Purpose of review

The dietary reference intake (DRI) for sodium has been highly debated with persuasive and elegant arguments made for both population sodium reduction and for maintenance of the status quo. After the 2015 Dietary Guidelines Advisory Committee (DGAC) report was published, controversy ensued, and by Congressional mandate, the sodium DRIs were updated in 2019. The 2019 DRIs defined adequate intake (AI) levels by age-sex groups that are largely consistent with the DRIs for sodium that were published in 2005. Given the overall similarities between the 2005 and 2019 DRIs, one may wonder how the recently published research on sodium and health outcomes was considered in determining the DRIs, particularly, the recent studies from very large observational cohort studies. We aim to address this concern and outline the major threats to ascertaining valid estimates of the relationship between dietary sodium and health outcomes in observational cohort studies. We use tools from modern epidemiology to demonstrate how unexpected and inconsistent findings in these relationships may emerge. We use directed acyclic graphs to illustrate specific examples in which biases may occur.

Recent findings

We identified the following key threats to internal validity: poorly defined target intervention, poorly measured sodium exposure, unmeasured or residual confounding, reverse causality, and selection bias. Researchers should consider these threats to internal validity while developing research questions and throughout the research process. For the DRIs to inform real-world interventions relating to sodium reduction, it is recommended that more specific research questions be asked that can clearly define potential interventions of interest.

Avocados are a nutrient-dense plant-food, but limited trial-derived evidence exists about the effects of avocado intake on family nutritional status. We investigated the impact of two levels of avocado allotment, plus a standard nutrition education intervention on the nutritional status of Hispanic/Latino families. Seventy-two families consisting of at least three members of ≥5 years of age and residing in the same home, free of severe chronic disease, not on specific diets, and self-identified of Hispanic heritage, were randomized to one of two levels of avocado allotment (low = 3/week/family or high = 14/week/family) for 6 months plus 12 bi-weekly nutrition education sessions. The primary outcomes included change in a family's total energy and macro- and micronutrient intakes. Primary analysis was intention-to-treat with unpaired, two-sided t-tests to assess mean changes between groups at 6 months. At 6 months, the high avocado allotment group had a significant reduction in energy intake, carbohydrate, animal and vegetable protein, saturated and polyunsaturated fat, calcium, magnesium, sodium, potassium, iron, and vitamin D intakes (all p < 0.05). A high allotment of avocados significantly reduced self-reported energy intake by 29% kcal/family/day, compared to a 3% kcal/family/day reduction in families who received a low allotment. Culturally-appropriate plant-food interventions may alter the nutritional status of at-risk families.

Background

Reducing dietary sodium has potential to benefit patients with chronic kidney disease (CKD). Little research is available defining dietary sodium knowledge gaps in patients with pre-dialysis CKD. We designed a brief screening tool to rapidly identify patient knowledge gaps related to dietary sodium for patients with CKD not yet on dialysis.

Methods

A Short Sodium Knowledge Survey (SSKS) was developed and administered to patients with pre-dialysis CKD. We also asked patients if they received counseling on dietary sodium reduction and about recommended intake limits. We performed logistic regression to examine the association between sodium knowledge and patient characteristics. Characteristics of patients who answered all SSKS questions correctly were compared to those who did not.

Results

One-hundred fifty-five patients were surveyed. The mean (SD) age was 56.6 (15.1) years, 84 (54%) were men, and 119 (77%) were white. Sixty-seven patients (43.2%) correctly identified their daily intake sodium limit. Fifty-eight (37.4%) were unable to answer all survey questions correctly. In analysis adjusted for age, sex, race, education, health literacy, CKD stage, self-reported hypertension and attendance in a kidney education class, women and patients of non-white race had lower odds of correctly answering survey questions (0.36 [0.16,0.81]; p = 0.01 women versus men and 0.33 [0.14,0.76]; p = 0.01 non-white versus white, respectively).

Conclusions

Our survey provides a mechanism to quickly identify dietary sodium knowledge gaps in patients with CKD. Women and patients of non-white race may have knowledge barriers impeding adherence to sodium reduction advice.

Background

South Asians are at high risk of metabolic syndrome, and dietary patterns may influence this risk.

Objectives

We aimed to determine prevalent dietary patterns for South Asians in the United States and their associations with risk factors for metabolic syndrome.

Methods

South Asians aged 40-84 y without known cardiovascular disease were enrolled in a community-based cohort called Mediators of Atherosclerosis in South Asians Living in America. A validated food frequency questionnaire and serum samples for fasting and 2-h glucose, insulin, glycated hemoglobin, triglycerides, and total and HDL cholesterol were collected cross-sectionally. We used principal component analysis with varimax rotation to determine dietary patterns, and sequential linear and logistic regression models for associations with metabolic factors.

Results

A total of 892 participants were included (47% women). We identified 3 major dietary patterns: animal protein; fried snacks, sweets, and high-fat dairy; and fruits, vegetables, nuts, and legumes. These were analyzed by tertile of factor score. The highest vs. the lowest tertile of the fried snacks, sweets, and high-fat dairy pattern was associated with higher homeostasis model assessment of insulin resistance (HOMA-IR) (β: 1.88 mmol/L ⋅ uIU/L) and lower HDL cholesterol (β: -4.48 mg/dL) in a model adjusted for age, sex, study site, and caloric intake (P < 0.05). The animal protein pattern was associated with higher body mass index (β: 0.73 m/kg(2)), waist circumference (β: 0.84 cm), total cholesterol (β: 8.16 mg/dL), and LDL cholesterol (β: 5.69 mg/dL) (all P < 0.05). The fruits, vegetables, nuts, and legumes pattern was associated with lower odds of hypertension (OR: 0.63) and metabolic syndrome (OR: 0.53), and lower HOMA-IR (β: 1.95 mmol/L ⋅ uIU/L) (P < 0.05).

Conclusions

The animal protein and the fried snacks, sweets, and high-fat dairy patterns were associated with adverse metabolic risk factors in South Asians in the United States, whereas the fruits, vegetables, nuts, and legumes pattern was linked with a decreased prevalence of hypertension and metabolic syndrome.

Non-alcoholic fatty liver disease (NAFLD) is a public health concern and Hispanic/Latinos are disproportionately affected. There is evidence for favorable effects of dietary intake of monounsaturated fatty acids (MUFA) on NAFLD, yet studies examining avocados as a source of MUFA on hepatic function have not been assessed. We investigated the effects of low (3) vs. high (14) avocado allotment on biomarkers of NAFLD, oxidative stress, and NAFLD fibrosis score in a sample of Hispanic/Latino adults. Primary outcomes include hepatic function biomarkers [gamma glutamyltransferase (GGT), high-sensitivity c-reactive protein (hsCRP), and NAFLD fibrosis score]. Unpaired, two-sided t-tests were used to assess mean differences between intervention groups at 6 months and analysis of covariance models were used to adjust for diet quality and change in avocado intake from baseline to 6 months. Multivariable linear regression models evaluated the baseline and post-intervention association between avocado allotment group and outcomes, adjusting for covariates and stratifying by prediabetes status. No statistically significant differences were observed between low and high avocado allotment groups in liver enzymes, GGT, hsCRP or NAFLD fibrosis score. Findings persisted after stratifying by prediabetes status. Varied intake of avocados resulted in no effects on biomarkers of NAFLD in healthy adults, free of severe chronic disease.

Serum carbon isotope values [13C-to-12C serum carbon isotope ratio (δ(13)C)], which reflect consumption of corn- and cane-based foods, differ between persons consuming high and low amounts of sugar-sweetened beverages (SSBs). In this study, we determined whether serum δ(13)C changes in response to change in SSB intake during an 18-mo behavioral intervention trial. Data were from a subset of 144 participants from the PREMIER trial, a completed behavioral intervention (Maryland, 1998-2004). SSB intake was assessed using 2 24-h dietary recall interviews. Blinded serum samples were assayed for δ(13)C by natural abundance stable isotope mass spectroscopy. Multiple linear regression models with generalized estimating equations and robust variance estimation were used. At baseline, mean SSB intake was 13.8 ± 14.2 fl oz/d, and mean δ(13)C serum value was -19.3 ± 0.6 units per mil (designated ‰). A reduction of 12 oz (355 mL)/d SSB (equivalent to 1 can of soda per day) was associated with 0.17‰ (95% CI: 0.08‰, 0.25‰ P < 0.0001) reduction in serum δ(13)C values over 18 mo (equivalent to a 1% reduction in δ(13)C from baseline). After adjusting for potential confounders, a reduction of 12 oz/d SSB (equivalent to 1 can of soda per day), over an 18-mo period, was associated with 0.12‰ (95% CI: 0.01‰, 0.22‰ P = 0.025) reduction in serum δ(13)C. These findings suggest that serum δ(13)C can be used as a measure of dietary changes in SSB intake.

Objective

Few studies examine the relationships between anthropometry and the body composition measures they approximate, or whether they differ by sex, and no studies have examined these relationships in South Asians living in the US.

Design

We conducted a cross-sectional study of 871 participants in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) Study who had BMI < 40 kg/m² and underwent abdominal CT scans for measurement of visceral and subcutaneous fat. Linear regression was used to model the associations between anthropometric measures and naturally log-transformed body composition measures.

Results

All measures of anthropometry, except height, were significantly associated with visceral fat and had a significant non-linear component (p < .05). The only associations for visceral fat that exhibited significant heterogeneity by sex were waist circumference (% difference in visceral fat slope: women 1.92, men 2.74, p = .007 for interaction) and waist-to-hip ratio (women 25.9, men 717.4, p < .001). Except for height, all measures of anthropometry were significantly associated with subcutaneous fat, had a significant quadratic component, and significant heterogeneity by sex (weight (kg): 2.74 for women, 4.08 for men; BMI (kg/m²): 10.3, 14.0; waist circumference (cm): 1.51, 3.36; hip circumference (cm): 2.53, 4.50) with p < .001 for each.

Conclusions

In MASALA participants, the relationships of anthropometric measures with visceral and subcutaneous fat appear similar to other race/ethnic groups, but with weaker non-linearity and heterogeneity by sex. Given these results, researchers should consider separate models by sex for US South Asians when approximating subcutaneous fat or when using waist circumference to approximate visceral fat.

Dietary patterns contribute to cardiovascular disease (CVD) risk. Asian Indians have earlier onset, more severe, and more prevalent CVD than many other racial/ethnic groups. We aimed to characterize dietary patterns in Asian Indians living in the United States and examine associations with cardiometabolic risk factors. One hundred fifty Asian Indians, aged 45 to 84 years, without known CVD, living in the San Francisco Bay, CA, area between August 2006 and October 2007 were enrolled into the Metabolic syndrome and Atherosclerosis in South Asians Living in America study. A food frequency questionnaire validated in Asian Indians, fasting blood samples, and computed tomography scans were obtained for all participants. Principal component analysis with varimax rotation was used to determine prevalent dietary patterns. Linear regression analyses were performed for associations between dietary patterns and metabolic factors, adjusting initially for age and sex, then additionally for BMI, income, education, metabolic equivalent of task-minutes of exercise, alcohol consumption, and smoking. Two distinct dietary patterns were identified that we termed "Western," and "Vegetarian." Compared with the Western diet, the Vegetarian diet was associated with lower homeostasis model of assessment-insulin resistance (-1.12 mmol/L × mU/L; P=0.05) and lower high-density lipoprotein cholesterol (-4.77 mg/dL; P=0.09). Given that the Western and Vegetarian dietary patterns were each associated with adverse metabolic changes, healthful diet choices may help Asian Indians improve risk factors for CVD.

This study examined fruit and vegetable intake by food store type shopped among US Hispanics. Using National Health and Nutrition Examination Survey 2011-2012 data, T test and chi-square tests examined differences between Hispanic consumers by food store type. Negative binomial regression analyses estimated associations between fruit and vegetable intake and food store type. Hispanics who only purchased fruits and vegetables from convenience stores were younger and more likely US born. They reported lower intakes of fruit and vegetables than individuals who purchased these foods from supermarket/grocery stores. Those who primarily purchased fruits and vegetables from supermarkets/grocery stores consumed 0.92 (p < .001) greater fruit cup equivalents and 0.26 (p = .001) greater vegetable cup equivalents than those who only purchased from convenience stores. Research on the influence of shopping in multiple food store types is needed to develop targeted in-store intervention strategies to encourage healthier food purchases. Results provide support for policy-level research such as minimum stocking requirements for healthy foods in convenience stores.