Nutrients, Digestion, and Dietary Guidelines – Study Notes (Stage 6 NSW Food Technology)
What are Nutrients?
Substances found in food that are essential for growth, energy, and body functions.
Divided into macronutrients and micronutrients; each nutrient has a unique role in maintaining health.
Stage 6 NSW Food Technology content emphasizes how nutrients support energy, growth, repair, digestion, and metabolism.
Macronutrients Overview
Macronutrients are needed in large amounts and provide energy.
They include:
Carbohydrates
Proteins
Lipids (Fats)
Carbohydrates
Primary source of energy for the body.
Found in bread, pasta, rice, fruits, and vegetables.
Types: Simple (sugars) and Complex (starches & fiber).
Main energy function: provide readily available glucose for body functions and activity.
Proteins
Essential for growth, repair, and maintenance of body tissues.
Found in meat, fish, eggs, dairy, legumes, and nuts.
Made up of amino acids, which can be essential or non-essential.
Energy content (when used as a fuel): 1 g protein yields .
Structure: proteins are polymers of amino acids; 22 amino acids are needed by the body.
Of these, humans synthesize 14 as adults and 13 in infancy; thus adults require 8 essential amino acids in the diet, and children require 9.
Eight essential amino acids for adulthood: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine.
Histidine is essential in infancy only.
Roles of proteins (examples): hair and nails (keratin), haemoglobin (oxygen transport), muscles (actin & myosin), receptors (cell signaling), enzymes (digestion), hormones (insulin, adrenaline, thyroxin), antibodies (immune defense).
Lipids (Fats)
Provide energy and support cell growth; important for fat-soluble vitamin absorption (A, D, E, K).
Types:
Saturated fats (animal products, coconut oil)
Unsaturated fats (olive oil, avocado, nuts)
Trans fats (processed foods)
Main triglyceride form: triglycerides are formed by three fatty acids and glycerol.
Sterols (e.g., cholesterol): about 1% of total lipids; cholesterol is found in animal cells and largely synthesized by the liver; ~25% of cholesterol comes from food.
Phospholipids are essential components of cell membranes (lecithin is a common example).
Essential fatty acids (EFAs): Omega-3 (linolenic acid) and Omega-6 (linoleic acid). EFAs cannot be made by the body and must be obtained from food.
Omega-3 reduces blood clot risk and may reduce inflammatory diseases.
Omega-6 helps reduce LDL but excessive intake may lower HDL.
Both are needed for brain development in babies.
Omega-3 and Omega-6 are important in breast milk for infant development.
Lipids are the body’s most concentrated energy source; unused lipids are stored as adipose tissue and support various functions.
Micronutrients Overview
Micronutrients are required in smaller amounts but are essential for health.
They include:
Vitamins
Minerals
Water
Dietary Fiber
Vitamins
Essential for various body functions, including immunity and metabolism.
Two main types:
Water-soluble (B-complex, Vitamin C) – must be consumed regularly; excess is excreted.
Fat-soluble (Vitamins A, D, E, K) – can be stored in the body; excess intake can lead to toxicity.
Found in fruits, vegetables, dairy, and meat.
Important notes:
Vitamin A exists as retinol (animal sources) or carotene (plants; body converts carotene to Vitamin A).
Vitamin C is heat sensitive and involved in collagen formation, iron absorption, wound healing, and immune support.
Vitamin D can be synthesized in the skin with sun exposure and is involved in calcium absorption and bone health.
Vitamin E acts as an antioxidant and supports cell membrane protection.
Vitamin K is required for blood coagulation.
The B-group vitamins are water-soluble co-enzymes essential for energy release from carbohydrates, fats, and proteins.
Minerals
Important for bone health, nerve function, metabolism, and more.
Examples and functions:
Calcium: 99% in bones/teeth; roles in bone formation, teeth formation, blood clotting, and nerve/muscle function.
Phosphorus: 90% in bones/teeth; forms calcium phosphate; involved in energy metabolism via ATP.
Iron: Forms hemoglobin and myoglobin; key for oxygen transport; absorption enhanced by Vitamin C; enhanced by sugars; decreased by fiber and starch; stored/relieved via daily turnover.
Sodium and Potassium: Work together to regulate osmotic balance, nerve impulses, muscle function, and acid/base balance; sodium aids glucose absorption; potassium crucial for heart rhythm; kidneys regulate excretion.
Zinc: Trace element; essential for energy and amino acid metabolism, collagen formation, growth, wound healing; absorption is rate-limited by plant-based fiber; animal sources enhance absorption.
Fluorine (Fluoride): Strengthens calcium phosphate in bones/teeth; helps reduce dental caries; required amount is about 1 mg/day via water supply.
Water: Essential solvent and transport medium; lubricates digestion; aids metabolism and temperature regulation; ~55–65% of body weight is water; most is found inside cells and 80% of blood is water.
Water and Dietary Fiber
Water: Essential for hydration, digestion, transport of nutrients, temperature regulation, and pH balance.
Dietary Fiber: Indigestible polysaccharide that supports digestive health and prevents constipation; found in whole grains, fruits, vegetables; some fibre is fermentable in the gut and affects gut flora.
Sources include water-containing foods and beverages, fruits, vegetables, and whole grains.
Balance and Diet Planning
A balanced diet provides all nutrients in the right proportions; needs vary by age, gender, activity level, and health conditions.
Australian Guide to Healthy Eating provides recommendations.
Dietary Guidelines and Planning Principles
The five major food groups and limiting unhealthy components are framed by the Australian Dietary Guidelines and NRVs (Nutrient Reference Values).
Six core principles for diet planning:
Adequacy: ensure enough energy and essential nutrients.
Balance: combine foods to meet the nutrient needs; some food combinations improve absorption.
Energy Control: balance kilojoules with energy expenditure; avoid excess energy storage as adipose tissue.
Nutrient Density: choose nutrient-dense foods over empty kilojoule foods.
Moderation: limit foods high in saturated fats, added sugars, added salt, and alcohol; avoid excessive intake of empty kilojoules.
Variety: include a wide range of foods from all groups for comprehensive nutrient coverage.
The five food groups (as per AGHE):
Vegetables and legumes/beans
Fruit
Grain (cereal) foods, mostly wholegrain/high fibre
Lean meats and poultry, fish, eggs, tofu, nuts and seeds, legumes/beans
Dairy products and alternatives (mostly reduced fat)
Additional recommendations include: drink plenty of water and eat a rainbow of foods to ensure variety of micronutrients.
The NRVs include two reference values:
Recommended Dietary Intake (RDI)
Adequate Intake (AI)
If there is insufficient evidence for an RDI, an AI is set.
The Healthy Eating Pyramid and the Australian Guide to Healthy Eating provide visual guidance for portions and proportions; Go for 2 & 5 campaign promotes at least two serves of fruit and five serves of vegetables daily.
Table references (Tables 8.2 and 8.3) provide recommended daily serves from the five groups for different ages and activity levels, including adjustments for pregnancy and lactation.
Life Cycle Nutritional Needs
Pregnancy: increased carbohydrates for energy; increased protein for foetus/placenta; increased vitamins (especially folate), minerals for bone/teeth; increased lipids for essential fatty acids.
Infancy (birth to 1 year): rapid growth; breast milk provides exact nutrients required; formula can be used; by ~6 months introduce semi-solid foods; higher energy needs due to rapid growth; trace elements required in higher amounts; proteins needed for muscle and immune development.
Toddler (1–3 years): rapid activity; risk of undernutrition with weaning; vegan diets require caution for B12, iron, calcium; should be able to sit with family and eat a variety of healthy foods.
Childhood (4–8 years): rapid growth; macro-nutrients support growth; micro-nutrients support energy and muscle development; obesity is a concern; balanced, quality produce to avoid malnutrition.
Puberty (9–13 years): rapid growth and maturation; energy needs increase; high-quality protein important for hormones and muscle; balanced, varied diet; external influences (peers/media) may affect food choices.
Older adolescence (14–18 years): growth slows; energy needs decrease somewhat; lifestyle may be sedentary; dietary choices influenced by peers.
Adulthood (19+): maintenance-focused nutrition; avoid malnutrition; energy intake should align with expenditure; protein for muscle maintenance; minerals for bones/teeth/hair/nails.
Senior years (60+): potential dietary adjustments (e.g., low-salt diet for hypertension); energy needs decline; lifestyle and physiological changes increase vulnerability; antioxidants in fruits/vegetables may slow aging.
Vitamins, Minerals, and Nutrition in Depth
Vitamin A
Two forms: retinol (animal sources) and carotene (plant-derived, converted to retinol in the body).
Sources: retinol from fish liver, liver, eggs, dairy; carotene in orange/yellow fruits and vegetables and dark green leafy vegetables.
Functions: growth/repair, mucus production, bone/teeth formation, vision (night vision).
Deficiency: night blindness, dry eyes.
Vitamin C
Functions: collagen formation, connective tissue maturation, wound healing, iron absorption, immune support.
Sources: citrus fruits, broccoli, leafy greens, potatoes (subject to cooking losses).
Deficiency: scurvy (gum bleeding, poor wound healing, anemia symptoms).
Vitamin D
Sources: sunlight (UV) enables skin synthesis; also fish liver oils, small amounts in fortified foods.
Functions: bone and teeth growth and repair; facilitates calcium and phosphorus metabolism; increases calcium absorption.
Deficiencies: Rickets in children; osteomalacia in adults.
Vitamin E
Group of compounds (tocopherols); sources include wheat germ, vegetable oils, margarine, egg yolk, nuts, legumes.
Function: antioxidant; protects cell membranes from oxidative damage.
Deficiency signs include muscle weakness, coordination problems, numbness, vision issues, immune problems.
Vitamin K
Sources: leafy greens (cabbage family), cauliflower, spinach; also cereals, fruits, plant oils.
Function: essential for blood coagulation; activation of clotting proteins.
B Group Vitamins (Water-Soluble)
Important for energy metabolism; act as co-enzymes in releasing energy from CHO, fats, and proteins.
Includes: Thiamin (B1), Riboflavin (B2), Niacin (B3), Pyridoxine (B6), Pantothenic acid, Biotin, Folate, Cobalamin (B12).
Deficiencies lead to fatigue, impaired metabolism, and specific disease states (e.g., pellagra with Niacin deficiency).
Thiamin (B1)
Found in meat, organs, poultry, fish, whole grains, wheat germ.
Role: carbohydrate metabolism; deficiency can cause anorexia, irritability, nerve dysfunction.
Riboflavin (B2)
Found in milk products, meat, whole grains, vegetables, eggs, yeast.
Role: energy release from proteins, fats, carbohydrates; deficiency (ariboflavinosis) causes oral and ocular symptoms.
Niacin (B3)
Found in organ meats, whole grains, dairy, fish; can be synthesized from tryptophan but inefficient.
Role: energy release from macronutrients; deficiency (pellagra) includes dermatitis, diarrhea, dementia, death.
Folate
Needed for DNA formation; important for red blood cell production and gut lining; crucial in pregnancy to prevent neural tube defects.
Sources: green leafy vegetables, yeast, organ meats; deficiencies linked to neural tube defects and placental complications.
Vitamin B12 (Cobalamin)
Essential for red blood cell formation and DNA maturation.
Sources: animal-derived foods; fortified plant-based foods can be important for vegans.
Minerals (selected)
Calcium: major bone/teeth mineral; calcium phosphate contributes to bone strength; 1% in fluids; absorption increased by Vitamin D, lactose, and Vitamin C; absorption decreases with age and high-fat meals; dairy is a key source.
Phosphorus: second most abundant mineral; forms calcium phosphate in bones/teeth; energy metabolism via ATP.
Iron: forms hemoglobin/myoglobin; absorption enhanced by Vitamin C and sugars; decreased by fiber/starch; stored in liver and reused; deficiency leads to anemia.
Sodium & Potassium: regulate osmotic balance, nerve impulses, muscle function; kidneys regulate excretion; sodium aids glucose absorption; imbalances can cause edema or hypertension; potassium is critical for heart rhythm.
Zinc: trace element; essential for energy metabolism, protein synthesis, collagen, growth, wound healing; absorption enhanced from animal sources; fiber can reduce zinc absorption.
Fluorine/Fluoride: strengthens calcium phosphate in bones/teeth; helps prevent dental caries; small daily requirement via fluoridated water.
Water: solvent and transport medium; lubrication; aids metabolism; maintains pH; 55–65% of body weight.
Interrelationships Between Nutrients
Iron and Vitamin C: Vitamin C enhances iron absorption; both contribute to red blood cell formation.
Calcium and Phosphorus: both needed for calcium phosphate; hormonal regulation maintains balance; dairy provides both for absorption.
Sodium and Potassium: work together for water balance and cardiovascular health; imbalances impact blood pressure and heart function.
Calcium and Fibre: insoluble fibre can impede calcium absorption; separate calcium-rich foods from high-fibre meals when necessary.
Folate and Vitamin B12: both essential for normal growth and red blood cell formation; pregnant women require adequate folate to prevent neural tube defects.
Calcium and Lactose: lactose enhances calcium absorption; lactose intolerance can be mitigated via phosphorus and Vitamin D for absorption.
Vitamin D and Calcium: Vitamin D promotes calcium absorption; low Vitamin D reduces calcium uptake; sun exposure and dietary sources help maintain levels.
Digestion, Absorption, and Metabolism
The GI tract is a tube ~8 meters long, from mouth to rectum; digestion breaks down food chemically and mechanically; absorption occurs through the intestinal walls to bloodstream or lymphatic system; metabolism includes catabolic (breaking down) and anabolic (building up) processes.
Common facts:
Food takes 24–36 hours to pass through the GI tract.
The gut contains ~1000x more bacteria than stars in the Milky Way.
Humans secrete more than 1 L of saliva daily.
Digestion Pathways (Overview)
Carbohydrates:
Mouth: Amylase in saliva begins starch breakdown.
Stomach: Mechanical digestion continues; chyme forms.
Small intestine: Pancreatic amylase breaks polysaccharides to disaccharides; disaccharides broken to monosaccharides by maltase, lactase, sucrase; absorption in the duodenum/jejunum via villi into the bloodstream as glucose, galactose, and fructose.
Proteins:
Mouth: Mechanical breakdown.
Stomach: Pepsin denatures proteins; polypeptides form chyme.
Small intestine: Pancreatic enzymes break proteins to amino acids; absorbed by carriers into intestinal cells; transported to liver for metabolism and use in hormones/enzymes/tissue synthesis.
Lipids:
Mouth/Stomach: Lipase begins breakdown; some fat emulsification.
Small intestine: Bile emulsifies fats; pancreatic lipase completes breakdown to monoglycerides and fatty acids; absorbed into intestinal cells; enter bloodstream or lymph as chylomicrons; liver processes fats.
Vitamins:
Fat-soluble vitamins (A, D, E, K) are absorbed with fats via bile; can be stored in liver/fat tissue.
Water-soluble vitamins (B and C) are absorbed into the bloodstream and must be replenished daily.
Minerals:
Absorbed mainly in the small intestine; not directly degraded by digestion; absorption varies with other nutrients and dietary factors.
Water absorption occurs rapidly; small amounts in the stomach; most absorption occurs in the duodenum/jejunum; large intestine also absorbs water.
The Absorptive Structures: The Villi
Villi increase the surface area of the small intestine for absorption.
Each villus is connected to a capillary network; absorbed nutrients are carried away by the bloodstream (except lipids, which enter the lymph via lacteals as chylomicrons).
There are more villi in the duodenum, decreasing toward the ileum.
The villus is made up of many cells; each cell bears microvilli to further increase surface area.
Catabolism and Anabolism (Metabolism)
Catabolism: large, complex molecules are broken down into smaller ones to release energy. Example: fat breakdown to fatty acids; proteins to amino acids.
Anabolism: smaller units built up into larger molecules; requires energy. Example: amino acids joining to form polypeptides.
Overall energy flow can be summarized as:
An example metabolic pathway schematic (simplified):
ATP production involves oxidative phosphorylation and the electron transport chain; NADH and FADH2 donate electrons to produce ATP.
Dietary Guidelines, Serves, and Food Guides
The Australian Dietary Guidelines provide five food groups and five core guidelines; the NRVs (RDI vs AI) guide nutrient intake.
The Australian Guide to Healthy Eating (AGHE) is a visual plate that shows portions from the five food groups and emphasizes water intake.
The Healthy Eating Pyramid (Nutrition Australia) is another visual guide with similar guidance to AGHE, but with different presentation.
The Go for 2 & 5 initiative encourages at least two serves of fruit and five serves of vegetables daily.
Table-based recommendations (Tables 8.2 and 8.3) show the recommended average daily serves from each group for different ages, stages, and activity levels (including pregnancy and lactation).
Practical Notes and Implications
Nutrient interactions matter: combinations of foods can enhance or inhibit absorption (e.g., Vitamin C with iron; Calcium with lactose; Vitamin D with calcium).
Vegan/vegetarian considerations: ensure intake of Vitamin B12, iron, calcium, and omega-3; fortified foods or supplements may be necessary.
Dietary fiber is essential for digestion but can affect mineral absorption; plan meals to optimize nutrient uptake.
Energy balance matters: energy intake (kilojoules) should align with energy expenditure to avoid unwanted fat storage.
Be mindful of dietary patterns in adolescence and adulthood shaped by social factors; promote informed and healthy choices.
Quick Reference: Key Nutrient Facts (from the slides)
Essential amino acids (adults): 8; in infancy: 9; list includes isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine (histidine essential in infancy).
Protein energy: .
Triglycerides comprise ~95% of fat in the diet.
Lipids include fatty acids, triglycerides, phospholipids, and sterols; EFAs Omega-3 (linolenic) and Omega-6 (linoleic) are essential.
Vitamin C deficiency = scurvy; Vitamin D deficiency = rickets/osteomalacia; Vitamin A deficiency = night blindness; Vitamin E deficiency = neuromuscular issues; Vitamin K deficiency = impaired coagulation.
Minerals: Calcium, Phosphorus, Iron, Sodium, Potassium, Zinc, Fluorine (Fluoride) – each with specific roles and dietary sources.
Water accounts for ~55–65% of total body weight; rapid absorption (water ~5 minutes after ingestion).
Carbohydrates: Monosaccharides ( glucose, galactose, fructose ); Disaccharides (sucrose, lactose, maltose); Polysaccharides (starch, dextrins, glycogen, cellulose [dietary fibre]); main energy source for body.
Lipid digestion involves bile and pancreatic lipase; fats are broken down to monoglycerides and fatty acids for absorption.
Carbohydrate absorption mainly occurs in the small intestine; glucose/galactose and amino acids enter blood; lipids enter lymphatic system as chylomicrons.
Vitamins: water-soluble vitamins require daily intake; fat-soluble vitamins can be stored and may accumulate.
References and Further Reading (as per transcript)
NSW Food Technology Stage 6 Syllabus
Australian Guide to Healthy Eating
National Health and Medical Research Council (NHMRC) guidelines
NRVs for Australia & New Zealand
Healthy Eating Pyramid and Go for 2 & 5 campaigns
Eat for Health resources and related dietary guidelines