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Administrative data

Endpoint:
additional toxicological information
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: scientifically valid review

Data source

Referenceopen allclose all

Reference Type:
review article or handbook
Title:
TOLERABLE UPPER INTAKE LEVELS FOR VITAMINS AND MINERALS
Author:
Scientific Committee on Food Scientific Panel on Dietetic Products, Nutrition and Allergies
Year:
2006
Report Date:
2006
Reference Type:
review article or handbook
Title:
Scientific opinion on the safety and efficacy of vitamin E as a feed additive for all animal species.
Author:
EFSA (FEEDAP)
Year:
2010
Bibliographic source:
EFSA Journal, 2010, 8(6), 1635

Materials and methods

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

Applicant's summary and conclusion

Conclusions:
Absorption and metabolism
The bioavailability of vitamin E (tocopherols) is related to the efficiency of absorption. Intestinal absorption of lipids and fat-soluble vitamins depends on pancreatic function, biliary secretion to form micelles with the hydrolysed fat, and transfer across intestinal membranes. Nearly all of the vitamin E absorbed across the intestinal mucosa is free tocopherol. In vivo and in vitro studies suggest that the rate of uptake of vitamin E is controlled by passive diffusion. Absorption of tocopherols is incomplete; the extent of absorption is dependent on intake and varies between 20-80%. The proportion absorbed decreases with increasing amount added to experimental diets; the average absorption is about 40-60% while pharmacological doses of 200 mg and more are absorbed to the extent of <10%. Cannulation studies indicate that there is no difference in absorption between α-tocopherol and α-tocopheryl acetate at physiological doses. At high levels of intake, (> 400 IU/day) a higher degree of absorption was obtained with free tocopherol than tocopheryl esters. About 90% of the free α-tocopherol is transported via the lymphatic system into the bloodstream,where it is distributed into lipoproteins on passage into the liver.
Executive summary:

Absorption and metabolism of Vitamin E

The bioavailability of vitamin E is related to the efficiency of absorption. Intestinal absorption of lipids and fat-soluble vitamins depends on pancreatic function, biliary secretion to form micelles with the hydrolysed fat, and transfer across intestinal membranes. Nearly all of the vitamin E absorbed across the intestinal mucosa is free tocopherol. In vivo and in vitro studies suggest that the rate of uptake of vitamin E is controlled by passive diffusion. Absorption of tocopherols is incomplete; the extent of absorption is dependent on intake and varies between 20-80%. The proportion absorbed decreases with increasing amount added to experimental diets; the average absorption is about 40-60% while pharmacological doses of 200 mg and more are absorbed to the extent of <10%. Cannulation studies indicate that there is no difference in absorption between α-tocopherol and α-tocopheryl acetate at physiological doses. At high levels of intake, (> 400 IU/day) a higher degree of absorption was obtained with free tocopherol than tocopheryl esters. About 90% of the free α-tocopherol is transported via the lymphatic system into the bloodstream,where it is distributed into lipoproteins on passage into the liver. The main systemic transport system of tocopherols is the LDL-fraction (55-65%) followed by the HDL (24-27%) and VLDL (8-18%). There is very close correlation (r=0.925) between the total serum α-tocopherol and that portion carried by LDL.

Tocopherol is excreted as a water soluble conjugated compound resulting from different oxidation steps.