Calcium

• What is the role of calcium in the body?


  Muscle stimulus (T-Tubules), Nerve stimulation (bind to nerves synapse) and cell function (signalling)
• Where does calcium come from in our diet?


  Cheese, Milk, fish, fortified cereal, white bread, white flour, fruit and vegetables
• Where is calcium stored in the body?


  99% in the bone and 1% in the intracellular
• What is the biggest store of calcium in the body?

  Bone
• How is calcium stored in the bones?


  calcium hydroxypatite
• Why is calcium levels so tightly regulated in the blood?

  Calcium plays such an important role in the body- so it is important to have enough available in the blood and circulating that is able to be used
• Calcium level are maintained between 8.5-10.5 mg/100ml
• Why can't you measure calcium levels based on blood serum levels?

  Levels are tightly regulated to stay within 8.5-10.5mg/100ml
• What happens when calcium level in the blood drop?

  Pituitary gland release parathyroid hormone that signal osteoclasts, D3 release from kidney. Lead to increase calcium re-uptake, increase absorption at the GI and increased release from bones.
• What happens when calcium levels are too high?

  The pituitary gland releases calcitonin. Calcitonin signals increased action of osteoblasts, which results in increased uptake of calcium into the bone via increase formation of calcium hydroxyapatite
• What are osteoclasts role in the body?


  They breakdown bone (resorption) by releasing enzymes. This breaks down collagen and releases both calcium and phosphate
• What are osteoblasts role?


  They are involved in bone reformation. They produce collagen to form new bone. Calcium is stored in the bone as calcium hydroxyapatite.
• How does oestrogen effect bone?

  Oestrogen promotes bone growth and helps maintain bone density. A lack of oestrogen can result in low bone mineral density- which can explain why fracture risk inc with age and BMD decreases with age
• What is BMD?


  Bone mineral density (g/cm^2)
• Why is low bone mineral density as you get older a problem?

  It can result in both vertebral and hip fractures- this can lead to being in the wheelchair for rest of your life
• How can a low BMD (when you are older) be prevented?

  Ensuring BMD peak (age 30) is high. Higher your BMD when you are younger the longer it take for BMD to reach a point where BMD is low enough
• What factors effect BMD peak?


  50-85% is genetics. However, diet, exercise and hormones can also have an effect
• What are the calcium recommendation for adults in the UK?

  700mg
• What are the recommendation for adolescent boys?

  1000mg
• What is the recommendation for adolescent females?

  800mg
• What is the recommendation for children?

  Between 350-550mg depending on age
• What is the recommendation for infants?


  525mg
• What is the issue with not enough adolescents meeting calcium requirements?


  Osteoporosis
• If you don't meet requirement of calcium in adolescents you run the risk of osteopenia in later life
• What is the difference between osteopenia and osteoporosis? Osteopenia is a condition where bone density is lower than normal, but not low enough to be considered osteoporosis.
• How many adolescent consume less than the LRNI?

  14-16% of adolescents. The LRNI means only 2.5% of the population will meet their needs. This would suggest alot of adolescent are not meeting their requirements
• Why do adolescent boys have a higher BMD?


  They stop puberty later, so they grow for a longer period of time
• Should you take calcium alone or in milk to improve BMD?


  Milk. Milk promotes bone growth via increased IGF-1 not just mineralisation. It also contain additional nutrients important for growth. Calcium supplement does work, but only effect mineralisation but not quantity of bone.
• What is bone resorption?

  It is the process of bone breakdown via osteoclast. It occurs regularly to remove old damaged cells. But also occurs to release calcium when levels are low
• What happens when resorption occurs more than bone mineralisation?

  Bone become weak. If breakdown occurs more and calcium is release but uptake does not occur, the bones become poris
• What is the structure of bone?


  Outer cortical layer- this layer is hard and trabecular softer spongey layer
• What factors effect calcium absorption?


  Vitamin D- status and polypmorphism in the gut (some are quicker), load- high load= slow absorp vs low load=fast absorp (to prevent too much being intake), pregnancy increases absorption fraction and puberty also increase fractional uptake