A Seventh-day Adventist Organization

Research Abstracts

Our postdoctoral fellows are currently working on several research topics. Some of their works have been submitted to scientific journals (in press), some are still being edited, and some have been published. Please note that some of these have not been peer-reviewed and some things may change slightly.

You may read the abstracts below.

Vegetarian Diet and the Incidence of Cancer in a Low-Risk Population

PRELIMINARY FINDINGS

Yessenia  Tantamango-Bartley, Karen Jaceldo-Siegl, Jing Fan, Gary Fraser   

Background

Cancer is the second leading cause of death in the U.S. Dietary factors account for at least 30% of all cancers in Western countries. Since people do not consume individual foods but rather combination of them, the assessment of dietary patterns may offer valuable information when determining associations between diet and cancer risk.

Methods

We examined the association between dietary patterns (non-vegetarians, lacto, pesco, vegan, and semi-vegetarian) and the overall cancer incidence among 69,120 participants of the Adventist Health Study-2. Cancer cases were identified by matching to cancer registries. Cox-proportional hazard regression analysis was performed to estimate hazard ratios, with “age-attained” as the primary time variable. 

Results

2,939 cancer cases were identified. The multivariate HR of overall cancer risk among vegetarians compared to non-vegetarians was statistically significant (HR=0.92;95%CI:0.85, 0.99) for both genders combined. Also, a statistically significant association was found between vegetarian diet and cancers of the gastrointestinal tract (HR=0.76; 95%CI: 0.63, 0.90). When analyzing the association of specific vegetarian dietary patterns, vegan diets showed statistically protection for overall cancer incidence (HR=0.84; 95%CI: 0.72, 0.99) in both genders combined and for female-specific cancers (HR=0.66; 95%CI:0.47, 0.92). Lacto-ovo-vegetarians appeared to be associated with decreased risk of cancers of the gastrointestinal system (HR=0.75; 95%CI: 0.60, 0.92).

Conclusion

Vegetarian diets seem to confer protection against cancer. Impact: Vegan diet seems to confer lower risk for overall and female-specific cancer compared to other dietary patterns. The lacto-ovo-vegetarian diets seem to confer protection from cancers of the gastrointestinal tract.


Vegetarian Diet Patterns and Mortality: Early Findings from Adventist Health Study 2

PRELIMINARY FINDINGS

Michael Orlich, Pramil Singh, Joan Sabate, Jing Fan, Gary Fraser   

Background

The relationship of vegetarian diet patterns to mortality remains uncertain, previous studies having yielded conflicting results.

Methods

Adventist Health Study-2 (AHS-2) is a cohort of 96,414 Seventh-day Adventists (SDAs) recruited between 2002 and 2007. Diets were classified into five patterns: vegan, lacto-ovo vegetarian, pesco vegetarian, semivegetarian and nonvegetarian. Proportional hazard regression was used to analyze the relationship of these diets to mortality through 2009, with attained age as the time variable and controlling for sex, race, income, marital status, smoking, alcohol, exercise, sleep, years as SDA, and in women: menopause and hormone replacement.

Results

Compared to nonvegetarians, pesco vegetarians had lower risk of all-cause mortality—hazard ratio (HR) 0.87 with 95% confidence interval (CI) (0.78-0.96)—but not CVD mortality or cancer mortality. Lacto-ovo vegetarians did not have an overall reduction in mortality; however, analysis revealed a significant interaction between diet and attained age for lacto-ovo vegetarians, but not for the other diet patterns. Lacto-ovo vegetarians had a reduced mortality risk up to approximately age 70. At the mean attained age of 64.3 years, the HR (95% CI) for lacto-ovo vegetarians was 0.85 (0.75-0.96) for all-cause mortality and 0.73 (0.57-0.93) for CVD mortality. No significant association with mortality was demonstrated for vegans or semivegetarians.

Conclusion

Preliminary results suggests an association between the pesco vegetarian diet and reduced mortality and between the lacto-ovo vegetarian diet and reduced mortality at younger ages (i.e., less than 70 years).


Utilization of Colorectal Cancer Screening in Persons with Different Dietary Patterns

PRELIMINARY FINDINGS

Yermek Ibrayev, Keiji Oda, Synnove Knutsen,Gary Fraser 

Background

Although several studies have investigated the association between some predictors (BMI, religious activity, impact of medical insurance’s recommendations) and the probability of utilization of cancer screening, data on dietary associations are meager. Furthermore, different attitudes to screening can possibly affect self-reported cancer incidence estimation in population studies.

Methods

Using multivariable ordinal logistic regression, we studied self-reported cancer screening utilization (colonoscopy and/or FOBT) within the last 0-4 and 5+ years vs. never among 52,967 subjects aged 50+ from the Adventist Health Study-2 cohort, with different dietary and lifestyle characteristics.

Results

Colonoscopy and fecal occult blood test (FOBT) are considered important screening methods for early detection of colorectal cancer. Vegetarians were less likely to report screening: vegans, odds ratio (OR) = 0.53 (95% confidence interval 0.49-0.57); lacto-ovo vegetarians (0.86, 0.82-0.90); pesco vegetarians (0.90, 0.84-0.96); and semivegetarians (0.96, 0.88-1.05) compared to nonvegetarians. Blacks were more likely than non-Blacks to be screened (1.22, 1.16-1.28) and males were less likely than females (0.91, 0.87-0.95). These findings with respect to diet were unchanged when stratifying by race and on demographic factors. Education and personal income were positively associated with recent screening, with ORs increasing from 0.62 to 1.22 and 0.81 to 1.10, respectively. Also for BMI, ORs increased from 0.85 (BMI=16-19.9) to 1.14 (BMI>30). Older subjects were more likely to be screened: OR=1.74, 2.11 and 1.66 for ages 60-69, 70-79, and 80+, respectively, compared to those aged 50-59. Unmarried and divorced/widowed subjects were less likely to screen (OR=0.75 and 0.85 respectively). Family history of colorectal and other cancers were associated with more frequent testing, OR=1.50 and 1.21, respectively.

Conclusion

In this low risk population of Adventists with focus on healthy lifestyle, we found that individual screening behaviors varied significantly. Lower screening rates in vegetarians were independent of income, education and BMI. Higher colorectal cancer screening use in the Black population was not anticipated and needs further study.


Utilization of Prostate Cancer Screening in Persons with Different Dietary Patterns

PRELIMINARY FINDINGS

Yermek Ibrayev, Keiji Oda, Synnove Knutsen, Gary Fraser  

Background

Although several studies have investigated the association between some predictors (BMI, religious activity, impact of medical insurance’s recommendations) and the probability of utilization of cancer screening, data on dietary associations are meager. Furthermore, different attitudes to screening can possibly affect self-reported cancer incidence estimation in population studies.

Methods

Using multivariable logistic regression, we investigated self-reported prostate cancer screening utilization (PSA blood test and/or Digital Rectal Exam) within the last 2 years vs. never and 5+ years among 18,373 men, aged 50+ years, from the Adventist Health Study-2 cohort, with different dietary patterns and lifestyle characteristics.

Results

Prostate-specific antigen test and digital rectal examination, despite some limitation, are considered important screening methods for early detection of prostate cancer. Blacks were more likely to be screened for prostate cancers compared to non-Blacks: odds ratio (OR) = 1.25 (1.13-1.39). Interaction between race and diet patterns was found in the prostate cancer screening utilization. After stratification by race, among non-Blacks vegetarians were less likely to have been screened: vegans, OR=0.48 (0.41-0.55); lacto-ovo vegetarians, OR=0.80 (0.72-0.87); and pesco vegetarians, OR=0.85 (0.72-0.99), compared to nonvegetarians. Education and annual personal income up to $75k were positively associated with recent screening with ORs increasing from 0.56 to 1.36 and 0.55 to 1.12, respectively [p(trend) for both <0.001]. Also for BMI, ORs increased from 0.67 (BMI=16-19) to 1.18 (BMI=25-29) to 1.34 (BMI>30) [p(trend)<0.001] compared to normal weight. Screening rates increased with age: OR=1.81, 2.39 and 1.88 for ages 60-69, 70-79, and 80+ respectively [p(trend) <0.001] compared to those aged 50-59. Unmarried and divorced/widowed men were less likely to use screening services (OR=0.52 and 0.66 respectively). Family history of prostate cancer and other cancers were associated with more frequent testing, OR=1.38 and 1.17 respectively. These trends remained unchanged after stratification on demographic variables.

Conclusion

In this low risk population of Adventists with focus on healthy lifestyle, we found that individual screening behaviors varied significantly. For Blacks there was no significant association between diet patterns and prostate cancer screening except among normal weight Blacks. For non-Blacks, vegetarians were less likely to screen.


Short- and long-term recall of vegetarian dietary patterns among participants of the Adventist Health Study-2: Is it reliable?

PRELIMINARY FINDINGS

Marcia Martins, Karen Jaceldo-Siegl, Gary Fraser

Background

Remote dietary patterns may be more important than recent dietary patterns in the etiology of chronic diseases because of the long latency in their development. 

Methods

We developed an instrument to recall vegetarian dietary patterns during the lifetime and examined its reliability of recall over 5.3 and 32.2 years on average. The short-term/5-year recall ability study (5-RAS) was done using 24,690 participants from the cohort of the Adventist Health Study-2 (AHS-2). The long-term/32-year recall ability study (32-RAS) included an overlap population of 1,721 individuals who joined the Adventist Health Study-1 (AHS-1) and AHS-2.

Results

Spearman correlation coefficients were 0.78 and 0.72 for 5-RAS and 32-RAS, respectively. In both studies, sensitivity and positive predictive values (PPV) were higher for the lacto-ovo vegetarian and nonvegetarian patterns. In the 5-RAS male, non-black, younger, and more educated participants, lifetime Adventists and those with more stability of consumption of animal products showed higher recall ability. Somewhat similar tendencies were shown for the 32-RAS. 

Conclusion

Our findings show that the instrument to recall vegetarian dietary patterns has good short- and long-term recall reliability for lacto-ovo vegetarian and nonvegetarian patterns. Short-term recall reliability was also good for the vegan pattern, while pesco vegetarian and semivegetarian patterns had lower short- and long-term recall reliability.