Nutrition, Diet and Body Weight Flashcards
What are the 4 Pathways of metabolism
- Oxidative pathways
Convert food into energy - Fuel storage & mobilisation pathways,
Allow fuel to be mobilised when we are not eating or need increased energy
3.Biosynthetic Pathways
Produce basic building blocks for cells
4.Detoxification Pathways
Remove toxins
What is a catabolic process
Catabolic processes:
Break down molecules to release energy in the form of reducing power
What is Anabolic processes
Anabolic processes:
Use energy & raw materials to make larger molecules for growth and maintenance
What do all living organisms need energy for (5)
- Biosynthetic work – synthesis of cellular components.
- Transport work – movement of ions & nutrients across membranes.
- Mechanical work – muscle contraction.
- Electrical work – nervous conduction.
- Osmotic work – kidney.
what form of energy do cells derive our energy from
Cells use Chemical bond energy to drive energy-requiring activities
What is oxidised for energy production
Energy production by oxidation of:
* Lipids
* Carbohydrates
* Protein
* Alcohol
What is the SI unit for Food energy
Kilojoule (kJ) is official SI unit of food energy
Which term for food energy is more commonly understood by patients
“calorie”
still in common use by physicians as better understood by patients.
What does 1 calorie , (1Kcal) equal
What is the conversion of Kcal to Kilojoules
1 Kcal = amount of energy needed to raise temperature of one kilogram of water by one degree Celsius
1 kcal = 4.2 Kilojoules
What are the Major Dietary Carbohydrates
- Starch (Carbohydrate storage molecule in plants. Polymer
of glucose) - Sucrose (Table sugar. Glucose-fructose disaccharide)
- Lactose (Milk sugar. Galactose-Glucose disaccharide)
- Fructose (Fruit sugar: Monosaccharide)
- Glucose (Predominant sugar in human blood)
- Maltose (Glucose-glucose disaccharide)
- Glycogen (Carbohydrate storage molecule in animals. Polymer of glucose)
Why is important to maintain plasma glucose levels
RBCs have no mitochondria,
thus cannot preform oxidative metabolism
This means its reliant in glycolysis from glucose to fuel RBC’s
If glucose drops below 2.8 milimolars
it can lead to a come.
How many different Amino Acids are used for Protein Synthesis
- 20 different amino acids used for protein synthesis in body
What are the 9 essential amino acids
9 Essential amino acids cannot be synthesised and must be obtained from diet
- Isoleucine
- Lysine
- Threonine
- Histidine
- Leucine
- Methionine
- Phenylalanine
- Tryptophan
- Valine
Why are proteins from plants considered low quality
Proteins of plant origin generally considered “lower quality” since most are deficient in one or more essential amino acids.
Therefore essential that vegetarian diet obtains protein from a wide variety of plant sources
What are Fats comprised of
Lipid composed of Triacylglycerols (3 fatty acids esterified to one glycerol.)
What are trans Fats
Trans fats are artificially produced, gives it a longer shelf life
Why does Fats yield more energy than carbs or proteins
Contain much less oxygen than carbohydrates or protein (i.e. more reduced so yields more energy when oxidised)
What are fats used for -3
Required for absorption of the fat-soluble vitamins
(A, D, E & K) from the gut.
Provides Energy (when oxidised)
Provides essential fatty acids
e.g. linoleic and linolenic acids which cannot be synthesised in body.
What are minerals used for in the body
- Electrolytes establish ion gradients across membranes & maintain water balance
- Calcium & Phosphorus essential for structure (Bones + teeth)
- Calcium also very important signalling molecule
- Enzyme co-factors (iron, magnesium, manganese, cobalt, copper, zinc, and molybdenum)
- Iron essential component of haemoglobin
What are the fat soluble Vitamins and what does the deficiency cause
Fat soluble. Deficiency
A Xerophthalmia
D Rickets
E Neurologic abnormalities
K Defective blood clotting
Water soluble Vitamins and what does the deficiency cause
Water soluble Deficiency
B1 (Thiamin) Beriberi
B12 Anaemia
B6 Dermatitis, Anaemia
BiotinAlopecia, Scaly skin, CNS defects
C Scurvy
Choline Liver damage
Folate Neural tube defects, Anaemia
Niacin Pellagra
Pantothenic acid Fatigue, apathy
Riboflavin Ariboflavinosis
What does Excess Vitamins cause
Hypovitaminosis, Can lead to death
HOW DOES FIBER LOWER CHOLESTEROL?
- Grabs on to fats and cholesterol in the small intestines so that it’s excreted instead of absorbed into the bloodstream.
- Reduces the amount of bile salts reabsorbed from the intestine. The body then needs to make more bile salts and uses cholesterol to do this.
- Slows digestion, which slows how fast blood sugar rises after eating. High blood sugar can cause more triglycerides to be formed, which can cause more cholesterol to be formed.
Where are dietary fibres found
Found in cereal foods, (e.g. bread, beans, fruit & veg)
Is fibre broken down
How much is recommended
what happens if you don’t have enough or have too much
- Cannot be broken down by human digestive enzymes but essential for normal functioning of gastrointestinal tract
- Recommended average intake for adults = 18g /day (average intake is below this: 12.8g/day for women and 14.8g/day for men).
- Low fibre intake associated with constipation and bowel cancer
- High fibre diet shown to reduce cholesterol and risk of diabetes
What are DRV’s
Dietary Reference Values (DRVs) published by SACN are a series of estimates of the amount of energy and nutrients needed by different groups of healthy UK population.
What is
*Reference Nutrient Intake (RNI)
*Estimated Average Requirement (EAR)
*Lower Reference Nutrient Intake (LRNI)
*Safe intake (used when insufficient data)
- RNI
used for protein, vitamins and minerals
Enough to ensure needs of 97.5% are being met. Many within the group will need less - EAR
used for energy.
Requirement for ~50% of group (50% will require more).
*LNRI
Intakes below LRNI are insufficient for most people.
Enough for only the small number of people who have low requirements (2.5%). The majority need more.
What is Basal Metabolic Rate
The BMR refers to the amount of energy your body needs to maintain homeostasis.
- Energy needed to keep the body alive
Maintenance of cells
*Ion transport across membranes
*Biochemical reactions
Organs BMI
Function of organs
*Skeletal muscle ~30% BMR
*Liver ~20% BMR
*Brain ~20% BMR
*Heart ~10% BMR
*Other ~20% BMR
Factors affecting BMR
Factors affecting BMR
-Body size (surface area)
-Gender
(males higher than female)
-Environmental temperature (increases in cold)
-Endocrine status
(increased in hyperthyroidism)
-Body temperature
(12% increase per degree)
What is the KJ/Kg/Day needed for different activity levels
Rough values
* Sedentary person - 30 kJ/Kg/day
* Moderate activity - 65 kJ/Kg/day
* Very active - 100 kJ/Kg/day
What are the Energy stores (4)
- Very short term stores of energy rich molecules in muscle – few seconds worth
- Carbohydrate stores for immediate use - minutes or hours depending on activity
- Long term stores in adipose: ~40 days worth
- Under extreme conditions muscle proteins can also be converted to energy
- Glycogen
Liver can hold 100g of glycogen
Sceletal muscle 300g
(can’t store anymore)
What is the typical composition of a 70 kg and 100 kg man
70kg man 100kg man
Carbohydrate
1 kg 1 kg
Lipid
12 kg 40 kg
Protein
11 kg 12 kg
Minerals
4 kg 4 kg
Water
42 kg 43 kg
What is Obesity
- Excessive fat accumulation in adipose tissue which impairs health.
- Usually measured using body mass index (>30)
- Result of energy intake exceeding energy expenditure over a period of years
- Major potentially preventable cause of death in developed countries
- In UK (and most other countries), prevalence of obesity has been
increasing over recent decades. - Associated with an increased risk of developing some cancers, cardiovascular disease and type 2 diabetes.
How to calculate BMI
BMI = Weight (kg) / Height ^2. (m^2)
Classifications of BMI
Male (kg/m2). Female (kg/m2) Classification
<18.5 <18.5 Underweight
18.5 - 24.9 18.5 - 24.9 Desirable weight
25 - 29.9 25 - 29.9 Overweight
30 - 34.9 30 - 34.9 Obese
>35 >35 Severely obese
How can Fat distribution affect Heath
Greater proportion of fat in upper body, (especially abdomen), compared with that on hips associated with
increased risk of:
* Insulin resistance
* Hyperinsulinism
* Type 2 diabetes
* Hypertension
* Hyperlipidaemia
* Stroke
* Premature death
What can LOW protein cause
Low protein intake can result in insufficient blood protein synthesis leading to a decreases in plasma oncotic pressure and oedema (as seen in the disease Kwashiorkor).
What is sterlings law of the capillary
The Starling Principle states that fluid movements between blood and tissues are determined by differences in hydrostatic and colloid osmotic (oncotic) pressures between plasma inside microvessels and fluid outside them
What is the equation of sterlings law
Flownet = (Pc- Pi) – (πc- πi)
Pc = Hydrostatic pressure of capillary
πc = Oncotic (protein) pressure of capillary
Pi = Hydrostatic pressure of interstitial fluid
πi = Oncotic pressure of interstitial fluid
Flownet = Net flow of fluid from capillary to interstitium
What is Marasmus
- Occurs due to insufficient energy intake
- A negative energy balance
- Multiple nutritional deficiencies
- Energy
- Protein
- Vitamins and Minerals
- Dehydration
What is the biochemistry behind Marasmus
- Negative energy balance –> mobilisation of
- Fatty acids are released –> loss of body fat
fat stores - These are converted to ketone bodies as a source of
energy for the CNS - CNS and RBC cannot use fatty acids – they need glucose.
- BUT there is not enough carbohydrate and glucose consumed.
- Glucose released from glycogen stores in the liver
- When these are exhausted, muscles protein is broken down to release amino acids for gluconeogenesis to occur —> loss of muscle protein
What is the anatomical changes from marasmus
- Severe body fat and muscle mass loss —> wasted appearance
- Unable to replace and repair tissues
– Entire GI tract affected – thin mucosal surfaces, impaired secretory functions
– Normochromic anaemia develops
– Pituitary hormones (growth, thyroid, sex hormones) affected - CV – heart muscle thins, impaired function, bradycardia, hypotension
- Brain affected in severe forms
What is Kwashiorkor
- Calorie intake normal
- Low protein intake
- Body needs essential amino acids from diet
– therefore the body is unable to synthesise some essential proteins
Hepatic Dysfunction in Kwashiorkor
- Liver functions:
- Metabolise carbohydrates to fat
- Synthesise lipoproteins required to transport this fat around body in blood (will be covered in MEH unit)
- Synthesise serum proteins (e.g. albumin)
- If liver is unable to synthesise sufficient lipoproteins due to dietary deficiency of essential amino acids, lipids will accumulate in liver instead of being transported around body —> fatty liver —> hepatic dysfunction
Oedema in Kwashiorkor
- Problem: insufficient protein intake means liver unable to synthesise albumin and other proteins
- Oedema occurs due to reduced oncotic (osmotic) pressure of plasma causing fluid shifts
- Symptoms conceal underlying wasting and poor growth (associated symptoms = fatigue, poor immune function, poor healing of damaged tissues)
What is re feeding syndrome
- Occurs clinically in anorexic patients, cancer patients, post surgery, alcoholics
- Can lead to confusion, coma, convulsion, death
- Precise cause unclear but electrolyte imbalance thought to play a role
- Rapid increase in metabolism on re-feeding will utilise more phosphate, Mg2+ and K+. Body stores are already depleted and electrolyte abnormalities such as hypophosphataemia can occur if re-feeding too rapid
- Re-feed at 5 -10 kcal/kg/day raised gradually over 1 week
