the body can make vitamin D in presence of UVB from what?
from cholesterol
Vitamin D is what type of hormone?
conditional
The vitamin D found in food and supplements…
ergocalciferol (D2): supplements
Cholecalciferol (D3): Food
What is the active form of Vitamin D?
1-25-dihydroxycholecalciferol
or
calcitriol
describe the absorption and transport of Vitamin D?
Micelles + enterocytes: dependent on bile and pancreatic lipase
Into chylomicrons, through lymphatic system and into circulation to the liver
Transported from liver via lipoproteins (VLDL, LDL, HDL) for tissue delivery
What the conversion of Vitamin D to its active form regulated by?
the parathyroid hormone
Where is vitamin D stored?
Adipose tissue, liver, and kidney
How is vitamin D excreted?
small about in urine
mainly in bile and feces
What are the functions of vitamin D?
- Calcium and phosphorus homeostasis
- Role in regulation of renin, insulin, parathyroid hormone secretion
- Cell differentiation
- Role in regulation of immune function
- Protection against diabetes type 2, cancer, dementia
What does vitamin D deficiency look like in children and adults?
In children: rickets.
Adults: osteomalacia = soft bones
What can vitamin D deficiency be related to?
- season
- location
- ageing skin
- liver and kidney disease
- dark skin
- intestinal disease (absorption issues)
What are the two forms of vitamin K?
Phylloquinones (K1)
Menaquinones (K2)
How much vitamin K is absorbed from dietary intake?
where is it absorbed and how?
80%
in small intestines by via micelle
Describe the transport of vitamin K?
Taken in chylomicrons through the lymphatic system to the circulation
Bacterial menaquinones absorbed in colon by passive diffusion
Transported via lipoproteins (VLDL and LDL) in the blood stream
Where is vitamin K stored?
some in the liver
How is vitamin K excreted?
Mainly via bile in feceas
but small amount in urine
What are the functions of vitamin K?
2
- Co-factor for blood clotting factors synthesis: conversion of preprothrombin to prothrombin
- Bone health: vitamin K-dependent proteins are synthesised in the bone and part of bone structure
What is the difference between the intrinsic and extrinsic pathway for activating prothrombin?
intrinsic pathway,
vitamin K converts pre-prothrombin to prothrombin and then activates prothrombin
extrinsic pathway
Vitamin K only activates prothrombin
How might vitamin K deficiency occur and what impact might this have?
High-dose (supplemental) vitamin A interferes with vitamin K absorption from GIT
High-dose (supplemental) vitamin E interferes with vitamin K activity on clotting factors
