Lecture 2 Flashcards
Bioavailability
Not all consumed is absorped
Absorption of Calcium
10-60% of intake
What effects uptake
Uptake control via PTH is dependant on demand for example pregnancy
Bioavailability differs between foods e.g. phytate, oxalate and dietary fibre decrease availability
Bioavailability of Ca from Milk
30-35%
Bioavailability of Ca from Spinach
5%
Reason for Vitamin C
Necessary for collagen synthesis
Electrolyte Balancing
We need a 1:1 balance between calcium and phosphorus
Result of consuming excess phosphorus
Causes leaching of Ca from bone mineral
Food examples of ratios
Milk: 1.25:1
Cola: 0.2:1
Nutrients required for the metabolic processes related to bone formation
Calcium, protein, magnesium, phosphate, Vitamin D, potassium, fluoride.
Nutrients required for the metabolic processes related to bone formation
Manganese, copper, boron, iron, zinc, Vitamins A, K, C and the B vitamins
Effect of caffeine on bone
Certain epidemiological studies have shown a correlation between consumption of high- caffeine beverages and low BMD, Too much caffeine is detrimental
How has caffeine shown to affect bone metabolism
Calciuresis, Altered Calcium Absorption, Altered Sex steroid Levels
The significance of calciuresis to calcium balance is questionable
Calciuretic effect of caffeine is biphasic
Other problems with caffeinated beverages
May contain other compounds that affect bone health, e.g. Phosphoric Acid.
Caffeine Conclusions
Any effect of caffeine upon BMD is likely to be mild for the majority of the population
Effect will be dependent on dose and factors related to : Diet Gender Genetic Predispostion Current physical states
What is Tea
Processed leaf of Camellia sinensis
Contributes up to 80% of the Uk dietary intake of Flavonols and Flavones.
Polyphenol
Flavonols and Flavones.
Black Tea
.
Bright orange colour, low astringency, sweet flavour
PPO
Polyphenol Oxidase
Oolong Tea
Fermentation stage half the time as for black tea,
Light, subtle flavour, bright yellow colour
Green Tea
No defined fermentation stage, PPO deactivated, very little oxidaisation of catechins, subtle, bitter flavour and pale in colour
Role of tea and bone health
Consumption of tea has been associated with high BMD/ low incidence of fracture in several populations e.g. MEDOS
Greater benefits for those with longer drinking habits Wu et al, 2002
Tea and Flavonoids
Increase numbers and activity of osteoblasts (Bone Making)
Decrease numbers and activity of osteoclasts (Bone reabsorbing)
Reduce damage to osteoblasts caused by oxidative stress.