Minerals: calcium / iron / fluride Flashcards
Calcium Functions
Bone structure Nerve function Blood clotting Muscle contraction Cellular metabolism
Calcium Dietary recommendations
RNI 700 mg day
LRNI 400 mg day
Calcium Food sources
1 portion Canned Sardines 390 mg >
1 cup Milk 225 mg > 40 g Cheese 290 mg >
20 g Almonds 50 mg > 1 portion Broccoli 72 mg
Dietary sources of calcium
Dairy products (Ca levels not reduced when milk is skimmed) Bread 94-156mg Ca/100g flour Green leafy vegetables Canned fish Hard water- 220mg Ca/day
UK- daily intake for Ca
940mg men & 730mg women
Ca intake teenage girls low
Ca absorption %
10-35% dietary Ca absorbed
absorption high from dairy products due to caesin and phosphopeptides
25-40% supplemental Ca absorbed
- CaCO3 and CaCM high absorption rates
Ca absorption by which transport system
Passive transport system
- nonsaturable paracellular - occurs when dietary Ca high - predominant means in infants on milk
Active transport system-
Ca uptake by ECaC [epithelial Ca channels]
–> bind to CaBP9K [calcium binding protein calbindin D 9K] with aid of Vit D… (VitD increases calbindin synthesis)
–> transport Ca to PMCA [ plasma membrane calcium ATPase] with ATP used or NCX [Na/Ca- exchanger]
(both into plasme)
Ca absorption efficiency highest in which part of gut
Duodenum & proximal jejunum-Ca
Factors increased Ca absorption
Vit D & parathyroid hormone
[PTH does not influence Ca absorption directly but upregulates vit D synthesis in the kidney. PTH is released in response to low plasma Ca]
Ingestion with a meal
lactose
increased need (e.g. pregnancy)
Factors decreased Ca absorption
oxalate- most potent inhibitor phytate fibers rapid GI movement very high fat diet/ fat malabsorption excess P or Mg age menopause decreased gastric acid (without a meal) diseases such as coeliac disease, Crohn’s Disease
which diets would increase Ca excretion
Very high protein diets , such as the Atkins Diet
Regulation of Blood Calcium
Hormones
- Vitamin D
- Parathyroid hormone
- Calcitonin
Target tissues
- Small intestine
- Kidneys
- Bone
if Ca lv too high
thyroid release calcitonin
- -> increase Ca deposition in bones
- -> decrease Ca uptake in intestine
- -> Decrease Ca reabsorption from urine
- -> Ca lv falls –> homeostasis
if Ca lv too low
Para_thyroid release Parathyroid hormone [PTH ]
- -> increase ca release from bone
- -> increase Ca absorption from gut
- -> increase Ca reabsorption from urine
- -> increase Ca lv
Bone Growth
Infant : 1% BW is Ca
Infrancy (1y) : Double bone weight = 400mg Ca/d
Childhood: growth slows 100mg Ca/ d
Pre-adolescene & puberty: growth spurt; 45% adult skeleton formed
10% increase bone Ca/ y
adolescence: 40% of adult skeleton formed
adult (18- 30y): bone growth slows, further 10% increase
adult (over 40y) : loss of bone
Peak bone mass
~30- 35y
loss of bone after age 40 when bone minerals reabsorbed
major factor for osteoporosis risk in later life
Peak bone mass factor
race/ gender/ genetics,
Ca, Vit D, protein, hormones (GH, PTH, calcitonin, sex hormones)
physical activity
anorexia nervosa
Calcium deficiency
5 % UK women consume less than LRNI
Gambia:
Lactating women ~200 mg day
No increased risk of bone fracture
Potassium recommendation
UK RNI 3500 mg day
Intake as a % of RNI: Men 96 (6 % below LRNI) Women 76 (19 % below LRNI)
roles of K in body
Major cellular cation:
- membrane potentials
- Osmotic gradients
- Water balance
- Active transport systems
K Deficiency
Hypokaleamia
Sodium Functions
Fluid balance
Nerve impulse transmission
Na & Cl RNI
Salt RNI 4.1 g, LRNI 1.5g
Sodium RNI 1.6 g, LRNI 575 mg/day
Chloride RNI 2.5 g, LRNI 888 mg/day
UK Na intake
Men 11g day
Women 8.3 g day
Salt and associated disease
Gastric cancer:
Japanese, highest rates of gastric cancers
Hypertension:
Coronary heart disease
Haemorrhagic stroke
Sodium and hypertension
Low Na lv –> low blood pressure
as population aged, % of hypertension increase exponentially
reduction in sodium
- decreases insulin sensitivity
- disrupts aldosterone agiotensin and renin pathways
- very low intakes increase mortality in heart disease patients
Factor affect Na sensitivity
After aerobic training, decrease Na sensitivity and increase Na resistant
Sodium induced damage of which heart disease was found to be independent of blood pressure
hypertrophic cadiomyopathy
reduction of salt can reduce how many % of stroke & CVD
a 23% reduction in the rate of stroke
a 17% overall reduction in the rate of CVD
salt reduction has more potential benefits in which population ?
black women [ middle age > elderly] > black men [same] > non- black men (slight more) non- black women
Sources of Dietary Sodium
75% in processed food
15% in cooking and on table
10% naturally in food
Fluoride recommendation
No RNI
0.05 mg/ kg BW safe intake for babies
Dietary sources of F
Tea / seafood
F Toxicity
Skeletal abnormalities
Dental action of fluoride
Plasma Fluoride combines with calcium phosphate hydroxyapetite –> Strengthens tooth enamel
Salivary fluoride inhibits bacterial enzymes in the mouth
Salivary fluoride increases remineralisation of damaged tooth enamel
Benefits of fluoridated toothpaste
Reduced missing tooth , decayed tooth or filled tooth index
