Unit 4: The Macronutrients-I – Carbohydrates and Water
4.1 Introduction:
- Nutrients are essential components in food, categorized as macronutrients (carbohydrates, fats, proteins, water) and micronutrients (vitamins, minerals).
- Macronutrients contribute significantly to the weight of food, essential for the body in larger quantities.
4.2 Digestion, Absorption, and Utilization Overview:
- Digestion breaks down complex substances in food into simpler ones for absorption.
- Absorption occurs in the small intestine, facilitated by villi.
- Utilization involves metabolic processes where absorbed nutrients undergo chemical changes.
4.3 Carbohydrates:
- Classified into available (sugars, starches) and non-available (fiber) carbohydrates.
- Digestible carbohydrates contribute to energy, found in cereals, roots, fruits, and sweeteners.
- Functions include energy provision, protein-sparing action, and aiding fat utilization.
4.4 Water:
- Unique status as both food and macronutrient.
- No digestion required; directly absorbed.
- Vital for various physiological functions.
4.5 Summing Up:
- Macronutrients (carbohydrates, fats, proteins, water) are essential for the body.
- Understanding digestion, absorption, and utilization lays the foundation for further study.
Check Your Progress Exercise 1:
1) Protein-sparing action of carbohydrates:
- The protein-sparing action of carbohydrates refers to the role of carbohydrates in preventing the body from breaking down proteins for energy. When sufficient carbohydrates are present in the diet, they spare proteins from being used as an energy source. Proteins can then fulfill their primary functions in supporting growth and body-building, rather than being utilized for energy production.
2) Harm of eating too little carbohydrate:
- Yes, it can be harmful to eat too little carbohydrate. In such a situation, the body may resort to breaking down proteins for energy, compromising their vital roles in growth and development. Additionally, insufficient carbohydrates can lead to an excessive breakdown of fats for energy, resulting in the accumulation of by-products that can negatively impact health. Therefore, maintaining an adequate intake of carbohydrates is essential for overall well-being.
Summary: Digestion, Absorption, and Utilization of Carbohydrates
Digestion of Carbohydrates:
- Involves breakdown of starch and sugars (e.g., common table sugar) into the simplest unit, glucose.
- Dietary fiber in whole grains, vegetables, and fruits cannot be digested by humans due to the lack of necessary enzymes.
Digestion Process:
- Mouth: Saliva contains enzymes that start breaking down cooked starch.
- Stomach: No carbohydrate-digesting enzymes present; minimal digestion occurs.
- Small Intestine: Principal site for carbohydrate digestion. Pancreatic enzymes act on both raw and cooked starch, converting it into smaller units.
- Small Intestine Cells: Enzymes further act on sugars and partially digested starch, breaking them into simple units (glucose, fructose, galactose).
Absorption and Utilization:
- Simple sugar units (glucose, fructose, galactose) are transported to body tissues and cells via the bloodstream.
- Glucose is converted within cells to release energy through combustion.
- Excess glucose is converted to glycogen and stored in the liver and muscles for future energy needs.
- Glycogen can be broken down to release glucose as needed, but there’s a storage limit.
- When glycogen storage is exceeded, excess glucose is converted into fat and stored in the body.
Note:
- Carbohydrate digestion begins in the mouth but is primarily carried out in the small intestine.
- The end products (glucose, etc.) are crucial for energy production and storage.
- Understanding these processes is vital for appreciating the role of carbohydrates in providing energy for the body.
Check Your Progress Exercise 2:
1) What are simple sugars?
- Simple sugars refer to the basic units into which carbohydrates are broken down during digestion. Examples include glucose, fructose, and galactose.
2) Fill in the blanks:
a) The principal site of carbohydrate digestion is the small intestine.
b) Cereals and roots are the major sources of carbohydrates in our diets.
c) One gram of carbohydrate provides approximately 4 Kcal.
d) Glycogen is the storage form of glucose in the body.
Summary: Non-available Carbohydrates (Fibre)
4.3.2 Non-available Carbohydrates (Fibre):
Nature of Fibre:
- Fibre is non-available carbohydrate, consisting of indigestible components like cellulose found in plant foods.
Is Fibre a Nutrient? Role in the Body:
- Fibre is considered a non-nutrient but plays a crucial role in regulating certain body processes.
Functions of Fibre:
- Satiety Value:
- Fibre cannot be chemically broken down but absorbs water in the digestive tract.
- It swells up, making food residue bulky and providing a feeling of fullness or satisfaction.
- Elimination:
- Facilitates easy elimination of unabsorbed food in stools or faeces.
- Fibre in stools holds water, softening them and aiding in easy elimination, preventing constipation.
- Disease Prevention:
- Some research suggests that fibre contributes to preventing diseases such as heart disease, diabetes, and large intestine cancer.
Food Sources of Fibre:
- Present in the outer covering of cereals and pulses.
- Whole grains (e.g., whole wheat flour, whole pulses) contain significant fibre.
- Refined cereals (e.g., maida, suji) have less fibre due to the removal of bran and germ during processing.
- Fibre is also found in the outer skin and seeds of vegetables and fruits.
- Examples of fibre-rich foods: lotus stem, green leafy vegetables, ladies finger, peas, beans, brinjal, guava, oranges, amla.
Distinguishing “Whole” and “Refined” Cereals:
- Grains have three main parts: bran (outer covering), germ (embryo), and endosperm (stores food).
- Whole grain cereals retain the outer covering (bran), while refined cereals undergo cleaning and removal of coarse particles, resulting in less fibre.
Animal Foods and Fibre:
- Animal foods like milk, milk products, meat, fish, poultry do not contain fibre.
Understanding the role of fibre is essential for maintaining digestive health, preventing constipation, and potentially reducing the risk of certain diseases. Incorporating fibre-rich foods into the diet is recommended for overall well-being.
Check Your Progress Exercise 3:
1) Role of fibre in relieving constipation:
- Fibre facilitates easy elimination of unabsorbed food by holding water in stools, making them softer and aiding in their smooth elimination. This helps in preventing or relieving constipation.
2) Fill in the blanks:
a) Maida and suji are termed refined cereals.
b) Fibre is the term used for non-available carbohydrates such.
c) Green leafy vegetables and ladies finger are some of the rich sources of fibre.
Summary: Water – Essential for Life
Functions of Water:
- Major Constituent of the Body:
- Makes up approximately 60% of the total weight in adults and nearly 75% in infants.
- Essential component of all cells and tissues, varying in amount in different body tissues.
- Medium for Body Fluids:
- Acts as the medium for all body fluids, including blood, saliva, digestive juices, urine, feces, and sweat.
- Temperature Regulation:
- Crucial role in regulating body temperature.
- Distributes heat produced in the body, and perspiration helps cool the body by using heat for evaporation.
- Dissolving and Transport:
- Dissolves various substances, including digestion products, and transports them via blood.
- Aids in the removal of waste products from the body.
- Serves as the medium for chemical reactions in the body.
- Lubrication:
- Acts as a lubricant by bathing body cells, keeping them moist.
- Lubricates joints, aiding in movement.
Sources of Water:
- Ingestion through liquids (water, tea, coffee, fruit juices, aerated drinks).
- Ingestion through solid foods, with varying water content (e.g., green leafy vegetables, pumpkin, apples).
- Water formed in the body during the metabolism of nutrients (carbohydrates, fats, proteins).
Importance of Clean Drinking Water:
- Essential to prevent waterborne diseases such as diarrhea, dysentery, and cholera.
Water Loss and Balance:
- Water is lost through kidneys (urine), skin (sweat), lungs (breath), and digestive tract (saliva, faeces).
- Body maintains water balance through the equilibrium of water intake (ingestion) and water loss (excretion).
Understanding the multifaceted role of water in the body is crucial for maintaining overall health and well-being. Regular intake of safe and clean water is essential for optimal functioning.
Check Your Progress Exercise 4:
1) Meaning of the term ‘water balance’:
- The term ‘water balance’ refers to the equilibrium maintained by the body between water intake (ingestion) and water loss (excretion) to ensure overall stability.
2) Fill in the blanks:
a) Our normal body temperature is 98.4°F or 37°C.
b) Water makes up approximately 60% per cent of the total weight of an adult.