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Vitamin A increases risk of fracture if too much or too little – meta-analysis April 2014

The Relationship Between Vitamin A and Risk of Fracture: Meta-Analysis of Prospective Studies

Journal of Bone and Mineral Research, DOI: 10.1002/jbmr.2237
Ai-Min Wu 1, Chao-Qun Huang 2, Zhong-Ke Lin 1, Naifeng Tian 1, Wen-Fei Ni1, Xiang-Yang Wang 1, Huazi Xu1 andYong-Long Chi1,*
1 Orthopaedic Institute, Second Affiliated Hospital of Wenzhou Medical University, Orthopaedics, Wenzhou, Zhejiang, China
2 Second Affiliated Hospital of Wenzhou Medical University, Nutritional Department, Wenzhou, Zhejiang, China
* Corresponding author: Yong-Long Chi: Orthopaedic Institute, Second Affiliated Hospital of Wenzhou Medical University, Orthopaedics, Wenzhou, Zhejiang, China; spinechi at 163.com

Osteoporotic fracture significant causes morbidity and mortality, is a challenged global health problem. The previous reports of the relation between vitamin A intake or blood retinol and risk of fracture were inconsistent. We searched Medline and Embase to assess the effects of vitamin A (or retinol or beta-carotene, but not vitamin A metabolites) on risk of hip and total fracture. Only prospective studies were included. We pooled data with a random effects meta-analysis with adj. RR (adjusted relative risk) and 95% CI (confidence interval). We used Q statistic and I2 statistic to assess heterogeneity and Egger's test to assess publication bias.

  • 8 Vitamin A (or retinol or beta-carotene) intake (283,930 participants) and
  • 4 blood retinol level (8,725 participants) prospective studies were included.

High intake of Vitamin A and retinol will increase risk of hip fracture, the value of adj.RRs (95%CIs) is 1.29 (1.07, 1.57) and 1.40 (1.03, 1.91), while beta-carotene intake is not increasing the risk of hip fracture with adj.RRs (95%CIs) of 0.82 (0.59, 1.14).
Both high or low level of blood retinol will increase the risk of hip fracture, adj.RRs (95%CIs) is 1.87 (1.31, 2.65) and 1.56 (1.09, 2.22). The risk of total fracture does not differ significantly by level of vitamin A (or retinol) intake or by blood retinol level.
Dose-response meta analysis shows U-shaped relationship between serum retinol level and hip fracture risk. Our meta analysis suggests that blood retinol level is a double edged sword for risk of hip fracture.
To avoid the risk of hip fracture caused by too lower or too higher level of retinol concentration, we suggest that intake beta-carotene (a provitamin A), which should be converted to retinol in blood, may be better than retinol from meat which will direct absorbed into blood after intake for risk of fracture. © 2014 American Society for Bone and Mineral Research

Note: Many studies have shown that Vitamin D needs vitamin A to work and than too much vitamin A restricts Vitamin D

See also VitaminDWiki

Survey from Grassroots Health July 2013