Nutrients PDF

# Chapter 8: Food and Digestive System ## 8.1 Nutrients - Have you heard the phrase "You are what you eat"? Well it is true! - The food we consume daily plays an important role in our well-being. Food is the source of the nutrients we need. ### Nutrients - Our body breaks down the food we eat in...

# Chapter 8: Food and Digestive System ## 8.1 Nutrients - Have you heard the phrase "You are what you eat"? Well it is true! - The food we consume daily plays an important role in our well-being. Food is the source of the nutrients we need. ### Nutrients - Our body breaks down the food we eat into basic nutrients. - The chart below shows the different types of nutrients that we obtain from food. #### Types of Nutrients | Type | Description | |---|---| | Carbohydrates | Carbohydrates, proteins and fats are three main types of macronutrients. They are essential nutrients the body needs in large quantities to keep healthy. Macronutrients supply the body with energy, help prevent diseases, and allow the body to function correctly. | | Proteins | Carbohydrates, proteins and fats are three main types of macronutrients. They are essential nutrients the body needs in large quantities to keep healthy. Macronutrients supply the body with energy, help prevent diseases, and allow the body to function correctly. | | Fats | Carbohydrates, proteins and fats are three main types of macronutrients. They are essential nutrients the body needs in large quantities to keep healthy. Macronutrients supply the body with energy, help prevent diseases, and allow the body to function correctly. | | Vitamins | Vitamins and minerals are micronutrients, they are essential in small amounts. | | Minerals | Vitamins and minerals are micronutrients, they are essential in small amounts. | - Apart from the nutrients shown, water is equally essential for our body. A combination of different nutrients is found in most types of food. However, some types of food contain more of a particular nutrient than others. ### Carbohydrates - Carbohydrates are organic compounds that contain three elements: carbon, hydrogen and oxygen. All carbohydrates are made up of units of sugar molecules, also known as saccharides. - There are two types of carbohydrates shown in the chart below: simple carbohydrates and complex carbohydrates. #### Carbohydrates | Category | Type | Description | |---|---|---| | Simple | Monosaccharides | such as glucose, fructose and galactose or two sugar units (disaccharides) such as sucrose, lactose and maltose. They are found in food such as fruits, table sugar and milk. | | Simple | Disaccharides | such as glucose, fructose and galactose or two sugar units (disaccharides) such as sucrose, lactose and maltose. They are found in food such as fruits, table sugar and milk. | | Complex | Polysaccharides | include starch and dietary fibre. | - Simple carbohydrates are small molecules that consist of one sugar unit (monosaccharides) - Complex carbohydrates are much larger molecules that consist of thousands of sugar units bonded together. - Starch is found in bread, cereal, pasta, potatoes, peas and corn. - The body breaks down starch into sugars that will then be used to provide energy. ### Dietary Fibre - Dietary fibre is found in fruits, vegetables, nuts, beans, wholemeal bread and cereal. - Consuming food rich in dietary fibre can help a person feel full and less likely to overeat because his body cannot break down most of the dietary fibre. - A deficiency of dietary fibre can cause constipation, a condition that occurs when undigested food that move along the large intestine becomes hard and dry and the removal of faeces from the rectum becomes painful. ### The Main Function of Carbohydrates - The main function of carbohydrate is to provide energy so that life processes such as growth, reproduction and movement can be carried out. - One gram of carbohydrate provides four calories of energy. - Both simple and complex carbohydrates, except dietary fibre, are eventually converted by our body into glucose, also known as blood sugar. - Glucose can be used immediately, serving as the main source of energy for cells, tissues and organs, or stored in the liver and muscles as glycogen to be used later. - Simple carbohydrates provide bursts of energy as they are digested quickly. - On the other hand, complex carbohydrates take longer to be digested and thus provide longer-lasting energy when compared to simple carbohydrates. ### Proteins - Proteins are organic compounds. Protein molecules consist of long chains of smaller molecules called amino acids. - The amino acids are composed of carbon, hydrogen, oxygen and nitrogen elements. - Some amino acids contain sulphur and phosphorus elements as well. - Our body needs 20 different types of amino acids to function well. - These 20 types of amino acids combine in various ways to make proteins in our body. - Out of the 20 types, 11 are non-essential amino acids and the other 9 are essential amino acids. - Non-essential amino acids are synthesised by our body whereas essential amino acids are obtained from the food we eat. - We can get proteins from many sources, including animals and plants. - Proteins obtained from animal sources have all the essential amino acids whereas proteins obtained from plants only have some of the essential amino acids. - The proteins we eat are digested into their basic units, which are amino acids. - The main function of protein is to build and repair body tissues. - Protein also supplies us with energy. - One gram of protein provides four calories of energy. ### Functions of Proteins - Build new cells or replace dead cells. - A source of energy to our body. - Some serve as enzymes, antibodies and hormones. - Help repair worn-out or damaged cells and tissues. - Required for growth. - In a healthy person, protein contributes only a small amount of energy to the body. - In a person whose diet does not contain enough carbohydrates and fats, the body will use amino acids to produce energy. - The body cannot store protein, so once their needs are met, the excess protein consumed is usually stored as fat, while the surplus of amino acids will be converted to urea and removed from the body through the urine. ### Kwashiorkor - A severe protein deficiency disorder that affects mainly children in regions facing famine. - Some of the symptoms of kwashiorkor are oedema (fluid retention in the belly), retarded growth and fatigue. ### Marasmus - A disorder caused by severe deficiency of protein and calories. It affects mainly children in regions of high poverty. - Some of the symptoms of marasmus are severe weight loss and muscle wasting. - If not treated properly, it can be fatal. ### Fats - Fat is an organic compound that consists of carbon, hydrogen and oxygen elements. - Fat is made up of glycerol and fatty acids. - Fat is an energy source for our body. - One gram of fat provides nine calories of energy which is two times the energy supplied by carbohydrates. - Fat can come from plant or animal sources. ### Animal Fats - Animal fats are found in butter, meat and cheese. ### Plant Fats - Plant fats are found in avocado, nuts and vegetable oil. ### Types of Fat - There are three types of fat, namely saturated fat, unsaturated fat and trans fat. - Most animal fat are saturated whereas most plant fat are unsaturated. - Saturated fat exists in solid form whereas unsaturated fat exists in liquid form at room temperature. - Trans fat is usually found in fried food. - A small amount of fat is important for good health. - Large amounts of fat can be harmful especially animal fat, which are saturated fat, as they can lead to obesity and problems in the circulatory system such as heart diseases. - Unsaturated fat is healthier to be consumed compared to saturated fat. - Therefore, it is advisable to have a diet low in saturated fat. - Trans fat is the unhealthiest one among all the types of fat. - Eating too much trans fat can cause weight gain, heart diseases and higher risk for type 2 diabetes.\ ### Saturated Fat - Saturated fat is found in beef and poultry. - Butter is an example of food containing saturated fat. ### Unsaturated Fat - Unsaturated fat is found in sunflower oil, olive oil and sesame oil. ### Trans Fat - Trans fat is found in French fries, cookies and fried chicken. ### Cholesterol - Cholesterol is a fat-like substance found in the blood and it helps the body make cell membranes, hormones and vitamin D. - The cholesterol in the blood comes from the food we eat and the liver. - The cholesterol produced by the liver is enough to meet the daily requirement, therefore there is no need to get it from food. - Cholesterol is carried in the bloodstream as lipoproteins, which is a combination of protein and fat found in the blood. - There are two types of lipoproteins, namely the low-density lipoproteins (LDL) and high-density lipoproteins (HDL). - When we consume a high amount of saturated fats, there will be an increase in the low-density lipoproteins (LDL), considered as the 'bad cholesterol'. - High levels of low-density lipoproteins (LDL) contribute to atherosclerosis, which is the fatty build-up in the walls of arteries making the arteries narrower, disrupting blood flow and increasing the risk for heart diseases such as heart attack and stroke. - On the other hand, high-density lipoproteins (HDL), considered as the "good cholesterol" carry cholesterol from other parts of the body back to the liver to be removed from the body. - A healthy level of HDL may protect a person against heart diseases. - Apart from supplying energy to our body, fat plays several other roles as shown in the chart below: ### Functions of Fats | Function | Description | |---|---| | As an energy source | | | Excess fat that is stored under the skin acts as a thermal insulator | | | Protects internal organs such as the heart and kidneys | | | Constituent of cell membranes and nerve cells | | | Adds flavour to food and contribute to the sense of fullness | | | Transports fat-soluble vitamins such as vitamin A, D, E and K to be effectively absorbed by the body | | ### Vitamins - In addition to carbohydrates, proteins and fats, we need vitamins in tiny amounts for good health and growth. - Vitamins are organic compounds that are absorbed directly from the food into our body with no digestion required. - A lack of vitamins in our diet can lead to various deficiencies and diseases. - On the other hand, vitamins must not be taken in excess because they can be toxic to the body. - There are two categories of vitamins: water-soluble and fat-soluble vitamins. - Water-soluble vitamins are vitamins B and C which cannot be stored in the body, thus they must be taken regularly from our diet. - Fat-soluble vitamins are vitamins A, D, E and K which can be stored in the body. #### Water-Soluble Vitamins | Vitamin | Description | Sources | |---|---|---| | Vitamin B₁ (thiamine) | releases energy from food and is required for the health of the nervous system. A deficiency of this vitamin can cause beriberi, characterised by weight loss and weakness in the limbs. | Eggs, Nuts, Legumes | | Vitamin B₂ (riboflavin) | releases energy from food and is required for the health of the nervous system and the heart. A deficiency of this vitamin can cause sore eyes, a swollen tongue, and skin lesions at the corners of the mouth, nose and ears. | Green leafy vegetables, Dairy products, Yeast | | Vitamin B₃ (niacin) | releases energy from food and is required for the health of the nervous system, skin, intestines and heart. A deficiency of this vitamin can cause pellagra, a disease characterised by dermatitis, diarrhoea and dementia. | Nuts, Liver, Unpolished rice | | Vitamin B₁₂ (cobalamin) | is required in the formation of red blood cells and for the health of nervous system. A deficiency of this vitamin causes anaemia, neurological disorders and weight loss. | Red meat, Dairy products, Eggs | #### Fat-Soluble Vitamins | Vitamin | Description | Sources | |---|---|---| | Vitamin A | is for maintaining healthy skin and good eyesight. A deficiency of this vitamin causes night blindness and scaly skin. | Carrots, Green vegetables, Dairy products| | Vitamin D | is for the growth and development of teeth and bones. A deficiency of this vitamin causes rickets, a disease in children where their bones become soft and weak. | Dairy products, Sunlight, Eggs | | Vitamin E | acts as an antioxidant, helps in the formation of red blood cells, maintains the functions of reproductive system and strengthens the immune system. A deficiency of this vitamin causes anaemia and infertility. | Green vegetables, Nuts, Olive oil | | Vitamin K | helps in the blood clotting process. A deficiency of this vitamin causes prolonged and excessive bleeding. | Egg yolk, Milk, Cabbage | ### Minerals - Minerals are non-organic substances required by our body. - We need tiny amounts of minerals for proper growth and to stay healthy. - The table below shows a variety of minerals, their sources, functions and symptoms of deficiencies. | Mineral | Sources | Functions | Symptoms of deficiency | |---|---|---|---| | Calcium | Milk, cheese, anchovies, green vegetables | Aids in blood-clotting Strengthens bones and teeth Regulates functions of muscles and nerves | Delayed blood clotting Rickets in children Osteoporosis in elderly people | | Magnesium | Green leafy vegetables, whole grains, meat | Regulates functions of muscles and nerves Keeps the bones strong | Weak bones Muscle weakness Fatigue | | Sodium | Table salt | Regulates body fluid For the proper functioning of nerves | Muscle cramps Fatigue | | Iron | Green leafy vegetables, liver, meat, egg | For the formation of haemoglobin in red blood cells | Anaemia | | Iodine | Seafood, seaweed, iodised salt, green vegetables | For the formation of hormones in the thyroid gland | Goitre (swelling of the thyroid gland) | | Phosphorus | Milk, cheese, eggs | For the formation of healthy bones and teeth For the contraction of muscles | Tooth decay Weak muscles | | Potassium | Bananas, potatoes, fish, meat, nuts | Regulates body fluid For the proper functioning of nerves and muscles | Weak muscles Fatigue | | Chlorine | Table salt | Regulates body fluid For the proper functioning of nerves | Muscle cramps Loss of appetite | ### Water - Water is essential in many life processes. - Water makes up about 60% to 70% of our body mass. - When proper water balance is maintained in the body, all the processes in the body can be carried out efficiently. #### Functions of Water | Function | Description | |---|---| | Enables the breakdown of food substances during digestion | | | Dissolves nutrients and transports them throughout the body | | | Removes excretory waste through sweat and urine | | | Regulates body temperature | | | Main component of cells and blood plasma | | | Medium of transportation for respiratory gases and nutrients | | | Medium for all cellular biochemical reactions | | - The daily water loss through our sweat, urine, and the air we breathe out needs to be replaced. - An average person needs to consume approximately six to eight glasses of water daily. - Water can also be obtained from food with high water content. - Water loss can affect the physiological processes and physical performance of the body. - If the water that is lost is not replaced, dehydration occurs. - An extreme water loss can be fatal. ## 8.2 A Balanced Diet - A balanced diet fulfils all the nutritional and energy needs of the body. - It consists of carbohydrates, fat, proteins, vitamins, minerals and water in the correct quantities and proportion. - A balanced diet for a person varies based on his lifestyle, health conditions and specific nutritional requirements. - In the latest recommendation by the USDA (United States Department of Agriculture) of the balanced meal known as the MyPlate guide, vegetables and fruits must form about half of the food plate serving since they are the healthiest food. - The remaining food plate serving should contain proteins and grains accompanied by a small serving of dairy product with low-fat content. - A person can be healthy and energised by eating the right food in the right amount. - A balanced diet is required for the healthy growth and development of the body. - Each food group plays a role: - Carbohydrates and fat are sources of energy. - Proteins repair and build new tissues for growth. - Vitamins and minerals keep us healthy. - Dietary fibre prevents constipation. - However, if a person overeats, the extra energy is stored as a layer of fat. - Too much fat may lead to health problems such as heart diseases and diabetes. - On the other hand, if a person eats less than what is required, he may suffer from malnutrition. - Malnutrition can weaken the immune system, making the person susceptible to diseases. - Therefore, by following the minimum daily energy requirements, health issues related to overeating and malnutrition can be prevented. ### Nutrition Facts Label - A nutrition facts label on packaged food product lists the types of nutrients found in the product, the serving size, and the calories per serving of the food product. - This enables consumers to make the best decision on how much to eat, or how they can better balance their food choices throughout the day. - They can choose food that are high in nutrients they need more of, such as protein and low in nutrients they need less of, such as fat. - The value of energy on labels shows how much energy the food contains. - It does not measure how much energy a person gets from it. - This is because certain foods use a lot more energy to digest than others. ### Energy Content of Food - All of us need energy to move around, grow and build new tissue and repair damaged tissue. - Food is the source of energy for our body. - The amount of energy in a food can be determined by burning a sample of food in a calorimeter and measuring the amount of heat released. - The amount of heat produced from the complete combustion of one gram of food is known as the energy value of the food. - It is measured in kilojoules per gram (kJ g-¹). - The energy value can also be measured in calories. - 1 kilojoule = 1000 joules - 1 calorie (cal) = 4.2 joules - 1 calorie or 4.2 joules is defined as the quantity of heat energy needed to raise the temperature of 1 gram of water by 1 degree Celsius at a pressure of 1 standard atmosphere. - The equation to calculate the energy value of a food sample by using a calorimeter is as follows: $Energy value of food (kJ g^{−1}) = \frac{Water mass (g) × 4.2 J g^{−1} °C^{−1} × Increase in water temperature (°C)}{Food sample mass (g) × 1000}$ - The quantity of energy in 1 g of each nutrient differs. - Although the energy value of carbohydrates is not the highest, our body uses carbohydrates as a source of energy first and only when carbohydrates are used up will fat be used. - The table shows the energy value of the three main classes of food. | Food class | Energy value (kJ/g) | Energy value (kcal/g) | |---|---|---| | Fat | 37 | 9 | | Protein | 17 | 4 | | Carbohydrate | 17 | 4 | - Our body uses energy from food to perform daily activities such as walking, breathing and working. - We need different amounts of energy from the food we consume, at various stages of our lives. - The average amount of calories a person needs is about 2000 calories per day to maintain his current weight. - However, the daily energy requirement or calory intake varies with individuals based on several factors such as work, size or body weight, condition or state of health, climate, age, gender and physical activity of a person. ### Factors that affect our daily energy requirement - **Work**: A person who does heavy work needs more energy than a person who has a sedentary job. For example, labourers, fishermen and construction workers need more energy compared to clerks and graphic designers. - **Size or body weight**: A person with a large body needs to eat more than a person with a smaller body. The larger the body size, the more energy the body needs to function as it has more cells and tissues. - **Condition or state of health**: Pregnant women require a lot of energy for the growing foetus and lactating women also need extra energy to produce milk for their baby. A person who is sick requires a lot of energy to recover from his illness. - **Climate**: People living in cold climate countries require more energy to maintain their body temperature compared to those living in hot climate countries. - **Age**: Children and teenagers require more energy compared to adults. This is due to their higher metabolic rate as they are more active and are undergoing rapid growth. - **Gender**: A male adult requires more energy than a female adult of the same age and body size. This is because the metabolic rate is higher in a male than a female. - **Physical activity**: Athletes need extra calories for both their physical activities and their growth. ### Consuming Healthy Meals - Food contains the nutrients our body needs to build new cells and tissue as well as to repair damaged cells and tissue. - Food provides us the substances needed to maintain good health and prevent diseases. - Food provides us the energy to do work and carry out life processes. - Although we love having a tasty meal, we must also consider its nutritional value. - By neglecting the nutritional value of the food we consume daily, we are risking our overall health in the long run. - Healthy meals consist of fruit and vegetables, whole grains, lean protein and nuts. These food are rich in nutrients and have a beneficial effect on our health. - On the other hand, unhealthy meals such as fast food and snacks, have less nutritional value and are high in fat, salt and sugar. We should avoid or take unhealthy food in small amounts. #### Healthy Meals - Fruit salad, Gado-gado, Nasi pecel #### Unhealthy Meals - Fast Food, Instant noodle, Sweet food ## 8.3 The Digestive System - Do you know how the nutrients from the food we consume are absorbed by our cells? - This is made possible by our digestive system through the process of food digestion. - Food digestion is the breakdown of food that are large, complex and insoluble into smaller, simple and soluble molecules that can be absorbed into the bloodstream and transported to different parts of the body. - There are two types of digestion: physical digestion and chemical digestion. - Both the processes involve the breakdown of food and occur in the digestive tract, also known as the alimentary canal. - Food digestion starts in the mouth with the aid of the teeth, saliva and tongue. ### Types of Digestion #### Physical Digestion - Occurs in the mouth, oesophagus, stomach and small intestine. - Does not involve any enzymes. - Involves peristalsis. #### Chemical Digestion - Occurs in the mouth, stomach and small intestine. - Breakdown of complex food molecules into simple molecules with the aid of the enzymes. - Does not involve peristalsis. #### Involves - **Breakdown of large pieces of food into smaller pieces by the grinding action of teeth with the aid of tongue and saliva (chewing)** - **Wave-like contraction and relaxation (peristalsis) by the muscles in the walls of the oesophagus and the whole length of the digestive tract, pushes the food down the tract** - **Squeezing and mixing of food by the muscles of the stomach lining (churning)** - **Contraction and relaxation of segments of muscles in the small intestine (segmentation)** ### Parts of the Digestive System - Food digestion takes place in the alimentary canal that extends from the mouth to the anus. - The alimentary canal is long and muscular. - It consists of the mouth, oesophagus, stomach, small intestine (duodenum, jejunum and ileum), large intestine (appendix, caecum, colon, rectum) and anus. - The total length of the alimentary canal is around 9 metres, and it is open at both ends, at one end is the mouth and at the other is the anus. - The small intestine makes up two thirds of the total length of the alimentary canal. - There are also other organs in the digestive system which are the liver, gallbladder and pancreas. - Each part of the digestive system has its own specialised function. ### Digestion in the Mouth - The digestive process begins in the mouth. - The chewing action of teeth cuts the food into smaller pieces to increase the surface area of the food for the digestive enzymes to act on. - The presence of food stimulates the salivary glands in the mouth to secrete saliva. - Saliva contains the digestive enzyme, salivary amylase, which breaks down starch into maltose. $Salivary amylase$ $Starch + Water → Maltose$ - The tongue then rolls the partially digested food into a small ball called bolus with the help of the saliva and pushes it into the oesophagus. - The oesophagus is a long, narrow tube with strong muscles in its walls. - The bolus is then pushed through the oesophagus into the stomach by peristalsis. - Peristalsis is the rhythmic contraction and relaxation of muscles which pushes food along the alimentary canal. ### Digestion in the Stomach - The stomach is a sac-like muscular organ at the end of the oesophagus. - The glands in the stomach wall secrete a liquid called gastric juice. - Gastric juice consists of hydrochloric acid, mucus, and the digestive enzyme, pepsin. - Hydrochloric acid kills bacteria in the food that enters the stomach, creating an acidic environment for the enzyme, pepsin, and stopping the action of the salivary amylase. - Mucus protects the stomach wall from the hydrochloric acid and digestive enzymes. - Pepsin breaks down protein into polypeptides. $Pepsin$ $Protein + Water → Polypeptides$ - The stomach stores food for about three to four hours, enabling the food to mix with the gastric juice. - From the stomach, the partly digested, semi-liquid mass called chyme moves into the small intestine when the sphincter muscle relaxes. - There is a sphincter, ring-shaped muscles at the top and bottom of the stomach each. - The cardiac sphincter regulates the food from the oesophagus entering the stomach and prevents the contents from the stomach re-entering the oesophagus. - The pyloric sphincter controls the flow of food out of the stomach and allows only small amount of food into the duodenum (first part of the small intestine) at one time. ### Digestion in the Small Intestine - The small intestine consists of the duodenum, jejunum and ileum. - Duodenum receives: - chyme from the stomach - bile produced by the liver - pancreatic juice secreted by the pancreas. - The liver produces a greenish liquid called bile and stores it in the gall bladder. - Bile flows into the duodenum through the bile duct. - Bile emulsifies fat into small droplets and creates an alkaline condition for the pancreatic enzymes to work. - The pancreas secretes pancreatic juice into the duodenum through the pancreatic duct. - The pancreatic juice contains digestive enzymes such as trypsin, lipase and pancreatic amylase. - Unlike pepsin, these enzymes require an alkaline environment to function. - **Trypsin** further breaks down polypeptides into peptides. $Trypsin$ $Polypeptides + Water → Peptides$ - **Lipase** breaks down fat molecules into fatty acids and glycerol. $Lipase$ $Fat + Water → Fatty acids and glycerol$ - **Pancreatic amylase** breaks down starch into maltose. $Pancreatic amylase$ $Starch + Water → Maltose$ - The final breakdown of food occurs in the ileum. - The glands on the ileum wall secretes intestinal juice which consists of the enzymes maltase, sucrase, lactase, erepsin and lipase. #### Digestion of Carbohydrate - **Maltase** breaks down maltose into glucose. $Maltase$ $Maltose + Water → Glucose$ #### Digestion of Sucrose - **Sucrase** breaks down sucrose into glucose and fructose $Sucrase$ $Sucrose + Water → Glucose + Fructose$ #### Digestion of Lactose - **Lactase** breaks down lactose into glucose and galactose. $Lactase$ $Lactose + Water → Glucose + Galactose$ #### Digestion of Protein - **Erepsin** breaks down peptides into amino acids. $Erepsin$ $Peptides + Water → Amino acids$ #### Digestion of Fat - **Lipase** breaks down fat into fatty acids and glycerol. $Lipase$ $Fat + Water → Fatty acids + Glycerol$ - Digestion ends in the small intestine with fatty acids, glycerol, amino acids and glucose as the final products. ### Absorption of Digested Food in the Small Intestine - The jejunum and ileum are adapted to enable simple molecules produced from the digested food to diffuse through its wall. - The small intestine is long, enabling greater absorption of nutrients. - Its internal layer is highly folded and covered with many finger-like projections called villi. - Villi play a major role in the absorption of digested food. - The villi wall is one-cell thick, which helps speed up nutrient absorption. - Each villus has many specialised epithelial cells with tiny projections called microvilli to increase the surface area for nutrient absorption. - The villi have a network of blood capillaries that ensures glucose, amino acids and water-soluble vitamins are absorbed easily. - Each villus contains a structure called lacteal to absorb fatty acids, glycerol and fat-soluble vitamins. - When nutrients enter the blood, they are carried away to the liver and then throughout the body. - Nutrients travel through the bloodstream to feed all the cells in the body. - There are some substances that cannot be absorbed by the villi. Thus, they are left in the small intestine. ### Defaecation - The digested food and most of the water we drink are absorbed into the body in the small intestine. - The remaining food that cannot be digested, dead cells, fibre and water enter the large intestine. - In the large intestine, some of the water is reabsorbed. - The remaining semi-solid waste is called faeces. - It moves slowly with the help of the peristaltic action. - It takes between 12 to 24 hours to reach the rectum. - When the faeces accumulates in the rectum, it puts pressure to the rectum and triggers the urge to expel the faeces out of the body. - The rectum muscles will contract to pass the faeces out of the body from the anus. - This process is called defaecation. - The waste from a meal you consume should be expelled from your body within about 24 hours if your gut is working well. - In people who suffer from constipation, the waste will remain in the large intestine for quite some time and almost all of the water will be removed. - This causes the faeces to become dry and hard. - The best way to relieve constipation is to add more fibre to the diet. ### Lacteals - Lacteals are specialised lymphatic vessels found in intestinal villi. - Lacteals transport the absorbed nutrients, forming a milky substance called chyle. - Chyle eventually enters the lymphatic system for distribution throughout the body. ## 8.4 Health Issues Related to the Digestive System - The digestive system is important to our well-being, but various health issues can impact its functioning. - These include gastroesophageal reflux disease (GERD), digestive tract cancers, irritable bowel syndrome (IBS), hiatal hernia and more. - Disorders like diarrhoea, constipation, appendicitis and diabetes mellitus further emphasise the balance required for digestive health. ### Gastroesophageal Reflux Disease (GERD) - Gastroesophageal reflux disease (GERD), a persistent and chronic condition, occurs when stomach acid frequently flows back into the oesophagus, causing symptoms like heartburn and discomfort. - The recurrent exposure to acidic content can lead to inflammation and damage the lining of the oesophagus. - In severe cases, complications such as Barrett's oesophagus may develop, increasing the risk of oesophageal cancer. - Lifestyle modifications, medications to reduce acid production, and, in some cases, surgical interventions aim to manage GERD and prevent complications. ### Digestive Tract Cancers - Digestive tract cancers, encompassing the oesophagus, stomach and intestines, present various symptoms, including weight loss, abdominal pain and changes in bowel habits. - Early detection plays an important role in treatment success. - Risk factors such as age, genetic predisposition and lifestyle choices like smoking and diet contribute to the development of these cancers. - Screening tests, such as colonoscopies, aid in identifying precancerous lesions. - Integrated approaches, combining surgery, chemotherapy, and radiation therapy, are often used to treat digestive tract cancers. ### Irritable Bowel Syndrome (IBS) - Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterised by abdominal pain, bloating and changes in bowel habits. - The symptoms of IBS are influenced by factors like stress and dietary patterns. - Treating IBS involves making changes in lifestyle and diet. - Try to manage stress, eat regular and balanced meals and drink plenty of water. - Adding fibre to the diet through fruits, vegetables and whole grains can also help. - If needed, the doctor may recommend medications to ease specific symptoms like pain or diarrhoea. ### Lactose Intolerance - Lactose intolerance occurs when the body has difficulty digesting lactose, the sugar in milk. - Symptoms like bloating, diarrhoea and abdominal pain can arise after consuming dairy products. - Controlling lactose intake is important for symptom relief. - This can involve choosing lactose-free alternatives, taking lactase supplements, and introducing dairy gradually to assess tolerance levels. ### Hiatal Hernia - In a hiatal hernia, the stomach protrudes into the chest through the diaphragm, leading to symptoms like acid reflux, chest pain and difficulty swallowing. - Treatment options may include making lifestyle changes such as dietary adjustments and elevating the head during sleep. - In severe cases, surgery might be recommended to repair the hernia and relieve symptoms. ### Stomach Ulcer - Stomach ulcers, also known as gastric ulcers, are sores that develop on the lining of the stomach. - Contributing factors can include Helicobacter pylori infection or prolonged use of nonsteroidal anti-inflammatory drugs (NSAIDs). - The symptoms of stomach ulcers often involve burning stomach pain, bloating and indigestion. - Treatment for stomach ulcers depends on the cause of the ulcer. - The treatments include taking antibiotics and acid-suppressing medications, limiting the use of NSAID pain relievers, managing stress, boosting immunity and controlling inflammation, and eating a low-processed, nutrient-dense diet. ### Diarrhoea - Diarrhoea is characterised by loose or watery stools. - Most cases of diarrhoea are due to bacterial, viral, or parasitic infections. - It can also result from certain medications or underlying health issues. - Diarrhoea is treated through various approaches, depending on the underlying cause. - Antibiotics or antiparasitic medications are administered to eliminate infection-causing germs.. - Additionally, probiotics, which are beneficial bacteria, are sometimes recommended to restore a healthy balance in the gut. ### Constipation - Constipation involves infrequent bowel movements and difficulty passing stools, often resulting from factors such as inadequate fibre intake, dehydration and the use of certain medications. - Conditions like irritable bowel syndrome (IBS) and hypothyroidism can also contribute to constipation. - Making lifestyle changes such as exercising regularly, drinking more water, and eating more high-fibre foods is important in relief. - In persistent cases, over-the-counter or prescription medications may be recommended to promote bowel regularity and ease discomfort. ### Appendicitis - Appendicitis, characterised by inflammation of the appendix, presents symptoms like abdominal pain, nausea and vomiting. - Surgical removal of the appendix is typically required to prevent complications, including the risk of rupture. ### Diabetes Mellitus - Diabetes mellitus is a chronic metabolic disorder characterised by elevated blood glucose levels. - It occurs due to either insufficient production of insulin by the pancreas or ineffective utilisation of insulin by the body's cells. - Digestive issues can arise, affecting nutrient absorption. - Symptoms include frequent urination, thirst and unintentional weight loss. - The treatment for diabetes mellitus typically involves a combination of lifestyle changes, medication and insulin therapy. - Lifestyle changes include a balanced diet, regular exercise and weight management. - In some cases, insulin injections are necessary to regulate blood sugar levels. - Maintaining blood sugar levels is important in diabetes care.