Week 1 - Introduction Flashcards
Nutrition definition
The science of food, the nutrients and the substances therein, their action, interaction, and balance related to health and disease, and the process which the organism ingests, absorbs, transports, utilises and excretes food substances
What is in food?
- Mainly made up of water, lipids, carbohydrates and proteins (macronutrients)
- Vitamins and minerals (micronutrients)
- Dietary fibre, phytochemicals and additives
Essential nutrients
- Required for normal human body function but cannot be synthesised by the body or cannot be synthesised in the correct amount
- Must be obtained from dietary sources
Body composition
- We are made up of what we eat
- Food enters gastrointestinal tract and Is digested into simpler compounds
- Nutrients can be absorbed, mainly in the small intestine
- Nutrients are transported, metabolised, stored and excreted
Macronutrients
- Are lipids, carbohydrates and protein
- Needed in large amounts and provides energy
- Measured in kJ or kcal
- 1kcal = 4.2kJ
Micronutrients
They are needed in very small amounts and do not provide energy
Energy content
Fat- 37kJ/g
Carbohydrate - 17kJ/g
Protein - 17kJ/g
They are adjusted for digestibility and metabolism
Fat
- Called triglycerides
- Made of 3 fatty acids and glycerol
- Is a solid, oil is liquid at room temperature
- Non polar
- Hydrophobic
- More double bonds means high chance of rancidity
Hydrogenation
Is the process of adding hydrogen artificially to make unsaturated fats saturated
Saturation
- The carbons in the fatty acids can be attached to each other as saturated or unsaturated (double bonds)
- Saturated = no double bonds
- Monounsaturated = 1 double bond
- Polyunsaturated = 2 or more double bonds
Essential fatty acids
- The body can only make some kinds of fatty acids and not others and therefore are essential in the diet
- Linoleic acid (omega 6) and alpha linolenic acid (omega 3) are the only 2 essential fatty acids, although docosahexaenoic acid and y-linilenic acid are conditionally essential
- Needed for immune function, vision, cell membrane and production of hormone like compounds
Fats and oils in food
- Carries fat soluble vitamins (A,D,E,K)
- Carries flavours (mostly nonpolar)
- Mouthfeel/ texture
- Tenderness
- Heat transfer
- Produces rich texture and good flavour
- Lower FFA content the more stable the fat
Carbohydrates
- Sugar, starches and dietary fibre (mainly cellulose, hemicelluloses, pectic substances) found mostly in plants
- Are carbs are saccharides: either monosaccharides, disaccharides or polysaccharides
- Starch and dietary fibre are all made up of many sugars bonded together (polysaccharides)
Monosaccharides
- Simplest form of carbs
- Contains one saccharide molecule
- Building blocks for disaccharides and polysaccharides
- Glucose, fructose, galactose
Disaccharides
- Formed when two sugars are joined together
- Two monosaccharides
Lactose (glucose and galactose)
Sucrose (glucose and fructose)
Maltose (glucose and glucose)
Polysaccharides
- Composed of long chains of monosaccharides
- Can be linear or highly branched
- Starch (plants): made from amylose (linear chain) and amylopectin (branched chain
- Glycogen (animals)
Carbohydrates in the body
- Starch is digested into glucose in the small intestine
- Some of our tissues (brain and muscle cells in particular) use glucose as the main energy source
- Blood sugar is tightly controlled
- Stored as glycogen in liver and muscles
Starch is important to cooks
Dietary fibre
- The edible parts of the plant or their extracts that are resistant to digestion in the small intestine
- Cellulose, ogliosaccharides and lignins
- We do not have the enzymes that break down and therefore remain as large molecules
Soluble fibre
Traps cholesterol and glucose (reducing absorption)
Reduces risk of CVD
Sources include fruits and vegetable
Insoluble fibre
Adds bulk to bolus ( draws in water)
Improves laxation and gut health
Sources include greens and wholegrains
Protein
- High in foods from animals but in all whole plants
- Composed of amino acids
- Needed for muscle maintenance, enzymes, immune function, blood pressure and hormones
- 20 amino acids, 9 essential acids
- Lean meats, poultry, eggs, legumes, nuts/seeds
Structure of proteins
- There are 4 structures of proteins, primary, secondary, tertiary and quartenary
- They can denature with different conditions (such as heat, light or bubbles) at different levels of the structure
Enzymes
They catalyse reactions
Water
- Major component of body and food
- Water molecules bond with themselves and therefore gives very unique properties
- Stable and liquid over high temperatures
- Bonds with other polar substances
Water in food
- Acts as a solvent as it is polar
- Involved in heat transfer
- Solid, liquid or gas
- Is a plasticiser
Properties of water
- It is a strong polar substance, H bonds are hard to break
- Good at dissolving other substances due to electric polarity
- Has high heat capacity
- High latent heat of vaporization
Phytochemicals
- Occur naturally in plant based foods
- Responsible for the colour of foods
- They may affect health
- Not nutrients
Alcohol
- Requires no digestion
- Passive diffusion from the stomach
- Food in stomach retards absorption
- Remainder absorbed from the small intestine
- Absorption increased by rapid gastric emptying, and empty stomach, carbonation
- It is water soluble and therefore cannot be stored and diffuses into all cells
- 95% is processed by the liver, it is oxidised and released into the bloodstream (80%)
- It can be excreted by sweat, urine or breath
Fat soluble vitamins
- A,D,E,K
- Stored in the body
- Negative consequences if consumed in excess
- In foods containing fat
Vitamin A sources
Dark leafy green vegetables, carrots, corn, sweet potato, liver oil, eggs
Vitamin D sources
Oily fish, egg yolks
Vitamin E sources
Sweet potato, nuts, seeds
Vitamin K sources
Liver, broccoli, cauliflower
Water soluble sources
- Include B group vitamins and Vitamin C
- Soluble in water
- Mostly excreted in urine
- Heat sensitive
Vitamin B1 sources
Thiamine sources include wholegrain bread, vegemite
Vitamin B2 sources
Riboflavin sources include vegemite, wholegrain bread, cheese, yoghurt, eggs, asparagus
Vitamin B3 sources
Niacin sources include eggs, potatoes, mushrooms
Vitamin B6 sources
Pyridoxine sources include meat, fish, bananas
Vitamin B9 sources
Folate sources include wholegrain bread, vegemite, leafy greens
Vitamin B12 sources
Sources include milk, yoghurt and meat
Vitamin C sources
Ascorbic acid sources include lemon, greens, tomato, mango
Minerals
- 22 minerals required for adequate body function
- Calcium, phosphorus, magnesium, iron, zinc, iodine, selenium
Calcium sources
Dairy products, salmon, green veggies
Phosphorus sources
Meat, poultry, eggs
Magnesium sources
Nuts, legumes, wholegrains
Iron sources
Red meat, poultry and dark green veggies and legumes
Zinc sources
Meat, legumes, oysters and dairy products
Selenium sources
Brazil nuts, seafood and meat
Iodine sources
Seafood and salt
