food: nutrition and malnutrition - MD2B1 Flashcards
(27 cards)
what is the difference between a food allergy and food intolerance?
food intolerance is in the digestive system
food allergy involves the immune system
what are symtoms of a food allergy?
> can manifest with GI symptoms
but generaally appears on the skin > (hives, itchiness, swelling)
respiratory symptoms
can induce anaphylaxis
wht are symptoms of food intolerance?
unpleasant GI symtoms - gas, bloating, flatulence, cramps, diarrhoea
what is a food allergy?
immune system in the GI tract protects against potential pathogens and what the body recognises as foreign
in a food allergt, the immune system identifies the food as an invasive threat
what are the categories of food intolerance?
- metabolic - enzyme deficiency, carbohydrat malabsorption
2. pharmacologic - chemical sensitivity - caffeine, MSG
what breaks down lactose?
lactose
a beta galactosidase enzyme
what is lactose broken down into?
glucose and galactose
how are glucose and galactose transported into the enterocytes before moving into the blood circulation?
sodium/glucose transporter SGLT1
what can lactose intolerance caused by? (3)
lactase deficiency
lactase non-persistence
hypolactasial
inability to digest lactose in the small intestine
describe the pathophyisology of lactose intolerance
lactose transits undigesred into the large intestine
here the gut bacteria metabolise it resulting in fermentation which produces gas (CO2, H, CH4) - this cuases flatulence, bloating, distension
the unabsorbed lactose and the fermentation products (e,.g, short chain FA) raise osmotic pressure in the colon
this increases flow of water into the lumen of the colon causing osmotic diarrhoea
what gene encodes lactase?
LCT gene regualted by MCM6 protein
mutations in MCM6 are assocated with keeping the LCT gene on
lactose intolerant indiviuals lack this mutation
what is primary lactase deficiency?
(NON-PERSISTENCE)
genetically inherited
absence of lactase persistence allele
age-related decrease in lactse deficiency leading to hypolactasia in adulthood
what is secondary alactaase deficiency?
caused by damaged lining of the intestinal wall where lactase is produced
caused by gastroenteritis, coeliac disease, IBS, medications, parasites
its transient and normally dissapearrs when the intestinal wall has recovered
what is congenital lactase deficiency?
alactasia
rare, autosomal ressesive mutation in the LCT gene causing complete lack of lactase from birth
what is the hydrogen breath test?
> patient is fasted overnight
consume 25-50g liquid lactose
breath samples taken every 15.20 minutes for up to 3 hrs
rise in breath hydrogen indicates lactose was not ingested
rise of more than 20ppm compared to individual baseline, lactose intolerance is suspected
what is the lactose tolerance test?
> This test measures the production of glucose that should normally occur if lactose is correctly digested and absorbed
The patient is fasted overnight
Blood glucose levels are measured before and 30 and 60 mins after consuming 50G of lactose
If glucose does not rise, lactose intolerance is diagnosed
A variation of this test is the milk tolerance test – milk instead of lactose
what is type 1 hypersensitivity?
involves immunoglobulin E (IgE) antibody against soluble antigen
triggers mast cell degeneration
what is type 2 hypersensitivity?
involves IgG and IgM antibodies directed agaisnt cellular antigens, leading to cell damage mediated by other immune system effectos
what is type 3 hypersensitivity?
interactions of IgG and IgM and occaasioanlly IgA antibodies to form immune complexes, accumulaation of immune complexes in tissues leads to tissue damage
what is type IV hypersensitivity
T-cell mediated reactions that can involve tissue damage mediated by activated macrophages and cytotoxic T cells
what foods are common to IgE associated food allergies?
milk, eggs, wheat, peanuts, sesame, fish, fruits and veg
what factors contribute yo yhe type and severity of the reactions?
smouunt of ingested allergen, stability of allergen against digestion, permeability of epithelil barrier
what is a food elimination diet?
monitor sympyyomd when they eat certian foods, eliminate it and then see what happens when these foods are reintroduced
what is the FODMAP diet?
Type of food elimination diet looking to eliminate specific symptoms which can trigger symptoms of IBS
