Vitamin A &
They don't know how, but scientists have found out that too much vitamin A can cause osteoporosis.
They speculate that too much vitamin A inhibits bone formation and enhances bone resorption. However, no markers of increased skeletal turnover can be detected accompanying excess vitamin A.
Could it be that vitamin A increases death of osteoblasts, thus accelerating the aging of osteoblast bone building activity?
It appears that vitamin A regulates apoptosis in many different cell lines. (2)
In fact, retinoic acid also induces cell death of osteoblasts specifically… (3)
Also, analysis shows that, in deer antlers, significant amounts of Vitamin A
(retinol) are found in tissues at all stages of differentiation. (4)
The fact that excessive vitamin A has both
differentiating and deteriorial effects on osteoblasts, and that it promotes osteoporosis, supports
my theory that osteoporosis is caused by
accelerating the aging of osteoblasts
Abstracts of most sources can be found at
Library of Medicine
(1) Kawahara TN, et al, Short-term vitamin A supplementation does not affect bone turnover in men. J Nutr 2002 Jun;132(6):1169-72
(2) Raouf A, et al, The Ets1 proto-oncogene is upregulated by retinoic acid: characterization of a functional retinoic acid response element in the Ets1 promoter. Oncogene 2000 Apr 6;19(15):1969-74.
(3) Haydon RC, et al, Nuclear receptor agonists as potential differentiation therapy agents for human osteosarcoma. Clin Cancer Res 2002 May;8(5):1288-94.
Allen SP, et al, A role for retinoic acid in regulating the regeneration of deer antlers. Dev Biol 2002 Nov 15;251(2):409-23.
Calcium Causes Osteoporosis
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