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
