Vitamin E intake status requires reassessment because the recommended levels have been increased and take into account only the alpha-tocopherol form of vitamin E. A database of alpha-tocopherol values for more than 7,000 foods was developed and applied to dietary data from the National Health and Nutrition Examination Survey 1999-2000. Usual intake distributions were determined and evaluated for adequacy. Ninety percent or more of the adults studied had their usual intakes below the current Estimated Average Requirement. Several observations-the prevalence of inadequate intakes of vitamin E, absence of signs of deficiency in the U.S. population, and increasing evidence that vitamin E helps reduce chronic disease risk-point to a need for further research.
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"Humans and other animals are not capable of synthesizing tocopherols or tocotrienols autonomously and must obtain them from their diet. Approximately 90% of children and adults in the United States do not consume the recommended amount of vitamin E (Drewel et al., 2006; Ahuja et al., 2004). "
[Show abstract][Hide abstract] ABSTRACT: Vitamin E (tocopherol) is a powerful antioxidant essential for human health and synthesized only by photosynthetic organisms. The effects of over-expression of tocopherol biosynthetic enzymes have been studied in leaves and seeds, but not in a non-photosynthetic, below-ground plant organ. Genetic and molecular approaches were used to determine if increased levels of tocopherols can be accumulated in potato (Solanum tuberosum L.) tubers through metabolic engineering. Two transgenes were constitutively over-expressed in potato: Arabidopsis thaliana p-hydroxyphenylpyruvate dioxygenase (At-HPPD) and A. thaliana homogentisate phytyltransferase (At-HPT). alpha-Tocopherol levels in the transgenic plants were determined by high-performance liquid chromatography. In potato tubers, over-expression of At-HPPD resulted in a maximum 266% increase in alpha-tocopherol, and over-expression of At-HPT yielded a 106% increase. However, tubers from transgenic plants still accumulated approximately 10- and 100-fold less alpha-tocopherol than leaves or seeds, respectively. The results indicate that physiological and regulatory constraints may be the most limiting factors for tocopherol accumulation in potato tubers. Studying regulation and induction of tocopherol biosynthesis should reveal approaches to more effectively engineer crops with enhanced tocopherol content.
Full-text · Article · May 2008 · Transgenic Research
[Show abstract][Hide abstract] ABSTRACT: African Americans in the southern United States have a high prevalence of chronic disease. Tocopherol intake and status have been associated with protection against several chronic diseases. Our objectives were, therefore, to examine the association between tocopherol intakes as measured by 2 regional FFQ and their corresponding concentrations in serum and to report on dietary sources of tocopherols in 404 men and women participating in the cross-sectional Diet and Physical Activity Sub-Study of the Jackson Heart Study. A large proportion (49% of men and 66% of women) reported dietary supplement use. Only 5.8% of men and 4.5% of women met the estimated average requirement (EAR) for vitamin E from foods alone, whereas 44.2% men and 49.2% women met it from foods and supplements. Total (diet 1 supplement) intake of a-tocopherol was associated with its corresponding measure in serum. Vitamin E supplement use, sex, serum cholesterol, education, and BMI, but not g-tocopherol intakes, were associated with serum g-tocopherol. For d-tocopherol, associated variables included sex and serum cholesterol. The top food sources of a- and g-tocopherol were snack chips and the top food source of d-tocopherol was margarine. Despite prevalent vitamin E supplement use, more than one-half of this population did not meet the EAR for a-tocopherol intake and very few met it from food alone. Supplement use was associated with higher a- but lower g-tocopherol concentration in serum. The possible health implications of this difference in relative tocopherol subtypes require further study. J. Nutr. 137: 2297-2303, 2007.
[Show abstract][Hide abstract] ABSTRACT: Background: Although the population distribution of serum con- centrations of -tocopherol has been described in the United States, little is known about the distribution of -tocopherol or the ratio of -tocopherol to -tocopherol. Objective: Our aim was to describe the distribution of serum con- centrations of -tocopherol and -tocopherol in a nationally repre- sentative sample of US adults. Design: We reviewed data from 4087 adults aged 20 y who par- ticipated in the National Health and Nutrition Examination Survey (1999-2000). Concentrations of -tocopherol and -tocopherol were measured by using HPLC with ultraviolet-visible wavelength detection. Results: The arithmetic mean (SEM) of serum concentrations of -tocopherol was 30.09 0.45 mol/L, the median was 25.94 mol/L, and the geometric mean (SEM) was 27.39 0.38 mol/L. The arithmetic mean of serum concentrations of -tocopherolwas5.740.22mol/L,themedianwas5.25mol/L, and the geometric mean was 4.79 0.18 mol/L. The median ratio of -tocopherol to total cholesterol was 4.93 mol/mmol, that of -tocopherol to total cholesterol was 1.03 mol/mmol, and that of -tocopherolto-tocopherolwas4.53mol/mmol.Concentrations of -tocopherol increased significantly (P for trend 0.001) with ageandweresignificantly(P0.015)lowerinmenthaninwomen. African Americans and Mexican Americans had significantly (P 0.001) lower concentrations of -tocopherol than did whites. The median concentrations of -tocopherol showed a trend with respect to age, did not differ significantly between men and women, and