T.Elaine Prewitt

Maintenance of lower proportions of (n − 6) eicosanoid precursors in phospholipids of human plasma in response to added dietary (n − 3) fatty acids

Competition between the (n - 3) and (n - 6) types of highly unsaturated fatty acids can diminish the abundance of (n - 6) eicosanoid precursors in a tissue, which in turn can diminish the intensity of tissue responses that are mediated by (n - 6) eicosanoids. The mixture of 20- and 22-carbon highly unsaturated fatty acids maintained in the phospholipids of human plasma is related to the dietary intake of 18:2 (n - 6) and 18:3 (n - 3) by empirical hyperbolic equations in a manner very similar to the relationship reported for laboratory rats (Lands, W.E.M., Morris, A. and Libelt, B. (1990) Lipids 25, 505-516). Analytical results from volunteers ingesting self-selected diets showed an inter-individual variance for the proportion of (n - 6) eicosanoid precursors in the fatty acids of plasma phospholipids of about 5%, but the variance among multiple samples taken from the same individual throughout the day was less (about 3%), closer to the experimental variance of the analytical procedure (about 1%). The reproducibility of the results makes it likely that analysis of fatty-acid composition of plasma lipids from individuals will prove useful in estimating the diet-related tendency for severe thrombotic, arthritic or other disorders that are mediated by (n - 6) eicosanoids. Additional constants and terms were included in the equations to account for the effects of 20- and 22-carbon highly unsaturated (n - 3) fatty acids in the diet. A lower constant for the 20- and 22-carbon (n - 3) fatty acids compared to that for the 18-carbon (n - 3) fatty acid in decreasing the ability of dietary 18:2 (n - 6) to maintain 20:4 (n - 6) in tissue lipids confirmed the greater competitive effectiveness of the more highly unsaturated n - 3 fatty acids in the elongation/desaturation process. Also, a lower constant for direct incorporation of 20-carbon fatty acids of the n - 6 vs. the n - 3 type indicated a greater competitive effectiveness of 20:4 (n - 6) relative to 20:5 (n - 3) in reesterification after release from tissue lipids. The equations may be used in reverse to estimate the dietary intakes of the (n - 3) and (n - 6) fatty acids by using the composition of the fatty acids that had been maintained in plasma lipids.

Relative weight and mortality in U.S. blacks and whites: Findings from representative national population samples ☆

PURPOSE To examine the impact of relative weight on mortality in black and white men and women. METHODS Two representative national populations samples were used: the NHANES-I Epidemiologic Follow-up Study (NHEFS), and the National Health Interview Survey (NHIS). The principal analysis focused on 13,242 participants in the NHEFS and 114,954 in the NHIS. Minimum mortality was estimated from both categorical analysis and a logistic model. RESULTS Minimum mortality ranged from a body mass index (BMI) of 25 to 32 kg/m2. The model-estimated BMI of minimum mortality for NHEFS was 27.1 (24.8-29.4, 95% CI), 26.8 (24.7-28.9, 95% CI), 24.8 (23.8-25.9, 95% CI) and 24.3 (23.2-25.4, 95% CI); for black men, black women, white men and white women, respectively, whereas for NHIS the corresponding values were 30.2 (24.8-35.6, 95% CI) 26.4 (24.2-28.7, 95% CI), 27.1 (25.5-28.7, 95% CI), and 25.6 (24.2-27.0, 95% CI). In all groups the shape of the relative risk curve was virtually identical and a broad range of BMI values in the middle of the distribution was associated with low relative mortality risk. Averaging the results from both surveys, the observed BMI of minimum risk was 3.1 kg/m2 higher in black men and 1.5 kg/m2 higher in black women than in their white counterparts; when adjusted for covariates these differences were only of borderline statistical significance, however. CONCLUSIONS Because of the wide range of BMI values associated with low risk, and the consistency of the point of the up-turn in risk, group specific definitions of optimal values do not appear to be warranted.

Voluntary Participation and Informed Consent to International Genetic Research

OBJECTIVES We compared voluntary participation and comprehension of informed consent among individuals of African ancestry enrolled in similarly designed genetic studies of hypertension in the United States and Nigeria. METHODS Survey questionnaires were used to evaluate factors associated with voluntariness (the number of people volunteering) and understanding of the studys genetic purpose. A total of 655 individuals (United States: 348; Nigeria: 307) were interviewed after participation in the genetic studies. RESULTS Most US respondents (99%), compared with 72% of Nigerian respondents, reported being told the study purpose. Fewer than half of the respondents at both sites reported that the study purpose was to learn about genetic inheritance of hypertension. Most respondents indicated that their participation was voluntary. In the United States, 97% reported that they could withdraw, compared with 67% in Nigeria. In Nigeria, nearly half the married women reported asking permission from husbands to enroll in the hypertension study; no respondents sought permission from local elders to participate in the study. CONCLUSIONS Our findings highlight the need for more effective approaches and interventions to improve comprehension of consent for genetic research among ethnically and linguistically diverse populations in all settings.

The Influence of Cigarette Smoking on the Association between Body Weight and Mortality. The Framingham Heart Study Revisited

PURPOSE To calculate for two measures of obesity, the Metropolitan Relative Weight (MRW) and body mass index (BMI), the value at which minimum mortality occurs. This was done to retest the hypothesis, in the Framingham Heart Study data, that the association between obesity and mortality can be obscured by an interaction between the measure of obesity and smoking. In the original analysis of the Framingham data it was suggested that there was a U- or J-shaped relationship between MRW and death in smokers but a linear relationship in nonsmokers. The design and setting were those of the NHLBI Framingham Heart Study. METHODS The 5209 members of the Framingham Heart Study underwent a baseline examination in 1948-1952 (Exam 1) and they were reexamined at approximately two-year intervals over a 30-year period. The study included both men (n = 2336) and women (n = 2873) in the age range of 28 to 62 years. After excluding persons with missing baseline data, the analytic sample size was 5163. Additional analyses were conducted by deleting persons with cardiovascular disease (CVD) at baseline (n = 135), the sample used by the original paper by Garrison and colleagues, and persons who died within the first four years of follow-up (n = 62). The main outcome measures consisted of thirty-year survival through Exam 16, approximately in 1980, as influenced by MRW or BMI, age, and smoking status at baseline (Exam 1). RESULTS We were able to show that the sample sizes of male nonsmokers were too small to test the hypothesis within age groups < 40 and 40-49 years. In men ages 50-62 there was a significant age-adjusted quadratic relationship between BMI or MRW, and risk of death. The estimated BMI at the minimum risk of death for smokers (24.5) and nonsmokers (23.8) were not statistically different. Identical results were found for MRW (minimum: smokers = 112.5, nonsmokers = 111.4). In men and women ages 28-62 there appeared to be a u- or j-shaped relationship between the 30-year crude mortality rate and MRW. After excluding persons with missing data, CVD at baseline, and persons who died within the first four years of follow-up, the age adjusted estimated BMI value at the minimum risk of death was nearly identical for men and women and for smokers and nonsmokers (Men: smokers = 22.8, nonsmokers = 22.8; Women: smokers = 22.9, nonsmokers = 23.3). Additionally, the estimates of the minimum were always below the mean. Identical results were found without deleting persons with CVD at baseline and deaths in the first four years of follow-up. Identical results were found for MRW. CONCLUSIONS Reanalysis of the Framingham Heart Study data does not support the hypothesis that there is an interaction between smoking and measures of obesity. Moreover, the estimated BMI or MRW at the minimum risk of death was similar for men and women smokers and nonsmokers alike even after deleting prevalent cases of CVD and deaths within the first four years of follow-up.

One Size Fits All: Implications for Assessing Dietary Behavior

Accurate assessment of dietary behavior is central to the design, implementation, and evaluation of intervention programs aimed at behavior change, and use of an Eating Behaviors Questionnaire (EBQ) has been suggested for measuring dimensions of dietary fat behavior. The EBQ has proven useful in characterizing fat-related dietary patterns among middle-class, highly educated, highly motivated white women. To investigate the generalizability of the instrument, we provide findings from a community-based sample of 235 African-Americans in Maywood, Illinois, a middle-class working community outside Chicago. The sample consisted of 159 women and 76 men with an average age of 47.4 +/- 13.8 years for women and 48.1 +/- 12.1 years for men (mean +/- standard deviation; range, 18 to 87 years). The EBQ is based on four broad behavioral domains (ie, avoidance, modification, substitution, and replacement) associated with fat-related eating patterns. These behavioral domains are composed of specific dietary behaviors (factors). Using a scoring system that allowed all participants to be included in all analyses, we identified a set of factors characterizing eating patterns in our sample that differed from those reported previously. When the factors were converted to scales using unit scoring, the average value suggested a tendency toward a higher fat eating pattern. Results indicate that although behavioral domains appear to be constant across populations, fat-related eating patterns are not. These observations have implications for understanding the diversity of fat-related dietary patterns across groups and for planning appropriate behavior change strategies.

Nutrient intake, lipids, and lipoprotein cholesterols in black and white children: The lipid research clinics prevalence study☆☆☆

Our specific aim was to assess differences in nutrient intake and in lipids and lipoprotein cholesterols between blacks and whites in 259 black children (129 boys, 130 girls) and in 811 white children (424 boys, 387 girls) ages 5-19. The nutrient intake data were obtained by 24-hr recall from the Houston and Cincinnati Lipid Research Clinics. The fundamental nutrient differences between blacks and whites were in total calories and in calories per kilogram of body weight, both of which were uniformly and significantly lower among black than white boys and generally, but less consistently and significantly, lower among black than white girls. No racial differences in total cholesterol or cholesterol intake per kilogram body weight were observed. After statistically controlling for education of the head of household, there were no consistent significant racial differences in Quetelet index. There was no significant independent effect of education of head of household on the childrens caloric intake and racial differences in socioeconomic status did not appear to systematically account for differences in total energy intake. In aggregate, black children had lower triglyceride and very-low-density lipoprotein cholesterol levels, and higher levels of high-density lipoprotein cholesterol than whites; there were no significant differences by race in low-density lipoprotein cholesterol levels. Race was a significant independent explanatory variable for high-density lipoprotein cholesterol levels (higher in blacks) and for very-low-density lipoprotein and triglyceride levels (higher in whites) (P less than 0.005), after covariance adjusting for education of head of household, sex, age, Quetelet index, calories, saturated fat (g/day/kg body wt), and clinic. Lower caloric intake among blacks compared with whites, the major nutrient difference in the current study, did not account for differences in lipoprotein cholesterol levels between the two groups.