Hannelore Bennett

Effects of walnuts on serum lipid levels and blood pressure in normal men

BACKGROUND In a recent six-year follow-up study, we found that frequent consumption of nuts was associated with a reduced risk of ischemic heart disease. To explore possible explanations for this finding, we studied the effects of nut consumption on serum lipids and blood pressure. METHODS We randomly placed 18 healthy men on two mixed natural diets, each diet to be followed for four weeks. Both diets conformed to the National Cholesterol Education Program Step 1 diet and contained identical foods and macronutrients, except that 20 percent of the calories of one diet (the walnut diet) were derived from walnuts (offset by lesser amounts of fatty foods, meat, and visible fat [oils, margarine, and butter]). RESULTS With the reference diet, the mean (+/- SD) serum values for total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol were, respectively, 182 +/- 23, 112 +/- 16, and 47 +/- 11 mg per deciliter (4.71 +/- 0.59, 2.90 +/- 0.41, and 1.22 +/- 0.28 mmol per liter). With the walnut diet, the mean total cholesterol level was 22.4 mg per deciliter (0.58 mmol per liter) lower than the mean level with the reference diet (95 percent confidence interval, 28 to 17 mg per deciliter [0.72 to 0.44 mmol per liter]); the LDL and HDL cholesterol levels were, respectively, 18.2 mg per deciliter (0.47 mmol per liter) (P < 0.001) and 2.3 mg per deciliter (0.06 mmol per liter) (P = 0.01) lower. These lower values represented reductions of 12.4, 16.3, and 4.9 percent in the levels of total, LDL, and HDL cholesterol, respectively. The ratio of LDL cholesterol to HDL cholesterol was also lowered (P < 0.001) by the walnut diet. Mean blood-pressure values did not change during either dietary period. CONCLUSIONS Incorporating moderate quantities of walnuts into the recommended cholesterol-lowering diet while maintaining the intake of total dietary fat and calories decreases serum levels of total cholesterol and favorably modifies the lipoprotein profile in normal men. The long-term effects of walnut consumption and the extension of this finding to other population groups deserve further study.

Effect on Body Weight of a Free 76 Kilojoule (320 Calorie) Daily Supplement of Almonds for Six Months

Objective: Regular nut consumption is associated with lower rates of heart attack. However, as nuts are fatty foods, they may in theory lead to weight gain, although preliminary evidence has suggested otherwise. We tested the hypothesis that a free daily supplement (averaging 76 kJ) of almonds for six months, with no dietary advice, would not change body weight. Methods: Eighty-one male and female subjects completed the randomized cross-over study. During two sequential six-month periods, diet, body weight and habitual exercise were evaluated repeatedly in each subject. Almonds were provided only during the second period. The design was balanced for seasonal and other calendar trends. Results: During the almond feeding period, average body weight increased only 0.40 (kg) (p ∼ 0.09). The weight change depended on baseline BMI (p = 0.05), and only those initially in the lower BMI tertiles experienced small and mainly unimportant weight gains with the almonds. We estimated that 54% (recalls) or 78% (diaries) of the extra energy from almonds was displaced by reductions in other foods. The ratio unsaturated/saturated dietary fat increased by 40% to 50% when almonds were included in the diet. Conclusion: Incorporating a modest quantity (76 kJ) of almonds in the diet each day for six months did not lead on average to statistically or biologically significant changes in body weight and did increase the consumption of unsaturated fats. Further studies are necessary to evaluate longer term effects, especially in men.

Vegetarian Dietary Patterns and the Risk of Colorectal Cancers

IMPORTANCE Colorectal cancers are a leading cause of cancer mortality, and their primary prevention by diet is highly desirable. The relationship of vegetarian dietary patterns to colorectal cancer risk is not well established. OBJECTIVE To evaluate the association between vegetarian dietary patterns and incident colorectal cancers. DESIGN, SETTING, AND PARTICIPANTS The Adventist Health Study 2 (AHS-2) is a large, prospective, North American cohort trial including 96,354 Seventh-Day Adventist men and women recruited between January 1, 2002, and December 31, 2007. Follow-up varied by state and was indicated by the cancer registry linkage dates. Of these participants, an analytic sample of 77,659 remained after exclusions. Analysis was conducted using Cox proportional hazards regression, controlling for important demographic and lifestyle confounders. The analysis was conducted between June 1, 2014, and October 20, 2014. EXPOSURES Diet was assessed at baseline by a validated quantitative food frequency questionnaire and categorized into 4 vegetarian dietary patterns (vegan, lacto-ovo vegetarian, pescovegetarian, and semivegetarian) and a nonvegetarian dietary pattern. MAIN OUTCOMES AND MEASURES The relationship between dietary patterns and incident cancers of the colon and rectum; colorectal cancer cases were identified primarily by state cancer registry linkages. RESULTS During a mean follow-up of 7.3 years, 380 cases of colon cancer and 110 cases of rectal cancer were documented. The adjusted hazard ratios (HRs) in all vegetarians combined vs nonvegetarians were 0.78 (95% CI, 0.64-0.95) for all colorectal cancers, 0.81 (95% CI, 0.65-1.00) for colon cancer, and 0.71 (95% CI, 0.47-1.06) for rectal cancer. The adjusted HR for colorectal cancer in vegans was 0.84 (95% CI, 0.59-1.19); in lacto-ovo vegetarians, 0.82 (95% CI, 0.65-1.02); in pescovegetarians, 0.57 (95% CI, 0.40-0.82); and in semivegetarians, 0.92 (95% CI, 0.62-1.37) compared with nonvegetarians. Effect estimates were similar for men and women and for black and nonblack individuals. CONCLUSIONS AND RELEVANCE Vegetarian diets are associated with an overall lower incidence of colorectal cancers. Pescovegetarians in particular have a much lower risk compared with nonvegetarians. If such associations are causal, they may be important for primary prevention of colorectal cancers.

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)

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 deattenuated energy-adjusted correlations >or=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.

Race-specific validation of food intake obtained from a comprehensive FFQ: the Adventist Health Study-2.

OBJECTIVE To assess race-specific validity of food and food group intakes measured using an FFQ. DESIGN Calibration study participants were randomly selected from the Adventist Health Study-2 (AHS-2) cohort by church, and then by subject-within-church. Intakes of forty-seven foods and food groups were assessed using an FFQ and then compared with intake estimates measured using six 24 h dietary recalls (24HDR). We used two approaches to assess the validity of the questionnaire: (i) cross-classification by quartile and (ii) de-attenuated correlation coefficients. SETTING Seventh-day Adventist church members geographically spread throughout the USA and Canada. SUBJECTS Members of the AHS-2 calibration study (550 whites and 461 blacks). RESULTS The proportion of participants with exact quartile agreement in the FFQ and 24HDR averaged 46 % (range: 29-87 %) in whites and 44 % (range: 25-88 %) in blacks. The proportion of quartile gross misclassification ranged from 1 % to 11 % in whites and from 1 % to 15 % in blacks. De-attenuated validity correlations averaged 0·59 in whites and 0·48 in blacks. Of the forty-seven foods and food groups, forty-three in whites and thirty-three in blacks had validity correlations >0·4. CONCLUSIONS The AHS-2 questionnaire has good validity for most foods in both races; however, validity correlations tend to be higher in whites than in blacks.

Biomarkers of Dietary Intake Are Correlated with Corresponding Measures from Repeated Dietary Recalls and Food-Frequency Questionnaires in the Adventist Health Study-2

BACKGROUND Accurate assessment of diet in study populations is still a challenge. Some statistical strategies that use biomarkers of dietary intake attempt to compensate for the biasing effects of reporting errors. OBJECTIVE The objective was to correlate biomarkers of dietary intake with 2 direct measures of dietary intake. METHODS Subjects provided repeated 24-h dietary recalls and 2 food-frequency questionnaires (FFQs) separated by ∼3 y. Correlations between biomarkers and reported dietary intakes as measured by the recalls and FFQs were de-attenuated for within-person variability. The Adventist Health Study-2 (AHS-2) has a large database of biomarkers of dietary intake (blood, urine, adipose tissue) from a calibration study (909 analytic subjects) representing the cohort. Participants were black and non-black Adventists in the United States and Canada. RESULTS Dietary items with higher-valued de-attenuated correlations (≥0.50) between biomarkers and recalls included some fatty acids (FAs), the non-fish meats, fruit (non-black subjects), some carotenoids, vitamin B-12 (non-black subjects), and vitamin E. Moderately valued correlations (0.30-0.49) were found for very long chain ω-3 (n-3) FAs, some carotenoids, folate, isoflavones, cruciferous vegetables, fruit (black subjects), and calcium. The highest correlation values in non-black and black subjects were 0.69 (urinary 1-methyl-histidine and meat consumption) and 0.72 (adipose and dietary 18:2 ω-6), respectively. Correlations comparing biomarkers with recalls were generally similar for black and non-black subjects, but correlations between biomarkers and the FFQ were slightly lower than corresponding recall correlations. Correlations between biomarkers and a single FFQ estimate (the usual cohort situation) were generally much lower. CONCLUSIONS Many biomarkers that have relatively high-valued correlations with dietary intake were identified and were usually of similar value in black and non-black subjects. These may be used to correct effects of dietary measurement errors in the AHS-2 cohort, and in some cases they also provide evidence supporting the validity of the dietary data.

Reliability of Serum and Urinary Isoflavone Estimates

Sporadic intake and short half-lives of serum or urinary biomarkers may make serum and urinary isoflavones quite unreliable indicators of longer-term dietary soy intake. In 26 participants in the Adventist Health Study-2 (AHS-2) we obtained two measures of fasting morning serum isoflavones, 1–2 years apart. In another 76 subjects we obtained an overnight urine sample and six 24-h dietary recalls over a period encompassing the time of the urine sample. Intraclass correlations (ICC) values for serum isoflavones were 0.11 (log(daidzein)) and 0.28 (log(genistein)). Assuming that the correlation (true dietary intake, true urinary excretion) <0.90, it is shown that this implies an ICC for urinary estimates that exceeds 0.56. As expected, the previous day’s soy intake, and its timing, influenced the next morning’s serum levels. These results suggest that fasting morning serum isoflavone estimates will provide a poor index of long-term soy intake, but that overnight urinary estimates perform much better.

Recruiting and motivating black subjects to complete a lengthy survey in a large cohort study: an exploration of different strategies

BackgroundThe effectiveness of multiple innovative recruitment strategies for enrolling Black/African American participants to the Adventist Health Study-2 (AHS-2) is described. The study’s focus is diet and breast, prostate and colon cancer.MethodsPromotions centered on trust, relationship building and incentives for increasing enrollment and questionnaire return rate. Of the sub-studies described, one had a randomized control group, and the others, informal controls. The subjects are from all states of the U.S. and some provinces of Canada. The offer of a Black art piece, follow-up calls, a competitive tournament as well as other strategies accounted for nearly 3,000 additional returns even though they were often used in small subsets.ResultsFlexibility and multiple strategies proved advantageous in gaining the cooperation of Blacks, who are usually reluctant to participate in research studies.ConclusionsLessons learned during initial enrollment should help us retain our final Black cohort of 26,000, and obtain new information when required.