Dietary macronutrient intake and kidney outcomes in patients with type 2 diabetes: a cross-sectional study

This study examined the relationship between dietary macronutrient intake and kidney outcomes, including estimated glomerular filtration rate (eGFR) and diabetic kidney disease (DKD), in patients with type 2 diabetes (T2D).

We conducted a cross-sectional analysis using baseline data from an ongoing cohort of patients with T2D (n = 472) in Tehran, Iran. To assess dietary intake, we used a reliable and validated semi-quantitative food frequency questionnaire (FFQ). Macronutrient intakes were calculated and expressed in grams per day (g/d) and as a percentage of total energy intake (%TE), Kidney function was measured by eGFR according to the CKD-EPI equation. DKD was defined as an eGFR < 60 mL/min/1.73 m² ² persisting for at least 3 months. We examined associations of macronutrient intake with kidney outcomes using multivariable linear and logistic regression models adjusted for potential confounders.

In crude linear regression analyses, higher protein intake was associated with lower eGFR (g/d: B = - 1.699, 95% CI: -3.279 to - 0.119). However, this relationship weakened and became non-statistically significant after adjusting for confounders. In logistic regression, protein intake was not significantly associated with odds of DKD in any model. Carbohydrate intake showed no significant association with eGFR in linear regression. Notably, in logistic regression, participants in the second quartile of carbohydrate intake had higher odds of DKD compared with those in the lowest quartile (g/d: OR = 2.633, 95% CI: 1.234-5.616; %TE: OR = 2.733, 95% CI: 1.304-5.727), while no significant associations were observed in the higher quartiles. Finally, fat intake (g/d and %TE) was not associated with eGFR or DKD in crude or fully adjusted models.

There was no significant association between protein or fat intake and kidney outcomes. Carbohydrate intake was not associated with eGFR and was associated with higher odds of DKD only in the second quartile. However, no dose-response relationship was observed across quartiles. Ongoing follow-up of this cohort may help clarify temporal and causal relationships between macronutrient intake and kidney outcomes.