7.1Human Nutrition
Diet — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions
5 min read 14 parts Lesson 2 of 6 1 quiz
Lesson summary
Human diet: nutrients, deficiencies and dietary needs — IGCSE BIOLOGY notes: Describe a balanced diet, the sources and importance of each nutrient, deficiency diseases and how dietary needs vary.Balanced diet — contains all the nutrients in the correct proportions and amounts to …
- Dietary fibre
- Common in sailors on long voyages without fresh produce
- Treated with vitamin C (food or supplements)
- Vitamin D is made in the skin when UV light acts on a cholesterol-derived substance
- Treated with foods rich in calcium and vitamin D, or vitamin D supplements
- Anaemia — lack of iron, so not enough haemoglobin can be made to carry oxygen
Part 1 of 5A balanced diet
- Balanced diet
- contains all the nutrients in the correct proportions and amounts to meet the body's needs.
- The seven groupscarbohydrates, fats and oils (lipids), proteins, vitamins, minerals, dietary fibre and water.
| Nutrient | Importance | Good sources |
|---|---|---|
| Carbohydrates | Source of energy | Bread, cereals, pasta, rice, potatoes |
| Fats and oils | Energy store, insulation, membranes | Butter, oils, nuts |
| Proteins | Growth and repair; make enzymes | Meat, fish, eggs, beans, pulses, nuts |
| Dietary fibre (roughage) | Provides bulk so the intestine can push food through (peristalsis); prevents constipation | Vegetables, wholemeal bread, whole grains |
| Vitamins and minerals | Needed in small quantities to maintain health | Fruit, vegetables, meat, dairy |
| Water | Solvent; transport; medium for chemical reactions in cells | Drinks, juice, milk, fruit and vegetables |
Part 2 of 5Vitamins and minerals you must know
| Nutrient | Function | Sources | Deficiency |
|---|---|---|---|
| Vitamin C | Forms collagen, found in skin, hair, gums and bones | Citrus fruit, strawberries, green vegetables | Scurvy |
| Vitamin D | Helps absorb calcium, so needed for strong bones and teeth | Oily fish, eggs, liver, dairy; made in skin in sunlight | Rickets |
| Calcium | Bones and teeth; blood clotting | Milk, cheese, eggs | Poor bones; osteoporosis later in life |
| Iron | Makes haemoglobin in red blood cells, which carries oxygen | Red meat, liver, spinach | Anaemia |
Part 3 of 5Deficiency diseases
Scurvy
- Scurvy severe lack of vitamin C in the diet, over about 3 months.
- Symptomsexhaustion, bleeding, limb pain, swelling, gum ulcers and tooth loss.
- Common in sailors on long voyages without fresh produce.
- Treated with vitamin C (food or supplements).
Rickets
- Rickets poor bone development in children, caused by severe lack of vitamin D.
- (and so poor calcium absorption)
- Symptoms: bone pain, lack of growth, soft weak bones that may deform.
- Vitamin D is made in the skin when UV light acts on a cholesterol-derived substance.
- Treated with foods rich in calcium and vitamin D, or vitamin D supplements.
Anaemia
- Anaemia lack of iron, so not enough haemoglobin can be made to carry oxygen.
Part 4 of 5Why dietary needs differ
| Factor | Dietary need |
|---|---|
| Age | Energy needs rise towards adulthood for growth; children need a higher proportion of protein; adults' energy needs fall with age |
| Activity level | More active people need more energy because their muscles respire more |
| Pregnancy | More energy for the growing foetus and extra mass carried; extra calcium and iron for the foetus's bones, teeth and blood |
| Breastfeeding | More energy, and extra calcium to make good-quality milk |
- Sex also affects needs, as body size and muscle mass differ.
Part 5 of 5More from the specification
More from the specification
Nutrient assimilation by bodily organs
- Nutrient assimilation by bodily organs digestive absorption delivers essential fatty acids and amino acids to maintain structural function throughout mammalian organs.
Mechanical versus Chemical Digestion
- Mechanical digestion physically breaks large food masses into smaller particles without severing chemical bonds,
- whereas chemical digestion uses hydrolytic enzymes to cleave complex macromolecules into small absorbable monomers.
Emulsification in the Duodenum
- Bile salts released into the duodenum disperse large fat globules into microscopic droplets, vastly expanding lipid surface area for accelerated pancreatic lipase digestion.
Nutritional Requirements During Pregnancy
- Pregnant mothers require elevated caloric intake and supplementary calcium and iron to satisfy embryonic cellular respiration, skeletal development,
- and fetal hemoglobin formation.
Adaptation
- The process by which populations become better suited to their environment.
Digestive system
- Organ system that breaks down and absorbs food.
Physical digestion
- Breaking food into smaller pieces without chemical change.
Fatty acid
- A hydrocarbon chain with a carboxyl group.
Amino acid
- The unit from which proteins are made; the sequence decides the protein's shape and function.
Digestion
- Breakdown of large insoluble food molecules into small soluble ones.
Duodenum
- First part of the small intestine.
Starch
- An insoluble polysaccharide of glucose used by plants for energy storage.
Emulsification
- Breaking large fat drops into smaller ones by bile.
Organ
- A structure of different tissues working together for specific functions.
Pancreas
- Gland producing insulin and glucagon.
Key terms
| Term | Meaning |
|---|---|
| Balanced diet | A diet containing all the nutrients in the correct proportions and amounts. |
| Dietary fibre | Indigestible plant material giving bulk to the intestine contents. |
| Scurvy | A deficiency disease caused by lack of vitamin C. |
| Rickets | A deficiency disease of children caused by lack of vitamin D, giving weak bones. |
| Anaemia | A condition caused by a lack of iron, so too little haemoglobin is made. |
| Collagen | A protein in skin, gums and bones that needs vitamin C to form. |
Avoid these mistakes
1
Vitamins and minerals provide energy — they are needed in small amounts to maintain health.
2
Fibre is digested for nutrients — fibre adds bulk and helps peristalsis but is not digested.
3
Scurvy is caused by lack of vitamin D — scurvy is vitamin C; rickets is vitamin D.
4
All people need the same diet — needs vary with age, sex, activity, pregnancy and breastfeeding.
5
Rickets is caused by a lack of calcium alone — vitamin D is needed to absorb it.
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