22/10/2007 - Simultaneous ingestion of carotenoids with alpha-tocopherol (vitamin E) may inhibit the absorption of vitamin E by 36 per cent, suggests new research from France.
An in vitro study, followed up by a study with eight healthy men, found that a mixture of the carotenoids lycopene, beta-carotene and lutein significantly reduced absorption of alpha-tocopherol, while vitamin C did not, wrote the researchers in the European Journal of Clinical Nutrition.
A number of epidemiological and animal studies have reported that antioxidants like vitamin E, vitamin C and beta-carotene might offer some protection against heart attack in individuals at risk.
However, if the results of the present study are supported by further study, multi-vitamin formulators may have to rethink formulations in order to maximise the nutritional quality of the supplements.
Researchers from France's Institut National de la Santé Et de la Recherche Médicale (INSERM) U476 in Marseille, report that the polyphenol naringenin and a carotenoids mixture (lycopene, beta-carotene and lutein) significantly impaired the absorption of alpha-tocopherol across a Caco-2 cell monolayer, a test of the absorption of compounds across the intestinal cell barrier.
Moreover, another form of vitamin E, gamma-tocopherol, also tended to reduce the absorption of the alpha-form.
On the other hand, vitamin C did not affect absorption, while the polyphenols gallic acid, caffeic acid, and (+)-catechin also had no effect.
(R,R,R)-alpha-tocopherol is a fat-soluble antioxidant vitamin generally ingested with other dietary antioxidants. The objective of this study was to assess whether the main dietary antioxidant classes, that is carotenoids, polyphenols, vitamin C and gamma-tocopherol, affect the intestinal absorption of alpha-tocopherol.
Feeding the male volunteers an alpha-tocopherol-rich meal (24 mg in sunflower oil) in the presence of two doses of lutein (18 or 36 mg) showed that the highest dose of lutein had the greatest impact on the post-meal alpha-tocopherol absorption measurement (616280 versus 1001287 nanomoles per litre per hour).
"The observed extent of reduction (38 per cent reduction) supported the inhibitory effect of carotenoids observed in the Caco-2 experiments," wrote the researchers, led by Patrick Borel.
Further study is needed to confirm these results, with additional human absorption studies and mechanistic research to highlight how the other nutrients may impact negatively on alpha-tocopherol absorption.
There are eight forms of vitamin E: four tocopherols (alpha, beta, gamma, delta) and four tocotrienols (alpha, beta, gamma, delta). Alpha-tocopherol (alpha-Toc) is the main source found in supplements and in the European diet, while gamma-tocopherol (gamma-Toc) is the most common form in the American diet.
Source: European Journal of Clinical Nutrition
Volume 61, Pages 1167-1173, doi:10.1038/sj.ejcn.1602635
"Effect of the main dietary antioxidants (carotenoids, gamma-tocopherol, polyphenols, and vitamin C) on alpha-tocopherol absorption"
Authors: E. Reboul, S. Thap, E. Perrot, M.-J. Amiot, D. Lairon and P. Borel