This application requests support for further testing of study hypotheses and exploratory analyses in the international cooperative INTERMAP Study, a basic epidemiologic investigation designed to help clarify unanswered questions on the role of dietary factors, particularly macronutrients, in the etiology of unfavorable blood pressure (BP) levels prevailing for a majority of middle-aged and older individuals in the U.S. population. A particular focus within the context of this overall objective is to help elucidate the role of these dietary factors in accounting for the even more adverse BP patterns of less educated population strata, e.g., in the U.S. for less educated African-Americans, Hispanics, and Whites. INTERMAP aims to achieve a major advance on these important issues, based on its design: a large sample size of 4,700 men and women ages 40 to 59 years of age from 17 diverse population samples of varied ethnicity, socioeconomic status (SES), and dietary habits in four countries (China, Japan, UK, and the U.S.). Efficiency has been assured by major cost-sharing by non-U.S. centers, so that resources requested have been much less than for research of this scope done solely in the U.S.
Specific aims i nvolve elucidating influences on BP of amount and type of protein, lipids, carbohydrates, also amino acids, Ca, Mg, antioxidants, fiber, and caffeine. Primary hypotheses to be tested, with control for BMI, intake of alcohol, Na, K, age, sex, and other confounders are as follow: dietary protein is inversely related to BP; inverse relations between education and BP are significantly accounted for by education-correlated differences in dietary protein intake; there is a direct relation to BP of dietary SFA, cholesterol, Keys score, starch; there is an inverse relation of PFA and of P/S. Participants, randomly selected, provided two timed 24-hr urine collections for assessment of Na, K, creatinine, urea, and completed four 24-hr dietary recalls. BP was measured twice at each of four clinic visits. The study has been coordinated by two Coordinating Centers -- Northwestern University, Chicago and Imperial College of Medicine, London. Urinary determinations were made at a Central Laboratory in Leuven, Belgium. The 24-hr dietary recalls have been converted into nutrients with use in each country of an up-to-date, extensive, high quality, well maintained national data base, with international study-wide standardization and quality control. Findings on relations of multiple dietary factors to BP are to be used to estimate favorable impact on BP of multiple improvements in nutrition by populations. The investigators point out that this, in turn, should aid in enhancing dietary recommendations toward achieving the goal of primary prevention of hypertension, and shifting BP distributions downward to avoid excess risk associated with present levels, generally above optimal.
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