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Vitamin E Benefits Improve With Enhanced food Intake
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American Journal of Clinical Nutrition
Vitamin E is poorly absorbed when consumed with a low-fat meal and that bioavailability can be enhanced by food fortification with vitamin E
"Vitamin E bioavailability from fortified breakfast cereal is greater than that from encapsulated supplements"
Scott W Leonard, Carolyn K Good, Eric T Gugger and Maret G Traber
1 From the Linus Pauling Institute (SWL and MGT) and the Department of Nutrition & Food Management (MGT), Oregon State University, Corvallis, and theBell Institute of Health and Nutrition, General Mills, Inc, Minneapolis (CKG and ETG).
2 Supported by a grant from General Mills, Inc. The purchase of a liquid chromatograph–mass spectrometer was supported in part by the Natural Source Vitamin E Association. Unlabeled -tocopherol (used as a standard) and RRR--5,7-(CD3)2-tocopheryl acetate (d6--tocopheryl acetate, used as an internal standard) were gifts from James Clark (Cognis Nutrition and Health, LaGrange, IL).
ABSTRACTBackground: Conflicting results from vitamin E intervention studies suggest supplemental vitamin E malabsorption.
The authors said: "……[results of this study] suggest that unless subjects are carefully instructed to consume encapsulated vitamin E supplements witha meal containing fat, the subjects may not benefit from such supplements.
Objective: We compared vitamin E bioavailability from a supplement with that from a fortified breakfast cereal.
Design: Vitamin E bioavailability was evaluated by using deuterium-labeled all-rac--tocopherol in three 4-d trials (2 wk apart). Five fasting subjects sequentially consumed the following (with 236 mL fat-free milk): 400 IU d9--tocopheryl acetate (400-IU capsule), 41 g ready-to-eat wheat cereal containing 30 IU d9--tocopheryl acetate (30-IU cereal), and 45 g cereal containing 400 IU d9--tocopheryl acetate (400-IU cereal). Five months later (trial 4), they consumed a 400-IU capsule with 41 g vitamin E–free cereal. Blood was obtained up to 72 h after the start of each trial.
Results: The mean (±SD) vitamin E bioavailabilities of the 30-IU cereal and the 400-IU cereal were 6 ± 2 and 26 ± 8 times, respectively, the vitamin E bioavailability of the 400-IU capsule. The areas under the 0–72-h d9--tocopherol curves for the 400-IU capsule, the 30-IU cereal, and the 400-IU cereal were 30 ± 7, 153 ± 43, and 765 ± 164 µmol · h/L (all trial comparisons, P < 0.0001). In trial 4, 3 subjects barely responded and 2 subjects had areas under the curve that were similar to their 400-IU cereal responses.
Conclusion: The low bioavailability of vitamin E from the 400-IU capsule and the variability observed when the capsule was consumed with cereal suggest that encapsulated vitamin E is poorly absorbed when consumed with a low-fat meal and that bioavailability can be enhanced by food fortification with vitamin E.
INTRODUCTION
Controversies have surrounded vitamin E since its discovery in 1922 and the subsequent description of forms other than -tocopherol that had some vitamin E biological activity. Currently, only -tocopherol has been shown to reverse human vitamin E deficiency symptoms, and -tocopherol is the only form of vitamin E that meets the year 2000 vitamin E recommended dietary allowance.
In addition to the prevention of deficiency symptoms, the potential of antioxidants, especially vitamin E, to decrease the risk of chronic disease hasbeen a popular topic in the nutrition field. Nonetheless, many Americans do not consume vitamin E–adequate diets. Vitamin E has been touted for decades as "heart protective," but credible scientific evidence has been lacking. In the 1990s, epidemiologic evidence and a relatively small (2002 subjects), randomized,placebo-controlled intervention study gave credence to the concept that vitamin E supplements could decrease heart attack risk. Subsequently, larger vitamin E intervention trials failed to show cardiovascular-protective effects. Moreover, dietary, but not supplemental, vitamin E has been reported to be associated with beneficial outcomes in heart disease, cancer, and Alzheimer disease.
The lack of consistency in the outcomes of vitamin E supplement studies prompted us to consider the hypothesis that the bioavailability of supplemental vitamin E is highly dependent on the way in which the supplement is consumed. It is well known that fat malabsorption syndromes (eg, cholestatic liver disease) and genetic abnormalities in lipoprotein synthesis (eg, abetalipoproteinemia) or in the -tocopherol transfer protein (eg, ataxia with vitamin E deficiency) result in vitamin E malabsorption or abnormally low plasma transport. Indeed, supplemental vitamin E bioavailability is highly influenced by prandial status. Despite the requirement for normal fat digestion and absorption, it is generally assumed that vitamin E malabsorption does not occur in healthy humans. However, the amount of dietary fat needed for optimal vitamin E absorption is unknown.
The possibility of vitamin E malabsorption from supplements led us to devise a trial to compare supplements with vitamin E–enriched foods. Vitamin E–fortified, ready-to-eat breakfast cereals are a major food source of -tocopherol in the American diet. Therefore, using stable-isotope-labeled -tocopherol, we tested whether encapsulated vitamin E consumed with fat-free milk was as effective in raising plasma -tocopherol concentrations as was vitamin E–fortified, wheat-based cereal eaten with fat-free milk. The doses used were equivalent to the US recommended dietary allowance for vitamin E (30 IU) or those in a typical vitamin E supplement (400 IU). The form of vitamin E used was synthetic (all-rac--tocopheryl acetate) because this is the form that is routinely used to fortify breakfast cereals. To estimate vitamin E bioavailability, plasma labeled and unlabeled –tocopherol concentrations were measured, and areas under the curves (AUCs) for deuterated tocopherol were approximated.
DISCUSSION
The bioavailability of vitamin E (400 IU d9--tocopheryl acetate) from a fortified breakfast cereal was 25-fold that from a supplement when both the cereal and the supplement were consumed with fat-free milk. Indeed, the 30-IU cereal had greater vitamin E bioavailability than did the 400-IU capsule: the 30-IU cereal, which was approximately one-tenth of the dose of the 400-IU capsule, resulted in a maximum plasma d9--tocopherol concentration that was 5-fold that observed with the 400-IU capsule. (Note that these comparisons do not take into accountdifferences in administered dose.) When the 400-IU capsule was consumed with cereal and milk (trial 4), plasma d9--tocopherol concentrations increased in only 2 of the 5 subjects.
The findings of the present study have important public health implications. When encapsulated vitamin E supplements are consumed with fat-free milk, -tocopherol absorption is minimal at best. The fat-free milk consumed with the breakfasts contained only 0.5% fat by wt (21), which may have contributed to the limited vitamin E absorption from the 400-IU capsule. This result was expected because vitamin E absorption requires biliary and pancreatic secretions, as well as chylomicron synthesis.
However, the breakfast that contained <5% fat (consisting of vitamin E–fortified cereal plus fat-free milk) unexpectedly increased vitamin E bioavailability. Hydrolysis of -tocopheryl acetate and absorption of –tocopherol were probably aided by the fine dispersal of vitamin E on the surface of the cereal flakes, in contrast to the capsule, in which the vitamin E was concentrated in a globule.
These findings are significant because fortified breakfast cereals are a major source of vitamin E in the American diet. It should be emphasized that the 30 IU in the breakfast cereal did not increase total -tocopherol concentrations, and this result is consistent with the findings of Hayes et al, who used unlabeled vitamin E and found that plasma –tocopherol concentrations did not differ whether 30 IU vitamin E was provided in capsules or as a fine emulsion in milk. Importantly, Hayes et al found that the vitamin E bioavailability, as estimated from plasma concentrations, of -tocopheryl acetate (100–200 mg/d) provided as a microdispersion in milk was double that of the same dose provided in capsules or orange juice. Again, these results emphasize that the physical properties involved in how vitamin E is presented to the intestinal absorptive surfaces have great bearing on its bioavailability.
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