02. Human Nutrition

Balanced diet definition

Diet consisting of the all dietary requirements needed in the right proportions

Carbohydrates

• Made up of simple sugars

• CHO - carbon, hydrogen, oxygen

• Carbs → glucose, maltose → glycogen, starch

Protein

• Made up of amino acids

• CHON - carbon, hydrogen, oxygen, nitrogen

Lipids

• Made up of fatty acids & glycerol

• CHO - carbon, hydrogen, oxygen

Carbohydrates function

• Provide energy

Protein function

• Growth & repair of tissues

Lipids functions (3)

• Provide energy

• Energy store

  • Provide energy in emergencies

• Insulation

Vitamin A function (3)

• Improve vision

• Keep skin & hair healthy

• Promote resistance of disease

Vitamin C function (3)

• Heal wounds

• Rebuild new tissue

• Prevent scurvy

Vitamin D function (3)

• Maintain level of calcium in blood to form strong bones & teeth

• Calcium absorption

• Made by the body when skin is exposed to sunlight

Iodine function

Make thyroxine in the thyroid gland

Iron function

• Make haemoglobin for blood to transport oxygen

Calcium functions (4)

• Make bones & teeth

• Control muscle contraction

• Production of milk

• Clotting of blood

Water (4)

• Solvent

• Transport medium

• Substrate in digestive reactions

• Lubrication (tears)

Dietary fibre (2)

• Provide some energy

• Aid movement of food through gut + prevent constipation

Source of starch (3)

• Potatoes

• Rice

• Pasta

Source of sugar (3)

• Sweets

• Cakes

• Fruits

Source of protein (4)

• Meat

• Fish

• Eggs

• Legumes

Source of lipids (3)

• Butter

• Cheese

• Milk

Source of Vitamin A (2)

• Carrots

• Liver

Source of Vitamin C (3)

• Citrus fruits [oranges]

• Berries

• Peppers

Source of Vitamin D (3)

• Eggs

• Fish liver oils

• Fatty fish

Source of iodine (2)

• Seaweed

• Fish

Source of iron (3)

• Red meat

• Liver

• Beans

Source of calcium (2)

• Milk

• Cheese

Source of water

• Drinks & Foods

Source of dietary fibre (2)

• Wholemeal bread

• Nuts

Too much refined sugar

• Tooth decay

  • Bacteria in mouth convert sugar to acid & damages tooth enamel

Too much saturated fats & cholesterol

• Heart diseases

  • Plaque build-up blocks arteries

    • Prevents glucose & oxygen from reaching heart muscle

Too much salt (3)

• Cause water retention

• Rise in blood pressure

• Arteries blocked / burst - stroke

Fibre deficiency

• Constipation + Colon cancer

  • Gut muscles become inefficient → faeces remain in the gut

Too high energy content (2)

• Excess energy stored in unlimited amounts of fat - obesity

• Extra mass & volume cause:

  • Joint damage

  • Increase risk of heart & circulatory diseases

  • Increase risk of diabetes

  • Infections of lungs as breathing becomes difficult

Vitamin A deficiency (2)

• Night blindness

  • Poor production of visual pigment

• Xerophthalmia

  • Hardening & flaking of the cornea

Iron deficiency

• Anaemia

  • Iron is needed for haemoglobin synthesis

  • Insufficient dietary iron limits oxygen transport by red blood cells

    • Energy release by aerobic respiration is reduced

Vitamin C deficiency

• Scurvy

  • Production of some structural tissues is inhibited

    • Teeth becomes loose

    • Skin becomes flaky

    • Wounds bleed freely

  • Make immune system less efficient

    • Body becomes more prone to infection

Protein deficiency

• Kwashiorkor
  [swollen abdomen, slow down mental & physical development]

  • Due to insufficient protein to be able to reabsorb water from tissues

Calcium / Vitamin D deficiency (3)

• Poor development of bones

• Children : Rickets [bow legs]

• Adults : Osteoporosis [easy fracturing + poor healing of bones]

Energy requirements (activity level)

Active ppl need more energy

Energy requirements (age)

Children & teens need more energy than older ppl as they need energy to grow & are generally more active

Energy requirements (pregnancy)

Pregnant women need more energy as they need to provide energy for their babies to develop

Digestion of starch into glucose

1. Amylase digests starch into maltose.

2. Maltase digests maltose into glucose.

Digestion of protein

Protease digests proteins into amino acids

Digestion of lipids

Lipase digests lipids into fatty acids & glycerol

Where is bile produced

Liver

Where is bile stored

Gall bladder

Where is bile released

Small intestine

Role of bile 1 (acid)

• Alkaline

• Neutralise HCl in stomach that is too acidic for enzyme activity in small intestine.

• Create alkaline pH for enzyme activity.

Role of bile 2 (fats)

• Emulsifies fats [breaks the fat into tiny droplets]

• Gives larger SA of fat for lipase to work on. Make digestion faster.

How does bolus move through the gut

Peristalsis [muscle contraction]

Full digestive system (7)

1. Mouth

2. Oesophagus

3. Stomach

4. Small intestine

5. Large intestine

6. Rectum

7. Anus

Mouth role

Chemical : Salivary glands in the mouth produce amylase enzyme in the saliva

Mechanical : Teeth break down food

Oesophagus role

Muscular tube connecting mouth to stomach

Stomach role (3)

1. Pummel food with muscular walls

2. Produces pepsin [protease enzyme]

3. Produce HCl for:

   1. Kill bacteria

   2. Give optimum pH for protease enzyme to work

Small intestine role (2)

1. Produce protease, amylase, lipase enzyme to complete digestion

2. Where nutrients are absorbed out of alimentary canal into the body

First part : duodenum

Last part : ileum

Large intestine role

• Colon

• Where excess water is absorbed from the food

Rectum role

Where faeces [undigested food] are stored

Anus role

Where faeces leave the body

Pancreas role

Produces protease, amylase, lipase enzymes then released into small intestine

Adaptation of small intestine (2)

1. Long - time to break down & absorb all the food before it reaches the end

2. Villi to increase SA for absorption

Adaptations of villi (4)

1. Many - increase SA for absorption

2. Each villi has microvilli to increase SA

3. Single cell thick wall - shorter distance for nutrients to diffuse into blood

4. Capillaries for good blood supply - maintain high conc. gradient for diffusion