Travis
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- Jul 14, 2016
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Just trying to get the word out that excessive Vitamin A is invariably associated with negative calcium balance and osteoporosis. Here are a few quotes from studies on this effect:
Excessive Dietary Intake of Vitamin A Is Associated with Reduced Bone Mineral Density and Increased Risk for Hip Fracture
Excessive Dietary Intake of Vitamin A Is Associated with Reduced Bone Mineral Density and Increased Risk for Hip Fracture
Bone resorption activity of all-trans retinoic acid is independent of vitamin D in ratsResults: In multivariate analysis, retinol intake was negatively associated with bone mineral density. For every 1-mg increase in daily intake of retinol, risk for hip fracture increased by 68% (95% CI, 18% to 140%; P for trend, 0.006). For intake greater than 1.5 mg/d compared with intake less than 0.5 mg/d, bone mineral density was reduced by 10% at the femoral neck (P = 0.05), 14% at the lumbar spine (P = 0.001), and 6% for the total body (P = 0.009) and risk for hip fracture was doubled (odds ratio, 2.1 [CI, 1.1 to 4.0]).
Vitamin A Intake and Hip Fractures Among Postmenopausal WomenThe mechanism by which all-trans retinoic acid (ATRA) induces bone resorption is unknown. However, an interaction between vitamin A and vitamin D has been established....vitamin A has been shown to be a weak antagonist of the actions of vitamin D....Various bone parameters were measured after 3-8 wk. Regardless of the presence or absence of vitamin D(3), ATRA was able to cause bone resorption...Changes in dietary levels of Ca and P did not affect the ability of ATRA to cause bone resorption....Overall, the ability of ATRA to cause bone resorption is not dependent on vitamin D(3), dietary Ca or dietary P.
Retinol Intake and Bone Mineral Density in the Elderly: The Rancho Bernardo StudyContext Ingestion of toxic amounts of vitamin A affects bone remodeling and can have adverse skeletal effects in animals...A total of 72 337 postmenopausal women aged 34 to 77 years...After controlling for confounding factors, women in the highest quintile of total vitamin A intake (≥3000 µg/d of retinol equivalents [RE]) had a significantly elevated relative risk (RR) of hip fracture (RR, 1.48; 95% confidence interval [CI], 1.05-2.07; P for trend = .003) compared with women in the lowest quintile of intake (<1250 µg/d of RE). This increased risk was attributable primarily to retinol (RR, 1.89; 95% CI, 1.33-2.68; P for trend <.001 comparing ≥2000 µg/d vs <500 µg/d)...Beta carotene did not contribute significantly to fracture risk (RR, 1.22; 95% CI, 0.90-1.66; P for trend = .10 comparing ≥6300 µg/d vs <2550 µg/d). Women currently taking a specific vitamin A supplement had a nonsignificant 40% increased risk of hip fracture (RR, 1.40; 95% CI, 0.99-1.99) compared with those not taking that supplement, and, among women not taking supplemental vitamin A, retinol from food was significantly associated with fracture risk (RR, 1.69; 95% CI, 1.05-2.74; P for trend = .05 comparing ≥1000 µg/d vs <400 µg/d)
These are just truncated abstracts, but there was a really good study done at UW Madison that I will post below. The data is presented in table form, but I should be able to find time to graph some of it.Retinol is involved in bone remodeling, and excessive intake has been linked to bone demineralization...showed an inverse U-shaped association of retinol...supplement users had 0.02 g/cm2 (p = 0.02) lower BMD and 0.23% (p = 0.05) greater annual bone loss, and nonusers had 0.02 g/cm2 (p = 0.04) greater BMD and 0.22% (p = 0.19) greater bone retention...suggesting total intake is more important than source. In both sexes, increasing retinol became negatively associated with skeletal health at intakes not far beyond the recommended daily allowance (RDA)...