Examining the quality and quantity of food intake by appropriate methods is critical in the management of patients with chronic kidney disease (CKD). The four commonly used dietary assessment methods in CKD patients include short-term dietary recalls, several days of food records with or without dietary interviews, urea kinetic based estimates such as protein nitrogen appearance calculation, and food histories including food screeners and food frequency questionnaires (FFQ). There are a number of strengths and limitations of these dietary assessment methods. Accordingly, none of the four methods is suitable in and of itself to give sufficiently accurate dietary information for all purposes. Food frequency questionnaires, which is the preferred method for epidemiological studies, should be used for dietary comparisons of patients within a given population rather than individual assessment. Food histories including FFQ and dietary recalls may underestimate important nutrients, especially in CKD patients. Given the large and increasing number of dialysis patients and work responsibilities of renal dietitians, routine analysis of dietary records and recalls is becoming less feasible. Ongoing and future studies will ascertain additional strengths and limitations of dietary assessment methods in CKD populations including the assessment of food intake during an actual hemodialysis treatment.

Background

Hyperkalemia has been associated with higher mortality in long-term hemodialysis (HD) patients. There are few data concerning the relationship between dietary potassium intake and outcome.

Study design

The mortality predictability of dietary potassium intake from reported food items estimated using the Block Food Frequency Questionnaire (FFQ) at the start of the cohort was examined in a 5-year (2001-2006) cohort of 224 HD patients in Southern California using Cox proportional hazards regression.

Setting & participants

224 long-term HD patients from 8 DaVita dialysis clinics.

Predictors

Dietary potassium intake ranking using the Block FFQ.

Outcomes

5-year survival.

Results

HD patients with higher potassium intake had greater dietary energy, protein, and phosphorus intakes and higher predialysis serum potassium and phosphorus levels. Greater dietary potassium intake was associated with significantly increased death HRs in unadjusted models and after incremental adjustments for case-mix, nutritional factors (including 3-month averaged predialysis serum creatinine, potassium, and phosphorus levels; body mass index; normalized protein nitrogen appearance; and energy, protein, and phosphorus intake) and inflammatory marker levels. HRs for death across the 3 higher quartiles of dietary potassium intake in the fully adjusted model (compared with the lowest quartile) were 1.4 (95% CI, 0.6-3.0), 2.2 (95% CI, 0.9-5.4), and 2.4 (95% CI, 1.1-7.5), respectively (P for trend = 0.03). Restricted cubic spline analyses confirmed the incremental mortality predictability of higher potassium intake.

Limitations

FFQs may underestimate individual potassium intake and should be used to rank dietary intake across the population.

Conclusions

Higher dietary potassium intake is associated with increased death risk in long-term HD patients, even after adjustments for serum potassium level; dietary protein; energy, and phosphorus intake; and nutritional and inflammatory marker levels. The potential role of dietary potassium in the high mortality rate of HD patients warrants clinical trials.

Background

Mortality in long-term hemodialysis patients is high, mostly attributed to cardiovascular events, and may be related to chronic inflammation. We hypothesized that the anti-inflammatory benefits of higher dietary intake of omega-3 compared with omega-6 polyunsaturated fatty acids may modulate the inflammatory processes and decrease death risk.

Study design

Prospective cohort study using linear and Cox proportional regressions.

Setting & participants

145 hemodialysis patients from 8 DaVita dialysis clinics in Southern California in 2001-2007.

Predictors

Intake of dietary omega-3 and ratio of omega-6 to omega-3 using 3-day food record supplemented by dietary interview.

Outcomes

1-year change in serum C-reactive protein (CRP) level and 6-year survival.

Results

Patients were aged 53 ± 14 years (mean ± SD) and included 43% women and 42% African Americans. Median dietary omega-3 intake, ratio of omega-6 to omega-3 intake, baseline serum CRP level, and change in CRP level over 1 year were 1.1 (25th-75th percentile, 0.8-1.6) g/d, 9.3 (25th-75th percentile, 7.6-11.3), 3.1 (25th-75th percentile, 0.8-6.8) mg/L, and +0.2 (25th-75th percentile, -0.4 to +0.8) mg/L, respectively. In regression models adjusted for case-mix, dietary calorie and fat intake, body mass index, and history of hypertension, each 1-unit higher ratio of omega-6 to omega-3 intake was associated with a 0.55-mg/L increase in serum CRP level (P = 0.03). In the fully adjusted model, death HRs for the first (1.7-<7.6), second (7.6-<9.3), third (9.3-<11.3), and fourth (11.3-17.4) quartiles of dietary omega-6 to omega-3 ratio were 0.39 (95% CI, 0.14-1.18), 0.30 (95% CI, 0.09-0.99), 0.67 (95% CI, 0.25-1.79), and 1.00 (reference), respectively (P for trend = 0.06).

Limitations

3-day food record may underestimate actual dietary fat intake at an individual level.

Conclusions

Higher dietary omega-6 to omega-3 ratio appears to be associated with both worsening inflammation over time and a trend toward higher death risk in hemodialysis patients. Additional studies including interventional trials are needed to examine the association of dietary fatty acids with clinical outcomes in these patients.

Objectives

Periodic assessment of dietary intake across a given dialysis population may help to improve the clinical outcomes related to nutrients such as dietary protein, phosphorus, or potassium. Although dietary recalls and food records are used to assess dietary intake at individual level and over shorter periods, food frequency questionnaires (FFQ) are used to rank subjects of a given population according to their nutrient intake over longer periods.

Design

To modify and refine the conventional Block FFQ to develop a specific FFQ for dialysis patients.

Setting

A total of 8 DaVita outpatient dialysis clinics in Los Angeles area, which participated in the "Nutrition and Inflammation in Dialysis Patients" study.

Patients

The study included 154 patients undergoing maintenance hemodialysis (MHD).

Main outcome measure

Dietary intake of participating MHD patients using a 3-day food record, supplemented by a person-to-person dietary interview, to capture food intake over the last hemodialysis treatment day of the week and the 2 subsequent nondialysis days.

Results

Analyses of the food records identified the key contributors to the daily nutrient intake in the 154 participating MHD patients. A "Dialysis-FFQ" was developed to include approximately 100 food items representing the total food intake of 90% of the patients of the "Nutrition and Inflammation in Dialysis Patients" study population. Distinctions were made in several food items on the basis of key nutritional issues, such as protein, phosphorus, and potassium, in dialysis patients.

Conclusions

We have developed a "Dialysis FFQ" to compare and rank dialysis patients according to their diverse nutrient intake. Although the Dialysis-FFQ may be a valuable tool to compare dialysis patients and to identify those who ingest higher or lower amounts of a given nutrient, studies are needed to examine the utility of the Dialysis-FFQ for nutritional assessment of dialysis patients.

Background and objectives

Maintenance hemodialysis (MHD) patients with larger body or fat mass have greater survival than normal to low mass. We hypothesized that mid-arm muscle circumference (MAMC), a conveniently measured surrogate of lean body mass (LBM), has stronger association with clinical outcomes than triceps skinfold (TSF), a surrogate of fat mass.

Design, settings, participants, & measurements

The associations of TSF, MAMC, and serum creatinine, another LBM surrogate, with baseline short form 36 quality-of-life scores and 5-year survival were examined in 792 MHD patients. In a randomly selected subsample of 118 subjects, LBM was measured by dual-energy x-ray absorptiometry.

Results

Dual-energy x-ray absorptiometry-assessed LBM correlated most strongly with MAMC and serum creatinine. Higher MAMC was associated with better short form 36 mental health scale and lower death hazard ratios (HRs) after adjustment for case-mix, malnutrition-inflammation-cachexia syndrome, and inflammatory markers. Adjusted death HRs were 1.00, 0.86, 0.69, and 0.63 for the first to fourth MAMC quartiles, respectively. Higher serum creatinine and TSF were also associated with lower death HRs, but these associations were mitigated after multivariate adjustments. Using median values of TSF and MAMC to dichotomize, combined high MAMC with either high or low TSF (compared with low MAMC/TSF) exhibited the greatest survival, i.e., death HRs of 0.52 and 0.59, respectively.

Conclusions

Higher MAMC is a surrogate of larger LBM and an independent predictor of better mental health and greater survival in MHD patients. Sarcopenia-correcting interventions to improve clinical outcomes in this patient population warrant controlled trials.