α-Tocopherol Stereoisomers in Human Plasma Are Affected by the Level and Form of the Vitamin E Supplement Used.
BACKGROUND
Studies examining vitamin E intake and the percentage of the population meeting dietary guidelines do not distinguish between natural (RRR-α-tocopherol) and synthetic (all-rac-α-tocopherol) intake, even though these different isomeric forms differ in bioactivity.


OBJECTIVE
This study aimed to determine the effect of RRR-α-tocopherol vs. all-rac-α-tocopherol intake on the percentage of the population meeting the vitamin E recommendation and on plasma α-tocopherol stereoisomer distribution.


METHODS
With the use of data from the Irish National Adult Nutrition Survey (NANS), this study examined the percentage of the Irish population meeting the European Union (EU) RDA for vitamin E of 12 mg/d, correcting for a bioactivity difference in all-rac- vs. RRR-α-tocopherol, where 1 mg of all-rac-α-tocopherol is considered to be equivalent to 1:1.36 (0.74) mg in the EU RDA. In a subcohort of supplement users and nonusers, plasma α- and γ-tocopherol concentrations and α-tocopherol stereoisomer distribution were measured. Receiver operating characteristic (ROC) curve analysis was conducted to determine ability to discriminate supplement user types.


RESULTS
Analysis of the NANS showed that 100% of participants still met the recommended intake of 12 mg/d, after all-rac-α-tocopherol intake was corrected for α-tocopherol equivalent bioactivity. In the subcohort analysis, the percentage of plasma RRR-α-tocopherol was significantly lower in high all-rac-α-tocopherol supplement (>11 mg/d) users (82%) compared with nonusers and with high RRR-α-tocopherol supplement (>35 mg/d) users (91% and 93% respectively, P < 0.01). High RRR-α-tocopherol supplement users had a significantly higher plasma α-tocopherol than low all-rac-α-tocopherol supplement (<2.5 mg/d) users (34 vs. 25 μmol/L, P = 0.01). ROC analysis demonstrated an ability to distinguish between RRR- and all-rac-α-tocopherol consumers, which may be useful in investigating the potential effect of RRR- and all-rac-α-tocopherol intake on health.


CONCLUSIONS
This study demonstrated that the percentage of the population meeting the vitamin E recommendation was unaffected when all-rac-α-tocopherol intake was corrected for α-tocopherol equivalent bioactivity. all-rac-α-Tocopherol intake led to a decrease in the percentage of plasma RRR-α-tocopherol relative to RRR-α-tocopherol intake.
UCD Institute of Food and Health, University College Dublin, Dublin, Ireland.
Yang
Y
Zhao
UCD Institute of Food and Health, University College Dublin, Dublin, Ireland.
Frank J
FJ
Monahan
UCD Institute of Food and Health, University College Dublin, Dublin, Ireland.
Breige A
BA
McNulty
UCD Institute of Food and Health, University College Dublin, Dublin, Ireland.
Lorraine
L
Brennan
UCD Institute of Food and Health, University College Dublin, Dublin, Ireland.
Mike J
MJ
Gibney
UCD Institute of Food and Health, University College Dublin, Dublin, Ireland eileen.gibney@ucd.ie.
Eileen R
ER
Gibney
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004032:Diet / Q000009:adverse effects; D019587:Dietary Supplements; D005062:European Union; D005260:Female; D006801:Humans; D007494:Ireland; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D009753:Nutritive Value; D010349:Patient Compliance; D012372:ROC Curve; D064167:Recommended Dietary Allowances; D013237:Stereoisomerism; D014810:Vitamin E / Q000008:administration & dosage*; D055815:Young Adult; D024502:alpha-Tocopherol / Q000031:analogs & derivatives / Q000097:blood* / Q000737:chemistry; D024504:gamma-Tocopherol / Q000031:analogs & derivatives / Q000097:blood / Q000737:chemistry
D014810:Vitamin E; D024504:gamma-Tocopherol; D024502:alpha-Tocopherol
RDA; ROC analysis; RRR-α-tocopherol; all-rac-α-tocopherol; bioactivity; plasma α-tocopherol stereoisomers; vitamin E supplement intake