Salt sensitivity, insulin resistance, and public health in India

Knowledge, Attitudes, and Practices Regarding Dietary Sodium in College Students

OBJECTIVE

Test a dietary sodium survey in a US adult population of college students using a survey previously validated in a non-US adult population.

METHODS

Cross-sectional study of a convenience sample of college students from a Midwest (n = 168) and Pacific Island (n = 152) university. Main outcome measures were knowledge, attitudes, and practices regarding dietary sodium (38 items). Sum scores and percentages for constructs were calculated. A score <75% was considered unfavorable; t test or ANOVA were used to examine group differences.

RESULTS

Midwest students were primarily non-Hispanic White individuals (81%) and 65% female. Pacific Island students were predominantly Asian (51%) and 66% female. Mean ± SD construct scores (percentage) for knowledge, attitudes, and practices were 58.69 ± 10.62, 63.96 ± 16.18, 66.00 ± 12.34 (Midwest) and 57.54 ± 10.93, 64.84 ± 14.96, 64.94 ± 13.18 (Pacific Island), respectively; there were no significant differences between schools or race.

CONCLUSIONS AND IMPLICATIONS

College students scored low in knowledge, attitudes, and practices regarding sodium. Results from this formative study may inform assessment strategies in future dietary sodium interventions.

The relationship between diabetic risk factors, diabetic complications and salt intake

The relationship between salt and hypertension is the focus of a large amount of research, there are few reviews of the relationship between salt and diabetes, despite the increasing incidence of diabetes. By searching PubMed and the Cochrane Library, we summarized the relationships between diabetic risk factors, diabetic complications and salt intake. The pathophysiological mechanisms underlying the effects of salt on diabetes risk factors and diabetic complications are also discussed. Our findings should assist experts and scholars to understand the current research of salt intake and to pay more attention to the prevention and treatment of related diseases caused by excessive salt intake; guide treatment for patients with diabetes mellitus; and provide a reference for government departments to formulate a reasonable salt restriction policy. We also recommend future research directions.

Salt sensitivity and its implication in clinical practice

Hypertension (HTN) is a complex multi-factorial disease and is considered one of the foremost modifiable risk factors for stroke, heart failure, ischemic heart disease and renal dysfunction. Over the past century, salt and its linkage to HTN and cardiovascular (CV) mortality has been the subject of intense scientific scrutiny. There is now consensus that different individuals have different susceptibilities to blood pressure (BP)-raising effects of salt and this susceptiveness is called as salt sensitivity. Several renal and extra-renal mechanisms are believed to play a role. Blunted activity of the renin–angiotensin–aldosterone system (RAAS), adrenal Rac1-MR-Sgk1-NCC/ENaC pathway, renal SNS-GR-WNK4-NCC pathway, defect of membrane ion transportation, inflammation and abnormalities of Na⁺/Ca²⁺ exchange have all been implicated as pathophysiological basis for salt sensitive HTN. While salt restriction is definitely beneficial recent observation suggests that treatment with Azilsartan may improve salt sensitivity by selectively reducing renal proximal tubule Na⁺/H⁺ exchange. This encourages the future potential benefits of recognizing and therapeutically addressing the salt sensitive phenotype in humans.

Asian American Dietary Sources of Sodium and Salt Behaviors Compared with Other Racial/ethnic Groups, NHANES, 2011-2012

OBJECTIVE

Asian Americans consume more sodium than other racial/ethnic groups. The purpose of this analysis was to describe major sources of sodium intake to inform sodium reduction initiatives.

METHODS

Cross-sectional data on adults (aged >18 years) from the National Health and Nutrition Examination Survey (NHANES) 2011-2012 with one 24-hour dietary recall were analyzed (n=5,076). Population proportions were calculated from "What We Eat in America" (WWEIA) food categories.

RESULTS

Asian Americans had a higher sodium density vs adults of other racial/ethnic groups (means in mg/1000kcal: Asian American, 2031.1; Hispanic,1691.6; White: 1666.5; Black: 1655.5; P<.05, all). Half of sodium consumed by Asian Americans came from the top 10 food categories, in contrast to Hispanics (43.6%), Whites (39.0%), and Blacks (36.0%). Four food categories were a top source of sodium for Hispanics, Whites, Blacks, and others, but not among Asian Americans: cold cuts and cured meats; meat mixed dishes; eggs and omelets; and cheese. The top three food category sources of sodium among Asians were soups, rice, and yeast breads accounting for 28.9% of dietary sodium. Asian Americans were less likely to add salt at the table, but used salt in food preparation 'very often' (P for both <.01).

CONCLUSIONS

Mean sodium consumption and sources vary across racial/ethnic groups with highest consumption in Asian Americans. Given the smaller number of food categories contributing to sodium intake in Asian Americans, results imply that targeted activities on a few food items would have a large impact on reducing sodium intake in this group.

Salt intake, blood pressure, and socioeconomic disparities among government employees in Sri Lanka: a cross-sectional study

Our study estimated salt intake, examined the association between blood pressure (BP) and salt intake, and explored the socioeconomic variations in salt intake among administrators (government employees). This is a cross-sectional study. We studied 168 randomly selected administrators aged 30-60 years attached to government offices in Colombo, Sri Lanka. Self-administered questionnaire gathered information on socio-demographic, work-related information, lifestyle practices, and medical history. BP, 24-hour urine collection, and anthropometric indices were measured. Mean salt intake levels measured by 24-hour Sodium (Na) excretion in hypertensives and non-hypertensives were 202.56 (SD ± 85.45) mmol/day and 176.79 (SD ± 82.02) mmol/day, respectively. A 100-mmol increase in sodium was associated with an average increase of 3.1 (95 per cent CI 2-4.2) mmHg in systolic BP and 1.8 (95 per cent CI 0.89-2.6) mmHg in diastolic BP. Higher salt intake was found in managerial assistants (12.38 ± 5.0 g) compared with senior officers (10.84 ± 4.9 g). Salt intake among these administrators was alarmingly high. High salt intake was positively associated with hypertension and more prevalent in lower socioeconomic strata.

Effect of low salt diet on insulin resistance in salt-sensitive versus salt-resistant hypertension

Accumulating evidence shows an increase in insulin resistance on salt restriction. We compared the effect of low salt diet on insulin resistance in salt-sensitive versus salt-resistant hypertensive subjects. We also evaluated the relationship between salt sensitivity of blood pressure and salt sensitivity of insulin resistance in a multivariate regression model. Studies were conducted after 1 week of high salt (200 mmol per day sodium) and 1 week of low salt (10 mmol per day sodium) diet. Salt sensitivity was defined as the fall in systolic blood pressure>15 mm Hg on low salt diet. The study includes 389 subjects (44% women; 16% blacks; body mass index, 28.5±4.2 kg/m2). As expected, blood pressure was lower on low salt (129±16/78±9 mm Hg) as compared with high salt diet (145±18/86±10 mm Hg). Fasting plasma glucose, insulin, and homeostasis model assessment were higher on low salt diet (95.4±19.4 mg/dL; 10.8±7.3 mIU/L; 2.6±1.9) as compared with high salt diet (90.6±10.8 mg/dL; 9.4±5.8 mIU/L; 2.1±1.4; P<0.0001 for all). There was no difference in homeostasis model assessment between salt-sensitive (n=193) versus salt-resistant (n=196) subjects on either diet. Increase in homeostasis model assessment on low salt diet was 0.5±1.4 in salt-sensitive and 0.4±1.5 in salt-resistant subjects (P=NS). On multivariate regression analysis, change in systolic blood pressure was not associated with change in homeostasis model assessment after including age, body mass index, sex, change in serum and urine aldosterone, and cortisol into the model. We conclude that the increase in insulin resistance on low salt diet is not affected by salt sensitivity of blood pressure.

The role of salt intake and salt sensitivity in the management of hypertension in South Asian people with chronic kidney disease: a randomised controlled trial

Background

The effectiveness of salt restriction to lower blood pressure (BP) in Bangladeshi patients with chronic kidney disease (CKD) is uncertain.

Objective

To test the hypothesis that a tailored intervention intended to reduce salt intake in addition to standard care will achieve a greater reduction in BP in UK Bangladeshi patients with CKD than standard care alone.

Design

A randomised parallel-group controlled trial conducted over a 6 month period.

Setting

A tertiary renal unit based in acute care hospital in East London.

Participants

56 adult participants of Bangladeshi origin with CKD and BP >130/80 mm Hg or on antihypertensive medication.

Intervention

Participants were randomly allocated to receive a tailored low-salt diet or the standard low-salt advice. BP medication, physical activity and weight were monitored.

Main outcome measures

The primary outcome was change in ambulatory BP. Adherence to dietary advice was assessed by measurement of 24 h urinary salt excretion.

Results

Of 56 participants randomised, six withdrew at the start of the study. During the study, one intervention group participant died, one control group participant moved to Bangladesh. Data were available for the primary endpoint on 48 participants. Compared with control group the intervention urinary sodium excretion fell from 260 mmol/d to 103 mmol/d (−131 to −76, p<0.001) at 6 months and resulted in mean (95% CI) falls in 24 h systolic/diastolic BP of −8 mm Hg (−11 to −5)/2 (−4 to −2) both p<0.001.

Conclusions

A tailored intervention can achieve moderate salt restriction in patients with CKD, resulting in clinically meaningful falls in BP independent of hypertensive medication.

Trial Registration

ClinicalTrials.gov NCT00702312.