Nutrition: Macronutrients

Objectives

  • Discuss the importance of a balanced diet.
  • Define nutrients and nutrition
  • Describe the major nutrients and identify their sources
  • State the functions of macronutrients and their deficiency

Food Groups

  • Fruit and vegetables
  • Meat, fish and alternatives
  • Foods containing fat and foods containing sugar
  • Bread, other cereals, and potatoes
  • Milk and dairy products

Nutrients

  • Purpose / Function
    • Fuel your energy.
    • Help you grow.
    • Repair the body.
    • Maintain basic bodily functions.

Essential Nutrients

  • The different types and amounts of food we eat make up our diet.
  • These different food contain many different nutrients.
  • Nutrients are essential in the diet and include:
    • Carbohydrates
    • Protein
    • Fats
    • Minerals
    • Vitamins
    • Water
    • Dietary Fibre
  • Carbohydrates, proteins, and fats are termed ‘macronutrients’ as they provide the bulk of our food.
  • Vitamins and minerals are termed ‘micronutrients’ as they are only needed in small quantities.

Define Nutrients and Nutrition

  • Nutrients:
    • The substances found in food that keep your body functioning
  • Nutrition:
    • The process of providing or obtaining the nutrients necessary for health and growth.

Major / Macronutrients:

  • Carbohydrates
  • Protein
  • Fats / Lipids

Minor / Micronutrients

  • Vitamins
  • Minerals

MACROnutrients: CARBOHYDRATES

  • Carbohydrate provides the MAIN source of energy for the body.
  • It provides 4 calories for every 1 gram.

Function of Carbohydrates in the Body

  • Provide energy which is released during respiration
  • Stored as Glycogen

Carbohydrates Two Types:

  • Simple sugars (reducing sugar) – made of 1 or 2 sugar molecules
  • Complex sugars – Made of long chains of sugar molecules joined together by condensation
  • Reducing sugars are able to reduce the test substance Benedict’s solution by removing its oxygen.

Types of Carbohydrates

  • Simple
    • Monosaccharides
      • Glucose
      • Fructose
      • Galactose
    • Disaccharides
      • Maltose
      • Lactose
      • Sucrose
  • Complex
    • Polysaccharides
      • Starches
      • Fibers
      • Glycogen

Common Simple Sugar

  • Glucose:
    • Most common reducing sugar
    • Main sugar carried in the blood
    • 1st sugar made by plants during photosynthesis
  • Fructose:
    • Reducing sugar
    • Found in fruit

Complex Sugar

  • Starch
    • Main food store in plants (forms a large part of the carbohydrate we eat)
  • Cellulose
    • Makes up plants cell walls
    • Not able to be digested by humans
    • It provides roughage in the diet
  • Glycogen (animal starch)
    • Important storage product in animals
    • Found in the liver and muscles

Carbohydrates

  • Molecules with two or more sugars attached can be broken down by combining with water. This process is called hydrolysis.
  • Sucrose + water \rightarrow glucose + fructose
  • Maltose + water \rightarrow glucose + glucose
  • Lactose + water \rightarrow glucose + galactose

Sources

  • Simple Sugars Juice, Honey, Jams, Candy, Enriched Processed foods, e.g. White bread and pasta
  • These carbohydrates are quickly digested and dispersed in the blood.
  • The body may experience high spikes in blood glucose which may cause a quick burst of energy.

Sources Complex Sugars

  • Whole wheat bread
  • Brown rice
  • Wheat crackers
  • Oatmeal
  • Vegetables
  • Whole grains
  • Complex carbohydrates take longer for the body to digest and distribute to the blood
  • Hence blood sugar spikes are not experienced.

Excess Consumption

  • What will happen if there is too much carbohydrate (e.g. Glucose) in the body Stored in the liver, muscles as glycogen stores for later use, or it’s converted to fat in the adipose tissue (fat cells) and stored if the glycogen stores not utilized.
  • Note the body will fill the liver and muscle reserves 1st before storing glucose as fat in the adipose tissue
  • Can lead to obesity and diabetes mellitus II

Deficiency

  • Lethargy -Lack of energy and enthusiasm
  • Marasmus – deficiency disease in babies and young children due to a lack of carbohydrate and protein causing an energy deficiency
    • Here the body has a shrunken appearance and the abdomen is swollen
    • Growth is slow and dehydration takes place.

Other signs / symptoms of Marasmus

  • Thin face.
  • Ribs and shoulders clearly visible through the skin.
  • Very loose skin that sometimes hangs in folds in the upper arms, thighs, and buttocks.
  • Persistent dizziness.
  • Sunken eyes.
  • Diarrhoea.
  • Irritable behaviour.
  • Shrunken liver

Lipids (Fats and Oil)

  • Constitutes a broad group of naturally occurring molecules such as Fats, Waxes: Plants secrete waxes into and on the surface of their cuticles as a way to control evaporation, Sterols (e.g. Cholesterol in animals), Oil

What’s the difference between Fats and Oil?

  • Fats are solids and oils are liquids at room temperature.

Sources of Lipids (Fats and Oil)

  • Plants fats (normally liquids at room temperature include: sunflower oil corn oil.
  • Margarine consist mainly of vegetable oils but they have been processed into a solid.
  • Peanuts, soya beans, castor oil Animal fat sources include pork and lard.

Function

  • Fats have TWO MAIN functions:
    • Provision of energy.
      • Fat is a concentrated source of energy (1 g provides 9 calories – double that of carbohydrate.)
      • They are used during respiration to produce energy.
      • Fats are only used usually when all carbohydrates have been used up.
    • As a storage of compounds in animals

Other Functions

  • Protects bones, muscles, and organs
  • Insulate us in the cold
  • Provide us with essential fatty acids to build materials for cell membranes, blood clotting, and other body tissues
  • Carry fat soluble vitamins (Vitamins A, D, E, and K) throughout the body.

Over consumption of fat

  • Eating too much saturated fat has become a problem in our society.
  • There are many health problems linked with too much saturated fat in the diet, e.g.
    • coronary heart disease (Disease resulting from build up of plaque inside the arteries) strokes.

Over consumption of fat

  • PLEASE remember an overconsumption of fats can lead to obesity.
  • Therefore, an overconsumption of fats (animal fats) will lead to obesity. This further leads to coronary heart disease.
  • Coronary heart disease (CHD) is a disease in which a waxy substance called plaque builds up inside the coronary arteries.
  • These arteries supply oxygen-rich blood to your heart muscle. When plaque builds up in the arteries, the condition is called atherosclerosis. This plaque is really fat that build up in the arteries. These fat deposits reduces the diameter of the artery and causes high blood pressure which is known as hypertension.

Over consumption of fat

  • Arteriosclerosis is another condition which is due to atherosclerosis. However, arteriosclerosis occurs when the walls of the arteries harden and become less elastic. This increases high blood pressure and therefore, hypertension.
  • Hypertension is dangerous as it causes blockage or reduced blood flow to the heart and vessels which in turn causes heart attacks which can be fatal.
  • Sometimes blood flow to the brain is blocked which results in the brain lacking oxygen. This can cause unconsciousness and even death.

Coronary heart disease

  • Plaque buildup narrows coronary arteries, reducing blood flow to the heart muscle.

Fat Deposits Under the Skin

  • The fat stored under the skin, helps keep the body warm as well as serving as an energy store
  • It is also used in the formation of cell membranes and as a solvent for vitamins A and D

Protein (C, H, O, N)

  • Protein forms are important forms of many molecules, e.g. haemoglobin and insulin
  • Protein consists of the elements Carbon, Hydrogen, Oxygen, Nitrogen, Sometimes phosphorous and sulphur

What are some sources of Protein

  • Meat
  • Fish
  • Eggs
  • Milk
  • Cheese
  • Plant contains protein but in smaller amounts (legumes: soya beans, peas and groundnuts)

Function

  • Used for growth and repair of cells
  • Are the structural components of enzymes which controls metabolic activity
  • Forms structural parts of haemoglobin
  • To make hormones which control various processes in the body, e.g. insulin
  • To make antibodies to fight disease.
  • To provide energy when carbohydrate and lipids have been used up

Protein Deficiency

  • Kwashiorkor
    • Growth is slowed
    • Arms and legs become thin
    • Protruding belly
    • Skin becomes dry and hair thin and loses pigment
    • A dull lifeless attitude occurs
    • This disease occurs in children when mothers can no longer breast-feed the baby.

Table summarizing nutrients

  • Macromolecules: Carbohydrates (contains C, H and O)
    • Monomer/ basic unit: Monosaccharides
      • Functions: Main source of energy (17kj per gram during respiration), Structural purposes (eg: cellulose in plant cell wall), Storage in plants and animals
      • Sources: Foods containing sugar such as cakes, biscuits, jam. Also, starchy foods such as potatoes, bread, yam, rice, etc.
      • Symptoms of deficiency diseases: Lethargy(lack of energy), Marasmus (which also includes a lack of protein). Symptoms of marasmus include swollen abdomen and shrunken appearance.

Table summarizing nutrients

  • Macromolecules: Protein (contains C, H, O, N and S)
    • Monomer/ basic unit: Amino acids (20 different amino acids that make protein)
      • Functions: Used for cell growth and repair, Makes hormones (eg: insulin), Makes enzymes which are biological molecules that speed up reactions, Source of energy (only used for energy once carbohydrate and lipid reserve have been depleted)
      • Sources: Meat, fish, eggs and milk, also Plant foods such as legumes which includes peas, soya beans, groundnuts
      • Symptoms of deficiency diseases: Kwashiorkor (symptoms include slowed growth and arms and legs become thin, abdomen may swell, dry skin that has thin hair and loss of pigment. Marasmus (includes lack of carbohydrates as well).

Table summarizing nutrients

  • Macromolecules: Lipids(contains C, H, O,)
    • Monomer/ basic unit: Liquids referred to as oil. Solids referred to as fats. Fats-solid at room temp. Oil- liquid at room temp. Contains 1 (one) glycerol and three (3) fatty acids.
      • Functions: Used for energy (39kj of energy), Storage (used for buoyancy in whales and some aquatic animals), Protection (found in adipose tissue that surrounds organs and found under skin., Insulation, Solvent for vitamins A, D and E.
      • Sources: Lard, butter, margarine, milk, soya beans, peanuts, castor oils

Food tests Perform tests to distinguish among food nutrients

  • Test for reducing sugars- Benedict’s test Also note test for non-reducing sugar
  • Test for starch- Iodine test
  • Test for lipid- Emulsion test or grease spot test
  • Test for protein- Biuret test
  • It is important that you know how to carry out a food test. Steps are in your lab manual. Read and become familiar with the process.