nutrition exam prep Flashcards
Q1) Using your knowledge of type 2 diabetes, provide a summary which outlines the pathophysiology of the disease and the role of a very-low-calorie-diet as a curative intervention: make specific reference to the twin cycle hypothesis (12 marks)
1) Type 2 diabetes is a metabolic disease caused by increased levels of fatty acids being stored and synthesised in b-cells, this leads to dysfunction of b-cells and causes impairment of glucose-stimulated insulin secretion.
2) A very low-calorie diet (VLCD) is commonly used as a way to reverse type 2 diabetes. The twin cycle is a hypothesis at a way of reversing the disease type 2 diabetes. The hypothesis involves…
3) A positive calorie balance causes an increase of fat stored in the liver and pancreas. Fat build up in the liver leads to impaired fasting glucose metabolism and increases exportation of VLDL triglyceride causing an increase in islet triglyceride. Insulin response to ingested glucose then decreases and post-prandial glucose increases which causes a rise in plasma glucose and basal insulin secretion leaving glucogenesis insulin suppression resistance to increase. Observations of the reversal of type 2 diabetes confirm that that if the primary influence of positive calorie balance is removed then the processes are reversible.
Q2) Outline the key pathophysiological mechanisms responsible for exercise-induced hypoglycaemia, provide evidence based recommendations for maintaining normal blood glucose levels in patients with type 1 diabetes
A) when insulin in injected into the blood stream, blood glucose levels decrease due to insulin preventing the liver from producing glucose. After exercise blood glucose decreases even more, individuals symphomatic awareness also decreases allowing symptoms of low blood glucose to go unnoticed this can become dangerous if untreated. Recommendations to help individuals maintain blood glucose levels, they are as follows:
1) 60 minutes before exercise consume 1.g.kg of CHO and reduce bolus insulin intake by 75%
2) 60 minutes post exercise consume 1.g.kg of low GI CHO and reduce bolus insulin intake by 50%
3) Before sleeping consume 0.3.g.kg of CHO and omit any insulin prandial administration
4) The following day reduce total basal insulin dose by 20% in addition to prandial adjustments
RED’S (relevant energy deficiency in sport)
Performance implications: • Decreased endurance performance • Decreased muscle strength • Decreased glycogen stores • Increased risk in injury • Depression
Health implications (specifically for females): • Cardiovascular • Metabolic • Psychological • Growth and development
Triad
Reds-Menstrual function-bone health (females
Treatment strategies
• Increase energy intake (EI)
• Decrease exercise
• Implement an eating plan that increases EI by 300-600kcal a day, spread consumption over the day and around exercise sessions
Tips for athletes travelling
• Plan ahead- investigate food patterns thoroughly as possible before leaving
Altitude
• Cross-country skiers should focus on ensuring high energy intakes throughout the duration of intense training camps, especially at altitude, to meet high energy demands.
• Ski jumpers have lowest energy requirements/ cross country skiers have highest
• Sports dietitians should teach skiers how to prepare for and recover from training in environmental extremes through adequate energy and nutrient intakes.
• Time trials require some winter sport athletes to train in thin body suits at temperatures around –158C. Shivering thermogenesis can be a side-effect, increasing glycogen utilization and accelerating the onset of fatigue.
Tips for athletes travelling
• Plan ahead- investigate food patterns thoroughly as possible before leaving
Recommendations
• It is recommended to adjust resting energy expenditure to altitude and increase energy intake by an extra 200–300 kcal _ day (Butterfield, 1996).
• athletes’ body weight, appetite, and sleep should be monitored
• During intense training, daily carbohydrate intakes should be 6 g/kg/day and may need to exceed 10 g/kg/day
• CHO intake should be adjusted according to intensity and volume of training (6-12g/kg/day) on high intensity/volume days
• Ingested adequate fibre (fruit/veg/wholegrain breads/cereals)
• It is recommended athletes ingest carbohydrates at a rate of 1.2–1.5 g kg and begin carbohydrate feeding within the first 30 min. This should optimize performance in subsequent sessions, especially if multiple sessions are held.
• Protein winter athletes need 1.4-1.7g/kg/day
• Fat winter athletes need 1.0-1.9g/kg/day
• Athletes are advised to ingest sport drinks with electrolytes at intervals of 15–20 min or as lift-rides and training infrastructure permit.
• Iron, antioxidants and vitamin D
Essential physiology/Metabolism/inflammation
What do we want nutrition to do for an athlete?
• Fuel for work required & recovery
(both interact with energy demands/system – metabolic consequences- recovery/inflammation)
• Within the cytoplasm nutrients are passed from the nutrient pool to either the mitochondria to be catabolised into ATP or heat or the results of anabolism (maintenance & repair/growth/secretion/stores reserves
FFA & PLASMA GLUCOSE OXIDATION INCREASE WITH EXERCISE DURATION !!!
- Longer duration exercise causes an increase of activation of glycogen phosphorylase
- Which causes an increase in glycolysis and decrease in glycogen
- Which leads to an increase in AMPK
- Passed on to GLUT 4 and CD36
Ingestion of CHO during exercise causes a decrease in FFA oxidation, spares liver and potentially muscle glycogen
‘glucose–FFA cycle’
proposed that an increased availability of plasma FFAs could stimulate fat oxidation and decrease carbohydrate oxidation by suppressing pyruvate dehydrogenase complex (PDC)
According to this concept, the relative utilisation of fat and carbohydrate is determined primarily by the availability of plasma FFAs. (randel)
The role of insulin in glucose disposal
Insulin stimulates a cascade of protein activity, which causes GLUT-4 transport proteins to translocate to the plasma membrane
Inflammation is the first physiological response to harmful stimuli which is required for the healing of injured tissue
(harmful stimuli = mechanical injury, chemical toxins, invasions by microorganisms, hypersensitivity reactions
• Causes a release of cytokines (signalling proteins)
• Causes an increase in blood supply to the affected area
• Capillary permeability is increased
• Leucocytes migrate from the capillary vessels into the surrounding interstitial spaces to the site of inflammation or injury
Key cytokines which activate the inflammatory response
- IL1
- IL6
- TNF
- INTERFERONS (IFNs)
Ergogenic aids/dietary manipulation
Fatigue is the accumulation of lactic acid
PGC-1A (master switch) – high volume/intensity training
High intensity training – ATP – AMP – AMPK – PGC-1A
75% vo2 max predominantly burning muscle glycogen
At rest predominantly burning FFA
55% vo2 max best fat burner
- Carnitine is a co-factor that is required for the transport of long-chain fatty acids across the inner mitochondrial membrane
- We propose that a mechanism involving the down-regulation of CPT I, either by a decrease in free carnitine availability or by a decrease in pH, is the most likely candidate to lead to the reduction in fat oxidation during high-intensity exercise
Cancer
Protective elements in a cancer prevention diet:
Does it reduce cancer by a %? When a diet implies these guidelines, it is likely you will see a:
• 60-70% decrease in breast colorectal & prostate cancers
• 40-50% decrease in lung cancer
• Such a diet could prevent cancer and would help recovery aswell
Overall Message? Eat a well-balanced diet foods rich in… • folic acid (green leafy veg) • 4 or more servings of fruit/day • vegetables (raw) (garlic, onion, leak) • Low fat, but fat containing essential fatty acids • Adequate vitamin D • No red meat • No refined flour • No refined sugar • Supplement 200mg selenium/day (Donaldson)
Sacropenia
Once you are classified as sacropenic = extremely frail
Sarcopenia = loss of muscle caused by atrophy (lose muscle fibres/can’t recruit as many muscle fibres)
Bed rest = can lose up to 1% of muscle mass a day and 4-5% a week
Recommendations for sarcopenia bed rest
• Maintain adequate energy intake
• Maintain adequate protein intake
Catabolic crises theory
Once someone has been omitted to hospital they are much more likely to be omitted again due to loss of muscle mass
Vitamin D
Vitamin D binds to a particular receptor (VDR) muscle increases uptake of calcium.
Bone, calcium and phosphorus resorption
• This can only be effective if you have really low levels of vitamin D
There is sufficient evidence of potential benefits for the use of supplemental vitamin D!!!
Microbiota
- Firmicutes/Bacteroidetes (Predominant species in the gut)
- A balance between the 2 = a healthy gut that provides adequate substrates
- These substrates regulate metabolic activity/the progression of autoimmunity /progression of diseases.
- An imbalance between the two (especially firmicutes) can have negative consequences and cause metabolic disturbances (disregulates substrates/disregulates protein synthesis and enzyme activity)
- Lipopolysaccharides from the gut increase endotoxemia (toxins in the blood)
- Causes a decrease in FIAF meaning suppressive effect is lost = weight gained
- FIAF decreasing =
- Decrease (CPT1/less FA entry into mitochondria)
- Decrease (PGC-1A/ less mitochondrial biosynthesis)
- Decrease (MCAD/less beta oxidation of medium chain)
- Decrease (lipoprotein lipase/
Imbalances in the gut can be altered by:
• Probiotic supplementation
• Plant based, fibre rich diet (observational rather than interventional) not strong evidence
