Barbara H. Dennis

Nutrient intakes of middle-aged men and women in China, Japan, United Kingdom, and United States in the late 1990s: the INTERMAP study

The purpose of the study was to compare nutrient intakes among Chinese, Japanese, UK, and US INTERMAP samples, and assess possible relationships of dietary patterns to differential patterns of cardiovascular diseases between East Asian and Western countries. Based on a common Protocol and Manuals of Operations, high-quality dietary data were collected by four standardized 24-h dietary recalls and two 24-h urine collections from 17 population samples in China (three samples), Japan (four samples), UK (two samples), and USA (eight samples). There were about 260 men and women aged 40–59 years per sample—total N=4680. Quality of dietary interview and data entry were monitored and enhanced by extensive systematic ongoing quality control procedures at local, country, and international level. Four databases on nutrient composition of foods from the four countries were updated and enhanced (76 nutrients for all four countries) by the Nutrition Coordinating Center, University of Minnesota, in cooperation with Country Nutritionists. The mean body mass index was much higher for Western than East Asian samples. Macronutrient intakes differed markedly across these samples, with Western diet higher in total fat, saturated and trans fatty acids, and Keys dietary lipid score, lower in total carbohydrate and starch, higher in sugars. Based on extensive published data, it is a reasonable inference that this pattern relates to higher average levels of serum total cholesterol and higher mortality from coronary heart disease in Western than East Asian populations. The rural Chinese diet was lower in protein, especially animal protein, in calcium, phosphorus, selenium, and vitamin A. Dietary sodium was higher, potassium lower, hence Na/K ratio was higher in the Asian diet, especially for Chinese samples. This pattern is known to relate to risks of adverse blood pressure level and stroke. At the end of the 20th century, East Asian and Western diets remain significantly different in macro- and micronutrient composition. Both dietary patterns have aspects that can be regarded, respectively, as adverse and protective in relation to the major adult cardiovascular diseases. In both Asian and Western countries, public efforts should be targeted at overcoming adverse aspects and maintaining protective patterns for prevention and control of cardiovascular diseases.

Effects of Reducing Dietary Saturated Fatty Acids on Plasma Lipids and Lipoproteins in Healthy Subjects: The Delta Study, Protocol 1

Few well-controlled diet studies have investigated the effects of reducing dietary saturated fatty acid (SFA) intake in premenopausal and postmenopausal women or in blacks. We conducted a multicenter, randomized, crossover-design trial of the effects of reducing dietary SFA on plasma lipids and lipoproteins in 103 healthy adults 22 to 67 years old. There were 46 men and 57 women, of whom 26 were black, 18 were postmenopausal women, and 16 were men > or =40 years old. All meals and snacks, except Saturday dinner, were prepared and served by the research centers. The study was designed to compare three diets: an average American diet (AAD), a Step 1 diet, and a low-SFA (Low-Sat) diet. Dietary cholesterol was constant. Diet composition was validated and monitored by a central laboratory. Each diet was consumed for 8 weeks, and blood samples were obtained during weeks 5 through 8. The compositions of the three diets were as follows: AAD, 34.3% kcal fat and 15.0% kcal SFA; Step 1, 28.6% kcal fat and 9.0% kcal SFA; and Low-Sat, 25.3% kcal fat and 6.1% kcal SFA. Each diet provided approximately 275 mg cholesterol/d. Compared with AAD, plasma total cholesterol in the whole group fell 5% on Step 1 and 9% on Low-Sat. LDL cholesterol was 7% lower on Step 1 and 11% lower on Low-Sat than on the AAD (both P<.01). Similar responses were seen in each subgroup. HDL cholesterol fell 7% on Step 1 and 11% on Low-Sat (both P<.01). Reductions in HDL cholesterol were seen in all subgroups except blacks and older men. Plasma triglyceride levels increased approximately 9% between AAD and Step 1 but did not increase further from Step 1 to Low-Sat. Changes in triglyceride levels were not significant in most subgroups. Surprisingly, plasma Lp(a) concentrations increased in a stepwise fashion as SFA was reduced. In a well-controlled feeding study, stepwise reductions in SFA resulted in parallel reductions in plasma total and LDL cholesterol levels. Diet effects were remarkably similar in several subgroups of men and women and in blacks. The reductions in total and LDL cholesterol achieved in these different subgroups indicate that diet can have a significant impact on risk for atherosclerotic cardiovascular disease in the total population.

INTERMAP : background, aims, design, methods, and descriptive statistics (nondietary)

Blood pressure (BP) above optimal (⩽120/⩽80 mmHg) is established as a major cardiovascular disease (CVD) risk factor. Prevalence of adverse BP is high in most adult populations; until recently research has been sparse on reasons for this. Since the 1980s, epidemiologic studies confirmed that salt, alcohol intake, and body mass relate directly to BP; dietary potassium, inversely. Several other nutrients also probably influence BP. The DASH feeding trials demonstrated that with the multiple modifications in the DASH combination diet, SBP/DBP (SBP: systolic blood pressure, DBP: diastolic blood pressure) was sizably reduced, independent of calorie balance, alcohol intake, and BP reduction with decreased dietary salt. A key challenge for research is to elucidate specific nutrients accounting for this effect. The general aim of the study was to clarify influences of multiple nutrients on SBP/DBP of individuals over and above effects of Na, K, alcohol, and body mass. Specific aims were, in a cross-sectional epidemiologic study of 4680 men and women aged 40–59 years from 17 diverse population samples in China, Japan, UK, and USA, test 10 prior hypotheses on relations of macronutrients to SBP/DBP and on role of dietary factors in inverse associations of education with BP; test four related subgroup hypotheses; explore associations with SBP/DBP of multiple other nutrients, urinary metabolites, and foods. For these purposes, for all 4680 participants, with standardized high-quality methods, assess individual intake of 76 nutrients from four 24-h dietary recalls/person; measure in two timed 24-h urine collections/person 24-h excretion of Na, K, Ca, Mg, creatinine, amino acids; microalbuminuria; multiple nutrients and metabolites by nuclear magnetic resonance and high-pressure liquid chromatography. Based on eight SBP/DBP measurements/person, and data on multiple possible confounders, utilize mainly multiple linear regression and quantile analyses to test prior hypotheses and explore relations of multiple dietary and urinary variables to SBP/DBP of individuals.The 4680 INTERMAP participants are equally divided across four age/gender strata: diverse in ethnicity, education, occupation, physical activity; use of cigarettes, alcohol; diagnosed high BP, CVD, diabetes; CVD family history; women vary in parity, use of contraceptive medication and hormone replacement therapy.

INTERMAP: the dietary data--process and quality control.

The aim of this report is to describe INTERMAP standardized procedures for assessing dietary intake of 4680 individuals from 17 population samples in China, Japan, UK and USA: Based on a common Protocol and Manuals of Operations, standardized collection by centrally trained certified staff of four 24 h dietary recalls, two timed 24-h urines, two 7-day histories of daily alcohol intake per participant; tape recording of all dietary interviews, and use of multiple methods for ongoing quality control of dietary data collection and processing (local, national, and international); one central laboratory for urine analyses; review, update, expansion of available databases for four countries to produce comparable data on 76 nutrients for all reported foods; use of these databases at international coordinating centres to compute nutrient composition. Chinese participants reported 2257 foods; Japanese, 2931; and UK, 3963. In US, use was made of 17 000 food items in the online automated Nutrition Data System. Average time/recall ranged from 22 min for China to 31 min for UK. Among indicators of dietary data quality, coding error rates (from recoding 10% random samples of recalls) were 2.3% for China, 1.4% for Japan, and UK; an analogous US procedure (re-entry of recalls into computer from tape recordings) also yielded low discrepancy rates. Average scores on assessment of taped dietary interviews were high, 40.4 (Japan) to 45.3 (China) (highest possible score: 48); correlations between urinary and dietary nutrient values—similar for men and women—were, for all 4680 participants, 0.51 for total protein, range across countries 0.40–0.52; 0.55 for potassium, range 0.30–0.58; 0.42 for sodium, range 0.33–0.46. The updated dietary databases are valuable international resources. Dietary quality control procedures yielded data generally indicative of high quality performance in the four countries. These procedures were time consuming. Ongoing recoding of random samples of recalls is deemed essential. Use of tape recorded dietary interviews contributed to quality control, despite feasibility problems, deemed remediable by protocol modification. For quality assessment, use of correlation data on dietary and urinary nutrient values yielded meaningful findings, including evidence of special difficulties in assessing sodium intake by dietary methods.

Blood Pressure Differences Between Northern and Southern Chinese: Role of Dietary Factors: The International Study on Macronutrients and Blood Pressure

Blood pressure and prevalence of high blood pressure are greater for northern than southern Chinese. Reasons for these differences are unclear. Relationships of north–south blood pressure differences with multiple dietary factors were investigated in 839 Chinese participants, International Study on Macronutrients and Blood Pressure (INTERMAP), 561 northern, 278 southern, aged 40 to 59 years. Daily nutrient intakes were determined from four 24-hour dietary recalls and 2 timed 24-hour urine collections. Average systolic/diastolic pressure levels were 7.4/6.9 mm Hg higher for northern than southern participants. Southern participants had lower body mass index, sodium intake, sodium/potassium ratio, and higher intake of calcium, magnesium, phosphorus, and vitamins A and C. Considered singly, with control for age and gender, several dietary variables (eg, body mass index, urinary sodium/potassium ratio, urinary sodium, dietary phosphorus, and magnesium) reduced north–south blood pressure differences by ≥10%. Controlled for age and gender, nondietary variables had little effect on north–south blood pressure differences. With inclusion in regression models of multiple dietary variables (sodium, potassium, magnesium or phosphorus, body mass index), north–south blood pressure differences became much smaller (systolic −1.1, diastolic 1.6 mm Hg) and statistically nonsignificant. In conclusion, multiple dietary factors accounted importantly for north–south blood pressure differences. Efforts are needed to improve nutrition in China, especially in the north, as well as in other populations including those in the United States, for prevention and control of adverse blood pressure levels and major adult cardiovascular disease.

Higher blood pressure in middle-aged American adults with less education-role of multiple dietary factors: the INTERMAP study.

Extensive evidence exists that an inverse relation between education and blood pressure prevails in many adult populations, but little research has been carried out on reasons for this finding. A prior goal of the INTERMAP Study was to investigate this phenomenon further, and to assess the role of dietary factors in accounting for it. Of the 4680 men and women aged 40–59 years, from 17 diverse population samples in Japan, Peoples Republic of China, UK, and USA, a strong significant inverse education–BP relation was manifest particularly for the 2195 USA participants, independent of ethnicity. With participants stratified by years of education, and assessment of 100+ dietary variables from four 24-h dietary recalls and two 24-h urine collections/person, graded relationships were found between education and intake of many macro- and micronutrients, electrolytes, fibre, and body mass index (BMI). In multiple linear regression analyses with systolic BP (SBP) and diastolic BP (DBP) of individuals the dependent variables (controlled for ethnicity, other possible nondietary confounders), BMI markedly reduced size of education–BP relations, more so for women than for men. Several nutrients considered singly further decreased size of this association by ⩾10%: urinary 24-h Na and K excretion, Keys dietary lipid score, vegetable protein, fibre, vitamins C and B6, thiamin, riboflavin, folate, calcium, magnesium, and iron. Combinations of these dietary variables and BMI attenuated the education–SBP inverse coefficient by 54–58%, and the education–DBP inverse coefficient by 59–67%, with over half these effects attributable to specific nutrients (independent of BMI). As a result, the inverse education–BP coefficients ceased to be statistically significant. Multiple specific dietary factors together with body mass largely account for the more adverse BP levels of less educated than more educated Americans. Special efforts to improve eating patterns of less educated strata can contribute importantly to overcoming this and related health disparities in the population.

Enhancing data on nutrient composition of foods eaten by participants in the INTERMAP study in China, Japan, the United Kingdom, and the United States

The International Study of Macronutrients and Blood Pressure (INTERMAP) is a four-country study investigating relationships between individual dietary intakes and blood pressure. Dietary intake patterns of individuals were estimated for macronutrients (proteins, lipids, carbohydrates, alcohol) and their components (amino acids, fatty acids, starch), as well as minerals, vitamins, caffeine, and dietary fiber. The dietary assessment phase of the study involved collection of four 24-h recalls and two 24-h urine specimens from each of 4680 adults, ages 40-59, at 16 centers located in the Peoples Republic of China, Japan, the United Kingdom and the United States. For each country, an available database of nutrient composition of locally consumed foods was updated for use in the analysis of dietary data collected within the country. The four original databases differed in number and types of foods and nutrients included, analytic methods used to derive nutrients, and percentage of missing nutrient values. The Nutrition Coordinating Center at the University of Minnesota updated the original databases in several ways to overcome the foregoing limitations and increase comparability in the analyses of nutrient intake of individuals across the four countries: (1) addition of new foods and preparation methods reported by study participants; (2) addition of missing nutrient fields important to the study objectives; (3) imputation of missing nutrient values to provide complete nutrient data for each food reported by participants; and (4) use of adjustment factors to enhance comparability among estimates of nutrient intake obtained through each countrys nutrient-coding methodology. It was possible to expand, enhance, and adjust the nutrient databases from the four countries to produce comparable (60 nutrients) or nearly comparable (ten nutrients) data on composition of all foods reported by INTERMAP participants.

Diet design for a multicenter controlled feeding trial : The DELTA Program

OBJECTIVE To describe the process and results of diet standardization, diet validation, and monitoring of diet composition, which were key components of protocol 1 of Dietary Effects on Lipoproteins and Thrombogenic Activity (DELTA-1), the initial protocol in a program of multicenter human feeding studies designed to evaluate the effects of amount and type of fat on lipoproteins and hemostasis parameters in various demographic groups. DESIGN DELTA-1 was based on a randomized, blinded, crossover experimental design. Three diets were fed for 8 weeks to 103 healthy men and women aged 22 to 67 years at 4 field centers. Diet A, an average American diet, was designed to provide 37% of energy from fat, 16% of energy from saturated fatty acids (SFAs); diet B (step 1 diet) was designed to provide 30% of energy from fat, 9% of energy from SFA; and diet C (low SFA diet) was designed to provide 26% of energy from fat, 5% of energy from SFA. Key features of diet standardization included central procurement of fat-containing foods, inclusion of standard ingredients, precision weighing of foods--especially sources of fat and cholesterol--and use of standardized written procedures. SETTING For menu validation, a set of 12 menus for each diet was prepared in duplicate and chemically assayed. For monitoring of diet composition during the study, an 8-day diet cycle (6 weekday and 2 weekend menus) was sampled by every field center twice during each of 3 feeding periods. STATISTICAL ANALYSES Means (+/- standard error) were calculated and compared with target nutrient specifications. RESULTS DELTA-1 was able to provide a standardized diet that met nutrient specifications across 4 field centers over 24 weeks of participant feeding spanning a total of 8 months. APPLICATIONS Prestudy chemical validation of menus and continuous sampling and assay of diets throughout the study are essential to standardize experimental diets and to ensure that nutrient target goals are met and maintained throughout a controlled multicenter feeding study.

A validation study on food composition tables for the international cooperative INTERMAP study in Japan.

ObjectiveThe INTERMAP Study is an international cooperative study on the relationship between macro- and micro-nutrient intakes and blood pressure. The present study—ancillary to INTERMAP—is to evaluate validity of the INTERMAP Tables of Food Composition in Japan (ITJ) formulated by modifying the Standard Tables of Food Composition in Japan (STJ), including factoring in changes in weight and nutrient composition of individual foods due to cooking.MethodsWith chemical analytical values of 96 meals prepared in two university hospitals in Japan as the “gold standard”, validity of calculated values based on the ITJ was examined for six major components (energy, protein, lipid, carbohydrate, sodium, potassium) by comparison of mean values, correlation, and linear regression analysis.ResultsAlthough both the ITJ-based and STJ-based calculated values for all six components were significantly higher than the analytical values, differences from the analytical values were generally less marked for the ITJ-based values than for the STJ-based values. The STJ-based values were significantly higher than the ITJ-based values for protein and potassium. Analytical values showed slightly stronger correlations with the ITJ-based calculated values (r=0.876 for total energy, r=0.789 for lipid, r=0.832 for potassium) than with the STJ-based calculated values, except for carbohydrates.ConclusionsThe ITJ was considered to have greater validity than the STJ. To obtain more accaurate data in nutritional surveys, food composition tables in which changes in nutrient compositions due to cooking methods are taken into consideration should be used.

Standardised coding of diet records: experiences from INTERMAP UK†

Coding diet records is a basic element of most dietary surveys, yet it often receives little attention even though errors in coding can lead to flawed study results. In the INTERnational study of MAcro- and micronutrients and blood Pressure (INTERMAP study), efforts were made to minimise errors in coding the 18, 720 diet records. Staff were centrally trained and certified before being able to process study data and ongoing quality control checks were performed. This involved the senior (site) nutritionist re-coding randomly selected diet records. To facilitate standardisation of coding in the UK, a code book was designed; it included information about coding brand items, density and portion size information, and default codes to be assigned when limited information was available for food items. It was found that trainees, despite previous experience in coding elsewhere, made coding errors that resulted in errors in estimates of daily energy and nutrient intakes. As training proceeded, the number of errors decreased. Compilation of the code book was labour-intensive, as information from food manufacturers and retailers had to be collected. Strategies are required to avoid repetition of this effort by other research groups. While the methods used in INTERMAP to reduce coding errors were time consuming, the experiences suggest that such errors are important and that they can be reduced.