooking, more bacteria and other microorganisms start to grow on it. Food borne diseases are caused when we consume food or beverages that are contaminated with bacteria or other disease causing agents. When we consume food that has already started breaking down due to bacterial activity we ingest these bacteria along with the food which leads to infection and disease. It is therefore very important to eat foods that are fresh and not left out in the open too long.
Some food borne diseases include:
- Salmonella poisoning
- Clostridium botulism
- Hepatitis A
Most food borne diseases display symptoms of diarrhoea, vomiting and stomach cramps and in some cases dizziness and blurred vision. Hepatitis A also causes enlargement of the liver. If any of these symptoms occur it is important to get medical help within twenty four hours. Dehydration is a common side effect of food borne illnesses, therefore it is important to keep oneself well hydrated when suffering these symptoms.
Healthy eating and Balanced Diet:
We all need food for our survival and growth. It is also important that we eat the right kinds of food and in the right quantities. We depend on our food to provide our bodies with the right nutrients it needs for life, therefore we must make sure to eat the food rich in the nutrients we require.
Vegetables are the healthiest of foods. Fresh, organic vegetables provide us with lots of healthy carbohydrates, vitamins, minerals and fibre. It is advisable to eat plenty of raw salads and cooked vegetables with every meal.
Fruits too are rich in many vitamins and minerals. Fruits are high in sugar and should therefore be eaten in less quantity than vegetables. It is always best to eat fruits that are season at that time of the year.
Grains like wheat and rice form an integral part of our diets and are often consumed in large quantities with each meal. However it is healthier to eat whole grain like whole wheat bread or chapattis and brown rice. Because the carbohydrates from grain gets broken down into sugar very quickly, the quantity of grains and grain product in our diet should be kept low
Meat, fish, eggs and milk are very good sources of protein and fats. Eating protein rich foods in moderate quantities is sufficient for a balanced diet.
Vegetarians who do not consume meat can get the protein from food like dhal and other pulses. Nuts and seeds are also rich in many of the nutrients that we require.
Eating fresh, healthy, wholesome food in the right quantities is the key to good health and wellbeing.