Validity and reproducibility of a food frequency interview in a Multi-Cultural Epidemiology Study

Methodology for adding glycemic index and glycemic load values to 24-hour dietary recall database

OBJECTIVES

We describe a method of adding the glycemic index (GI) and glycemic load (GL) values to the nutrient database of the 24-hour dietary recall interview (24HR), a widely used dietary assessment. We also calculated daily GI and GL values from the 24HR.

METHODS

Subjects were 641 healthy adults from central Massachusetts who completed 9067 24HRs. The 24HR-derived food data were matched to the International Table of Glycemic Index and Glycemic Load Values. The GI values for specific foods not in the table were estimated against similar foods according to physical and chemical factors that determine GI. Mixed foods were disaggregated into individual ingredients.

RESULTS

Of 1261 carbohydrate-containing foods in the database, GI values of 602 foods were obtained from a direct match (47.7%), accounting for 22.36% of dietary carbohydrate. GI values from 656 foods (52.1%) were estimated, contributing to 77.64% of dietary carbohydrate. The GI values from three unknown foods (0.2%) could not be assigned. The average daily GI was 84 (SD 5.1, white bread as referent) and the average GL was 196 (SD 63).

CONCLUSION

Using this methodology for adding GI and GL values to nutrient databases, it is possible to assess associations between GI and/or GL and body weight and chronic disease outcomes (diabetes, cancer, heart disease). This method can be used in clinical and survey research settings where 24HRs are a practical means for assessing diet. The implications for using this methodology compel a broader evaluation of diet with disease outcomes.

The influence of age on the effects of lifestyle modification and metformin in prevention of diabetes

BACKGROUND

The incidence of type 2 diabetes increases with age. It is unknown whether interventions to prevent diabetes are as effective in elderly persons as in younger adults.

METHODS

The Diabetes Prevention Program (DPP) demonstrated that an intensive lifestyle intervention (ILS) or metformin could prevent or delay diabetes. A predefined secondary outcome of DPP was to determine if treatment effects varied by age.

RESULTS

At baseline, participants aged 60-85 years were leaner and had the best insulin sensitivity and lowest insulin secretion compared to younger age groups. Diabetes incidence rates did not differ by age in the placebo group, but ILS was more effective with increasing age (6.3, 4.9, and 3.3 cases per 100 person-years, in the 25-44, 45-59, and 60-85 year age groups, respectively; p(trend) =.007). Participants aged 60-85 years had the most weight loss and metabolic equivalent (MET)-hours of physical activity. The metformin group showed a trend toward higher diabetes incidence among older participants (6.7, 7.7, and 9.3 cases per 100 person-years in the 25-44, 45-59, and 60-85 year age groups, respectively; p(trend) =.07); and diabetes risk increased with age (hazard ratio [age 60-85 vs 25-44] 1.63, p =.02), after adjusting for the greater weight loss in the 60-85 year age group.

CONCLUSIONS

Lifestyle modification was exceptionally effective in preventing diabetes in older individuals; this finding was largely explained by greater weight loss and physical activity. The limited effectiveness of metformin in older persons may reflect age-related differences in insulin action and secretion. A lifestyle modification program can be recommended for older individuals at high risk for type 2 diabetes.

Dairy, magnesium, and calcium intake in relation to insulin sensitivity: approaches to modeling a dose-dependent association

Dairy intake has been inversely associated with insulin resistance, which may be partly due to the specific effects of calcium and magnesium. Data from the Insulin Resistance Atherosclerosis Study (1992-1999) for 1,036 US adults without diabetes at baseline were examined to evaluate the cross-sectional association of habitual dairy, magnesium, and calcium intake with insulin sensitivity at baseline and after 5 years of follow-up. Insulin sensitivity was directly measured with a validated, 12-sample, insulin-enhanced, intravenous glucose tolerance test with minimal model analysis. Dietary intake was assessed by a validated food frequency interview, and dietary supplement dose was confirmed by reviewing the supplement label. Several statistical approaches were used to ensure appropriate modeling of the dose-dependent association. No association was found between dairy intake and insulin sensitivity (p=0.41); however, associations were positive for magnesium and calcium intake (p=0.016) after adjusting for demographic, nondietary lifestyle and dietary factors, and food groups. Furthermore, magnesium intake was associated with insulin sensitivity in a threshold fashion, with a Bayesian method-estimated threshold (325 mg) (beta=0.0607/100 mg, p=0.0008 for <325 mg of magnesium/day; and beta=-0.001/100 mg, p=0.82 for >or=325 mg of magnesium/day). This study suggests that magnesium and calcium intake specifically, but not dairy intake, is associated with insulin sensitivity.

Effect of weight loss with lifestyle intervention on risk of diabetes

OBJECTIVE

Diabetes Prevention Program (DPP) participants randomized to the intensive lifestyle intervention (ILS) had significantly reduced risk of diabetes compared with placebo participants. We explored the contribution of changes in weight, diet, and physical activity on the risk of developing diabetes among ILS participants.

RESEARCH DESIGN AND METHODS

For this study, we analyzed one arm of a randomized trial using Cox proportional hazards regression over 3.2 years of follow-up.

RESULTS

A total of 1,079 participants were aged 25-84 years (mean 50.6 years, BMI 33.9 kg/m(2)). Weight loss was the dominant predictor of reduced diabetes incidence (hazard ratio per 5-kg weight loss 0.42 [95% CI 0.35-0.51]; P < 0.0001). For every kilogram of weight loss, there was a 16% reduction in risk, adjusted for changes in diet and activity. Lower percent of calories from fat and increased physical activity predicted weight loss. Increased physical activity was important to help sustain weight loss. Among 495 participants not meeting the weight loss goal at year 1, those who achieved the physical activity goal had 44% lower diabetes incidence.

CONCLUSIONS

Interventions to reduce diabetes risk should primarily target weight reduction.

The influence of education in the validation process of a food frequency questionnaire for adults in Viçosa, Minas Gerais, Brazil

OBJECTIVE

To evaluate the educational influence in the relative validation of a semiquantitative food frequency questionnaire (FFQs) for adults in the city of Viçosa, Brazil.

DESIGN AND SUBJECTS

Four 24-h dietary recalls (reference method) were applied to a sample of 94 adults of both genders, at intervals of 1 month. At the end of the study, an FFQs consisting of 58 food items was also applied. Then, the individuals were divided into two main groups according to their educational level (lower and higher). The dietary data were calculated by the Diet Pro 4.0 software and analyzed according to differences of means or medians and Pearson's correlation coefficients. These coefficients were adjusted by the energy and corrected by the within-person variance for each educational group, considering the extreme quartiles of the data distribution.

RESULTS

The intake of energy and nutrients, based on the 24 h dietary recalls, was inferior for the lower educational group (P < 0.05). For the FFQs, just the protein and calcium intakes were statistically different, suggesting interference of the education variable in this assessment. Over estimations in the FFQs were identified in the analyses of means and medians for vitamin C and retinol intakes in the lower education group and for retinol in the higher education one. However, when evaluated by correlation coefficients non-adjusted and adjusted, they were well correlated. On the other hand, lipid (r = 0.34) and calcium (r = 0.13) coefficients of the group with less instruction showed beneath the desirable values, suggesting weak consistence of the estimates provided by the FFQs for these nutrients. Correlation means of r = 0.65 and 0.54 were found for the higher and lower educational groups, respectively.

CONCLUSIONS

The results indicate that FFQs showed acceptable performance on evaluating the habitual food consumption for most of the nutrients in the studied population. A tendency for better quantifications in the groups with higher education was observed, inferring its influence in the assessment of the dietary intake.

Dietary patterns are associated with biochemical markers of inflammation and endothelial activation in the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Dietary patterns may influence cardiovascular disease risk through effects on inflammation and endothelial activation.

OBJECTIVE

We examined relations between dietary patterns and markers of inflammation and endothelial activation.

DESIGN

At baseline, diet (food-frequency questionnaire) and concentrations of C-reactive protein (CRP), interleukin 6 (IL-6), homocysteine, soluble intercellular adhesion molecule-1 (sICAM-1), and soluble E selectin were assessed in 5089 nondiabetic participants in the Multi-Ethnic Study of Atherosclerosis.

RESULTS

Four dietary patterns were derived by using factor analysis. The fats and processed meats pattern (fats, oils, processed meats, fried potatoes, salty snacks, and desserts) was positively associated with CRP (P for trend < 0.001), IL-6 (P for trend < 0.001), and homocysteine (P for trend = 0.002). The beans, tomatoes, and refined grains pattern (beans, tomatoes, refined grains, and high-fat dairy products) was positively related to sICAM-1 (P for trend = 0.007). In contrast, the whole grains and fruit pattern (whole grains, fruit, nuts, and green leafy vegetables) was inversely associated with CRP, IL-6, homocysteine (P for trend < or = 0.001), and sICAM-1 (P for trend = 0.034), and the vegetables and fish pattern (fish and dark-yellow, cruciferous, and other vegetables) was inversely related to IL-6 (P for trend = 0.009). CRP, IL-6, and homocysteine relations across the fats and processed meats and whole grains and fruit patterns were independent of demographics and lifestyle factors and were not modified by race-ethnicity. CRP and homocysteine relations were independent of waist circumference.

CONCLUSIONS

These results corroborate previous findings that empirically derived dietary patterns are associated with inflammation and show that these relations in an ethnically diverse population with unique dietary habits are similar to findings in more homogeneous populations.

Nut and seed consumption and inflammatory markers in the multi-ethnic study of atherosclerosis

Nuts and seeds are rich in unsaturated fat and other nutrients that may reduce inflammation. Frequent nut consumption is associated with lower risk of cardiovascular disease and type 2 diabetes. The authors examined associations between nut and seed consumption and C-reactive protein, interleukin-6, and fibrinogen in the Multi-Ethnic Study of Atherosclerosis. This 2000 cross-sectional analysis included 6,080 US participants aged 45-84 years with adequate information on diet and biomarkers. Nut and seed consumption was categorized as never/rare, less than once/week, 1-4 times/week, and five or more times/week. After adjustment for age, gender, race/ethnicity, site, education, income, smoking, physical activity, use of fish oil supplements, and other dietary factors, mean biomarker levels in categories of increasing consumption were as follows: C-reactive protein-1.98, 1.97, 1.80, and 1.72 mg/liter; interleukin-6-1.25, 1.24, 1.21, and 1.15 pg/ml; and fibrinogen-343, 338, 338, and 331 mg/dl (all p's for trend < 0.01). Further adjustment for hypertension, diabetes, medication use, and lipid levels yielded similar results. Additional adjustment for body mass index moderately attenuated the magnitude of the associations, yielding borderline statistical significance. Associations of nut and seed consumption with these biomarkers were not modified by body mass index, waist:hip ratio, or race/ethnicity. Frequent nut and seed consumption was associated with lower levels of inflammatory markers, which may partially explain the inverse association of nut consumption with cardiovascular disease and diabetes risk.

Dietary glycemic index and glycemic load, carbohydrate and fiber intake, and measures of insulin sensitivity, secretion, and adiposity in the Insulin Resistance Atherosclerosis Study

OBJECTIVE

We studied the association of digestible carbohydrates, fiber intake, glycemic index, and glycemic load with insulin sensitivity (S(I)), fasting insulin, acute insulin response (AIR), disposition index, BMI, and waist circumference.

RESEARCH DESIGN AND METHODS

Data on 979 adults with normal (67%) and impaired (33%) glucose tolerance from the Insulin Resistance Atherosclerosis Study (1992-1994) were analyzed. Usual dietary intake was assessed via a 114-item interviewer-administered food frequency questionnaire from which nutrient intakes were estimated. Published glycemic index values were assigned to food items and average dietary glycemic index and glycemic load calculated per subject. S(I) and AIR were determined by frequently sampled intravenous glucose tolerance test. Disposition index was calculated by multiplying S(I) with AIR. Multiple linear regression modeling was employed.

RESULTS

No association was observed between glycemic index and S(I), fasting insulin, AIR, disposition index, BMI, or waist circumference after adjustment for demographic characteristics or family history of diabetes, energy expenditure, and smoking. Associations observed for digestible carbohydrates and glycemic load, respectively, with S(I), insulin secretion, and adiposity (adjusted for demographics and main confounders) were entirely explained by energy intake. In contrast, fiber was associated positively with S(I) and disposition index and inversely with fasting insulin, BMI, and waist circumference but not with AIR.

CONCLUSION

Carbohydrates as reflected in glycemic index and glycemic load may not be related to measures of insulin sensitivity, insulin secretion, and adiposity. Fiber intake may not only have beneficial effects on insulin sensitivity and adiposity, but also on pancreatic functionality.

Two ethnic-specific polymorphisms in the human Agouti-related protein gene are associated with macronutrient intake

BACKGROUND

The Agouti-related protein (AGRP), an appetite modulator, induces hyperphagia when administered intracerebroventricularly or when overexpressed in transgenic mice. Exogenous administration of AGRP in rodents predisposes to high fat and high sugar intakes.

OBJECTIVE

The objective was to examine the potential associations of 2 ethnic-specific polymorphisms in the AGRP gene (Ala67Thr in whites and -38C>T in blacks) in the Health, Risk Factors, Exercise Training, and Genetics (HERITAGE) Family Study.

DESIGN

We examined the effect of the 2 polymorphisms in the AGRP gene on self-reported macronutrient intakes in 478 white and 272 black participants in the HERITAGE Family Study.

RESULTS

Both AGRP polymorphisms showed a significant association with energy intake. In whites, a smaller proportion of total energy was derived from fat by the Ala67Thr heterozygotes (mean +/- SEM: 29.4 +/- 0.7%) than by the Ala67Ala homozygotes (31.5 +/- 0.5%; P = 0.009), mainly because of a lower intake of saturated (P = 0.06) and monounsaturated (P = 0.01) fats by the Ala67Thr heterozygotes. The percentage of energy from carbohydrates was 2.6% greater in the Ala67Thr heterozygotes (55.1 +/- 1.1%) than in the Ala67Ala homozygotes (52.5 +/- 0.6%; P = 0.03). In blacks, protein intake was associated with the -38C>T promoter polymorphism. T/T homozygotes had a significantly lower protein intake than did the C-allele carriers (C/C: 16.8 +/- 0.4%; C/T: 17.2 +/- 0.2%; T/T: 15.4 +/- 0.7%; P = 0.04). No significant differences in total energy and alcohol intakes existed between genotype groups in blacks or whites.

CONCLUSIONS

The present study suggests that 2 ethnic-specific AGRP variants, previously shown to be associated with leanness in the HERITAGE Family Study, are also associated with macronutrient intake.

Whole grain intake and insulin sensitivity: evidence from observational studies

Observational studies have found that diets rich in whole-grain foods are associated with improved insulin sensitivity. The improved insulin sensitivity may be mediated in part by magnesium and dietary fiber, two nutrients found in whole-grain foods. By incorporating whole-grain foods into the diet, therefore, insulin sensitivity might be improved.

The validity of questionnaire-based micronutrient intake estimates is increased by including dietary supplement use in Swedish men

Although many validation studies of FFQ have been reported, only a few addressed the effect of inclusion of dietary supplement use on the validity of micronutrient estimates. The purpose of the present study was to assess reproducibility and validity of a self-administered FFQ, intended to measure total nutrient intake from diet and from dietary supplements, in a random population-based sample of 248 middle-aged and elderly men (40-74 y old) in central Sweden. Fourteen 24-h recall interviews were used as the reference method. Participants were telephoned about once a month for 1 y, covering every day of the week, twice in random order. Spearman correlation coefficients increased 13% (from 0.49 to 0.62), between FFQ-based micronutrient estimates and the fourteen 24-h recall interviews (reference method) when supplement use was included. Correct classification into highest quintiles was also improved by 14% (from 37 to 51%). There were no differences in mean intraclass correlation coefficients for 1-y reproducibility between total micronutrient intake and micronutrients from foods only. The increase in the validity of micronutrient estimates due to inclusion of supplements in nutrient intake assessment has important implications for sample size in epidemiologic studies. Because a dramatic increase in dietary supplement use has occurred in recent decades in many countries, the issue of including supplements in dietary assessment should be of highest priority in nutritional epidemiologic studies of chronic diseases.

Validity and reproducibility of the food frequency questionnaire used in the Shanghai Women's Health Study

To evaluate the validity and reliability of the food frequency questionnaire (FFQ) used in the Shanghai Women's Health Study (SWHS), 200 SWHS participants were recruited for a dietary calibration study. Study participants completed an FFQ at baseline and 24-h dietary recalls (24-HDR) twice per month consecutively for 12 months. At the end of the study, a second FFQ was administered. Of the 200 study participants, 196 completed 24 or more days of 24-h dietary recalls, 191 completed two FFQs from whom the results of this report were based. The FFQ included the foods that accounted for 86% of the foods recorded in the 24-HDR surveys. Validity of the FFQ was evaluated by comparing intake levels of major nutrients and foods obtained from the second FFQ with those derived from the multiple 24-HDR. The median intake for major nutrients, rice, poultry and meat derived from the second FFQ and the 24-HDR was similar, with the differences ranging from 1.3 to 12.1%. The FFQ tended to overestimate the intake level of total vegetables and total fruits, and the differences were explained mainly by over-reporting seasonal vegetables and fruits consumption in the FFQ. Nutrient and food intake assessed by the FFQ and the multiple 24-HDR correlated very well, with the correlation coefficients being 0.59-0.66 for macronutrients, 0.41-0.59 for micronutrients, and 0.41-0.66 for major food groups. The reliability of the FFQ was assessed by comparing the correlation and median intake of nutrients and food groups obtained from the two FFQs that were administered approximately 2 y apart. The median intake levels for selected nutrients and food groups derived from the two FFQs were similar with differences below 10%. At the individual level, the intake levels of these dietary variables obtained from two FFQs also correlated well. When nutrient and food group intakes were categorized into quartiles, FFQ and 24-HDR produced exact agreement rates between 33 and 50%. Misclassification to adjacent quartile was common, ranging from 34-48%, while misclassification to an extreme quartile was rare (1-6%). These data indicate that the SWHS FFQ can reliably and accurately measure usual intake of major nutrients and food groups among women in Shanghai.

Differences between estimated caloric requirements and self-reported caloric intake in the women's health initiative

PURPOSE

To compare energy intake derived from a food frequency questionnaire (FFQ) with estimated energy expenditure in postmenopausal women participating in a large clinical study.

METHODS

A total of 161,856 women aged 50 to 79 years enrolled in the Women's Health Initiative (WHI) Observational Study (OS) or Clinical Trial (CT) [including the Diet Modification (DM) component] completed the WHI FFQ, from which energy intake (FFQEI) was derived. Population-adjusted total energy expenditure (PATEE) was calculated according to the Harris-Benedict equation weighted by caloric intakes derived from the National Health and Nutrition Examination Survey. Stepwise regression was used to examine the influence of independent variables (e.g., demographic, anthropometric) on FFQEI-PATEE. Race, region, and education were forced into the model; other variables were retained if they increased model explanatory ability by more than 1%.

RESULTS

On average, FFQEI was approximately 25% lower than PATEE. Regression results (intercept=-799 kcal/d) indicated that body mass index (b=-23 kcal/day/kg.m(-2)); age (b=15 kcal/day/year of age); and study arm (relative to women in the OS, for DM women b=169 kcal/d, indicating better agreement with PATEE) increased model partial R(2)>.01. Results for CT women not eligible for DM were similar to those of women in the OS (b=14 kcal/d). There also were apparent differences by race (b=-152 kcal/d in Blacks) and education (b=-67 kcal/d in women with<high school).

CONCLUSION

This large, carefully studied population confirms previous observations regarding underestimates in self-reported caloric intake relative to estimates of metabolic need in younger women, and those with higher weight, with less education, and in Blacks. These differences, along with effects related to intervention assignment, underline the need for additional research to enhance understanding of errors in dietary measurement.

Edentulism and nutritional status in a biracial sample of well-functioning, community-dwelling elderly: the health, aging, and body composition study

BACKGROUND

Edentulism may affect dietary intake in older adults, but the relation between edentulism and nutritional status is not completely understood.

OBJECTIVE

The present study examined whether edentulism is associated with nutritional status and whether there is an interaction between race and edentulism on nutritional status among well-functioning, community-dwelling elderly.

DESIGN

The study cohort included 3075 elderly aged 70-79 y (52% women, 42% black) in the Health, Aging, and Body Composition Study. Dietary intake, anthropometric variables, weight change, and serum albumin and lipid concentrations were compared between edentate and dentate participants by the use of multiple linear and logistic regressions.

RESULTS

Edentulism was not associated with total energy or food intake but was associated with the food groups consumed, particularly fat, micronutrients, and hard-to-chew foods. Edentulism was more strongly linked to dietary intake in whites than in blacks. Unlike black edentate elderly, white edentate elderly consumed significantly lower energy-adjusted amounts of vitamin A and beta-carotene, higher amounts of energy-adjusted total and saturated fat and cholesterol, and higher percentages of energy from fat than did white dentate elderly. Anthropometry and biochemical indexes were not significantly different by edentulism status in both races. Edentulism was associated with weight gains of >5% in 1 y in both races.

CONCLUSIONS

Edentulism was associated with differences in the nutritional status of well-functioning, community-dwelling elderly, more so in whites than blacks. Edentate elders may benefit from dental, medical, and nutrition interventions targeted to addressing these findings.

Food consumption patterns of rural older African American, Native American, and white adults in North Carolina

This paper describes the major food sources of selected nutrients for an ethnically diverse sample of older adults in rural North Carolina. A representative sample of 130 elders (> 70 years) completed semi-quantitative food frequency questionnaires. Percentages of foods most frequently consumed as the lead source of seven nutrients were calculated overall, by gender and ethnic group. Foods eaten at least one time per week were identified, and percentages of participants consuming that frequency were calculated. Major food sources included: salad oil/cooking oil for calories, total fat and saturated fat; miscellaneous vegetables for dietary fiber and folate; and orange/grapefruit juice for vitamin C. Heterogeneity in food sources was greatest for zinc and least for vitamin C. Variation across gender and ethnic groups was observed only in the degree to which specific food sources contributed to nutrient intake. These data provide greater insight into the dietary patterns of rural elders than examining nutrient intakes.

Whole-grain intake and insulin sensitivity: the Insulin Resistance Atherosclerosis Study

BACKGROUND

Increased intake of whole-grain foods has been related to a reduced risk of developing diabetes and heart disease. One underlying pathway for this relation may be increased insulin sensitivity.

OBJECTIVE

We assessed the relation between dietary intake of whole grain-containing foods and insulin sensitivity (S(I)).

DESIGN

We evaluated data from the Insulin Resistance Atherosclerosis Study (IRAS Exam I, 1992-1994). Usual dietary intakes in 978 middle-aged adults with normal (67%) or impaired (33%) glucose tolerance were ascertained by using an interviewer-administered, validated food-frequency questionnaire. Whole-grain intake (servings per day) was derived from dark breads and high-fiber and cooked cereals. S(I) was assessed by minimal model analyses of the frequently sampled intravenous-glucose-tolerance test. Fasting insulin was measured by using a radioimmunoassay. We modeled the relation of whole-grain intake to log(S(I) + 1) and to log(insulin) by using multivariable linear regression.

RESULTS

On average, IRAS participants consumed 0.8 servings of whole grains/d. Whole-grain intake was significantly associated with S(I) (beta = 0.082, P = 0.0005) and insulin (beta = -0.0646, P = 0.019) after adjustment for demographics, total energy intake and expenditure, smoking, and family history of diabetes. The addition of body mass index and waist circumference attenuated but did not explain the association with S(I). The addition of fiber and magnesium resulted in a nonsignificant association that is consistent with the hypothesis that these constituents account for some of the effect of whole grains on S(I).

CONCLUSION

Higher intakes of whole grains were associated with increases in insulin sensitivity.

Baseline fat-related dietary behaviors of white, Hispanic, and black participants in a cholesterol screening and education project in New England

OBJECTIVE

To examine baseline fat-related dietary behaviors of white, Hispanic, and black participants in Minimal Contact Education for Cholesterol Change, a National Institutes for Health-funded cholesterol screening and education project conducted in New England.

SUBJECTS

A sample of 9,803 participants who joined the study at baseline (n=7,817 white; n=1,425 Hispanic; and n=561 black).

METHODS

Participants completed baseline questionnaires that included demographic and psychosocial items as well as the Food Habits Questionnaire, a dietary assessment tool measuring fat-related dietary behaviors. They also had their blood cholesterol level and height and weight measured.

STATISTICAL ANALYSES

Analysis of variance (ANOVA) was used to compare racial/ethnic groups on continuous demographic variables, and the chi(2) test of association was used to compare groups on demographic categorical variables. Multivariate analysis of variance (MANOVA) was used to compare mean differences between racial/ethnic groups on six behavioral subscales (Fat Factors) differentiating domains of behavior related to fat intake and to compare 27 individual fat-related dietary behaviors.

RESULTS

After adjusting for sex, age, marital status, education, employment status, and percent time lived in the United States, white participants had the lowest Food Habits Questionnaire summary score (2.44) (indicating a lower fat diet), followed by Hispanic (2.61) and black (2.68) participants. The three ethnic groups also differed on the prevalence of Fat Factors and specific fat-related dietary behaviors. White participants were more likely to use lower-fat alternatives, to avoid frying, to replace meat, and to modify meat to make it lower in fat. However, they were least likely to eat fruits and vegetables for snacks and desserts. Hispanic participants were more likely to engage in fat-avoidance behaviors and to eat fruits and vegetables for snacks and desserts. Black participants were less likely to eat meatless meals and modify meats to make them lower in fat. Black and Hispanic participants were more likely than white participants to fry foods. Hispanics were less likely to read food labels for nutrition information. The most and least prevalent fat-related behaviors also differed by each ethnic group, showing that different behaviors were more and less easily implemented by each ethnic group.

CONCLUSIONS/APPLICATIONS

The results of this study suggest that there is a need for improvement in dietary behaviors related to fat intake, especially for blacks and Hispanics, and that the specific dietary behavior issues differ widely by ethnicity. These results can be used by nutrition educators and researchers to help them decide what messages to emphasize in dietary counseling, nutrition education programs, and materials. The results can also be used to help design better dietary assessment tools and more effective interventions for culturally diverse populations.

Differences in LDL oxidizability by glycemic status: the insulin resistance atherosclerosis study

OBJECTIVE

To investigate differences in LDL oxidizability by glycemic status within the Insulin Resistance Atherosclerosis Study cohort.

RESEARCH DESIGN AND METHODS

LDL oxidizability (lag time and oxidation rate) after exposure to copper was compared among 352 subjects with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), newly diagnosed type 2 diabetes, and known type 2 diabetes.

RESULTS

After adjustment for age, clinic, ethnicity, sex, and smoking status, LDL oxidation rates differed by glycemic status (P = 0.001), with a strong trend (P = 0.0001) for reduced LDL oxidation rate with increasing extent and duration of glucose intolerance (2,378 +/- 54, 2,208 +/- 65, 2,145 +/- 71, and 2,115 +/- 48 arbitrary units [mean +/- SE] for NGT, IGT, newly diagnosed type 2 diabetes, and known type 2 diabetes, respectively). Differences in LDL oxidation rate among groups were relatively unaltered by adjustment for lipids and lipoproteins, hypertension, BMI, and waist-to-hip ratio (WHR) and remained significant even after further adjustment for dietary antioxidants and fatty acids, as well as medications. LDL lag times differed marginally by glycemic status (P = 0.058), with similar values for NGT, IGT, and newly diagnosed type 2 diabetes (57-60 min) but higher values for known type 2 diabetes (65 +/- 2). These differences were eliminated by further adjustment for lipids and lipoproteins, hypertension, BMI, and WHR.

CONCLUSIONS

We found that glycemic status influenced LDL oxidizability, with a paradoxical reduction in LDL oxidizability, as indicated by a lower LDL oxidation rate with increased extent and duration of glucose intolerance. This difference was only slightly attenuated by adjustment for relevant demographic, metabolic, dietary, and pharmacological factors that potentially influence LDL oxidation.

Plasma and dietary vitamin E in relation to incidence of type 2 diabetes: The Insulin Resistance and Atherosclerosis Study (IRAS)

OBJECTIVE

To evaluate the association of vitamin E with incidence of type 2 diabetes and to do so separately among individuals who did and those who did not report regular use of vitamin supplementation.

RESEARCH DESIGN AND METHODS

The Insulin Resistance Atherosclerosis Study (IRAS) included 895 nondiabetic adults at baseline (including 303 with impaired glucose tolerance [IGT]), 148 of whom developed type 2 diabetes according to World Health Organization (WHO) criteria during the 5-year follow-up. At baseline, dietary vitamin E was estimated by a validated food frequency interview, usual supplement use was confirmed by supplement label, and plasma alpha-tocopherol was measured. Analyses were conducted separately for individuals who did (n = 318) and did not (n = 577) use vitamin E supplements.

RESULTS

Among supplement nonusers, reported mean intake of vitamin E (mg alpha-tocopherol equivalents [alpha-TE]) did not differ between those who remained nondiabetic (n = 490) and those who developed diabetes (n = 87) (10.5 +/- 5.5 vs. 9.5 +/- 4.8 [means +/- SD], respectively, NS). After adjustment for demographic variables, obesity, physical activity, and other nutrients, the association remained nonsignificant (odds ratio [OR] 0.80, 95% CI 0.13-5.06) for the highest level of intake (> or =20 mg alpha-TE) compared with the lowest level (1-4 alpha-TE). However, results for plasma concentration of alpha-tocopherol showed a significant protective effect both before and after adjustment for potential confounders (adjusted OR 0.12, 95% CI 0.02-0.68, for the highest quintile vs. the lowest quintile; overall test for trend, P < 0.01). Among individuals who reported habitual use of vitamin E supplements (at least once per month in the year before baseline; 259 remained nondiabetic and 59 developed diabetes), no protective effect was observed for either reported intake of vitamin E or plasma concentration of alpha-tocopherol

CONCLUSIONS

A protective effect of vitamin E may exist within the range of intake available from food. This effect may go undetected within studies of high-dose supplement use, which appears to hold no additional protective benefit.

Development, validation and utilisation of food-frequency questionnaires - a review

OBJECTIVE

The purpose of this review is to provide guidance on the development, validation and use of food-frequency questionnaires (FFQs) for different study designs. It does not include any recommendations about the most appropriate method for dietary assessment (e.g. food-frequency questionnaire versus weighed record).

METHODS

A comprehensive search of electronic databases was carried out for publications from 1980 to 1999. Findings from the review were then commented upon and added to by a group of international experts.

RESULTS

Recommendations have been developed to aid in the design, validation and use of FFQs. Specific details of each of these areas are discussed in the text.

CONCLUSIONS

FFQs are being used in a variety of ways and different study designs. There is no gold standard for directly assessing the validity of FFQs. Nevertheless, the outcome of this review should help those wishing to develop or adapt an FFQ to validate it for its intended use.

Quality of diets consumed by older rural adults

Older adults residing in rural communities are at risk for low dietary quality because of a variety of social, physical and environmental circumstances. Minority elders are at additional risk because of poorer health status and lower socioeconomic status. This study evaluated the food group intake of 130 older (>70 years) African American (34%), European American (36%), and Native American (30%) residents of two rural communities in central North Carolina. An interviewer-administered food frequency questionnaire was used to measure dietary intake. Food items were classified into food groups similar to the United States Department of Agriculture (USDA) Food Guide Pyramid and the National Cancer Institutes 5 A Day for Better Health program. None of the survey participants met minimum intake recommendations and most over-consumed fats, oils, sweets and snacks. African Americans and Native Americans consumed fewer servings of meats,fruits and vegetables, and fats, oils, sweets and snacks than European Americans. African American men consumed the fewest servings of fruits and vegetables of all gender/ethnic groups. Consumption of fats, oils and sweets was greatest among those 85 years and older and was more common among denture users. National strategies to educate the public about the importance of consuming a varied diet based on the recommendations presented in national nutrition education campaigns may not be reaching older adults in rural communities, particularly minority group members.

Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin

BACKGROUND

Type 2 diabetes affects approximately 8 percent of adults in the United States. Some risk factors--elevated plasma glucose concentrations in the fasting state and after an oral glucose load, overweight, and a sedentary lifestyle--are potentially reversible. We hypothesized that modifying these factors with a lifestyle-intervention program or the administration of metformin would prevent or delay the development of diabetes.

METHODS

We randomly assigned 3234 nondiabetic persons with elevated fasting and post-load plasma glucose concentrations to placebo, metformin (850 mg twice daily), or a lifestyle-modification program with the goals of at least a 7 percent weight loss and at least 150 minutes of physical activity per week. The mean age of the participants was 51 years, and the mean body-mass index (the weight in kilograms divided by the square of the height in meters) was 34.0; 68 percent were women, and 45 percent were members of minority groups.

RESULTS

The average follow-up was 2.8 years. The incidence of diabetes was 11.0, 7.8, and 4.8 cases per 100 person-years in the placebo, metformin, and lifestyle groups, respectively. The lifestyle intervention reduced the incidence by 58 percent (95 percent confidence interval, 48 to 66 percent) and metformin by 31 percent (95 percent confidence interval, 17 to 43 percent), as compared with placebo; the lifestyle intervention was significantly more effective than metformin. To prevent one case of diabetes during a period of three years, 6.9 persons would have to participate in the lifestyle-intervention program, and 13.9 would have to receive metformin.

CONCLUSIONS

Lifestyle changes and treatment with metformin both reduced the incidence of diabetes in persons at high risk. The lifestyle intervention was more effective than metformin.

The effect of social desirability trait on self-reported dietary measures among multi-ethnic female health center employees

PURPOSE

To evaluate the effect of social desirability trait, the tendency to respond in a manner consistent with societal expectations, on self-reported fruit, vegetable, and macronutrient intake.

METHODS

A 61-item food frequency questionnaire (FFQ), 7-item fruit and vegetable screener, and a single question on combined fruit and vegetable intake were completed by 132 female employees at five health centers in eastern Massachusetts. Intake of fruit and vegetables derived from all three methods and macronutrients from the FFQ were fit as dependent variables in multiple linear regression models (overall and by race/ethnicity and education); independent variables included 3-day mean intakes derived from 24-hour recalls (24HR) and score on the 33-point Marlowe-Crowne Social Desirability scale (the regression coefficient for which reflects its effect on estimates of dietary intake based on the comparison method relative to 24HR).

RESULTS

Results are based on the 93 women with complete data and FFQ-derived caloric intake between 450 and 4500 kcal/day. In women with college education, FFQ-derived estimates of total caloric were associated with under-reporting by social desirability trait (e.g., the regression coefficient for total caloric intake was -23.6 kcal/day/point in that group versus 36.1 kcal/day/point in women with education less than college) (difference = 59.7 kcal/day/point, 95% confidence interval (CI) = 13.2, 106.2). Except for the single question on which women with college education tended to under-report (difference =.103 servings/day/point, 95% CI = 0.003, 0.203), there was no association of social desirability trait with self-reported fruit and vegetable intake.

CONCLUSIONS

The effect of social desirability trait on FFQ reports of macronutrient intake appeared to differ by education, but not by ethnicity or race. The results of this study may have important implications for epidemiologic studies of diet and health in women.

Insulin secretion, obesity, and potential behavioral influences: results from the Insulin Resistance Atherosclerosis Study (IRAS)

BACKGROUND

This work was conducted to evaluate associations of insulin secretion with overall and central obesity, dietary fats, physical activity, and alcohol.

METHODS

A frequently sampled intravenous glucose tolerance test (FSIGT) was used to assess acute insulin response to glucose (AIR) and insulin sensitivity (S(I)) among adult participants (n=675 with normal, NGT; n=332 with impaired glucose tolerance, IGT) in the Insulin Resistance Atherosclerosis Study (IRAS). Disposition index (DI) was calculated as the sum of the log-transformed AIR and S(I) to reflect pancreatic compensation for insulin resistance. Obesity was measured as body mass index (kg/m(2), BMI) and central fat distribution by waist circumference (cm). Dietary fat intake (total, saturated, polyunsaturated, oleic acid), physical activity, and alcohol intake were assessed by standardized interview.

RESULTS

In unadjusted analyses, BMI and waist were each positively correlated with AIR among NGTs (r=0.26 and 0.23, respectively; p<0.0001) but correlations were weaker among the IGTs (r=0.10, NS; r=0.13, p<0.05 for BMI and waist, respectively). BMI and waist were inversely correlated with DI among NGTs (r=-0.13 and -0.20, respectively; p<0.0001) and among IGTs (r=-0.20 and -0.19, respectively, p<0.0001). Dietary fat variables were positively related, and alcohol was inversely related, to AIR among NGTs (p<0.01) but not among IGTs. With all factors considered simultaneously in a pooled analysis of IGTs and NGTs, waist, but not BMI, was positively associated with AIR (p<0.001) and inversely associated with DI (p<0.01). None of the behavioral variables were independently related to either outcome.

CONCLUSION

Among non-diabetic patients, central obesity appears to be related to higher insulin secretion, but to lower capacity of the pancreas to respond to the ambient insulin resistance.

Vitamin and mineral supplement use by older rural adults

BACKGROUND

Vitamin and mineral supplement products are widely consumed by older adults. This study describes supplement product use in a multiethnic rural population, relates supplement usage to dietary nutrient intake, and determines predictors of supplement usage.

METHODS

Data are from a population-based sample of 130 community-dwelling adults aged 70 years and older in two rural North Carolina counties. The sample was 34% African American, 36% European American, and 30% Native American. Interviewer-administered semiquantitative food frequency questionnaires were used to obtain data on usual diet and supplement use. In-home interviews allowed verification of supplement composition. Intakes from diet and supplement products were examined for vitamins A, E, B6, C, folate, iron, zinc, and calcium.

RESULTS

Of those who participated in the study, 47% reported using one or more supplement products. African Americans were significantly less likely to take supplements than Native Americans or European Americans. Based on dietary intakes, 65% of the participants were deficient (<2/3 recommended dietary allowance [RDA]) for at least one nutrient. The use of supplement products for the eight nutrients investigated was not related to dietary nutrient deficiency. For all nutrients investigated, except iron and calcium, a greater proportion of those without dietary deficiency took a supplement product than those with deficiency. Using logistic regression, ethnicity (European American and Native American), and gender (women) were significant predictors of supplement use.

CONCLUSIONS

These findings suggest that although both dietary deficiencies of vitamins and minerals and supplement use are relatively high in this population, there is no association between supplement use and deficient dietary intakes for the eight nutrients examined. Health care providers should be aware that nutritional counseling and guidance on appropriate supplement usage is needed in this population.