Irwin H. Rosenberg

Relation Between Folate Status, a Common Mutation in Methylenetetrahydrofolate Reductase, and Plasma Homocysteine Concentrations

BACKGROUND Methylenetetrahydrofolate reductase (MTHFR) synthesizes 5-methyltetrahydrofolate, the major carbon donor in remethylation of homocysteine to methionine. A common MTHFR mutation, an alanine-to-valine substitution, renders the enzyme thermolabile and may cause elevated plasma levels of the amino acid homocysteine. METHODS AND RESULTS To assess the potential interaction between this mutation and vitamin coenzymes in homocysteine metabolism, we screened 365 individuals from the NHLBI Family Heart Study. Among individuals with lower plasma folate concentrations ( < 15.4 nmol/L), those with the homozygous mutant genotype had total fasting homocysteine levels that were 24% greater (P<.05) than individuals with the normal genotype. A difference between genotypes was not seen among individuals with folate levels > or = 15.4 nmol/L. CONCLUSIONS Individuals with thermolabile MTHFR may have a higher folate requirement for regulation of plasma homocysteine concentrations; folate supplementation may be necessary to prevent fasting hyperhomocysteinemia in such persons.

The Effect of Folic Acid Fortification on Plasma Folate and Total Homocysteine Concentrations

BACKGROUND In 1996, the Food and Drug Administration issued a regulation requiring all enriched grain products to be fortified with folic acid to reduce the risk of neural-tube defects in newborns. Fortification (140 microg per 100 g) began in 1996, and the process was essentially complete by mid-1997. METHODS To assess the effect of folic acid fortification on folate status, we measured plasma folate and total homocysteine concentrations (a sensitive marker of folate status) using blood samples from the fifth examination (January 1991 to December 1994) of the Framingham Offspring Study cohort for baseline values and the sixth examination (January 1995 to August 1998) for follow-up values. We divided the cohort into two groups on the basis of the date of their follow-up examination: the study group consisted of 350 subjects who were seen after fortification (September 1997 to March 1998), and the control group consisted of 756 subjects who were seen before fortification (January 1995 to September 1996). RESULTS Among the subjects in the study group who did not use vitamin supplements, the mean folate concentrations increased from 4.6 to 10.0 ng per milliliter (11 to 23 nmol per liter) (P<0.001) from the baseline visit to the follow-up visit, and the prevalence of low folate concentrations (<3 ng per milliliter [7 nmol per liter]) decreased from 22.0 to 1.7 percent (P< 0.001). The mean total homocysteine concentration decreased from 10.1 to 9.4 micromol per liter during this period (P<0.001), and the prevalence of high homocysteine concentrations (>13 micromol per liter) decreased from 18.7 to 9.8 percent (P<0.001). In the control group, there were no statistically significant changes in concentrations of folate or homocysteine. CONCLUSIONS The fortification of enriched grain products with folic acid was associated with a substantial improvement in folate status in a population of middle-aged and older adults.

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/μg 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.

Sarcopenia: Origins and Clinical Relevance

This presentation reflects on the origins of the term sarcopenia. The Greek roots of the word are sarx for flesh and penia for loss. The term actually describes important changes in body composition and related functions. Clearly defining sarcopenia will allow investigators to appropriately classify patients and examine underlying pathogenic mechanisms and will allow funding agencies to appropriately target research funds to a taxonomically distinct syndrome.

Rheumatoid cachexia: cytokine-driven hypermetabolism accompanying reduced body cell mass in chronic inflammation.

The cytokines IL-1 beta and TNF-alpha cause cachexia and hypermetabolism in animal models, but their role in human inflammation remains controversial. The relationship between in vitro cytokine production and metabolism was examined in 23 adults with RA and 23 healthy control subjects matched on age, sex, race, and weight. Body composition was measured by multicompartmental analysis of body cell mass, water, fat, and bone mass. Resting energy expenditure (REE) was measured by indirect calorimetry. Cytokine production by PBMC was measured by radioimmunoassay. Usual energy intake, physical activity, disability scores, medication use, and other confounders were also measured. Body cell mass was 13% lower (P < 0.00001), REE was 12% higher (P < 0.008), and physical activity was much lower (P < 0.001) in subjects with RA. Production of TNF-alpha was higher in RA than controls, both before and after stimulation with endotoxin (P < 0.05), while production of IL-1 beta was higher with endotoxin stimulation (P < 0.01). In multivariate analysis, cytokine production was directly associated with REE (P < 0.001) in patients but not in controls. While energy and protein intake were similar in the two groups and exceeded the Recommended Dietary Allowances, energy intake in subjects with RA was inversely associated with IL-1 beta production (P < 0.005). In this study we conclude that: loss of body cell mass is common in RA; cytokine production in RA is associated with altered energy metabolism and intake, despite a theoretically adequate diet; and TNF-alpha and IL-1 beta modulate energy metabolism and body composition in RA.

A Temporal Association between Folic Acid Fortification and an Increase in Colorectal Cancer Rates May Be Illuminating Important Biological Principles: A Hypothesis

Nationwide fortification of enriched uncooked cereal grains with folic acid began in the United States and Canada in 1996 and 1997, respectively, and became mandatory in 1998. The rationale was to reduce the number of births complicated by neural tube defects. Concurrently, the United States and Canada experienced abrupt reversals of the downward trend in colorectal cancer (CRC) incidence that the two countries had enjoyed in the preceding decade: absolute rates of CRC began to increase in 1996 (United States) and 1998 (Canada), peaked in 1998 (United States) and 2000 (Canada), and have continued to exceed the pre-1996/1997 trends by 4 to 6 additional cases per 100,000 individuals. In each country, the increase in CRC incidence from the prefortification trend falls significantly outside of the downward linear fit based on nonparametric 95% confidence intervals. The statistically significant increase in rates is also evident when the data for each country are analyzed separately for men and women. Changes in the rate of colorectal endoscopic procedures do not seem to account for this increase in CRC incidence. These observations alone do not prove causality but are consistent with the known effects of folate on existing neoplasms, as shown in both preclinical and clinical studies. We therefore hypothesize that the institution of folic acid fortification may have been wholly or partly responsible for the observed increase in CRC rates in the mid-1990s. Further work is needed to definitively establish the nature of this relationship. In the meantime, deliberations about the institution or enhancement of fortification programs should be undertaken with these considerations in mind. (Cancer Epidemiol Biomarkers Prev 2007;16(7):1325–9)

Nonfasting plasma total homocysteine levels and stroke incidence in elderly persons: the Framingham Study.

Meta-analyses (1, 2) strongly suggest that mildly to moderately elevated circulating levels of the sulfur amino acid homocysteine, either fasting or nonfasting, confer an independent risk for clinical arteriosclerotic outcomes, including stroke. However, just four reports (3-6) have provided somewhat limited, conflicting prospective data on the potential relation between total homocysteine levels and stroke incidence. Only one of these studies (3) used a population-based sample. Samples from two studies were limited to middle-aged men (4, 5): One consisted of U.S. physicians responding to a survey (4), and the other was derived from family practice registries in Great Britain (5). The fourth study (6) was a longitudinal investigation that primarily included women with systemic lupus erythematosus (mean age at baseline, 35 years). No prospective studies have specifically evaluated mild hyperhomocysteinemia as a potential risk factor for stroke in men and women 60 years of age or older, an age group that experiences the most pronounced morbidity and mortality from cerebrovascular disease (7). Accordingly, we examined the association between baseline nonfasting plasma total homocysteine levels and incident stroke in a well-characterized, population-based cohort of elderly women and men who at baseline had not had stroke. Methods The study sample consisted of the original Framingham Study cohort (8). Baseline examinations for the current analyses took place between May 1979 and May 1982, with follow-up occurring through May 1992. Of 2351 persons examined during the baseline period, 1947 had not previously had stroke and had specimens available for measurement of plasma total homocysteine levels. Additional baseline covariables assessed for the current analyses were age, sex, cigarette smoking, diabetes, history of atrial fibrillation, history of coronary heart disease, systolic blood pressure, and creatinine levels. Detailed operational definitions for all these covariables are provided elsewhere (8). Stroke outcome ascertainment and definition methods used in the Framingham Study, including subtype classification, have been described in detail previously (8, 9). Total homocysteine levels were determined by high-performance liquid chromatography with fluorescence detection (10). Nonfasting plasma aliquots were stored at 20 C from the baseline examination period until mid-1997. Data from long-term storage studies conducted at 20 C have confirmed both the biochemical stability and long-term within-person reproducibility of total homocysteine determinations (10). Creatinine levels were measured in nonfasting plasma by the Jaffe method, adapted for autoanalyzers. The skewed total homocysteine data were natural log-transformed, and differences in geometric mean total homocysteine levels according to sex, diabetes, history of atrial fibrillation or coronary heart disease, and smoking status were compared by using unpaired t-tests. The Spearman rho was used to assess unadjusted rank-order correlations between untransformed total homocysteine levels and age, creatinine level, and systolic blood pressure. Unadjusted and adjusted (for age, sex, history of atrial fibrillation or coronary heart disease, diabetes, smoking, systolic blood pressure, and creatinine level) relative risk estimates (hazards ratios with 95% CIs) for total stroke, nonhemorrhagic stroke, and atherothrombotic brain infarction were generated by proportional hazards modeling. Total homocysteine level (natural log-transformed or expressed in quartiles) was the independent variable. All statistical analyses were performed by using SAS software, version 6.12 (SAS Institute, Inc., Cary, North Carolina). Results The study sample (n=1947) consisted of 1158 women (59.5%) and 789 men (40.5%). Four hundred thirteen patients (21.2%) were cigarette smokers, 340 (17.5%) had a history of coronary heart disease, 182 (9.3%) were diabetic, and 81 (4.2%) had a history of atrial fibrillation. Arithmetic means (SD) for key continuous variables were as follows: age, 70 7 years (range, 59 to 91 years); systolic blood pressure, 141 21 mm Hg (range, 86 to 225 mm Hg); creatinine level, 97.2 26.5 mol/L (range, 35.3 to 442 mol/L); and total homocysteine level, 12.65 7.19 mol/L (range, 4.13 to 219.84 mol/L). Geometric mean total homocysteine levels were higher in men than in women (12.35 compared with 11.32 mol/L; P<0.001), in patients with a history of atrial fibrillation than in those without (13.17 compared with 11.66 mol/L; P=0.003), and in patients with a history of coronary heart disease than in those without (12.49 compared with 11.57 mol/L; P<0.001). However, these levels did not differ according to the presence or absence of diabetes (11.83 compared with 11.71 mol/L; P>0.2) or between current cigarette smokers and nonsmokers (11.67 compared with 11.74 mol/L; P>0.2). Weak but significant Spearman correlations were observed between total homocysteine levels and age (r=0.212; P<0.001), creatinine level (r=0.178; P<0.001), and systolic blood pressure (r=0.111; P<0.001). Quartiles of total homocysteine were as follows: quartile 1, 4.13 to 9.25 mol/L; quartile 2, 9.26 to 11.43 mol/L; quartile 3, 11.44 to 14.23 mol/L; quartile 4, 14.24 to 219.84 mol/L. During a median follow-up of 9.9 years, 165 incident total strokes occurred; 153 of these were incident nonhemorrhagic strokes, and 100 were incident atherothrombotic brain infarctions. Five hundred twenty-four persons were censored during follow-up because of death from causes other than stroke. Age, systolic blood pressure, current smoking, diabetes, and history of atrial fibrillation or coronary heart disease were independently predictive of total stroke occurrence (Table 1). Levels of total homocysteine (natural log) as a continuous variable (data not shown) and across quartiles (P<0.001 for linear trend) were associated with all stroke outcomes in unadjusted and multivariable-adjusted proportional hazards analyses (Tables 1 and 2). The interaction term between sex and total homocysteine level (quartile analyses) was nonsignificant (P=0.1); thus, the stroke incidence analyses were not stratified by sex. Further adjustment for creatinine level did not change the results of any of these analyses (data not shown). Table 1. Predictors of Incident Total Stroke in Elderly Women and Men in the Framingham Study Cohort Table 2. Relative Risk Estimates in Elderly Women and Men in the Framingham Study Cohort: Comparison of Each of the Upper Three Quartiles to the Lowest Quartile of Nonfasting Plasma Total Homocysteine Level Discussion Our findings are consistent with previously reported data, derived primarily from elderly female and male participants in the Framingham Study (9, 11), indicating that age, systolic blood pressure, diabetes, cigarette smoking, and history of atrial fibrillation or coronary heart disease were independently predictive of stroke incidence. We report population-based evidence that elevated nonfasting total homocysteine levels are also independently associated with stroke incidence among elderly women and men. Four earlier studies (3-6) have examined the relation between total homocysteine levels and stroke incidence. Alfthan and colleagues (3) did not find an association between total homocysteine levels and incident stroke among Finnish men and women 40 to 64 years of age (total events, 76). Similarly, Verhoef and coworkers (4) found only a weak, nonsignificant association between total homocysteine level and stroke incidence (total events, 109) in a cohort of male physicians whose mean age was 59.7 years (upper quintile compared with lower four quintiles: odds ratio, 1.2 [CI, 0.7 to 2.0]). In contrast, Perry and colleagues (5) reported a robust, independent association between total homocysteine levels (across quartiles) and incident stroke (total events, 107) among British men whose mean age was 54.0 years (quartile 3 compared with quartile 1: odds ratio, 3.3 [CI, 0.9 to 11.5]; quartile 4 compared with quartile 1: odds ratio, 7.4 [CI, 1.9 to 29.0]). More recently, elevated total homocysteine levels were independently linked to the development of stroke outcomes in a cohort of predominantly younger women (mean age, 34.9 years) with systemic lupus erythematosus (6). The two negative studies (3, 4) were characterized by modest stroke event rates and overall exposure to lower total homocysteine levels on the basis of sound nutritional (4) or, possibly, favorable genetic (3) influences. More widespread exposure to elevated total homocysteine levels, due perhaps to worse nutritional status, may have accounted for the strong association between total homocysteine level and incident stroke reported by Perry and colleagues (5). The positive relation between total homocysteine level and stroke occurrence described by Petri and associates in the Hopkins Lupus Cohort (6) was confined to patients with the highest total homocysteine levels (>14 mol/L). Our analyses, which revealed an independent association between total homocysteine level and incident stroke (total events, 165), were performed in an elderly sample characterized, as expected, by a relatively higher stroke event rate (7, 9, 11, 12). This higher rate occurred in conjunction with an increased prevalence of mild hyperhomocysteinemia (that is, in approximately 25% of patients with total homocysteine level>14 mol/L) at the baseline examination. Despite the lack of substantiation by either proven or biologically plausible mechanisms, it has nevertheless been proposed that hyperhomocysteinemia is an epiphenomenon of clinical or even subclinical arteriosclerosis (13, 14). This hypothesis appears untenable in view of the following published findings from both human and animal studies. First, despite the absence of any traditional arteriosclerotic risk factors, 50% of untreated children and young adults with homocystinuria due to cystathionine synthase deficiency ex

Serum Total Homocysteine Concentrations in the Third National Health and Nutrition Examination Survey (1991-1994): Population Reference Ranges and Contribution of Vitamin Status to High Serum Concentrations

Homocysteine, a non-protein-forming sulfur amino acid, has attracted attention because elevated concentrations of circulating total homocysteine are associated with an increased risk for vascular disease (1, 2). Homocysteine is also a sensitive functional marker of inadequate cellular folate and vitamin B12 concentrations (3). Inadequate status of these vitamins has important health consequences that may be independent of their role in homocysteine metabolism. Low folate concentrations increase a womans risk for having a baby with a neural tube defect (4, 5), and an inadequate vitamin B12 concentration is known to produce various neurologic and cognitive effects (6, 7). Persons with low circulating folate or vitamin B12 concentrations have higher fasting total homocysteine concentrations (8-10), and elevated fasting total homocysteine concentrations are usually normalized by treatment with folic acid and vitamin B12 (6, 11-14). However, less is known about the importance of these vitamins as risk factors for high homocysteine concentration in the general population. Only three studies have examined the relation between homocysteine concentration and its vitamin determinants in samples that were designed to be representative of U.S. national (8) or regional (9, 10) populations. One of these studies (9) reported that approximately two thirds of all cases of moderately elevated total homocysteine concentrations were potentially attributable to low vitamin concentrations, but estimation of the proportion of cases with high homocysteine concentrations that can be attributed to inadequate vitamin status is complicated by the lack of a standard definition of a high total homocysteine concentration. In the absence of a definition based on increased risk for an adverse health outcome, such as vascular disease, upper reference limits from samples of healthy persons without established risk factors for high homocysteine concentrations have been used to define a high total homocysteine concentration (10, 15-17). We previously described the distribution of total serum homocysteine concentrations in participants 12 years of age or older from the third National Health and Nutrition Examination Survey (NHANES III), a population-based sample of U.S. residents (18). These data present a unique opportunity to develop population reference ranges for serum total homocysteine concentration and to determine the extent to which elevated homocysteine concentrations are associated with low circulating vitamin concentrations in a representative sample of U.S. residents. Methods Participants The NHANES III was developed to obtain nationally representative information on the health and nutritional status of the civilian, noninstitutionalized U.S. population (19, 20). Homocysteine concentrations were measured as part of an NHANES III surplus sera project on serum samples from participants 12 years of age or older who were seen during phase II of this survey (19911994). This project is described in greater detail elsewhere (18). Homocysteine concentrations were measured at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University by using the high-performance liquid chromatography method of Araki and Sako (21). The interassay coefficient of variation for this assay was 6%. Folate and vitamin B12 were determined for phase 2 specimens at the Centers for Disease Control and Prevention central laboratory by using a Quanta Phase II radioassay kit (Bio-Rad Laboratories, Hercules, California), and analyses are described in detail in the NHANES III Laboratory Procedures Manual (22). The coefficients of variation for folate and vitamin B12 were 6% and 7%, respectively. Informed consent was obtained from all respondents. The NHANES III protocol was approved by the National Center for Health Statistics NHANES Institutional Review Board, and measurement of serum homocysteine was approved by the Human Investigations Review Committee at the New England Medical Center. We used the following search strategy, combining Medical Subject Headings (MeSH terms) and text words, to identify all population-based studies relating vitamin status to circulating homocysteine concentrations: ([homocysteine (MeSH] OR homocysteine [Text Word]) AND (vitamins [MeSH] OR vitamin [Text Word]]) AND (epidemiologic studies [MeSH] OR data collection [MeSH] OR survey [Text Word]]. This search identified 137 citations, of which 16 were reviews. We selected original studies that 1) were designed to be representative of national, regional, or local populations and 2) described the relation between circulating homocysteine concentrations and either intake or circulating concentrations of folate or vitamin B12. As of 1 March 1999, 3 articles met our criteria (8-10). Statistical Analysis We used sample weights in analyses to account for unequal probability of selection and nonresponse and to produce estimates of means and percentiles that were representative of the noninstitutionalized, civilian U.S. population. We used SUDAAN statistical software (23) to account for the complex survey design in the variance estimates. Because total homocysteine, folate, and vitamin B12 values were skewed, logarithmic transformations were applied. To show the relations between total homocysteine concentrations and vitamin concentrations, we classified participants into age- and sex-specific vitamin decile categories and estimated the geometric mean of the serum total homocysteine concentration within each decile. Analyses were adjusted for ethnicity and serum creatinine concentration. In addition, the relation between total homocysteine and folate concentrations was adjusted for vitamin B12 concentrations, and the relation between total homocysteine and vitamin B12 was adjusted for folate concentrations. We tested the associations between homocysteine and vitamins for interactions with age, sex, and ethnicity. We tested for trend of total homocysteine concentration across vitamin concentrations by using linear regression with the logarithm of the continuous vitamin concentration as the independent variable, adjusting as described above. We showed the trend by using the SYSTAT LOWESS procedure to fit smoothed curves (24) to the geometric mean total homocysteine concentrations in the vitamin decile categories (25). It has been suggested that population reference ranges for the total homocysteine concentration be established in samples of persons without established risk factors for a high homocysteine concentration (10, 15-17). For our reference sample, we included persons whom we assumed to be folate- and vitamin B12-replete (that is, their serum concentrations of both vitamins were above the 50th percentile) and had normal serum creatinine concentrations (<90 mol/L for women and<110 mol/L for men). Pregnant women were excluded. We used the 5th and the 95th percentiles from the reference sample to estimate population reference ranges. To identify the potential impact of low vitamin concentrations on high total homocysteine concentration, we needed to establish values for high total homocysteine and low vitamin concentrations. We used the sex-specific 95th percentiles in the participants 20 to 39 years of age (the reference sample) to define high total homocysteine concentrations for all age groups. We used this reference sample because homocysteine concentrations changed little with age in this group, unlike in the other age groups (18). We defined low vitamin concentrations as a folate concentration less than 11 nmol/L (26, 27) and a vitamin B12 concentration less than 185 pmol/L (28, 29). We calculated the prevalence of high total homocysteine concentration; the prevalence ratio for high total homocysteine concentration; the attributable risk percentage; and the population attributable risk percentage for persons with low concentrations of folate, vitamin B12, or both compared with persons who had adequate concentrations of both of these vitamins. The attributable risk percentage estimates the excess cases of high homocysteine concentrations among persons with low vitamin concentrations, whereas the population attributable risk percentage takes into account the prevalence of low vitamin concentrations in the population and estimates the excess of high homocysteine concentrations associated with low vitamin concentrations in the entire population. We used the design effect for total homocysteine concentration, which is the ratio of the complex sampling design variance derived by using SUDAAN software (23) to the simple random sample variance calculated by using SAS software (30), to determine the recommended minimum sample size needed to achieve stable estimates of means, proportions, and percentiles according to the National Center for Health Statistics analytic guidelines (19). On the basis of an average design effect of approximately 1.4 for our sample, means and medians derived from fewer than 42 participants, 10th and 90th percentiles derived from fewer than 112 participants, and 5th and 95th percentiles derived from fewer than 224 participants were deemed unstable. Sample size for stable estimates of the proportions varied by the magnitude of the proportion, ranging from 42 for proportions of 0.5 to 224 for proportions of 0.05 or 0.95. We indicate in the text and tables statistics that did not meet the appropriate sample size. We categorized participants into three ethnic groups: non-Hispanic white, non-Hispanic black, and Mexican American. We excluded persons from other ethnic groups (n=436) because their inclusion produced unstable estimates of mean total homocysteine concentration after adjustment for ethnicity. Our analyses are based on 8086 participants with complete data on serum total homocysteine, folate, vitamin B12, and creatinine concentrations. Results Table 1 shows selected characteristics of the sample by sex and ethnic group. On average, non-Hispanic white pa

Water, hydration, and health

This review examines the current knowledge of water intake as it pertains to human health, including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, and the effects of variation in water intake on health and energy intake, weight, and human performance and functioning. Water represents a critical nutrient, the absence of which will be lethal within days. Waters importance for the prevention of nutrition-related noncommunicable diseases has received more attention recently because of the shift toward consumption of large proportions of fluids as caloric beverages. Despite this focus, there are major gaps in knowledge related to the measurement of total fluid intake and hydration status at the population level; there are also few longer-term systematic interventions and no published randomized, controlled longer-term trials. This review provides suggestions for ways to examine water requirements and encourages more dialogue on this important topic.

High homocysteine and low B vitamins predict cognitive decline in aging men: the Veterans Affairs Normative Aging Study

BACKGROUND Elevated homocysteine concentrations may contribute to cognitive impairment. Most elevations in homocysteine result from inadequate folate, vitamin B-12, or vitamin B-6 intake. It is not clear whether the observed associations between homocysteine and cognitive measures are causal or whether they are due to homocysteine, to independent actions of the B vitamins, or to both. OBJECTIVE We aimed to assess the individual and independent effects of baseline plasma homocysteine, folate, vitamin B-12, and vitamin B-6 and of dietary B vitamin intakes on 3-y changes in cognitive measures in 321 aging men. DESIGN Participants were from the Veterans Affairs Normative Aging Study. Cognitive function was assessed with the Mini-Mental State Examination and on the basis of measures of memory, verbal fluency, and constructional praxis, which were adapted from the revised Wechsler Adult Intelligence Scale and the Consortium to Establish a Registry for Alzheimers Disease batteries at 2 time points. At baseline, dietary intakes were assessed with a food-frequency questionnaire, and blood was drawn for the measurement of B vitamins and homocysteine. RESULTS Over a mean 3-y follow-up, declines in constructional praxis, measured by spatial copying, were significantly associated with plasma homocysteine, folate, and vitamins B-6 and B-12 and with the dietary intake of each vitamin. Folate (plasma and dietary) remained independently protective against a decline in spatial copying score after adjustment for other vitamins and for plasma homocysteine. Dietary folate was also protective against a decline in verbal fluency. A high homocysteine concentration was associated with a decline in recall memory. CONCLUSIONS Low B vitamin and high homocysteine concentrations predict cognitive decline. Spatial copying measures appear to be most sensitive to these effects in a general population of aging men.