Physiology and Nutrition

Amino acids: 22 found in animal tissue, 9 essential amino acids directly needed in the diet. 

• Threonine, Methionine, Lysine, Valine, Leucine ect.

Non-essential- Formed 'endogenously' by 'transmutation reaction.

60-70% of the body composed of water. 

Temperature: Adults consume 2-2.5L/day 

--> Sweat = water loss

Salt: Intake average 9g - recommended 6g.

Age: Immune and system, retain water through joints and swelling. 

Altitude: dehydration 

-Essential fatty acids include linoleic/ Alpha - Linolenic 

-Carriers of fat soluble vitamins A,E,D and K. 

Fat: Stored 

Water soluble: Vitamins B and C. 

40-75% - Dietary energy, the UK suggests no more than 50%.

Refined sugars --> sweets and sugary cakes 

Staple food at a low cost. 

Water soluble - B and C

Fat Soluble - A,D,E and K 

Function as co-enzymes and antioxidants (Fight disease) 

-Inorganic (Naturally found) - Needed in small amounts for life (mg/ug) 

Needed for - Muscle contraction, neural control (mg), oxygen transport (fe), Nerve impulse conduction (Na,K) 

(Individual rate) 

Balanced (Being able to support.) Growth, reproduction and good ongoing - physical/ mental health.

Energy is the capasity to do things. 

-Comes from the sun through photosynthesis light energy --> chemical energy. 

- Have to consume plants or animals that eat plants. 

-CHO+O2 +   H2O + CO2 +Energy (ATP)

Energy released due to the breakdown of organic substances (Cellular respiration) Energy then captured in ATP.

The Metabolic processes whereby certain organisms obtain energy from organic molecules. 

KREBS CYCLE -  stream of protons for electron transport. 

Electron transport chain. 

Units of energy. 

- Joule - Used when a mass of 1kg is moved through 1m by a force of 1N (kJ/MJ)

-Calorie - Energy required to raise the temperature of 1g of water from 14.5 to 15.5◦C .

-Kcal - Used in relation to nutritional context. --> Metabolises energy. 

Bomb calorimeter : Energy measured this way - Gross energy (GE) 

Gross energy is not always available. 

1. Not all food is absorbed from the digestive tract. 

2. Protein not completley metabolised. 

Energy available after digestion - digestable energy (DE) - Urinary energy loss -- Metabolisable energy. (ME) 

CHO 4 

PROTEIN  4         per gram (kcal) 

FAT        9 

Determined using direct calorimetry. 

- Involves measurement of energy expenditure (EE) over a given period by measuring the heat emitted from the body. 

Indirect calorimetry 

- When food is oxidised 0_{2 and}  C0_{2 produced in proportion to make heat generate.}

_{- Formula calculated in human energy expenditure.}     

-Basal metabolic rate (BMR) - Lying at physical and mental rest, at least after the last meal 60-65%.

-Physical activity - Accounts for 25-35% (Depending on type/duration of activity.) 

-Ingestion of food - Causes an increase in EE (Post prandial thermogenesis PPT) - 10% of EE.

Body size: The more cells the more energy is needed. 

Body coposition: Adipose tissue has a lower metabolic rate than other (ESP muscle tissues) 

Gender: Accounted for by difference in body size and coposition. 

Age: EE increases as the body grows to adult size, then decreases with advancing age. 

Diet: Overfeeding increases EE by 5-10%. / Underfeeding reduces EE by 5-10%. 

Genetic differences: EE varies upto 10% between individuals of the same age, sex, body weight and fat free mass. 

Hormonal state: EG. Hyperthyridism increases EE, hypothroidism decreases EE. 

Psychological state: Acute anxiety stimulates adrenaline secretion - increases EE. 

Pharmacological agents: Nictotene and caffine increases EE, Amphetamine increases EE. Some antideppresants decrease EE.

Disease Process: Can increase, metabolic rate, E.G. fever and burns to the skin. 

Mechanical Processing: Movement, chewing, mixing. 

Secretion: Fluid, digestive enzymes and hormes, bile, alkali and mucus. 

Digestion: Breaking down food to absorbale units. 

Absorption: Through mucosa, into blood or lymph vessels. 

Elimination: Undigestable material eliminated. 

Motility of the GI tract. 

Peristalsis: Propels content through the GI tract.

Segmentation: Mixes content --> (Mixes up) 

Gut nervous system. 

- A collection of nerve cell bodies within the wall of the GI tract. 

- Consists of two basic regions - Regulates motility/ secretion of the GI tract. 

- Vital component of reflex pathways. 

Secretion and digestion 

- Salivary glands produce secretion and amylase. 

- Stomach - stores ingested food, produces mucus, HCI and pepsinogen. HCI converts pepsinogen into pepsiri, pepsin digests proteins into peptide fragments. 

1. Cephalic Phase- (controlled in the brain) - sight and smell of food. 

2. Gastric Phase - In the stomach. 

3 Intestinal phase - Triggers release of hormones (Cholecystokinin.) 

Pancreas 

Pancreas secretes a range of digestive enzymes. Liver has a variety if actions (role in digestion in bile production.) 

Pancreatic Secretion 

1. Mostly stimulated by the intestinal phase. 

2. Bicarboncite stimulated by seretin (H+ in lumen.) 

3. Enzyme secretion stimulated by CCK - Fatty acids in the lumen. 

4. Partly controlled by the parasympathetic system. 

CARBOHYDRATES - Digests carbohydrate 

PROTEASES - digests protein 

LIPASES - digests fat. 

Absorption 

- Epithelia of intestines are specialised in different ways to faciliate absorption. 

- Small intestine: Specialised for the absoroption of nutrients. 

- Large intestines: Specialised for re - uptake of water. 

- Little absorption in the stomach - absorbed in the small intestine. 

Fat: Chylomicrons passed in lacteal system. 

-Metabolic processing of nutrients.

-Detoxification of  chemicals.

- Synthesis of plasma proteins 

- Storage of glycogen, fat, iron, copper and vitamins. 

- Activation of Vitamin D.

- Excretion/re-uptake of cholesterol/

-Secretion of bile salts. 

There are 3 main types of micro nutrients. 

Macronutrients (Needed in large amounts.) 

- Protein.

-Fat

-CHO 

Protein 

- Essential fatty acids - synthesis (4kcal/g) 

- 10-15% - total energy expenditure

- Cellular component. 

- Formation of hormones, coenzymes, nucleic acids and neurotransmitters. 

Fat 

Essential fatty acids (- synthesis of hormones and key bioactive molecules - energy provider - (9kcal/g) 

Linoleic (Linoleic) - Omega 6 - Cardiovascular 

Linolenic (Linolenic) - Omgea 3. 

Structure and Function 

- Important in maintaing cellular and membrane - integrity. 

- Needed in production. 

Saturated Fats 

Hard to break down - body stores instead. 

Provides energy (4kcal/g) made in liver from fat and protein. 

- 40-85% TDEI (DRV: no more than 50%) 

- Polysaccharides starch - Multiple sugar units joined together - starch is the storage CHO of cereal grains. Root vegetables (e.g. protein.) 

2 main forms - Amylose (Unbranched) / Amylopectin (Branched) 

- Most abundant CHO is a complex - CHO.

Non starch Polysaccharides (NSP) 

AKA - fibre/roughage - indigestable. 

- Derived mainly from plant cells walls.

CLASSIFIED AS: Soluble: hemicellulose, pectin

                            Insoluble: Cellulose 

NSP - Delays gastric emptying, reduces speed and overall transit time. 

- Some are broken down by fermentation in the large intestine. 

- Produces SCFA'S - Short chain fatty acids. 

- Binds cholesterol in bile and carries it out the body -> Reduces overall cholesterol levels. 

Simple CHO'S - Sugars are mono or disaccharides 

- Oligosaccharides - A few.

Glucose, Fructose, Galactose are monomers combined to form: 

Sucrose -  Table sugar - Glucose + fructose 

Lactose- Milk sugar - glucose + galactose. 

- Non - essential 

- No recommended units. 

Pint, ml, units,

Fat soluble A,D,E and K

Stored in fat depot (Adipose tissue/ Liver) 

Fat soluble vitamins only absorb in the presence of fat. 

Water soluble vitamins- absorption only occurs by simple diffusion. 

Water soluble  B and C. 

Limited storage, found in all tissues. 

Pro vitamins 

- Compounds - function as vitamins only after they have undergone a chemical change. 

E.G. carotenes - Vitamin A (In intestinal way) 

Pro- vitamin D - (Subcut fat) - vitamin D by irradition. 

-Inorganic elements required as major minerals or trace minerals. 

- Both are vital. 

Glucostatic theory.

Glucose = the brains primary fuel 

- This is a stimulas for hunger and decreases in the level of blood glucose below a set point. 

The glucostat= a neuron that detects the level of blood glucose. 

This focuses on the storage of fats in the adipocytes and ciculating free fatty acid (FFA) levels. 

Set point for body fat: Deviations - compensatory adjustments in food intake to maintain energy stores. 

Mouth= Forward feed mechanism oesophageal fistula - a tempory reduction in hunger. 

Stomach= Forward feed mechansim temporary reductions in hunger. 

Stretch receptors= in the stomach wall signal distension (in presence of food )

Hormones released as food enters the duodenum. 

What happens after a meal 

Food is absorbed. Hepatic and CNS receptors sensitive to circulating macronutrients. 

Summerised 

Factors initiating eating 

- Low blood glucose, hunger hormones.

Events during a meal 

- Forward feed and post absorptive

Events after a meal 

Circulating nutrients. 

Neurotransmitters known to influence food eating. 

- Serotonin - This leads to an reduction in food intake. - e.g. CHO

-Noradrenaline leads to a rise in food intake - e.g. CHO 

These effects promote a cycling of preference between CHO and Fats and protein. 

Ensures a steady supple of energy and essential nutrients from different food groups.

Physiology of starvation 

- 25% weight loss is dangerous 

Death occurs between 25%- 55% body weight loss.

Autopsy - Little adipose tissue left muscle is atrophied (Skeletal and heart.) GI walls are thin and dysfunctional. 

This is the starvation and not the same as pathological ketoacidosis of diabetes. 

Syndromes in children. 

Kwashiorkor - The failure to grow, skin lesions, fatty liver, oedema, irritability. 

Marasmus - Generalized wasting, stunting, lethargy. 

Undernutriton of phychological cause. 

Anorexia nervosa is a serious psychological illness that kills many of those that are affected.

10:1 ratio of females to male sufferers. 

Peak on set - 12-18 years. 

Frequent association with with exercise.

Metal illness. 

Depression 

Schizophrenia 

Drug abuse 

Clinical 

Cashexia - The general state of wasting. 

Decrease in food intake and increase in energy expenditure also due to circulating immune products e.g. cytokines - TNF, Cashectin, interleukins. 

Physiology of undernutrition 

Glucogenolysis - Gluconegenesis - protein sparing 

Undernutrition in developing countries

Famine - Kwashiorkor - marasmus 

Undernutrition in developed world

Clinical 

Psychological. 

Dietary: Food intake over time 

Anthropometry: Body dimensions and composition. 

Biochemical: Body chemistry

Functional: Function of body systems 

Clinical: Clinical appraisal. 

Underweight: <18.5

Normal weight: 18.5-24.9 

Overweight: 25.0-29.9 

Functional

Muscuclar function, metabolic, immune function, biochemical pathway. 

Functional assesment 

Grip strength is a better indicator of likelihood of post-operative complication than weight loss or loss of subcataneous fat. 

Biochemical 

Tests are used primarily to detect subclinical deficiency states.

Procedures can be used to supplement other methods - enabling specific nutritional problems to be indentified. 

-Glucose fasting 

-CHolesterol total: HDL:LDL 

-Iron: Serum iron Hb 

Electrolytes (Na,K) 

Dietary assessment 

Methods can be classified into 2 groups 

1) Recall - includes 24hr recall (or longer)

2) Record - Consists of records (e.g. food diary)

Advantages - 

Low repondent burden. 

Disadvantages - 

Memory dependant, many errors. 

Unsuitable for children and the elderly, 

May not reflect the normal eating pattern - alcohol often left out. 

Caused by energy in - energy out. 

Changes that occur - 

Hypertrophy - of existing adipocytes

Hyperplasia - develepment of new adipocytes. 

Genetic factors 

- Obese parents frequently have obese children and pets. 

- Risk in developing serious diseases. 

- Main causes of premature death is CVD.

-Insulin insensitivity - e.g. type two diabeties. 

Metabolic syndrome 

Central obesity, high blood pressure, Low HDL - cholesterol , insulin resistance. 

Health risks of obesity 

- Gallstone formation - Bile - supersaturated with cholesterol - gallstones. 

- Risk of cancers - colon, prostate, breast, cervix, ovary 

Various formations 

- Single: e.g. calcium 

-Combined e.g. calcium and vitamin D 

- Multi - vitamins and minerals. 

Specific - cure deficiciency or disease 

Precise- e.g. folate dose - 0.4mg. 

Therapeutic does upto 10x the RDA of a nutrient.

Why use supplement 

Improves nutritional status of specific groups. - Dieters, vegetarians, elderly, pregnancy ect. 

Zinc/iron/vitamin c - improves immune function. 

Toxicity 

- High doses of: 

Vitamin A - Death 

Vitamin C - abdominal cramps 

Vitamin B6 - Nerve damage .

Vitamin D - Abnormal tissue calcification.