Introduction to Nutrition Flashcards
What 3 things will a healthy diet supply?
- energy
- building blocks for metabolism
- essential nutrients
what types of diets can lead to disease?
diets which fail to meet or significantly exceed an individual’s needs
What type of pattern is shown by dietary intake?
What does the graph look like?
a normal distribution
x axis - nutrient requirements
y axis - number of people
What is the EAR and where would it be found on the dietary intake graph?
estimated average requirement
it is in the centre of the normal distribution graph
What is described by the EAR?
Half of the population usually needs more than the EAR, and half needs less
The EAR is sufficient for 50% of the population
What is the LRNI and where would it be found on the dietary intake graph?
Lower reference nutrient intake
This is 2 standard deviations below the EAR (mean)
What is described by the LRNI?
LRNI is sufficient for 2.5% of the population, who have low needs
It does not meet the needs of 97.5% of the population
what is the RNI and where is it found on the dietary intake graph?
Reference nutrient intake
It is 2 standard deviations above the EAR (mean)
What is described by the RNI?
This is sufficient for around 97.5% of the population
The risk of deficiency is very small if the average intake of the population is the RNI
What is meant by the ‘safe intake’?
This is the safe upper limit for vitamins and minerals where an excess may be harmful
Why is safe intake used?
It is a range for which there is not enough information to estimate RNI, LRNI and EAR
Why is energy balance important?
it is the key to maintenance of a healthy weight
What is the “equation” for energy balance in someone of a healthy weight?
energy intake = energy expenditure
What does energy intake depend on?
Energy intake varies depending on age and gender
Why do people tend to gain weight as they get older?
In young adults, there is little change in requirements for energy intake
As you get older, requirements begin to decline
If you carry on eating as much as you used to, you will begin to gain weight with age
what does energy expenditure depend on?
Basic metabolic rate and the amount/intensity of physical activity
basic metabolic rate depends on age, weight and sex
What are macronutrients?
Macronutrients include fats, carbohydrates and proteins
They can be used immediately for energy generation
How are excess fats and carbohydrates stored?
Excess fats are stored as triacylglycerols in the adipose tissue
Excess carbohydrates are stored as glycogen
What is the main source of energy?
Fat stores provide 80-90% of total energy
Why is there no storage of protein?
what happens if there is a need for protein?
Amino acids cannot be stored
In starvation, muscle tissue can be metabolised for energy or to provide amino acids for other reactions
How much protein is required by an average adult daily?
an average adult requires 0.75g protein per kg of body weight
A typical 75kg man needs 50g protein daily
How much protein would be required by an athlete/bodybuilder daily?
1.2-1.7 g per kg of body weight
why are proteins not stable?
They are constantly being synthesised and degraded
If a muscle is not used, it is rapidly degraded
How do proteins vary in their rate of turnover?
Enzymes have a rapid turnover and a half-life in terms of seconds
Structural proteins (e.g. collagen) have a half-life in terms of tens of days
what is the equation for nitrogen balance in a healthy individual?
nitrogen intake = nitrogen excretion
When does negative nitrogen balance occur?
when nitrogen intake is less than nitrogen excretion
This occurs during fasting and illness
what happens if insufficient amino acids are taken in through the diet?
the body begins to break down proteins for energy
it secretes more ammonia in the urine (in the form of urea) than is being taken in
When does positive nitrogen balance occur?
When nitrogen intake exceeds nitrogen excretion
This happens during growth, pregnancy and after major surgery as the body is building new tissue
How many essential amino acids are there?
What is meant by an essential amino acid?
There are 9 essential amino acids
These cannot be synthesised by humans and must be obtained from the diet
what are the 9 essential amino acids and how can they be remembered?
Methionine Valine Histidine Leucine Phenylalanine Tryptophan Isoleucine Lysine Threonine
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