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. An average increase in folic acid intake of 100 micro g/d was projected as a result of this fortification. The objective of the present study was to estimate the effect of this fortification on the intake of folic acid and total folate, and on the prevalence of individuals with inadequate folate intake and with high folic acid intake. We used data on food and nutrient intake from 1480 individuals who participated in the 5th and 6th examinations of the Framingham Offspring Cohort Study. Fortification was instituted during the 6th examination so that 931 participants were examined before its implementation (nonexposed) and 549 after implementation (exposed). Published data on total folate in enriched cereal-grain products were used to correct folate content in these foods to reflect fortification. Among nonsupplement users, folic acid intake increased by a mean of 190 [95% confidence interval (CI): 176, 204] micro g/d (P < 0.001) and total folate intake increased by a mean of 323 (95% CI: 296-350) micro g dietary folate equivalents (DFE)/d (P < 0.001) in the exposed participants. Similar increases were seen among supplement users exposed to fortification. The prevalence of exposed individuals with total folate intake below the estimated average requirement (320 micro g DFE/d) decreased from 48.6% (95% CI: 44.2-53.1%) before fortification to 7.0% (95% CI: 3.1-10.9%) after fortification in individuals who did not use folic acid supplements. This prevalence was approximately 1% or less for users of supplements both before and after fortification. 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.

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. An average increase in folic acid intake of 100 micro g/d was projected as a result of this fortification. The objective of the present study was to estimate the effect of this fortification on the intake of folic acid and total folate, and on the prevalence of individuals with inadequate folate intake and with high folic acid intake. We used data on food and nutrient intake from 1480 individuals who participated in the 5th and 6th examinations of the Framingham Offspring Cohort Study. Fortification was instituted during the 6th examination so that 931 participants were examined before its implementation (nonexposed) and 549 after implementation (exposed). Published data on total folate in enriched cereal-grain products were used to correct folate content in these foods to reflect fortification. Among nonsupplement users, folic acid intake increased by a mean of 190 [95% confidence interval (CI): 176, 204] micro g/d (P < 0.001) and total folate intake increased by a mean of 323 (95% CI: 296-350) micro g dietary folate equivalents (DFE)/d (P < 0.001) in the exposed participants. Similar increases were seen among supplement users exposed to fortification. The prevalence of exposed individuals with total folate intake below the estimated average requirement (320 micro g DFE/d) decreased from 48.6% (95% CI: 44.2-53.1%) before fortification to 7.0% (95% CI: 3.1-10.9%) after fortification in individuals who did not use folic acid supplements. This prevalence was approximately 1% or less for users of supplements both before and after fortification. 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.

Plasma homocysteine and parental myocardial infarction in young adults in Jerusalem

BACKGROUND

A causal role for mildly elevated plasma homocysteine (tHcy) in cardiovascular disease remains undetermined. To address the unresolved issue of the antecedent-consequent directionality of the relationship, we assessed the familial association of tHcy with parental myocardial infarction (MI) in young Israeli men and women. We also compared tHcy concentrations in Jerusalem, where rates of coronary heart disease (CHD) are high, with the United States Third National Health and Examination Survey (NHANES III).

METHODS AND RESULTS

A total of 8646 17-year-olds and 6952 parents were examined from 1976 to 1979 in Jerusalem. At ages 28 to 32 years, offspring of parents who experienced a documented MI during a 10-year follow-up (n=133 men, 62 women; 72% response) and offspring of CHD-free parents (n=389 men, 208 women; 71% response) were reexamined. tHcy levels were determined by the same laboratory for the NHANES non-Hispanic white population aged 25 to 34 years (n=379) and the Jerusalem population sample (n=858). Men from Jerusalem, but not women, had clearly higher tHcy levels than the sample from the United States (90th percentile, 23 versus 14 micromol/L). This difference was largely attributable to lower plasma vitamin B12 levels in the Israeli population. Male case offspring had higher adjusted tHcy than did controls (1.9 micromol/L, P=0.002). Logistic modeling revealed a graded increase in risk of parental MI across quintiles of offspring tHcy, with an adjusted odds ratio of 2.7 in the 5th quintile (P=0.0026 for trend).

CONCLUSIONS

The higher tHcy in young male offspring of parents with CHD suggests that elevated tHcy precedes manifestation of CHD. The elevated population tHcy in men may contribute to the high incidence of CHD in Israel.

Endothelial function in healthy younger and older hyperhomocysteinemic subjects

OBJECTIVES

To compare endothelium-dependent vasomotor response in healthy younger and older subjects without classic cardiovascular risk factors, with high and normal fasting homocysteine (tHcy) levels.

DESIGN

We compared endothelium-dependent vasodilatation, using ultrasound, in healthy younger (aged 18-40) and older (> or =70) people with normal (<13 micromol/L) and high (>15 micromol/L) tHcy levels. Exclusion criteria were smoking, personal history of cardiovascular disease, hypertension, chronic diseases, vitamin intake, obesity, abnormal serum lipids levels, and creatinine higher than 130 micromol/L.

SETTING

Research laboratory.

MEASUREMENTS

In addition to tHcy levels, serum folate and vitamin B12 levels were measured.

RESULTS

We studied 17 younger and 12 older hyperhomocysteinemic subjects and respective aged-matched normohocysteinemic subjects. Endothelium-dependent vasodilatation was lower in the hyperhomocysteinemic older people (P <.01) than in all younger subjects and in normohomocysteinemic older people. Serum vitamin B12 levels were higher in younger and older normal controls. Folic acid levels were higher in younger controls and in both older groups.

CONCLUSIONS

This study shows an effect of high circulating tHcy on vascular reactivity in older people. Because serum levels of tHcy are associated with nutritional status of vitamin B12 and folic acid, prospective studies are necessary to demonstrate the effects of a long-term nutritional supplementation with vitamins on vascular function and global cardiovascular risk.

A common mutation in the 5,10-methylenetetrahydrofolate reductase gene affects genomic DNA methylation through an interaction with folate status

DNA methylation, an essential epigenetic feature of DNA that modulates gene expression and genomic integrity, is catalyzed by methyltransferases that use the universal methyl donor S-adenosyl-l-methionine. Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate (5-methylTHF), the methyl donor for synthesis of methionine from homocysteine and precursor of S-adenosyl-l-methionine. In the present study we sought to determine the effect of folate status on genomic DNA methylation with an emphasis on the interaction with the common C677T mutation in the MTHFR gene. A liquid chromatography/MS method for the analysis of nucleotide bases was used to assess genomic DNA methylation in peripheral blood mononuclear cell DNA from 105 subjects homozygous for this mutation (T/T) and 187 homozygous for the wild-type (C/C) MTHFR genotype. The results show that genomic DNA methylation directly correlates with folate status and inversely with plasma homocysteine (tHcy) levels (P < 0.01). T/T genotypes had a diminished level of DNA methylation compared with those with the C/C wild-type (32.23 vs.62.24 ng 5-methylcytosine/microg DNA, P < 0.0001). When analyzed according to folate status, however, only the T/T subjects with low levels of folate accounted for the diminished DNA methylation (P < 0.0001). Moreover, in T/T subjects DNA methylation status correlated with the methylated proportion of red blood cell folate and was inversely related to the formylated proportion of red blood cell folates (P < 0.03) that is known to be solely represented in those individuals. These results indicate that the MTHFR C677T polymorphism influences DNA methylation status through an interaction with folate status.

Hyperhomocysteinemia in renal transplant recipients

Renal transplantation is a commonly performed curative procedure for end-stage renal disease. With the increase in renal allograft half-lives, attention is now being focused on cardiovascular morbidity and death in the renal transplant recipient (RTR) population. Among the more novel cardiovascular disease (CVD) risk factors for which this group is at risk is hyperhomocysteinemia. Hyperhomocysteinemia has been associated with an increased risk of CVD, although prospective randomized trials designed to prove causality are still ongoing. Since plasma total homocysteine levels are inversely related to renal function, RTRs have a greatly increased prevalence of hyperhomocysteinemia. Other determinants of homocysteine include B-vitamins, albumin, age, and genetic polymorphisms. Although RTRs are resistant to the typical B-vitamin doses used to correct hyperhomocysteinemia in the general population, they do respond to supraphysiologic dose therapy. In terms of prevalence, etiology, and treatment of hyperhomocysteinemia, RTRs are very similar to the much larger chronic renal insufficiency population. For this reason, RTRs have been chosen as an ideal study population in investigating the effect of reducing hyperhomocysteinemia on CVD outcomes.

Total homocysteine lowering treatment among coronary artery disease patients in the era of folic acid-fortified cereal grain flour

The prevalence of deficient plasma folate status and elevated total plasma levels of homocysteine (tHcy), have been dramatically reduced after fortification of all enriched cereal grain flour products with folic acid at 140 microg/100 g flour. Against this new background fortification, we evaluated the tHcy-lowering efficacy of pharmacological dose, folic acid-based vitamin B supplementation among stable coronary artery disease (CAD) patients. Using a 2x2 factorial design, 131 stable CAD patients (mean age 60.1 years; 29.8% women) were randomly assigned to receive a combination of folic acid 2.5 mg/d, riboflavin 5 mg/d, + B12 0.4 mg/d, or placebo, with or without vitamin B6 50 mg/d, for 12 weeks of treatment. ANCOVA adjusted for baseline fasting tHcy levels revealed only very modest (ie, approximately 1.0 micromol/L), albeit statistically significant (P<0.05), reductions in mean fasting tHcy levels afforded by the folic acid-containing treatments. Additional analyses indicated that none of the treatments provided a statistically significant reduction in the 2-hour post-methionine increase in tHcy levels, relative to placebo treatment. CAD patients exposed to cereal grain flour products fortified with folic acid who receive high-dose, folic acid-containing vitamin B regimens, experience only very modest reductions in their mean fasting plasma tHcy levels. These findings have important implications for the statistical power of clinical trials testing the hypothesis that tHcy-lowering treatment may reduce recurrent atherothrombotic event rates.

Plasma homocysteine as a risk factor for dementia and Alzheimer's disease

BACKGROUND

In cross-sectional studies, elevated plasma homocysteine levels have been associated with poor cognition and dementia. Studies of newly diagnosed dementia are required in order to establish whether the elevated homocysteine levels precede the onset of dementia or result from dementia-related nutritional and vitamin deficiencies.

METHODS

A total of 1092 subjects without dementia (667 women and 425 men; mean age, 76 years) from the Framingham Study constituted our study sample. We examined the relation of the plasma total homocysteine level measured at base line and that measured eight years earlier to the risk of newly diagnosed dementia on follow-up. We used multivariable proportional-hazards regression to adjust for age, sex, apolipoprotein E genotype, vascular risk factors other than homocysteine, and plasma levels of folate and vitamins B12 and B6.

RESULTS

Over a median follow-up period of eight years, dementia developed in 111 subjects, including 83 given a diagnosis of Alzheimer's disease. The multivariable-adjusted relative risk of dementia was 1.4 (95 percent confidence interval, 1.1 to 1.9) for each increase of 1 SD in the log-transformed homocysteine value either at base line or eight years earlier. The relative risk of Alzheimer's disease was 1.8 (95 percent confidence interval, 1.3 to 2.5) per increase of 1 SD at base line and 1.6 (95 percent confidence interval, 1.2 to 2.1) per increase of 1 SD eight years before base line. With a plasma homocysteine level greater than 14 micromol per liter, the risk of Alzheimer's disease nearly doubled.

CONCLUSIONS

An increased plasma homocysteine level is a strong, independent risk factor for the development of dementia and Alzheimer's disease.

The relationship between riboflavin and plasma total homocysteine in the Framingham Offspring cohort is influenced by folate status and the C677T transition in the methylenetetrahydrofolate reductase gene

Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate, the methyl donor for remethylation of homocysteine to methionine. The C677T MTHFR polymorphism is associated with mild hyperhomocysteinemia, but only in the presence of low folate status. Because MTHFR contains flavin adenine dinucleotide (FAD) as a prosthetic group, riboflavin status may also influence homocysteine metabolism. The objective of this study was to examine the association between riboflavin status and fasting plasma total homocysteine (tHcy) concentration while also considering MTHFR C677T genotype and folate status. The study was conducted using fasting plasma samples (n = 450) from the fifth examination of the Framingham Offspring Study cohort. All persons with the TT genotype and age- and sex-matched sets of individuals with the CT and CC genotypes were selected for determination of plasma riboflavin and flavin mono- and dinucleotide levels. Plasma riboflavin was associated with tHcy concentrations, but the association was largely confined to persons with plasma folate <12.5 nmol/L and TT genotype. In these persons, the mean tHcy among individuals with riboflavin levels <6.89 nmol/L was 14.5 micromol/L, whereas the mean tHcy for those with riboflavin > or = 11 nmol/L was 11.6 micromol/L (P-trend <0.03). Plasma flavin nucleotides were unrelated to tHcy concentrations. Our data suggest that riboflavin status may affect homocysteine metabolism, but only in a small segment of the population who have both low folate status and are homozygotes for the MTHFR C677T mutation.

Plasma total homocysteine levels among patients undergoing nocturnal versus standard hemodialysis

Mild hyperhomocysteinemia, a putative risk factor for arteriosclerotic outcomes, is seen in >85% of hemodialysis patients. Therapeutic strategies, including pharmacologic-dose B vitamin supplementation and "high-flux" or "super-flux" hemodialysis, have consistently failed to normalize total homocysteine (tHcy) levels in these patients. Predialysis plasma tHcy levels in 23 patients who were undergoing nocturnal hemodialysis (NHD) six or seven nights/wk were compared with those in 31 patients from the same Canadian dialysis unit who were undergoing chronic standard hemodialysis (SHD) (all <65 yr of age, undergoing thrice-weekly treatments). The SHD patients were similar to typical North American chronic hemodialysis patients with respect to B vitamin status and albumin, creatinine, and tHcy levels. Geometric mean tHcy levels for the NHD patients were significantly lower (12.7 versus 20.0 microM, P < 0.0001), as was the prevalence of mild-to-moderate hyperhomocysteinemia (>12 microM; NHD, 57%; SHD, 94%; P = 0.002). Analysis of covariance adjusted for plasma folate, vitamin B12, and pyridoxal 5'-phosphate levels, age, and gender confirmed that NHD was independently associated with 6.0 microM lower geometric mean tHcy levels (P = 0.001). It is concluded that tHcy levels are significantly lower among NHD patients, compared with SHD patients. Clinical trials will be necessary to confirm that NHD is effective in reducing tHcy levels among patients with dialysis-dependent end-stage renal disease.

Folic acid fortification increases red blood cell folate concentrations in the Framingham study

In 1996 the Food and Drug Administration (FDA) issued a regulation to take effect in January 1998 that all enriched cereal grain products include 140 microg of folic acid/100 g. The present cross-sectional study was undertaken to assess the effect of this fortification on RBC folate concentrations in the Framingham Offspring Cohort. Among those who did not take B-vitamin supplements, we compared RBC folate in 561 individuals who were examined before implementation of the FDA mandatory folic acid fortification (not exposed) vs. 354 individuals who were examined after implementation of fortification (exposed). We calculated the prevalence of deficient (<160 microg/L, 362.6 nmol/L) and acceptable (>200 microg/L, 453.2 nmol/L) RBC folate concentrations in both groups. Those exposed to folic acid fortification had a mean RBC folate of 450.0 microg/L (1019.7 nmol/L), a value 38% higher than the mean RBC folate of 325.3 microg/L (737.1 nmol/L) in those who were not exposed to fortification (P < 0.001). The prevalence of individuals with deficient RBC folate was 4.9% in the group not exposed to fortification compared with 1.9% in the group exposed to fortification (P < 0.02), and the prevalence of individuals with acceptable RBC folate was 87.0% in the group not exposed to fortification compared with 96.1% in the group exposed to fortification (P < 0.001). Similar results were seen in individuals who used supplements containing B-vitamins. The results of this study showed that in this cohort, the introduction of folic acid fortification significantly improved folate nutritional status measured as RBC folate.

The kidney and homocysteine metabolism

Homocysteine (Hcy) is an intermediate of methionine metabolism that, at elevated levels, is an independent risk factor for vascular disease and atherothrombosis. Patients with renal disease, who exhibit unusually high rates of cardiovascular morbidity and death, tend to be hyperhomocysteinemic, particularly as renal function declines. This observation and the inverse relationship between Hcy levels and GFR implicate the kidney as an important participant in Hcy handling. The normal kidney plays a major role in plasma amino acid clearance and metabolism. The existence in the kidney of specific Hcy uptake mechanisms and Hcy-metabolizing enzymes suggests that this role extends to Hcy. Dietary protein intake may affect renal Hcy handling and should be considered when measuring Hcy plasma flux and renal clearance. The underlying cause of hyperhomocysteinemia in renal disease is not entirely understood but seems to involve reduced clearance of plasma Hcy. This reduction may be attributable to defective renal clearance and/or extrarenal clearance and metabolism, the latter possibly resulting from retained uremic inhibitory substances. Although the currently available evidence is not conclusive, it seems more likely that a reduction in renal Hcy clearance and metabolism is the cause of the hyperhomocysteinemic state. Efforts to resolve this important issue will advance the search for effective Hcy-lowering therapies in patients with renal disease.

Renal insufficiency, vitamin B(12) status, and population attributable risk for mild hyperhomocysteinemia among coronary artery disease patients in the era of folic acid-fortified cereal grain flour

Fortification of enriched cereal grain flour products with folic acid has drastically reduced the prevalence of deficient plasma folate status, a major determinant of plasma total homocysteine (tHcy) levels. We hypothesized that even more liberally defined "suboptimal" plasma folate status might no longer contribute importantly to the population attributable risk (PAR) for mild hyperhomocysteinemia, a putative atherothrombotic risk factor. We determined fasting plasma tHcy, folate, vitamin B(12), and pyridoxal 5'-phosphate levels, along with serum creatinine and albumin levels, in 267 consecutive patients (aged 61+/-9 [mean+/-SD] years, 76.4% men and 26.6% women) with stable coronary artery disease (CAD) who were nonusers of vitamin supplements or had abstained from supplement use for at least 6 weeks before examination. Subjects were evaluated a minimum of 3 months after the implementation of flour fortification was largely completed. Relative risk estimates for the calculation of PAR were derived from a multivariable-adjusted logistic regression model with >/=12 micromol/L tHcy as the dependent variable and with age, sex, pyridoxal 5'-phosphate (continuous), albumin (continuous), <5 ng/mL folate, <250 pg/mL vitamin B(12), and >/=1.3 mg/dL creatinine as the independent variables. The prevalence of >/=12 micromol/L plasma tHcy was 11.2% (30 of 267 patients). PAR estimates (percentage) for >/=12 micromol/L tHcy were as follows: <5 ng/mL folate (<1%), <250 pg/mL vitamin B(12) (24.5%), and >/=1.3 mg/dL creatinine (37.5%). In the era of folic acid-fortified cereal grain flour, renal insufficiency and suboptimal vitamin B(12) status (but not folate status) contribute importantly to the PAR for mild hyperhomocysteinemia among patients with stable CAD.

Power Shortage: clinical trials testing the "homocysteine hypothesis" against a background of folic acid-fortified cereal grain flour

Large randomized, controlled trials of total homocysteine-lowering therapy for the potential reduction of cardiovascular disease outcomes are ongoing in the United States and Canada. These trials are the Vitamin Intervention for Stroke Prevention (VISP) trial, the Women's Antioxidant Cardiovascular Disease Study (WACS), and the Heart Outcomes Prevention Evaluation (HOPE-2). However, the dramatic effect of policies mandating fortification of cereal grain flour products with folic acid may reduce the statistical power of these trials. All three trials assume that the active treatment groups will achieve the same mean effects of total homocysteine-lowering therapy as those reported in the absence of folic acid-fortified cereal grain flour. This paper examines this assumption using data from studies of total homocysteine-lowering therapy in U.S. and Canadian patients with cardiovascular disease who were exposed to products made with folic acid-fortified cereal grain flour. These data showed that the VISP trial, HOPE-2, and WACS will probably achieve only approximately 20% to 25% of the projected treatment effects of mean total homocysteine-lowering therapy (1.0 to 1.5 micromol/L vs. 4.0 to 6.0 micromol/L). As a result, all three trials will be substantially underpowered to test the specific hypotheses of total homocysteine-lowering therapy identified a priori. In contrast, renal transplant recipients have a persistent excess prevalence of hyperhomocysteinemia in the era of fortification but remain very responsive to supraphysiologic doses of folic acid-based supplementation (mean reduction in total homocysteine level, 5.0 to 6.0 micromol/L). Therefore, unlike other populations with normal renal function that are at high risk for cardiovascular disease but are profoundly affected by fortification efforts, renal transplant recipients continue to merit serious consideration for a controlled trial of the "homocysteine hypothesis."

Relationship between plasma homocysteine and vitamin status in the Framingham study population. Impact of folic acid fortification

Recent studies have demonstrated associations between occlusive vascular disease and hyperhomocysteinemia of both genetic and nutritional origin. In the present study we analyzed plasma samples from the 20th biannual examination of the Framingham Heart Study cohort to determine distribution of plasma homocysteine concentrations with emphasis on relationships to vitamins that serve as coenzymes in homocysteine metabolism and to prevalence of carotid artery stenosis. Results showed that homocysteine exhibited strong inverse association with plasma folate and weaker associations with plasma vitamin B12 and pyridoxal-5'-phosphate. We saw similar inverse associations between homocysteine and intakes of folate and vitamin B6, but not vitamin B12. Prevalence of high homocysteine (> 14 mumol/L) was 29.3% in this cohort, and was greatest among subjects with low folate status. Inadequate plasma concentrations of one or more B vitamins appear to contribute to 67% of the cases of high homocysteine. Prevalence of stenosis > or = 25% was 43% in men and 34% in women, with an odds ratio of 2.0 for individuals in the highest homocysteine quartile (> or = 14.4 mumol/L) compared with those in the lowest quartile (< or = 9.1 mumol/L), after adjustment for sex, age, HDL cholesterol, systolic blood pressure, and cigarette smoking (Ptrend < 0.001). Plasma concentrations of folate and pyridoxal-5'-phosphate and folate intake were inversely associated with extracranial carotid stenosis after adjustment for age, sex, and other risk factors. Studies using samples from the Framingham Study Offspring Cohort have shown that the US-mandated folic acid fortification of flour and cereal grain products resulted in an increase in the mean folate concentrations from 4.8 to 10.0 ng/mL (P < 0.001) and prevalence of low folate (< 3 ng/mL) decreased from 22.0 to 1.7% (P < 0.001) between the baseline and follow-up visits. Mean homocysteine concentration decreased from 10.1 to 9.4 microM (P < 0.001), and prevalence of high homocysteine (> 13 mumol/L) decreased from 18.7 to 9.8% (P < 0.001) between study visits. There were no statistically significant changes in the control group for folate or homocysteine between examinations. These data indicate a high prevalence of hyperhomocysteinemia in the Framingham Study population, the majority of which can be attributed to vitamin status and that this hyperhomocysteinemia is clinically relevant because of its association with increased risk of occlusive extracranial carotid stenosis. Insufficient levels of folate, and to a lesser extent vitamin B6, appear to predict part of this elevated risk through their role in homocysteine metabolism. These studies also indicate that the recently-implemented fortification of grain and cereal products with folic acid resulted in a substantial decline in plasma homocysteine. The impact of fortification on the US population is likely to be similar; however it awaits the next survey for further confirmation.

Low circulating vitamin B(6) is associated with elevation of the inflammation marker C-reactive protein independently of plasma homocysteine levels

BACKGROUND

Lower vitamin B(6) concentrations are reported to confer an increased and independent risk for cardiovascular disease (CVD). The mechanism underlying this relationship, however, remains to be defined. Other diseases, such as rheumatoid arthritis, are associated with reduced vitamin B(6) levels. Despite a clear distinction in pathophysiology, inflammatory reaction may be the major link between these diseases. We hypothesized a relationship between pyridoxal 5'-phosphate (PLP), the active form of vitamin B(6), and the marker of inflammation C-reactive protein (CRP). We also evaluated whether total plasma homocysteine (tHcy), a well-defined risk factor for CVD and a major determinant of plasma PLP levels, had a possible role as a mediator of this hypothesized relationship.

METHODS AND RESULTS

Data from 891 participants from the population-based Framingham Heart Study cohort were analyzed. Subjects were divided into 2 groups according to normal or elevated CRP values: group 1, CRP <6 mg/L; group 2, CRP >/=6 mg/L. Plasma PLP levels were substantially lower in group 2 than in group 1 (mean values in group 2, 36.5 nmol/L versus 55.8 nmol/L in group 1, P<0.001). In a multiple logistic regression model adjusted for tHcy, the association of PLP with CRP remained highly significant (P=0.003).

CONCLUSIONS

Low plasma PLP is associated with higher CRP levels independently of tHcy. This observation may reflect a vitamin B(6) utilization in the presence of an underlying inflammatory process and represent a possible mechanism to explain the decreased vitamin B(6) levels in CVD.

Hyperhomocysteinemia associated with poor recall in the third National Health and Nutrition Examination Survey

BACKGROUND

High circulating total homocysteine (tHcy) concentrations are associated with stroke, which is a major cause of cognitive dysfunction. Blood homocysteine concentrations are inversely correlated with performance on some cognitive-function tests and a relation was recently shown between hyperhomocysteinemia and Alzheimer disease.

OBJECTIVE

The objective was to evaluate the relation between serum tHcy concentrations and performance on short delayed-recall tests of elderly men and women participating in the third National Health and Nutrition Examination Survey, phase 2 (1991--1994).

DESIGN

Subjects were aged > or =60 y. Subjects reported no previous stroke, completed > or =8 y of education, and took a test of delayed recall of story ideas (n = 1200) or words (n = 1270).

RESULTS

After adjustment for sex, age, race-ethnicity, income, years of education, and serum creatinine concentration, subjects in the upper half of the folate distribution recalled, on average, >4 of 6 story ideas; subjects with lower folate status recalled significantly fewer ideas (P < 0.001). Of the subjects with low folate status, story recall was significantly poorer in those with serum tHcy concentrations above the 80th percentile of the distribution (13.7 micromol/L) than in those with lower tHcy concentrations (P < 0.03). The odds ratio relating hyperhomocysteinemia to recall of > or =1 of 3 previously learned words was 0.3 (95% CI: 0.2, 0.7) after adjustment for the 5 demographic factors alone and was 0.4 (0.2, 0.9) after further adjustment for serum folate concentration.

CONCLUSION

Hyperhomocysteinemia is related to poor recall and this association was partially independent of folate status.

Hyperhomocysteinemia and hypercholesterolemia associated with hypothyroidism in the third US National Health and Nutrition Examination Survey

Hypothyroid (thyroid stimulating hormone (TSH)> or =20 mIU/l; N=32) participants in the third National Health and Nutrition Examination Survey, Phase 2 (1991-1994) were compared with non-hypothyroid subjects (0.5 mIU/l<TSH<20 mIU/l; N=6490) to examine the relationship between hypothyroidism and hyperhomocysteinemia (serum total homocysteine>12 micromol/l) and hypercholesterolemia (serum total cholesterol>6.2 mmol/l). After controlling for age, gender, and race ethnicity, the odds ratios (95% confidence interval (CI)) relating hypothyroidism to hyperhomocysteinemia and high total cholesterol were 4.9 (1.8-14.0) and 8.0 (2.9-21.9), respectively. Based on 26 hypothyroid and 5811 non-hypothyroid subjects with triglyceride concentration < or =2.82 mmol/l, the odds ratio for the relationship between hypothyroidism and high low-density lipoprotein (LDL)-cholesterol (>4.6 mmol/l by the Friedewald equation) was 5.3 (95% CI, 1.3-20.9). Adding additional terms to the multivariate logistic regression model had little effect on the odds ratios relating hypothyroidism to high total or LDL-cholesterol, but adding terms for serum creatinine concentration >123.8 micromol/l and for red blood cell folate and serum vitamin B-12 concentrations resulted in an attenuated, but still significant (P<0.05), odds ratio relating hypothyroidism to hyperhomocysteinemia (2.5; 95% CI, 1.0-6.1). Controlling for cigarette smoking, heart attack/stroke history, body mass index, and serum albumin concentration did not affect the odds ratios. Hyperhomocysteinemia and hypercholesterolemia could help to explain the increased risk for arteriosclerotic coronary artery disease in hypothyroidism.

Determinants of plasma total homocysteine concentration in the Framingham Offspring cohort

BACKGROUND

Established determinants of fasting total homocysteine (tHcy) concentration include folate and vitamin B-12 status, serum creatinine concentration, and renal function.

OBJECTIVE

Our objective was to examine the relation between known and suspected determinants of fasting plasma tHcy in a population-based cohort.

DESIGN

We examined the relations between fasting plasma tHcy concentrations and nutritional and other health factors in 1960 men and women, aged 28-82 y, from the fifth examination cycle of the Framingham Offspring Study between 1991 and 1994, before the implementation of folic acid fortification.

RESULTS

Geometric mean tHcy was 11% higher in men than in women and 23% higher in persons aged > or = 65 y than in persons aged < 45 y (P < 0.001). tHcy was associated with plasma folate, vitamin B-12, and pyridoxal phosphate (P for trend < 0.001). Dietary folate, vitamin B-6, and riboflavin were associated with tHcy among non-supplement users (P for trend < 0.01). The tHcy concentrations of persons who used vitamin B supplements were 18% lower than those of persons who did not (P < 0.001). tHcy was positively associated with alcohol intake (P for trend = 0.004), caffeine intake (P for trend < 0.001), serum creatinine (P for trend < 0.001), number of cigarettes smoked (P for trend < 0.001), and antihypertensive medication use (P < 0.001).

CONCLUSIONS

Our study confirmed, in a population-based setting, the importance of the known determinants of fasting tHcy and suggested that other dietary and lifestyle factors, including vitamin B-6, riboflavin, alcohol, and caffeine intakes as well as smoking and hypertension, influence circulating tHcy concentrations.

Serum total homocysteine concentration is related to self-reported heart attack or stroke history among men and women in the NHANES III

High circulating total homocysteine (tHcy) concentration, which is influenced by folate and vitamin B-12 status, is a suspected cause of cardiovascular events. This relation has been investigated in both case-control and prospective studies but has not been evaluated for different sex x age subgroups of the general U.S. population. We used data on adult (i.e., aged > or =40 y) male (n = 1097) and female (n = 1107) participants in the third National Health and Nutrition Examination Survey, excluding diabetics and those supplemented with estrogen, vitamins or minerals, to evaluate the association between serum tHcy concentration and self-report of heart attack or stroke. After adjustment for age, race-ethnicity, smoking, blood pressure, blood pressure medication, body mass index and serum concentrations of creatinine and cholesterol, past events were reported 2.4 (95% confidence interval 1.0-5.5) times as often by men with tHcy concentration of >12 micromol/L as by men with lower values. The odds ratio for women was 2.6 (95% confidence interval 1.1-6.6) after adjustment for the same factors plus menopausal status. A stronger relation in men aged < or =60 y compared with older men may help reconcile conflicting results of earlier studies.