Diet & Deficiencies (Cambridge (CIE) O Level Biology): Revision Note

Balanced Diet

• A balanced diet consists of all of the food groups in the correct proportions

• The necessary food groups are:

  • Carbohydrates

  • Proteins

  • Lipids

  • Vitamins

  • Minerals

  • Dietary Fibre

  • Water

• A balanced diet provides everything needed for successful growth and repair of tissues

• There must also be enough energy that can be used for metabolic processes

• There must also be enough roughage to maintain the function of the digestive tract

• A diet can be unbalanced by having too little of a food group (called a deficiency) or by having too much (a surplus)

Food Groups Table

Vitamin and Mineral Sources and Functions Table

Varying Dietary Needs of Individuals Table

Scurvy, Rickets & Anaemia

Scurvy

Bleeding gums caused by scurvy

Centers for Disease Control and Prevention, Public domain, via Wikimedia Commons

• Scurvy is the name for a severe vitamin C deficiency

  • It is caused by a lack of vitamin C in the diet for over 3 months

• Its symptoms include:

  • Anaemia

  • Exhaustion

  • Spontaneous bleeding

  • Pain in the limbs

  • Swelling

  • Gum ulcerations

  • Tooth loss

• It is a condition that was commonly seen in sailors between the 15th to 18th centuries

  • Long sea voyages made it very hard to access a ready supply of fresh produce

• Scurvy can be treated with oral or intravenous vitamin C supplements

Rickets

Rickets as seen in three children

Friends' Relief Mission, Vienna, CC BY 4.0, via Wikimedia Commons

• Rickets is a condition in children characterised by poor bone development

• Symptoms include: 

  • Bone pain

  • Lack of bone growth

  • Soft, weak bones (sometimes causing deformities)

• Rickets is caused by a severe lack of vitamin D  or a lack of calcium in the diet

  • Vitamin D is required for the absorption of calcium into the body

    • Calcium is a key component of bones and teeth

• Vitamin D mostly comes from exposure to sunlight but it can also be found in some foods (fish, eggs and butter)

• The treatment for rickets is to increase consumption of foods containing calcium and vitamin D

  • Alternatively, vitamin D supplements can be prescribed

Anaemia

• Anaemia is caused by a lack of iron in the diet

• Iron is an important component of the blood pigment haemoglobin

  • Haemoglobin carries oxygen to all cells and tissues inside red blood cells

• A lack of iron in the diet can cause a decrease in the number of red blood cells circulating in the blood

• This can cause the person's skin to appear pale (called 'pallor')

• Anaemia can also cause fatigue and exhaustion because there is not enough haemoglobin to carry oxygen to respiring cells all over the body