ddjd
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Risks of Consuming Too Much Vitamin A
The primary risks of too much vitamin A (either acute or chronic excess) are birth defects, liver abnormalities, central nervous system disorders, and lower bone mineral density that might increase osteoporosis risk. Since the American diet contains many fortified foods, the relationship between vitamin A and decreased bone density has become a greater concern.
Both human and animal studies show that a higher vitamin A intake interferes with bone metabolism. Specifically, excess vitamin A suppresses osteoblast (bone-building) activity, stimulates osteoclast (bone breakdown) formation, and interferes with vitamin D’s role in calcium absorption and regulation.
In one study, women consuming more than 6,660 IU daily of vitamin A as retinol in food or supplements (the daily recommendation for adult women is 2,310 IU) were found to have twice the hip fracture risk compared to those consuming 1,700 IU daily or less. Men with the highest blood levels of retinol are seven times more likely to fracture a hip than men with lower levels (study details). There is evidence that older individuals have higher blood levels of vitamin A because of a reduced ability to metabolize vitamin A as efficiently as one ages.
The chart below shows the most concentrated vitamin A sources, both animal and plant. As you can see, fortification (see blue section) makes it easy to surpass the 6,660 IU level, especially if you regularly consume liver, cod liver oil, margarine, butter, and cheese.
Note: All vitamin A toxicity issues pertain to retinol intake (in foods and supplements containing retinol, retinyl palmitate, or retinyl acetate) and NOT supplemental or food-based carotenoid intake (like beta-carotene).
Risks of Consuming Too Much Vitamin A
The primary risks of too much vitamin A (either acute or chronic excess) are birth defects, liver abnormalities, central nervous system disorders, and lower bone mineral density that might increase osteoporosis risk. Since the American diet contains many fortified foods, the relationship between vitamin A and decreased bone density has become a greater concern.
Both human and animal studies show that a higher vitamin A intake interferes with bone metabolism. Specifically, excess vitamin A suppresses osteoblast (bone-building) activity, stimulates osteoclast (bone breakdown) formation, and interferes with vitamin D’s role in calcium absorption and regulation.
In one study, women consuming more than 6,660 IU daily of vitamin A as retinol in food or supplements (the daily recommendation for adult women is 2,310 IU) were found to have twice the hip fracture risk compared to those consuming 1,700 IU daily or less. Men with the highest blood levels of retinol are seven times more likely to fracture a hip than men with lower levels (study details). There is evidence that older individuals have higher blood levels of vitamin A because of a reduced ability to metabolize vitamin A as efficiently as one ages.
The chart below shows the most concentrated vitamin A sources, both animal and plant. As you can see, fortification (see blue section) makes it easy to surpass the 6,660 IU level, especially if you regularly consume liver, cod liver oil, margarine, butter, and cheese.
Note: All vitamin A toxicity issues pertain to retinol intake (in foods and supplements containing retinol, retinyl palmitate, or retinyl acetate) and NOT supplemental or food-based carotenoid intake (like beta-carotene).