Optimisation of vitamin D status in global populations.

Vitamin D is important for musculoskeletal health. Concentrations of 25-hydroxyvitamin D, the most commonly measured metabolite, vary markedly around the world and are influenced by many factors including sun exposure, skin pigmentation, covering, season and supplement use. Whilst overt vitamin D deficiency with biochemical consequences presents an increased risk of severe sequelae such as rickets, osteomalacia or cardiomyopathy and usually warrants prompt replacement treatment, the role of vitamin D supplementation in the population presents a different set of considerations. Here the issue is to keep, on average, the population at a level whereby the risk of adverse health outcomes in the population is minimised. This position paper, which complements recently published work from the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases, addresses key considerations regarding vitamin D assessment and intervention from the population perspective. This position paper, on behalf of the International Osteoporosis Foundation Vitamin D Working Group, summarises the burden and possible amelioration of vitamin D deficiency in global populations. It addresses key issues including screening, supplementation and food fortification.

Consensus statement from 2nd International Conference on Controversies in Vitamin D.

The 2nd International Conference on Controversies in Vitamin D was held in Monteriggioni (Siena), Italy, September 11-14, 2018. The aim of this meeting was to address ongoing controversies and timely topics in vitamin D research, to review available data related to these topics and controversies, to promote discussion to help resolve lingering issues and ultimately to suggest a research agenda to clarify areas of uncertainty. Several issues from the first conference, held in 2017, were revisited, such as assays used to determine serum 25-hydroxyvitamin D [25(OH)D] concentration, which remains a critical and controversial issue for defining vitamin D status. Definitions of vitamin D nutritional status (i.e. sufficiency, insufficiency and deficiency) were also revisited. New areas were reviewed, including vitamin D threshold values and how they should be defined in the context of specific diseases, sources of vitamin D and risk factors associated with vitamin D deficiency. Non-skeletal aspects related to vitamin D were also discussed, including the reproductive system, neurology, chronic kidney disease and falls. The therapeutic role of vitamin D and findings from recent clinical trials were also addressed. The topics were considered by 3 focus groups and divided into three main areas: 1) "Laboratory": assays and threshold values to define vitamin D status; 2) "Clinical": sources of vitamin D and risk factors and role of vitamin D in non-skeletal disease and 3) "Therapeutics": controversial issues on observational studies and recent randomized controlled trials. In this report, we present a summary of our findings.

Biotin supplementation causes erroneous elevations of results in some commercial serum 25-hydroxyvitamin d (25OHD) assays.

The Vitamin D External Quality Assessment Scheme (DEQAS) distributes serum samples globally, on a quarterly basis, to assess participants' performance of specific methods for 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (1,25-(OH)2D). DEQAS occasionally circulates samples containing high levels of substances found in certain clinical situations e.g. 25-OHD2, 24,25-(OH)2D3, hypertriglyceridemia. The increased availability and use of health supplements containing biotin has led to case reports of assay interference in methods utilizing a biotin-streptavidin detection system. In October 2018, DEQAS included a serum sample (545) containing exogenous biotin (concentration =586 µg/L) which was analyzed by a total of 683 laboratories using 35 different methods. The same serum sample (544) without exogenous biotin was also included in the 5-sample set. All methods (760 laboratories) performed satisfactorily on sample 544 giving an All-Laboratory Trimmed Mean = 50.2 ± 6.5 nmol/L (±SD, CV = 12.9 %). The target value for this sample 544 (& 555) was 47.4 nmol/L as determined by Centers for Disease Control and Prevention (CDC) Atlanta, Georgia using their LC-MS/MS reference method. In contrast, #545 containing the exogenous biotin was reported by only 683 laboratories and gave an All-Laboratory Trimmed Mean = 66.8 ± 37.6 nmol/L (±SD, CV = 56.3 %). As expected, LC-MS/MS methods (143 labs) reported similar results for both 544 = 48.9 ± 4.4 nmol/L (±SD) and 545 = 48.3 ± 4.5 nmol/L (±SD) showing that assays involving chromatographic steps are unaffected by the presence of biotin. Several of the antibody-based assays including Abbott Architect, DiaSorin Liaison, Beckman Unicel and Siemens Centaur are also unaffected by the addition of biotin. Two assays, IDS-iSYS and Roche Total 25OHD, both of which use biotin-streptavidin, exhibit biotin interference yielding values with a significant positive bias for 545 of 102.6 nmol/L ± 78.7 nmol/L (±SD) and 517.8 nmol/L ± 209.8 nmol/L (±SD) respectively. Interestingly, the failure to report sample 545 data from 77 laboratories is due solely to those running Roche Total 25OHD or Roche Vitamin D Total II assays. Given the prevalence of the adversely affected assays (25 % of DEQAS users) and the high volume of 25OHD testing, clinicians using these assays should, where possible, only measure 25OHD when patients are off biotin.

Estimating uncertainty of target values for DEQAS serum materials.

The External Quality Assessment (EQA) scheme for vitamin D metabolites (DEQAS) distributes human serum samples to laboratories across the world to assess their performance in measuring serum total 25-hydroxyvitamin D [25(OH)D], i.e. the sum of the concentrations of serum 25(OH)D2 and 25(OH)D3. In 2013 DEQAS, in collaboration with the Vitamin D Standardization Program (VDSP), became an accuracy-based EQAS when the National Institute for Standards and Technology (NIST) began assigning 25(OH)D target values to DEQAS serum samples using their Joint Committee for Traceability in Laboratory Medicine (JCTLM) approved reference measurement procedure (RMP). Historically, NIST has performed 4 determinations of 25-OHD2 and 25-OHD3 on each sample and used the mean values to calculate a single 'target value' for Total 25-OHD against which performance was judged. By definition the target values cannot be exact and each is associated with a level of uncertainty. The total uncertainty (UNIST) has two components, one from the 25(OH)D2, and 25(OH)D3 measurements and the other associated with the calibration procedure. The total combined uncertainty is calculated by adding up these uncertainties. In future, uncertainties will be attached to the target value in each DEQAS serum sample, starting with the next distribution cycle in 2019. Confidence intervals obtained using these uncertainties will allow DEQAS participants to determine if their result agrees with the NIST assigned target value. Furthermore, if the value falls within the confidence interval the laboratory's assay would be regarded as traceable, i.e. standardized, to the NIST RMP.

External Quality Assessment of 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) assays.

The discovery that mutations of the CYP24A1 gene are a cause of idiopathic infantile hypercalcemia (IIH) has revived interest in measuring serum 24,25(OH)2D3. Several studies have also suggested that a high 25-hydroxyvitamin D3(25-OHD3):24,25(OH)2D3 ratio might provide additional diagnostic information in the investigation of vitamin D deficiency. Measurement of 24,25(OH)2D3 is necessarily restricted to laboratories with mass spectrometry methods although cross reactivity of the metabolite in immunoassays for 25-OHD is a potential cause of misleading results. The international External Quality Assessment (EQA) scheme for vitamin D metabolites (DEQAS) was set up in 1989. In 2013 DEQAS became an accuracy based EQA for 25-OHD with 'target values' assigned by the National Institute of Standards and Technology (NIST) Reference Measurement Procedure (RMP). A pilot scheme for serum 24,25(OH)2D3 was started in 2015 and participants were asked to measure the metabolite on each of the 5 samples sent out for 25-OHD. Inter-laboratory agreement was poor but this may reflect methodological differences, in particular different approaches to assay standardization. An important potential contribution to reducing variability among assays was the development by NIST of a 24,25(OH)2D3 RMP and its use in assigning values to SRMs 972a, 2973 and 2971, supported by the NIH Office of Dietary Supplements (ODS) as part of the Vitamin D Standardization Program (VDSP) effort.

Hydroxyvitamin D assays: An historical perspective from DEQAS.

Recent years have seen a substantial increase in demand for 25-hydroxyvitamin D (25-OHD) assays. DEQAS (the Vitamin D External Quality Assessment Scheme) has been monitoring the performance of these assays since 1989. The first DEQAS distribution was in June 1989 and results were submitted by 13 laboratories in the UK, two of which used HPLC/UV; the rest used ligand binding assays with a tritium tracer. Inter-laboratory CVs (ALTM) ranged from 29.3% (42.7nmol/L) to 53.7% (20.0nmol/L). Currently the scheme has participants in 56 countries using 30 methods or variants of methods. In January 2017, 918 participants returned results and inter-laboratory CVs (ALTM) ranged from 10.3% (73.1nmol/L) to 15.3% (29.4nmol/L). Over the last 27 years, there have been a number of significant milestones in assay development. The first major advance was the development of an iodinated 25-OHD tracer by Hollis and Napoli in 1992, subsequently used in an RIA kit marketed by DiaSorin. This and other commercial radioimmunoassays that followed brought 25-OHD assays within reach of many more non-specialist routine laboratories. With the introduction of fully automated non-isotopic assays without solvent extraction, measurement of 25-OHD became available to any clinical chemistry laboratory with an appropriate analytical platform. However, as the limitations of these non-extraction assays became apparent more laboratories started using LC-MS/MS methodology. Meanwhile the variable accuracy of 25-OHD methods has been addressed by the Vitamin D Standardization Program (VDSP) which encourages manufacturers to produce methods traceable to the reference measurement procedures (RMPs) of NIST, University of Ghent and the Centers for Disease Control and Prevention (CDC). DEQAS changed to an accuracy-based scheme in 2013 and now assesses assay accuracy against the NIST RMP. This review will use DEQAS results and statistics to chart the historical development in 25-OHD assay technology and highlight some of the problems encountered in obtaining reliable results for this most challenging of analytes.

Vitamin D measurement standardization: The way out of the chaos.

Substantial variability is associated with laboratory measurement of serum total 25-hydroxyvitamin D [25(OH)D]. The resulting chaos impedes development of consensus 25(OH)D values to define stages of vitamin D status. As resolving this situation requires standardized measurement of 25(OH)D, the Vitamin D Standardization Program (VDSP) developed methodology to standardize 25(OH)D measurement to the gold standard reference measurement procedures of NIST, Ghent University and CDC. Importantly, VDSP developed protocols for standardizing 25(OH)D values from prior research based on availability of stored serum samples. The effect of such retrospective standardization on prevalence of "low" vitamin D status in national studies reported here for The Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994) and the German Health Interview and Examination Survey for Children and Adolescents (KIGGS, 2003-2006) was such that in NHANES III 25(OH)D values were lower than original values while higher in KIGGS. In NHANES III the percentage with values below 30, 50 and 75 nmol/L increased from 4% to 6%, 22% to 31% and 55% to 71%, respectively. Whereas in KIGGS after standardization the percentage below 30, 50, and 70 nmol/L decreased from 28% to 13%, 64% to 47% and 87% to 85% respectively. Moreover, in a hypothetical example, depending on whether the 25(OH)D assay was positively or negatively biased by 12%, the 25(OH)D concentration which maximally suppressed PTH could vary from 20 to 35ng/mL. These examples underscore the challenges (perhaps impossibility) of developing vitamin D guidelines using unstandardized 25(OH)D data. Retrospective 25(OH)D standardization can be applied to old studies where stored serum samples exist. As a way forward, we suggest an international effort to identify key prior studies with stored samples for re-analysis and standardization initially to define the 25(OH)D level associated with vitamin D deficiency (rickets/osteomalacia). Subsequent work could focus on defining inadequacy. Finally, examples reported here highlight the importance of suspending publication of meta-analyses based on unstandardized 25(OH)D results.

Quality assessment of vitamin D metabolite assays used by clinical and research laboratories.

The Vitamin D External Quality Assessment Scheme (DEQAS) was launched in 1989 and monitors the performance of 25-hydroxyvitamin D (25-OHD) and 1,25- dihydroxyvitamin D (1,25(OH)2D) assays. In April 2015 a pilot scheme for 24,25-dihydroxyvitamin D (24,25(OH)2D) was introduced. The 25-OHD scheme is accuracy - based with target values assigned by the NIST Reference Measurement Procedure (RMP) for 25-OHD2 and 25-OHD3. A similar method is used to assign values for 3-epi-25-OHD. Five samples of human serum are distributed quarterly to over 1000 participants in 58 countries (April 2016) and clinical laboratories are expected to submit results within approximately 5 weeks. Research laboratories with assays run less frequently are not given a deadline. Archived samples with NIST- assigned values are also available. Performance is assessed on the first four samples with the fifth reserved for investigations e.g. recovery experiments or to assess the influence of other serum constituents such as lipids. DEQAS provides rapid feedback, with an on-line preliminary report available immediately after a participant submits results and a comprehensive report soon after the results deadline. In 2015, DEQAS investigations revealed that several 25-OHD immunoassays under-recovered 25-OHD2 and 25-OHD results were falsely low on a sample with a modestly raised triglyceride concentration. An RMP for 1,25 (OH)2D is not yet available and results are judged against the Method Mean. Free advice is available from the DEQAS Advisory Panel which includes experts on methodology and biostatistics. DEQAS collaborates closely with the Vitamin D Standardization Program (VDSP) and both organizations have successfully worked with participants and manufacturers to improve the accuracy of vitamin D assays.

Antioxidants, oxidative stress, and pulmonary function in individuals diagnosed with asthma or COPD.

OBJECTIVE: The objective of this study was to investigate the association between antioxidant nutrients and markers of oxidative stress with pulmonary function in persons with chronic airflow limitation. DESIGN: Cross-sectional study exploring the association of antioxidant nutrients and markers of oxidative stress with forced expiratory volume in the first second (FEV1%) and forced vital capacity (FVC%). SETTING/SUBJECTS: The study data included 218 persons with chronic airflow limitation recruited randomly from the general population of Erie and Niagara counties, New York State, USA. RESULTS: After adjustment for covariates, multiple linear regression analysis showed that serum beta-cryptoxanthin, lutein/zeaxanthin, and retinol, and dietary beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin, vitamin C, and lycopene were positively associated with FEV1% (P < 0.05, all associations). Serum vitamins beta-cryptoxanthin, lutein/zeaxanthin, and lycopene, and dietary beta-cryptoxanthin, beta-carotene, vitamin C, and lutein/zeaxanthin were positively associated with FVC% (P < 0.05, all associations). Erythrocytic glutathione was negatively associated with FEV1%, while plasma thiobarbituric acid-reactive substances (TBARS) were negatively associated with FVC% (P < 0.05). CONCLUSION: These results support the hypothesis that an imbalance in antioxidant/oxidant status is associated with chronic airflow limitation, and that dietary habits and/or oxidative stress play contributing roles.

Developing vitamin D dietary guidelines and the lack of 25-hydroxyvitamin D assay standardization: The ever-present past.

Unstandardized laboratory measurement of 25-hydroxyvitamin D (25(OH)D) confounds efforts to develop clinical and public health vitamin D guidelines. The Vitamin D Standardization Program (VDSP), an international collaborative effort, was founded in 2010 to correct this problem. Nearly all published vitamin D research is based on unstandardized laboratory 25(OH)D measurements. While it is impossible to standardize all old data, it may be possible to identify a small subset of prior studies critical to guidelines development. Once identified it may be possible to calibrate their 25(OH)D values to the NIST and Ghent University reference measurement procedures using VDSP methods thereby permitting future guidelines to be based on standardized results. We simulated the calibration of a small set of ten clinical trials of vitamin D supplementation on achieved 25(OH)D under minimal sun exposure. These studies were selected because they played a prominent role in setting the 2010 vitamin D dietary reference intakes (DRI). Using random-effects meta-regression analysis, Vitamin D External Quality Assessment (DEQAS) data on assay bias was used to simulate the potential bias due to the lack of assay standardization by calibrating the achieved 25(OH)D levels from those 10 studies to: (1) the largest negative, and (2) the largest positive bias from the DEQAS all laboratory trimmed mean (ALTM) for the appropriate assay and year of analysis. For a usual vitamin D intake of 600IU/day the difference in mean achieved 25(OH)D values for those two options was 20nmol/L. However, without re-calibration of 25(OH)D values it is impossible to know the degree to which any of the current guidelines may have been biased. This approach may help stimulate the search for and standardization of that small subset of key studies and, in the cases where standardization is impossible, to identify areas of urgently needed vitamin D research.

25-Hydroxyvitamin D assays: Potential interference from other circulating vitamin D metabolites.

The vitamin D External Quality Assessment Scheme (DEQAS) for 25-hydroxyvitamin D (25-OHD) has approximately 1100 participants in 53 countries using 26 different methods or variants of methods (October 2014). In April 2015, the scheme was extended to cover 24,25-dihydroxyvitamin D (24,25(OH)2D). Since 2013, the 25-OHD scheme has been accuracy-based with values assigned by the NIST reference measurement procedure (RMP). DEQAS is uniquely placed to assess the accuracy (bias) and specificity of 25-OHD methods in a routine laboratory setting. Other vitamin D metabolites are known to interfere in 25-OHD assays and DEQAS has distributed samples spiked with 3-epi-25-OHD3 (52.4nmol/L), 24R,25(OH)2D3 (14.4nmol/L) and 24S,25(OH)2D3 (57.9nmol/L). The 3-epimer showed a cross reactivity of 56% in a competitive protein binding assay but was not detected in any antibody-based methods. Not all HPLC/UV or LC-MS/MS methods were able to resolve 3-epi-25-OHD3 from 25-OHD3 and thus overestimated total 25-OHD. The cross reactivity of 24R,25(OH)2D3 (24S,25(OH)2D3) ranged from <5% (<5%) to 548% (643%) in ligand binding assays. Both 24-hydroxylated metabolites were resolved by HPLC/UV and LC-MS/MS methods and thus caused no complications in the measurement of 25-OHD. Most antibodies to 25-OHD are known to cross-react with dihydroxylated metabolites but interference in some assays was far greater than expected. This may be related to the anomalous behaviour of exogenously added metabolites in these 25-OHD methods.

Excess body weight. An under-recognized contributor to dyslipidemia in white American women.

BACKGROUND: Whether the association between excess body weight and dyslipidemia is consistent across different age ranges in women has yet to be determined. METHODS: The relationship between body weight adjusted for height as calculated by body mass index (BMI; kilograms per square meter) and serum lipid and lipoprotein levels in white women was examined using cross-sectional data from the Second National Health and Nutrition Examination Survey. Mean lipid levels were determined for six different categories of BMI: (1) 21.0 or less; (2) 21.1 to 23.0; (3) 23.1 to 25.0; (4) 25.1 to 27.0; (5) 27.1 to 30.0; and (6) more than 30.0, and three age groups: premenopausal women, 20 through 44 years; perimenopausal women, 45 through 59 years; and postmenopausal women, 60 through 74 years. RESULTS: Compared with BMI category 2, a BMI in category 5 for premenopausal women was associated with 0.46 mmol/L (18 mg/dL) higher total cholesterol levels, 0.68 mmol/L (26 mg/dL) higher non-high-density lipoprotein (HDL) cholesterol levels, and 0.44 mmol/L (17 mg/dL) higher low-density lipoprotein (LDL) cholesterol levels. For perimenopausal women and postmenopausal women the same change in BMI was associated with much smaller differences in total cholesterol of 0.16 and 0.16 mmol/L (6 and 5 mg/dL), non-HDL of 0.24 and 0.20 mmol/L (9 and 8 mg/dL), and LDL levels of 0.13 and 0.03 mmol/L (5 and 1 mg/dL). More impressively, rising BMI was associated with consistently higher triglyceride levels of 0.54 to 0.40 mmol/L (48 to 35 mg/dL) and consistently lower HDL levels of 0.23 to 0.13 mmol/L (9 to 5 mg/dL), in all three age groups. CONCLUSION: For young women, excess body weight was associated with higher total, non-HDL and LDL-cholesterol levels, higher triglyceride levels, and lower HDL-cholesterol levels. In older women, although similar differences in triglyceride levels and HDL-cholesterol levels were observed, excess body weight was associated with smaller differences in total, non-HDL, and LDL cholesterol. More striking than the weight-associated differences in total, non-HDL, and LDL-cholesterol levels were the differences in these lipid parameters observed with age alone. Specifically, age category differences were twofold to eightfold greater than differences observed between categories of BMI within a given age. Nevertheless, because the lower HDL cholesterol concentrations associated with excess body weight were age independent, total cholesterol-HDL cholesterol ratios were highest in obese postmenopausal women. Although age and hormonal status are important affecters of lipoprotein risk factors, body weight also worsens the degree of dyslipidemia in white women.

Excess body weight. An underrecognized contributor to high blood cholesterol levels in white American men.

BACKGROUND: The influence of body weight on serum lipids is often overlooked in clinical practice. METHODS: The association between body weight adjusted for height as calculated by body-mass index (BMI) and serum lipid and lipoprotein levels in white men was examined using the second National Health and Nutrition Examination Survey (NHANES II). Lipid results were categorized into six different levels of BMI: (1) 21.0 kg/m2 or lower, (2) 21.1 to 23.0 kg/m2, (3) 23.1 to 25.0 kg/m2, (4) 25.1 to 27.0 kg/m2, (5) 27.1 to 30.0 kg/m2, and (6) greater than 30.0 kg/m2, and three age groups: (1) young men (20 through 44 years), (2) middle-aged men (45 through 59 years), and (3) older men (60 through 74 years). RESULTS: Using linear trend analysis, changes in BMI from categories 2 to 5 in young men were associated with a total cholesterol level 0.59 mmol/L (23 mg/dL) higher (P < .01), a non-high-density lipoprotein (non-HDL) cholesterol level 0.70 mmol/L (27 mg/dL) higher (P < .01), and a low-density lipoprotein (LDL) cholesterol level 0.59 mmol/L (23 mg/dL) higher (P = .03). For middle-aged men and older men, the same change in BMI was associated with smaller but still significant differences in total cholesterol levels (higher by 0.31 mmol/L [12 mg/dL] [P < .01] and 0.28 mmol/L [11 mg/dL] [P < .01], respectively) and non-HDL cholesterol levels (higher by 0.37 mmol/L [14 mg/dL] [P < .01] and 0.25 mmol/L [10 mg/dL] [P < .01], respectively), whereas the LDL cholesterol levels were unchanged. Although advancing age may blunt the BMI-associated differences in total and LDL cholesterol levels, the BMI-associated differences in triglyceride levels (higher by 0.70 to 1.33 mmol/L [62 to 118 mg/dL] [P < .001]) and HDL cholesterol levels (lower by 0.18 to 0.39 mmol/L [7 to 15 mg/dL] [P < .001]) were of similar magnitude in all age groups. CONCLUSION: Excess body weight is associated with deleterious changes in the lipoprotein profile. Higher BMI was associated at all ages with higher plasma triglyceride level, lower HDL cholesterol level, and higher total and non-HDL cholesterol levels. In young men, the higher total cholesterol level was reflected mainly in the LDL cholesterol level; in middle-aged and older men, in the non-HDL fraction. Programs to reduce coronary heart disease by improving lipid levels should include more emphasis on achieving and maintaining ideal body weight.

Periodontal disease and risk of cerebrovascular disease: the first national health and nutrition examination survey and its follow-up study.

BACKGROUND: Periodontal disease has been found to be a potential risk factor for coronary heart disease. However, its association with cerebrovascular accidents (CVAs) is much less studied. METHODS: This study examines the association between periodontal disease and CVA. The study cohort comprises 9962 adults aged 25 to 74 years who participated in the First National Health and Nutrition Examination Survey and its follow-up study. Baseline periodontal status was categorized into (1) no periodontal disease, (2) gingivitis, (3) periodontitis, and (4) edentulousness. All CVAs (International Classification of Diseases, Ninth Revision [ICD-9], codes 430-438) were ascertained by hospital records for nonfatal events and death certificates for fatal events. The first CVA, nonfatal or fatal, was used to define incidence. Relative risks were estimated by hazard ratios from the Cox proportional hazard model with adjustment for several demographic variables and well-established cardiovascular risk factors. Weights were used to generate risk estimates. RESULTS: Periodontitis is a significant risk factor for total CVA and, in particular, nonhemorrhagic stroke (ICD-9, 433-434 and 436-438). Compared with no periodontal disease, the relative risks (95% confidence intervals) for incident nonhemorrhagic stroke were 1.24 (0.74-2.08) for gingivitis, 2.11 (1.30-3.42) for periodontitis, and 1.41 (0.96-2.06) for edentulousness. For total CVA, the results were 1.02 (0.70-1.48) for gingivitis, 1.66 (1.15-2.39) for periodontitis, and 1.23 (0.91-1.66) for edentulousness. Increased relative risks for total CVA and nonhemorrhagic stroke associated with periodontitis were also seen in white men, white women, and African Americans. Similar results were found for fatal CVA. CONCLUSION: Periodontal disease is an important risk factor for total CVA and, in particular, nonhemorrhagic stroke.

Leisure-time physical activity among US adults. Results from the Third National Health and Nutrition Examination Survey.

BACKGROUND: The prevalence of no leisure-time physical activity (LTPA) among US adults is estimated to be between 24% and 30%. Such information, however, usually does not include prevalence estimates for non-Hispanic blacks, Mexican Americans, and the elderly. OBJECTIVE: To assess the prevalence of participation in leisure-time physical activity among US adults. METHODS: Between 1988 and 1991, 9488 adults aged 20 years and older were interviewed in their home as part of the third National Health and Nutrition Examination Survey. A clinic examination in a mobile center was also included. Mexican Americans, non-Hispanic blacks, and the elderly were oversampled to produce reliable estimates for these groups. Questions were asked about the type and frequency of physically active hobbies, sports, and exercises. RESULTS: The prevalence of no LTPA for US adults aged 20 years or older from 1988 through 1991 was 22%. The rate was higher in women (27%) than in men (17%). Mexican-American men (33%) and women (46%) and non-Hispanic black women (40%) had the highest rates of no LTPA. Participation in moderate to vigorous LTPA five or more times per week decreased with age, with the largest decreases observed among non-Hispanic black men and women. In almost all subpopulations, gardening and/or yard work and walking were stated as the two top LTPAs of choice. CONCLUSIONS: Many Americans are inactive or irregularly active during their leisure time. Rates of inactivity are greater for women, older persons, non-Hispanic blacks, and Mexican Americans. Intervention strategies meant to promote lifetime physical activities among all Americans represents a major health priority.

Dietary calcium and blood pressure in National Health and Nutrition Examination Surveys I and II.

It has recently been reported that a low intake of calcium may be a risk factor for hypertension. In view of the contradictory results, even when the same survey data base has been used by different researchers, an in-depth analysis was undertaken of the data provided by the two cycles of the National Health and Nutrition Examination Survey (NHANES). Both surveys, conducted in consecutive 4-year intervals during the 1970s, were designed to examine representative samples of the U.S. civilian noninstitutionalized population. The overall descriptive findings in relation to mean blood pressure and calcium intake were virtually identical in the two surveys. Based on "quantile" analysis, neither mean levels of blood pressure nor the prevalence of hypertension was related to calcium intake. Only among black men in NHANES I was a relationship between calcium intake and blood pressure noted. This finding was not apparent among black men in NHANES II or among any of the other sex-race groups in either survey. We conclude that the data of NHANES I and II do not show an association between low calcium intake and blood pressure.

Effect of dietary sodium reduction on red blood cell sodium concentration and sodium-lithium countertransport.

A randomized, crossover trial was carried out on the effect of moderate sodium reduction on red-blood-cell sodium metabolism. The participants were healthy high school students (mean age = 16 years, n = 33). Changes in sodium-lithium countertransport and intracellular sodium concentration were evaluated 24 days after a decrease in dietary sodium from approximately 110 to 40 mEq per day. Dietary sodium restriction had no significant effect on either sodium-lithium countertransport or intracellular sodium concentration.

Food and nutrient exposures: what to consider when evaluating epidemiologic evidence.

Nutritional epidemiology is the science concerned with conducting research into the relation between diet and disease risk. The public has a great deal of interest in this issue. Much of that interest, however, is fueled by the publication of sensationalized, startling, and often contradictory health messages. Unfortunately, there is a great deal of confusion in both the scientific press and the public or lay press about the nature of nutritional epidemiology, its strengths, and its limitations. The purpose of this article is to discuss these strengths and limitations. It is hoped that clarification of these issues can help lead to a resolution of the research community's and lay public's misunderstandings about nutritional epidemiology research.