Absorption and metabolism
Tocopherols and tocotrienols are absorbed unchanged from the small intestine, in micelles with other dietary lipids, and incorporated into chylomicrons. The major route of excretion is in the bile, largely as gluc-uronides and other conjugates.
There are two mechanisms for tissue uptake of vitamin E. Lipoprotein lipase releases the vitamin by hydrolyzing the triacylglycerols in chylomicrons and VLDLs, while separately there is uptake of low-density lipoprotein (LDL)-bound vitamin E by means of LDL receptors. Retention within tissues depends on intra-cellular binding proteins, and it is likely that the dif-ferences in biological activity of the vitamers are due to differences in the affinity of these proteins for the different vitamers.
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