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INTERMAP
INTERMAP is a basic epidemiologic investigation designed to help clarify unanswered
questions on the role of dietary factors, particularly macronutrients, in the
development 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. both less educated African-Americans
and whites. INTERMAP aims to achieve a major advance on these important issues,
based on its design, patterned after the tested INTERSALT model: large sample
size of 5,200 persons (2,600 men and 2,600 women), ages 40-59, from 20 diverse
population samples of varied ethnicity, SES, and dietary habits in four countries
(China, Japan, U.K., U.S.) (260 persons per sample).
Specific aims of the study involve elucidating influences on BP of amount
and type of protein, lipids, carbohydrates, also amino acids, calcium, magnesium,
antioxidants, fiber, caffeine. The primary hypotheses to be tested include:
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 saturated
fatty acids, cholesterol, Keys score, starch; there is an inverse relation
of polyunsaturated fatty acids and of P/S.
Participants, randomly selected, provide two timed 24-hour urine collections
for assessment of sodium, potassium, creatinine, and urea, and also complete
four 24-hour dietary recalls. BP is measured twice at each of four clinic visits.
The study is coordinated by two Coordinating Centers, one at NUMS and one
at Imperial College School of Medicine in London. Laboratory analysis is performed
at a Central Laboratory in Leuven, Belgium.
Findings on relations of multiple dietary factors to BP will be used to estimate
favorable impact on BP of multiple improvements in nutrition by populations.
This, in turn, should aid in making dietary recommendations toward achieving
the goal of primary prevention of hypertension, and shifting BP distributions
downward to avoid excess risk associated with present, generally above-optimal
levels.
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