Malnutrition and the risk of hypertension in a disadvantaged rural Indian population

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Background: The prevalence of hypertension is increasing in rural populations of India, but the contribution of diet and socio-economic position (SEP) to hypertension in these regions is not well understood. Moreover, there are limited data on the assessment of diet in rural populations of India using culturally specific dietary tools. Aims: To (1) validate a culturally modified 24 hour dietary recall questionnaire for use in rural Indian populations; (2) determine the prevalence of malnutrition in a disadvantaged population; (3) assess the proportion of households consuming non-iodised salt; (4) investigate the association between dietary factors and hypertension; and (5) investigate the relationship between SEP and hypertension. Methods: This study was conducted in a rural farming population in the Rishi Valley, Andhra Pradesh. Data were collected from a case-control study of hypertension, on 300 age-, sex-, and, where possible, village- matched pairs of adults. Blood pressure and anthropometry was assessed by trained field workers. Blood and urine samples were collected for 229 individuals. Socio-demographic and lifestyle information were obtained using questionnaires. Data on daily intake of energy and nutrients were calculated from a culturally modified 24 hour recall questionnaire. Conditional logistic regression models were used to assess the associations between dietary and socio-economic variables, with the outcome of hypertension. Results: There was strong agreement between the amount of food reported to be consumed from 24 hour recall interviews and those weighed (n = 45). Individuals were severely deficient in energy and all macro- and micro- nutrients, with women being significantly more deficient than men in iron (n = 600, P < 0.001). Additionally, 82% of households (n = 37) were not receiving adequate iodine from salt. In a sub sample of the population (total n = 215), serum potassium (odds ratio (OR) 0.40 95% confidence interval (CI) 0.20−0.84, P = 0.01) and magnesium (OR 0.23 95% CI 0.06– 0.90, P = 0.03) were inversely associated with hypertension. We did not detect a statistical association between intake of salt and hypertension, despite salt intake being high (7.3 g/day). Physical inactivity (OR 3.0, 95% CI 2.0−4.6, P < 0.001) and belonging to an advantaged social class (OR 3.2, 95% CI 1.4−7.7, P = 0.008) were positively associated with hypertension. In men alone, polygamy, consuming alcohol and consumption of at least one egg a week were positively associated with hypertension. In women, body mass index (BMI) was associated with hypertension. Conclusion: Traditional risk factors for hypertension such as alcohol consumption, sedentary lifestyle and obesity, exist in the setting of poverty in this rural Indian community. These risk factors co-exist with population specific risk factors such as social class and polygamy. Failure to detect an association between fruit and vegetable intake with hypertension could relate to the homogeneity of inadequate intake of food exhibited by the entire population. We found that intake of micronutrients, other than salt, were inversely associated with hypertension. Therefore, interventions should be developed to encourage the consumption of foods rich in magnesium and potassium in this population to help reduce hypertension.