1 healthy balanced diet Flashcards
what are the components of a healthy balanced diet?
Macros: cho, protein, fats micros: vitamins and minerals fibre water
what are the classifications of CHO?
- mono and disaccharides (sugars) - oligosaccharides: inulin, 3-9 degree of polymerisation - polysaccharides : starch and non starches (NSP)
what are the functions of CHO?
- energy source (TCA and glycolysis) 2. fuel for CNS (120g/day brain) 3. control of blood glucose and insulin metabolism 4. satiety and gastric emptying 5. cholesterol and triglyceride metabolism 6. fermentation and control of colonic epithelial cell function 7. bowel laxation/ motor activity
what is the concept of glycemic index?
allows quantitative comparison of blood glucose response to ingestion of equivalent amounts of CHO from different foods relative to pure glucose (GI= 100)
examples of low GI foods and GI
GI <55 muesli, legumes, oats, fructose, apples
examples and high GI foods and GI
GI > 75 white bread, instant mashed potatoes correlation with diabetes
what is the glycemic load
determines whether a diet is high or low GI depends on CHO content as well Total carbohydrate content is not detrimental to diseases- more to do with type of carbohydrate
state the dietary recommendations of CHO
up to 50% of daily intake of total energy no more than 5% of calorie intake from free sugars - no more than 30g a day of added sugar >11 years daily intake fibre 30g
what are the types of dietary fibre
Soluble: pectin, beta glucans. forms gel, slow digestion insoluble: cellulose, adds water and bulks so good for constipation (plants and wholegrains)
functions of fibre
- bulking effect- speeds up colonic transit time- constipation and cancer (carcinogenic compounds) 2. decreases cholesterol- dietary fibre changes secretions of bile acid, modifies glyceamia and insulinea 3. fermentation- produces SCFA (butyrate, acetate and propionate) - fuel for colonocytes - acetate and propionate absorbed by hepatic portal vein, used as energy in liver - maintains healthy bowels
define vitamins
organic substances required in small amounts for normal metabolism but cannot be synthesised by body in sufficient quantities
water soluble vitamins
- intermediary metabolism (coenzymes): thiamin, nicotinic acid, riboflavin, panthothenic acid 2. anaemia preventing: B12 and folate 3. antioxidants: vit C and E
why is B12 and folate important?
needed for thymidylate synthesis, DNA synthesis
B12 deficiency
megaloblastic anaemia, neuropathy (myelin sheath) intrinsic factor to allow B12 to be absorbed- same protein that secreted from cells that secret Hcl gastric acid so anything that limits this would affect, binds to B12 to be absorbed; atrophic gastritis- functional deficiency- common in older people
folate deficiency
anaemia, neural tube defect, green veg
Methionine synthetase
B12 dependent enzyme which catalyses a reaction that yields free folate in tissues via methylation of homocysteine to methionine provides link between physiological functions of B12 and folate • Danger that consume enough folate but if less B12 than there is neuropathy Deficiency of B12 would effect folic acid deficiency (functional if the enzyme has an issue
actions of vitamin D
- intestinal absorption of calcium and phosphorous 2. renal absorption of calcium and phosphate 3. neuromuscular and immune functions, apoptosis and inflammation (VDRs (receptors) form dimers with RXR (retinoid X receptor- related to vit A)& regulate gene expression)
low levels of plasma Ca
PTH stimulated and vitamin D synthesis activated vitamin D increases intestinal Ca absorption and regulates Ca excretion from kidneys and bone
high levels of plasma Ca
calcitonin secreted from thyroid gland, promotes Ca excretion and prevents bone releasing Ca
Through heat isomerisation
Hydroxylation in liver -> storage in adipose tissue and main transport
Hydroxylation in kidney -> active form of vit D
calcidiol form measured in blood
vitamin d deficiency
rickets (child) and osteomalacia (adults- de mineralisation of bone)
vitamin d toxicity
nausea, loss of appetitie, headache, abdo pain
hypercalcemia
what is iron needed for?
- electron transport chain
- Hb in RBC
- cytochrome P450
dietary sources of vitamin D
supplements, oily fish,
define minerals
inorganic elements needed for physiological functions in body. must be supplied by diet
calcium and iron
dietary sources of iron
10% haem- meat
90% non-haem- veg
Different absorption mechanisms into mucosal cells
Absorption approx. 10% intake, can be up and down regulated (15-35 haem, 1-90 non-haem)
Absorption: only in ferrous form so enhanced by reducing agents (eg. Ascorbic acid)
enhances and inhibitors of iron absorption
Enhances:
D: Vit C, fructose, alcohol, meat
P: Fe deficiency and anaemia. Pregnancy
Inhibitors:
D: Tannins (tea and coffee), polyphenols, phosphates, phytates, bran, lignin, other minerals (Ca etc)
P: Fe overload, Cu deficiency
