The Journal of nutrition
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The Journal of nutrition · Sep 2002
Folic acid intake from fortification in United States exceeds predictions.
In 1996, the U. S. Food and Drug Administration issued a regulation requiring that all enriched cereal-grain products be fortified with folic acid by January 1998. ⋯ Prevalence of individuals with folic acid intake above the upper tolerable intake level (1000 micro g folic acid/d) increased only among supplement users exposed to fortification (from 1.3 to 11.3%, P < 0.001). No changes in folic acid intake were observed over time in the nonexposed participants. By these estimations, folic acid fortification resulted in a mean increase in folic acid intake that was approximately twice as large as previously projected.
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The Journal of nutrition · Jul 2002
Comparative StudyVitamin B-12 status is inversely associated with plasma homocysteine in young women with C677T and/or A1298C methylenetetrahydrofolate reductase polymorphisms.
Methylenetetrahydrofolate reductase (MTHFR) polymorphisms may negatively influence one-carbon metabolism and increase health risks in women of reproductive age. The effect of MTHFR single nucleotide polymorphisms at bp 677 and/or 1298 and differences in folate and vitamin B-12 status on plasma homocysteine concentration in women of reproductive age (20-30 y; n = 186) were investigated. From the multivariate regression model, homozygotes (n = 23) for the C677T MTHFR variant had plasma homocysteine concentrations that were higher (P < 0.05) than those observed in the other 5 genotype groups, including those who were heterozygous for both variants (677CT/1298AC; n = 32). ⋯ Plasma homocysteine decreased as vitamin B-12 concentration increased (P = 0.0005) in individuals who were heterozygous for both the C677T and A1298C variants with nonsignificant trends (P = 0.114-0.128) in individuals homozygous for either the C677T or A1298C variants. In contrast, within the group of individuals with the wild-type genotype for both the C677T and A1298C MTHFR variants, homocysteine was not associated with changes in plasma vitamin B-12 concentrations. These data suggest that enhancing vitamin B-12 status may significantly decrease homocysteine in young women with C677T and/or A1298C MTHFR polymorphisms, even when vitamin B-12 concentrations are within the normal range.
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The Journal of nutrition · Jun 2002
High intra/interindividual variance ratios for energy and nutrient intakes of pregnant women in rural Malawi show that many days are required to estimate usual intake.
Conventional wisdom suggests that because there is less variety in food intake, fewer days may be needed to capture "usual intake" of individuals in developing countries, but it is also known that intakes may vary considerably across seasons. Because few studies have examined the sources of variation in nutrient intake in subsistence communities, where food availability also may limit day-to-day food choices, our objective was to examine intraindividual and interindividual variability in energy and nutrient intakes in pregnant subsistence farmers in Africa. From 1988 through 1991, we collected a total of 1061 diet days (mean = 6; range; 2-12 d/woman), using the direct food weighing method, from 184 pregnant women in a farming community west of Lilongwe City, Malawi. ⋯ Adjustment for season and stage of pregnancy did not reduce variance ratios. To estimate true individual intakes within an error range of +/- 20% required 8-23 d for energy, protein, carbohydrates and fiber; and 95-213 d for micronutrients. Thus, despite limited dietary diversity, large within-person variation in nutrient intake demonstrated that more, rather than fewer days of dietary intake were required to correctly identify usual intake in subsistence farmers compared with previous reports for urbanized or Western populations.
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The Journal of nutrition · Jun 2002
ReviewLiving fast, dying when? The link between aging and energetics.
The idea that aging should be linked to energy expenditure has a long history that can be traced to the late 1800s and the industrial revolution. Machines that are run fast wear out more quickly, so the notion was born that humans and animals might experience similar fates: the faster they live (expressed as greater energy expenditure), the sooner they die. Evidence supporting the "rate-of-living" theory was gleaned from the scaling of resting metabolism and life span as functions of body mass. ⋯ However, the link between energetics and aging across species is reconcilable within the framework of the "free-radical damage hypothesis" and the "disposable soma hypothesis." Within species one might anticipate the rate-of-living model would be more appropriate. We reviewed data generated from three different sources to evaluate whether this were so, studies in which metabolic rate is experimentally increased and impacts on life span followed, studies of caloric restriction and studies where links between natural variation in metabolism and life span are sought. This review reveals that there might be contrasting effects of resting and nonresting energy expenditure on aging, with increases in the former being protective and increases in the latter being harmful.
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The Journal of nutrition · Apr 2002
Securing the future of nutritional sciences through integrative graduate education.
The new millennium has ushered in unprecedented opportunities for research and discovery in the nutritional sciences. These have arisen from major advancements in the social and biological sciences, notably genetics, genomic technologies, computational statistics, and behavioral sciences. ⋯ The committee proposes that these objectives are best engaged at the level of graduate education and that the future of ASNS will be secured by strengthening graduate nutrition programs. This manuscript reviews educational strategies that address these challenges and advocates that ASNS actively engage graduate doctoral programs in nutritional sciences.