Salt intake and cardiovascular disease: why are the data inconsistent?

Effective population-based interventions are required to reduce the global burden of cardiovascular disease (CVD). Reducing salt intake has emerged as a leading target, with many guidelines recommending sodium intakes of 2.3 g/day or lower. These guideline thresholds are based largely on clinical trials reporting a reduction in blood pressure with low, compared with moderate, intake. However, no large-scale randomized trials have been conducted to determine the effect of low sodium intake on CV events. Prospective cohort studies evaluating the association between sodium intake and CV outcomes have been inconsistent and a number of recent studies have reported an association between low sodium intake (in the range recommended by current guidelines) and an increased risk of CV death. In the largest of these studies, a J-shaped association between sodium intake and CV death and heart failure was found. Despite a large body of research in this area, there are divergent interpretations of these data, with some advocating a re-evaluation of the current guideline recommendations. In this article, we explore potential reasons for the differing interpretations of existing evidence on the association between sodium intake and CVD. Similar to other areas in prevention, the controversy is likely to remain unresolved until large-scale definitive randomized controlled trials are conducted to determine the effect of low sodium intake (compared to moderate intake) on CVD incidence.

Effects of higher- versus lower-protein diets on health outcomes: a systematic review and meta-analysis.

BACKGROUND/OBJECTIVES: Numerous randomised controlled trials (RCTs) published in first tier medical journals have evaluated the health effects of diets high in protein. We conducted a rigorous systematic review of RCTs comparing higher- and lower-protein diets. METHODS: We searched several electronic databases up to July 2011 for studies focusing on patient-important outcomes (for example, cardiovascular disease) and secondary outcomes such as risk factors for chronic disease (for example, adiposity). RESULTS: We identified 111 articles reporting on 74 trials. Pooled effect sizes using standardised mean differences (SMDs) were small to moderate and favoured higher-protein diets for weight loss (SMD -0.36, 95% confidence interval (CI) -0.56 to -0.17), body mass index (-0.37, CI -0.56 to 0.19), waist circumference (-0.43, CI -0.69 to -0.16), blood pressure (systolic: -0.21, CI -0.32 to -0.09 and diastolic: -0.18, CI -0.29 to -0.06), high-density lipoproteins (HDL 0.25, CI 0.07 to 0.44), fasting insulin (-0.20, CI -0.39 to -0.01) and triglycerides (-0.51, CI -0.78 to -0.24). Sensitivity analysis of studies with lower risk of bias abolished the effect on HDL and fasting insulin, and reduced the effect on triglycerides. We observed nonsignificant effects on total cholesterol, low-density lipoproteins, C-reactive protein, HbA1c, fasting blood glucose, and surrogates for bone and kidney health. Adverse gastrointestinal events were more common with high-protein diets. Multivariable meta-regression analysis showed no significant dose response with higher protein intake. CONCLUSIONS: Higher-protein diets probably improve adiposity, blood pressure and triglyceride levels, but these effects are small and need to be weighed against the potential for harms.

Development, reproducibility and validity of the food frequency questionnaire in the Poland arm of the Prospective Urban and Rural Epidemiological (PURE) study.

BACKGROUND: A food frequency questionnaire (FFQ) is the most commonly used method in large epidemiological studies. The validation of an FFQ is essential for specific populations because foods are culture-dependent. The present study aimed to develop an FFQ and evaluate its validity and reproducibility in estimating the intake of nutrients in urban and rural areas of Poland. METHODS: Adult participants (n = 146) in the Polish arm of the ongoing Prospective Urban and Rural Epidemiological (PURE) study completed FFQs on two occasions, as well as four 24-h dietary recalls (DRs) during a 12-month period. Correlation coefficients (r) and de-attenuated correlation coefficients between dietary recalls and both FFQs were calculated for selected macro- and micronutrients. Agreement between the two methods was evaluated by classification into quartiles and the Bland-Altman method. Reproducibility was assessed by the intra-class correlation coefficient (ICC). RESULTS: The final food list contained 134 food items. For urban participants, FFQ2 generally underestimated energy, protein and fat compared to the FFQ1 and mean of DRs. In rural areas, compared to DRs, both FFQs overestimated energy and macronutrients. For both urban and rural settings, de-attenuated correlation exceeded 0.4 for almost all nutrients and the exact agreement in quartile categorisation was >66%. When assessing repeatability, ICC varied from 0.39-0.63 in an urban setting and 0.19-0.45 in a rural setting. CONCLUSIONS: This 134-item FFQ has good validity and reproducibility in relation to the reference method and can be used to rank individuals based on their macro- and micronutrient intake.

High prevalence of unrecognized sleep apnoea in drug-resistant hypertension.

OBJECTIVES: To determine the prevalence of obstructive sleep apnoea (OSA) in adult patients with drug-resistant hypertension, a common problem in a tertiary care facility. DESIGN: Cross-sectional study. SETTING: University hypertension clinic. PATIENTS AND METHODS: Adults with drug-resistant hypertension, defined as a clinic blood pressure of > or = 140/90 mmHg, while taking a sensible combination of three or more antihypertensive drugs, titrated to maximally recommended doses. Each of the 41 participants completed an overnight polysomnographic study and all but two had a 24 h ambulatory blood pressure measurement. RESULTS: Prevalence of OSA, defined as an apnoea-hypopnoea index of > or = 10 obstructive events per hour of sleep, was 83% in the 24 men and 17 women studied. Patients were generally late middle-aged (57.2 +/- 1.6 years, mean +/- SE), predominantly white (85%), obese (body mass index, 34.0 +/- 0.9 kg/m2) and taking a mean of 3.6 +/- 0.1 different antihypertensive medications daily. OSA was more prevalent in men than in women (96 versus 65%, P = 0.014) and more severe (mean apnoea-hypopnoea index of 32.2 +/- 4.5 versus 14.0 +/- 3.1 events/h, P = 0.004). There was no gender difference in body mass index or age. Women with OSA were significantly older and had a higher systolic blood pressure, lower diastolic blood pressure, wider pulse pressure and slower heart rate than women without OSA. CONCLUSIONS: The extraordinarily high prevalence of OSA in these patients supports its potential role in the pathogenesis of drug-resistant hypertension, and justifies the undertaking of a randomized controlled trial to corroborate this hypothesis.

Alexithymia and health behaviors in healthy male volunteers.

The association between alexithymia and maladaptive health behaviors was evaluated in 118 young, healthy men, aged 18-45 years. Subjects completed the Toronto Alexithymia Scale (TAS-26), and a health behaviors questionnaire, measuring alcohol and drug use, sedentary lifestyle, poor nutritional consumption, and risky sexual practices. In forced hierarchical regression analyses, the association between alexithymia and health behaviors was evaluated after adjusting for age, body mass index, social support, ambivalence over expression of emotion, and the expression of emotion. Results indicated that: (1) the TAS-26 and difficulty identifying feelings was associated with poor nutritional consumption; (2) difficulty identifying feelings was associated with greater alcohol and drug use; and (3) difficulty communicating feelings was associated with a more sedentary lifestyle. There was no association between risky sexual practices and alexithymia. These results suggest that, in young men, difficulties with identifying emotions and communicating emotions are associated with maladaptive nutritional habits, a sedentary lifestyle, and substance abuse, even after adjusting for other psychosocial and demographic variables. Such maladaptive health behaviors may help explain the association between alexithymia and premature mortality.