Role of Diet Flashcards
What amino acid do cats require in their diet?
Taurine
What neurobiological effect does eating have?
Positive dopamine
What factors influence taste preference?
Experiences and genetics
Give three “popular beliefs” about diet and behaviour in dogs
Hyperactive/aggresive dogs need a low protein diet to calm them
High carbohydrate diets calm anxious dogs
Artificial preservatives eg. ethoxyquin affect behaviour more than natural preservative eg. vit C
What amino acids is serotonin made up from?
Tryptophan and tyrosine
Which NT does tryptophan contribute to?
Serotonin (MOOD)
Which NT does tyrosine contribute to?
Catecholamines (STRESS)
Which NT does histidine contribute to?
Histamine (IMMUNE)
Which factors affect how much the NT levels are affected by food?
Timing of food, composition of diet, Digestability of diet
What have diets high in tryptophan shown?
Conflicting results - Decreased and increased aggression (rodents and primates)
Reduced self injurious behaviour in primates
Increased exploratory behaviour in foxes
What have diets low in tryptophan shown?
^Aggression, anger and frustration in humans
Increased turnover of tryptophan and serotonin in acute stress
Decreased turnover of tryptophan and serotonin in chronic stress/depression
Where does conversion of tryptophan to serotonin occur? How much trypotohan is converted? What is tae of conversion affected by?
1% in GIT
Conversion affected by - trypotphan, other LNAAs, fatty acids, carbohydrates (->insulin release -> aa uptake, often aa other than tryptophan are more favourable)
Why is getting int o the brain difficult?
Has to compete with other Large Neutral Amino Acids (LNAAs) to cross BBB
What happens to free tryptophan?
Binds to albumin in plasma and cants cross BBB
Fat levels important for albumin
How do carbohydrates affect tryptophan levels?
Stimulate relase of insulin -> aa uptake (other aa than tryptophan more favourable so decreased competition at the BBB)
Which enzyme is the rate limited step for trypotophan -> serotonin conversion?
Tyrptophan hydroxylase
What is the purpose of albumen in tryptophan transport?
Binding to tryptophan “keeping it safe” until reaching the BBB
What NTs does tyrosine form?
Catecholamines - Dopamine, noradrenaline, adrenaline
When does NA turnover increase?
During periods of high stress therefore high tyrosine diet protective of effects of acute stress (rodent studies)
How does tyrosine impact other aa levels?
Competes with other AAs at BBB
Generally higher concentration in normal protein than tryptophan so high protein meal ^tyrosine, vtryptophan
What did Dodman et al 1996 show?
No effect of dietary protein levels for dominance aggressive, hyperactive or control dogs
Significant effect of protein level of territorial aggression dogs due to fear (low protein -> v aggression)
What did De Napoli et al 2000 show?
No change in behaviour within each group (dominance/territorial/hyper)
But combined, decrease in territorial aggression for dogs fed low protein + tryptophan supplement (i.e. ^trypotophan)
Increase in dominance aggression for dogs fed high protein no tryptophan supplementation (ie. vtryptophan)
What did Bosch et al 2009 show?
No difference in response in mildly anxious dogs
How may carbohydrates affect behaviour?
Digestible - Starch ->monosaccharides eg. glucose. Fluctuations in blood glucose -> hyperactivity etc. Also impacts aa uptake into muscles by ^insulin release from pancreas. Uptake of other aa leaves ^conc of tryptophan at BBB
Indigestible - Fibre-> fermented in colon to produce fatty acids, lactate and gases, affects feeling of satiety
What form of tryptophan will not be affected by insulin release?
Albumin bound tryptophan
What is the popular diet theory for dogs?
Feed wholemeal pasta 2x daily after protein meal
Supplement vit B6 (cofactor for enzymes breaking down protein, direct hormonal effect (?))
Does the impact of carbohydrate intake actually have an impact of tryptophan levels?
Yes, but minute - an increase of 4% protein in the diet eliminates the effect totally
Change in protein level has a more significant effect
What other factor also influences change in mood and tryptophan levels?
Genetics
Does high or low viscosity food take longer to digest?
Low! eg. soup
What effects does dietary fibre have on satiety?
^ satiety
^ viscosity in stomach
^ release of GLP to inhibit gastric emptying
^ intestinal transit time
What did Bosch 2009a show?
Decreased food seeking behaviour and voluntary food consumption with high fibre diet
What did Bosch 2009b show?
Decreased activity with high fermentable fibre diet
No change in response to stressors with high fermentable fibre diet
What are lipids used for in the body?
cell membranes
steroid hormone precursor
energy source
What are PUFAs? What are they used for in the body?
Poly unsaturated fatty acids - Brain tissue, eg. omega 6
What effect of PUFA in the diet have been shown?
V learning ability in rodent when deficient in PUFAs and ^ when supplemented
PUFA deficient rats sometimes show ^behavioural stress response
How has fat been shown to affect humans?
Increased reaction times (slower) with low fat diet
What has been shown to reduce the rate of cognitive decline in lab dogs?
Anti-oxidant enrichment and mitochondrial cofactor enrichment
What have lipids been shown to affect in dogs?
Retinal development in puppies
Cognitive decline
Difference in ratio of some fatty acids found in association with aggressive v non-aggressive dogs, but no causality proven.
What is the overall conclusion regarding role of diet on behaviour?
Insufficient evidence to conclude effects
- small scale studies, results not in agreement
Tryptophan uptake important bu only small part of the picture
What is a neutraceutical?
Food substance marketed as having a pharmaceutical effect
Non prescription
Often limited evidence
Marketed as natural and with decreased side effects
Give an example of a neutracuetical
Zylkene - Alpha casein hydrosylate protein from milk
Thought to act at GABA a receptor (=benzodiazepene mechanism of action) calming
Some effect shown in rodent and human studies
Mixed results in dogs and cats (Beeta 2007, Palestrini 2010)
