Scholarly Journals--Published

  • Jaceldo-Siegl K, Knutsen S F, Sabate J, Beeson W L, Chan J, . . . Fraser G E. (2010). Validation of nutrient intake using an FFQ and repeated 24 h recalls in black and white subjects of the Adventist Health Study-2 (AHS-2). Public Health Nutrition, 13(6), 812-819. Objective: To validate a 204-item quantitative FFQ for measurement of nutrient intake in the Adventist Health Study-2 (AHS-2). Design: Calibration study participants were randomly selected from the AHS-2 cohort by church, and then subject-within-church. Each participant provided two sets of three weighted 24 h dietary recalls and a 204-item FFQ. Race-specific correlation coefficients (r), corrected for attenuation from within-person variation in the recalls, were calculated for selected energy-adjusted macro- and micronutrients. Setting: Adult members of the AHS-2 cohort geographically spread throughout the USA and Canada. Subjects: Calibration study participants included 461 blacks of American and Caribbean origin and 550 whites. Results: Calibration study subjects represented the total cohort very well with respect to demographic variables. Approximately 33% were males. Whites were older, had higher education and lower BMI compared with blacks. Across fifty-one variables, average deattenuated energy-adjusted validity correlations were 0.60 in whites and 0.52 in blacks. Individual components of protein had validity ranging from 0.40 to 0.68 in blacks and from 0.63 to 0.85 in whites; for total fat and fatty acids, validity ranged from 0.43 to 0.75 in blacks and from 0.46 to 0.77 in whites. Of the eighteen micronutrients assessed, sixteen in blacks and sixteen in whites had deatttenuated energy-adjusted correlations >= 0.4, averaging 0.60 and 0.53 in whites and blacks, respectively. Conclusions: With few exceptions validity coefficients were moderate to high for macronutrients, fatty acids, vitamins, minerals and fibre. We expect to successfully use these data for measurement error correction in analyses of diet and disease risk. (06/2010) (link)
  • Chan J, Jaceldo-Siegl K, & Fraser G E. (2010). Determinants of serum 25 hydroxyvitamin D levels in a nationwide cohort of blacks and non-Hispanic whites. Cancer Causes & Control, 21(4), 501-511. To develop algorithms predicting serum 25 hydroxyvitamin D [s25(OH)D] for a large epidemiological study whose subjects come from large geographic areas, are racially diverse and have a wide range in age, skin types, and month of blood sample collection. This will allow a regression calibration approach to determine s25(OH)D levels replacing the more costly method of collection and analysis of blood samples. Questionnaire data from a subsample of 236 non-Hispanic whites (whites) and 209 blacks from the widely dispersed Adventist Health Study-2 (n = 96,000) were used to develop prediction algorithms for races separately and combined. A single blood sample was collected from each subject, at different times throughout the year. Models with independent variables age, sex, BMI, skin type, UV season, erythemal zone, total dietary vitamin D intake, and sun exposure factor explained 22 and 31% of the variance of s25(OH)D levels in white and black populations, respectively (42% when combined). UV season and erythemal zone determined from measured UV radiation produced models with higher R (2) than season and latitude. Combining races with a term for race and using variables with measured UV radiation capture the variance in s25(OH)D levels better than analyzing races separately. (04/2010) (link)
  • Chan J, Jaceldo-Siegl K, & Fraser G E. (2009). Serum 25-hydroxyvitamin D status of vegetarians, partial vegetarians, and nonvegetarians: the Adventist Health Study-2. American Journal of Clinical Nutrition, 89(5), S1686-S1692. Background: Vegans and other vegetarians who limit their intake of animal products may be at greater risk of vitamin D deficiency than nonvegetarians, because foods providing the highest amount of vitamin D per gram naturally are all from animal sources, and fortification with vitamin D currently occurs in few foods. Objective: We assessed serum 25-hydroxyvitamin D [s25(OH)D] concentrations and factors affecting them in vegetarians, partial vegetarians, and nonvegetarians in a sample of calibration study subjects from the Adventist Health Study-2. Design: Food-frequency questionnaires and sun-exposure data were obtained from 199 black and 229 non-Hispanic white adults. We compared s25(OH)D concentration, dietary and supplemental vitamin D intake, and sun exposure in the different dietary groups. Results: We found no significant difference in s25(OH)D by vegetarian status for either white or black subjects. Among whites, dietary vitamin D intake and sun behavior were different between vegetarian groups, but there was no difference in skin type distribution. Among blacks, no significant differences were observed for any of these variables between vegetarian groups. The mean (+/- SD) s25(OH)D was higher in whites (77.1 +/- 10.33 nmol/L) than in blacks (50.7 +/- 27.4 nmol/ L) ( P < 0.0001). Conclusions: s25(OH)D concentrations were not associated with vegetarian status. Other factors, such as vitamin D supplementation, degree of skin pigmentation, and amount and intensity of sun exposure have greater influence on s25( OH) D than does diet. Am J Clin Nutr 2009; 89(suppl): 1686S-92S. (05/2009) (link)
  • Fraser G E, Yan R, Butler T L, Jaceldo-Siegl K, Beeson W L, & Chan J. (2009). Missing Data in a Long Food Frequency Questionnaire Are Imputed Zeroes Correct?. Epidemiology, 20(2), 289-294. Background: Missing data are a common problem in nutritional epidemiology. Little is known of the characteristics of these missing data, which makes it difficult to conduct appropriate imputation. Methods: We telephoned, at random, 20% of subjects (n = 2091) from the Adventist Health Study-2 cohort who had any of 80 key variables missing from a dietary questionnaire. We were able to obtain responses for 92% of the missing variables. Results: We found a consistent excess of "zero" intakes in the filled-in data that were initially missing. However, for frequently consumed foods, most missing data were not zero, and these were usually not distinguishable from a random sample of nonzero data. Older, black, and less-well-educated subjects had more missing data. Missing data are more likely to be true zeroes in older subjects and those with more missing data. Zero imputation for missing data may create little bias except for more frequently consumed foods, in which case, zero imputation will be suboptimal if there is more than 5%-10% missing. Conclusions: Although some missing data represent true zeroes, much of it does not, and data are usually not missing at random. Automatic imputation of zeroes for missing data will usually be incorrect, although there is a little bias unless the foods are frequently consumed. Certain identifiable subgroups have greater amounts of missing data, and require greater care in making imputations. (03/2009) (link)
  • S. Montgomery, P. Herring, A. Yancey, L. Beeson, T. Butler, S. Knutsen, J. Sabate, J. Chan, S. Preston-Martin, G. Fraser, . "Comparing self-reported disease outcomes, diet and lifestyles in a national cohort of Black and White Seventh-Day Adventists." Preventing Chronic Disease . (2007): -. (07/2007)
  • Chan J, Knutsen SF, Sabate JS, Haddad E, Yan R, Fraser GE. "Feasibility of Running Clinics to Collect Biological Specimens in a Nationwide Cohort Study-Adventist Health Study-2: A Brief Report." Annals of Epidemiology . (2007): -. Purpose: Collecting biologic and questionnaire data allows analyses that can include both genetic/biomarker and behavioral factors. Therefore the feasibility of collecting biological specimens from a nationally dispersed cohort (Adventist Health Study-2) was tested. Methods: We selected 2,130 subjects from California, Washington, Texas and Louisiana to simulate a widely scattered cohort. Clinics were held at local church halls. Non-clinic attendees were invited to mail in their blood samples. The remaining non-participants were offered a home visit by a venipuncturist Results: Sixty-four percent of non-black and 38.4% of black invitees attended the clinics. Another 11.3% of non-black and 5.9% of black subjects from a sub-sample mailed in their blood samples. A venipuncturist visited to collected samples from another 5.3% of non-black subjects but hurricanes disrupted this method among blacks. This experience suggests that we could collect biological samples from 81.2% and at least 44.3% of the non-black and black subjects respectively. Conclusions: We have demonstrated the feasibility of collecting biological specimens from black as well as non-black subjects, with an efficient, cost-effective system and limited manpower, overcoming many of the complexities imposed by scattered subjects, diversity of culture, as well as cumbersome and varied state legislation governing clinics and clinic personnel. (03/2007)
  • Chan J, Knutsen SF, Blix GG, Lee JW & Fraser, G. "Water, Other Fluids and Fatal Coronary Heart Disease. The Adventist Health Study (AHS).." American Journal of Epidemiology 155.9 (2002): 827-833. (01/2002)


  • (PEER REVIEWED) Chan J, Jaceldo-Siegl K and Fraser GE . "Predicting serum 25 hydroxy vitamin d2 & 3 levels in a national bi-racial population ." Journal of Steroid Biochemistry and Molecular Biology. . (): -.
  • (PEER REVIEWED) Chan J, Jaceldo-Siegl K and Fraser GE . "Predictors of Serum Levels of 25 Hydroxyvitamin D in a National Bi-Racial Population.." American Journal of Epidemiology . (): -.