Absorption by rats of tocopherols present in edible vegetable oils

Abstract

The absorption of tocopherols (alpha, gamma, and delta) and fatty acids from rapeseed (RO), soybean (SOO), and sunflower (SUO) oil, both from the natural oils and from the oils following moderate heating (180 degrees C for 15 min), was measured in lymph-cannulated rats. Oils were administered as emulsions through a gastrostomy tube, and lymph samples were collected for 24 h. The composition of tocopherols in oils and lymph fractions was measured by high-performance liquid chromatography, and fatty acids were measured by gas-liquid chromatography. The highest accumulated transport of alpha-tocopherol was observed after SUO administration, the lowest after SOO, with RO in between, corresponding to their relative contents (41.6 +/- 8.8, 32.7 +/- 5.0, and 24.9 +/- 4.3 microg at 24 h after administration of SUO, RO, and SOO, respectively). The calculated recoveries (in %) 24 h after oil administration were 21.4 +/- 4.5, 45.7 +/- 7.0, and 78.8 +/- 13.5 for SUO, RO, and SOO, respectively, suggesting that the absorption efficiency decreased when the alpha-tocopherol concentration increased. The recovery of alpha-tocopherol was higher than the recoveries of gamma- and delta-tocopherol, indicating that the different tocopherols were not absorbed to the same extent or with similar rates. No differences between unheated and heated oils were observed in the absorption of tocopherols, whereas heating led to lower absorption of fatty acids, thus showing no direct association between absorption of tocopherols and fatty acids.

Comparison of the lymphatic transport of a lipophilic drug from vehicles containing α-tocopherol and/or triglycerides in rats

“…They found that the lymphatic recoveries 24 h after oil administrations decreased when the α-tocopherol concentration increased, although there still was a positive correlation between the amounts of α-tocopherol transported via the lymph and the concentrations in the oils : 78.8 % (25.2 µg) was recovered from the soybean oil that contained 32 µg α-tocopherol per dose, whereas only 21.4 % (41.5 µg) was recovered from the sunflower oil that contained 194 µg α-tocopherol per dose. Higher concentrations of α-tocopherol in the lymph were obtained in this study, as compared with the study by Porsgaard & Høy (2000), but our recoveries were lower.…”

“…The cumulative mass of α-tocopherol 24 h after administration of the triglyceride emulsion was significantly lower (P 0.05) than after administration of the two emulsions containing α-tocopherol. Porsgaard & Høy (2000) investigated the absorption efficiencies of tocopherols in naturally occurring concentrations from rapeseed, soybean and sunflower oil. They found that the lymphatic recoveries 24 h after oil administrations decreased when the α-tocopherol concentration increased, although there still was a positive correlation between the amounts of α-tocopherol transported via the lymph and the concentrations in the oils : 78.8 % (25.2 µg) was recovered from the soybean oil that contained 32 µg α-tocopherol per dose, whereas only 21.4 % (41.5 µg) was recovered from the sunflower oil that contained 194 µg α-tocopherol per dose.…”

Mechanisms for the prevention of vitamin E excess

“…There is evidence for a limitation in ␣ -tocopherol absorption, with high doses being absorbed at lower fractional rates ( 44,(50)(51)(52)(53).…”

Incorporation of α‐tocopherol in marine lipid‐based liposomes: in vitro and in vivo studies

“…Rat lymphatic absorption rates ranging from 40 to 65% of total ingested α-tocopherol have been found (51,52). Whether αtocopherol absorption is influenced by unsaturation of the administered oil remains controversial (53)(54)(55). However, αtocopherol absorption is largely influenced by the co-ingested lipids (25,56) as well as by α-tocopherol concentration (53).…”