Food Literacy and Adherence to Mediterranean-Style Diet in Transplant Recipients

The optimal treatment for end-stage kidney disease is kidney transplantation, providing improved quality of life and longer life expectancy compared with maintenance dialysis. However, compared with the general population, life expectancy of kidney transplant recipients is still lower, due primarily to high cardiovascular morbidity and mortality. Kidney transplant recipients commonly have an unfavorable cardiovascular profile, characterized by post-transplantation weight gain, obesity, metabolic syndrome, post-transplantation diabetes mellitus, and hypertension.

As in the general population and in other high risk groups, there is an association between a healthy diet, including a variety of wholegrain products, fruit and vegetables, nuts, legumes, lean meats and fish, and an avoidance of high sodium intake and lower cardiovascular risks in kidney transplant recipients. Results of previous studies have shown an association between adherence to a Mediterranean-style diet and a lower risk of post-transplantation diabetes and all-cause mortality in addition to improved kidney function outcomes. Dietary sodium restriction has also been proven effective in lowering blood pressure in kidney transplant recipients.

As part of the TransplantLines Cohort and Biobank study at the University Medical Center Groningen in the Netherlands, Karin Boslooper-Meulenbelt and colleagues conducted a cross-sectional study to examine levels of food literacy among kidney transplant recipients and assess its association with adherence to a Mediterranean-style diet and with dietary sodium intake. Results of the study were reported in the Journal of Renal Nutrition [2021;31(6):628-636].

A total of 148 kidney transplant recipients 1 year or more post-transplantation who completed a Food Frequency Questionnaire (FFQ) were invited to complete the Self-Perceived Food Literacy (SPFL) questionnaire and All Aspects of Health Literacy Scale (AAHLS). The collection of data occurred between June 2019 and January 2020.

Mean age of the study cohort was 56 years, 66% were male, mean estimated glomerular filtration rate was 53.7 mL/min/1.73 m², and mean plasma potassium level was 4.02 mmol/L. One participant had end-stage kidney failure requiring dietary restrictions. Mean consumption of fruit and vegetables was 129 g/day and 127 g/day respectively. Mean SPFL score was 3.63. The majority of participants reported maximum scores at the functional and communicative domain of the AAHLS.

Participants with higher food literacy levels (SPFL score ≥3.41) were more often female, were older, had higher level of education, and were less often an active smoker than those with lower food literacy levels. There were no significant differences in transplant-related and cardiometabolic parameters across levels of food literacy with the exception of time since transplantation: those with lower food literacy levels had longer time since transplantation.

Mediterranean Diet Score was significantly higher among participants with higher food literacy levels as well as higher fruit, vegetable, and fish consumption compared with those with lower food literacy levels. Participants in the group with higher food literacy generally limited salt intake to <6 g/day more often than did those in the group with lower food literacy (P=.08). However, the majority of participants in both groups exceeded the advised salt consumption of 6 g/day. Participants with lower food literacy were involved in meal preparation less often than those with higher food literacy.

Results of univariable linear regression analysis demonstrated an association between higher mean SPFL scores and a higher Mediterranean Diet Score, reflecting better adherence to a Mediterranean-style diet (P<.001). Following adjustment for age and sex, cardiometabolic parameters, transplant-related parameters, employment status, level of education, smoking status, and alcohol use, the associations remained significant.

In both unadjusted and adjusted linear regression analyses, there were no significant associations between sodium intake and SPFL score.

Limitations to the study cited by the authors included the use of the SPFL that has subjective, self-reported questions to determine the level of food literacy, the possibility of selection bias, and the inability to correct for changes in dietary intake over time.

In conclusion, the researchers said, “Higher levels of food literacy, measured with the SPFL questionnaire, are associated with better adherence to a Mediterranean-style diet in kidney transplant recipients. The association between food literacy and sodium intake is less consistent. Further studies are needed to determine if interventions focused on improving food literacy may contribute to a healthier diet and better long-term outcomes in kidney transplant recipients.”

Takeaway Points

1. Researchers in the Netherlands conducted a cross-sectional study to examine food literacy levels in kidney transplant recipients and the association with adherence to a Mediterranean-style diet and restriction of sodium intake.
2. Those with higher food literacy level were more likely to have better adherence to a Mediterranean-style diet. The associations between higher food literacy and a higher Mediterranean Diet Score were significant in unadjusted and adjusted linear regression analyses.
3. There were no significant associations between higher food literacy and dietary sodium intake.