A total of 589 million patients aged 20–79 are diagnosed with diabetes in the world. Type 2 diabetes (T2D) is the most prevalent form of diabetes globally, accounting for 96.0% of all diabetes cases, and is associated with numerous complications that significantly impact patient quality of life and life expectancy.1,2 Diabetic kidney disease (DKD), a key microvascular complication of T2D, affects roughly 50% of T2D patients who eventually progress to this condition.3 In 2021, the global number of DKD cases related to T2D will reach 107 million, with 477,000 deaths. The age-standardized incidence rate is expected to continue to rise in the future,4 placing an immense burden on global public health. Moreover, DKD is associated with excess mortality in diabetes patients, with the crude all-cause mortality rate in the DKD cohort being nearly twice that of the control group (simple T2D patients) (50.3 vs 28.4 per 1000 person-years).5 DKD remains a primary cause of end-stage renal disease, triggering arterial diseases and cardiovascular complications that complicate treatment for patients.6 Consequently, identifying means to curb the progression of DKD is crucial for reducing the mortality risk among T2D patients.

Nutrition interventions are key to diabetes management, with a balanced diet contributing to improved glucose metabolism and reduced DKD risk in patients with diabetes.7 The United States Dietary Guidelines recommend assessing the quality of American diets using the Healthy Eating Index (HEI), which serves to identify healthy dietary patterns for various populations. The HEI is updated in tandem with the Dietary Guidelines, with the most recent version being HEI-2020.8 It has been widely employed in research on chronic diseases, with the highest quintile array of HEI scores demonstrating significantly lower risk for chronic diseases (including diabetes) compared to the lowest quintile array.9 A systematic review has also shown that better adherence to HEI can lower risks for diabetes and cardiovascular diseases (CVD).10 It is noteworthy that higher HEI adherence can lower the risk of CVD in diabetes patients by 50%.11 Given this, we speculate that enhancing HEI adherence is likely to also lower the risk of DKD in patients with diabetes. Moreover, there is evidence that an increase in HEI-2020 scores is linked with a reduced risk of chronic kidney disease (CKD),12 although the active effect on diabetic patients has not yet been adequately validated.

Thus, this work investigates the relationship between HEI-2020 scores and the prevalence of DKD in T2D patients enrolled in the National Health and Nutrition Examination Survey (NHANES) database, aiming to shed valuable insights into the prevention and dietary guidance for T2D patients with DKD.

Our findings demonstrated a significant negative correlation between HEI-2020 scores and the prevalence of DKD among T2D patients. This association was observed in individuals who were overweight, obese, non-smoking, had previously smoked, had high blood pressure, and engaged in intense PA. Furthermore, dairy products, total protein foods, and total vegetables were the most impactful components in HEI-2020.

HEI has been considered to be associated with the prevalence of diabetes and CKD. Specifically, the HEI-2005 score is positively correlated with reduced risk of diabetes,9 while the HEI-2010 score was discovered to be negatively correlated with microalbuminuria concentration in diabetic patients.21 A prospective cohort study revealed that compared with those in the lowest quintile, participants in the highest quintile of the HEI-2015 score had a 17% lower risk of developing CKD,22 and the highest quintile was also associated with a composite risk of kidney outcomes reduction.23 The new version of the HEI-2020 showed a significant negative correlation with the prevalence of DKD in T2D patients, further emphasizing the favorable effect of HEI scoring. The components and scorings of different versions of HEI are shown in Table S4. Furthermore, HEI-2020 is associated with the risk of heart failure and reduced levels of inflammatory markers,24 which exacerbate DKD progression.25 Therefore, for individuals with diabetes, adhering to the healthy eating patterns advocated by HEI-2020 not only aids in lowering the risk of DKD but may also positively impact the prevention and control of other chronic diseases, thereby improving overall well-being.

In different populations characterized by distinct features, the HEI-2020 score exhibited disparities in the prevalence of DKD among patients with T2D. While metabolic abnormalities may be more pronounced in overweight and obese patients, the prevalence of DKD is potentially higher.26 However, increased HEI scores can alleviate weight gain and enhance overall health.27 Therefore, it may be more beneficial for such patients. For those with hypertension, HEI emphasizes limiting sodium intake and consuming more vegetables and fruits, which effectively reduces the risk of hypertension,28 exhibiting potential renal protective effects. High-intensity exercise can improve blood sugar control, reduce renal oxidative stress and inflammation, and synergistically improve risk factors such as obesity and hypertension with HEI diet, thereby being associated with a lower risk of DKD.29 In addition, high-intensity interval training is superior to continuous training with moderate intensity in controlling blood glucose control.30 On the contrary, patients who lack exercise often have more metabolic abnormalities, obesity, and sedentary behavior, which increases their risk of DKD,31 and possibly masks the true association between HEI-2020 and DKD risk.

Upon further analysis, it was found that dairy products, total protein foods, and total vegetables were the most influential components within the HEI-2020. Dairy products are a class of food made from milk, which have numerous health benefits for the human body.32 Research shows that higher intake of milk and yogurt is associated with lower risk of DKD and metabolic syndrome.33 Probiotic yogurt (such as kefir) can also lower blood glucose, creatinine, and urea levels in diabetic rats, and improve renal glomerular casts, tubular degeneration, and renal epithelial tissue, thereby slowing down the progression of DKD.34 In addition, camel milk has been shown to downregulate the expression of DKD-related genes and preserve normal glomerular morphology.35

Protein is an indispensable nutrient for human life activities and physiological functions. A higher protein intake is associated with a lower prevalence of prediabetes and diabetes,36 as well as improved blood lipid levels and insulin resistance in T2D.37 Protein intake can augment satiety, reduce lipid absorption in the gut, and repress fat deposition by curbing the growth of lactobacilli,38 thereby aiding in appetite control and weight maintenance. These changes are all associated with a decrease in the incidence of DKD.

The consumption of total vegetables also holds significant sway over the prevalence of DKD. Genetic evidence suggests that vegetable intake is determined as a protective factor for DKD.39 A case–control study also demonstrated that vegetable consumption was associated with lower DKD prevalence.40 Dietary fiber can regulate gut microbiota, enrich bacteria that secrete short-chain fatty acids (such as Prevotella and Bifidobacterium), and increase short-chain fatty acids. It can also reduce the expression of genes encoding inflammatory cytokines and chemokines in DKD, thereby preventing the occurrence of DKD.41 In addition, the antioxidants found in vegetables, including vitamin E, carotenoids, and vitamin C, can effectively alleviate oxidative stress and chronic inflammation associated with diabetes,42 thereby contributing to slowing down the development of DKD.

We also found that consuming more seafood and plant protein was associated with a lower risk of DKD, while consuming added sugar was associated with a higher risk of DKD. Seafood products are rich in omega-3 fatty acids, which have anti-inflammatory and antioxidant properties.43 Increased intake of omega-3 fatty acids can lower blood pressure, which is a key risk factor for the development of CKD.44 Regarding plant protein, research has shown that plant or white meat protein is more beneficial for kidney function protection compared to red meat protein.45 Beans are an important source of plant protein. A study compared the effects of different soy protein intake ratios (0%, 35%, 100%) on DKD patients, and the results showed that a 35% soy protein diet was most effective in improving kidney function and glucose and lipid metabolism.46 Added sugar is commonly believed to cause insulin resistance, increase oxidative stress and inflammation levels, thereby impairing kidney function, which is consistent with our findings.47 Therefore, it is advisable to limit the intake of added sugars as much as possible, which can help maintain kidney health.

This study further explored the impact of diabetes duration on the association between HEI-2020 and DKD. In the previously diagnosed T2D patients, HEI-2020 was significantly negatively correlated with DKD, while no significant correlation was observed in the newly diagnosed patients, which suggested that the course of diabetes may affect the effect of diet-related interventions. The longer duration of diabetes is proven to be associated with more obvious renal damage caused by chronic hyperglycemia.20 Long-term adherence to a healthy diet may alleviate the sustained adverse effects of high blood sugar on the kidneys to some extent by improving metabolic status, reducing inflammation levels, and oxidative stress.48 In contrast, the risk of DKD in newly diagnosed patients is mainly influenced by genetic factors and other comorbid risk factors, and the effect of dietary intervention may not have been fully demonstrated. Subgroup analysis of previously diagnosed T2D patients found that smoking status had a significant interaction on the association between HEI-2020 and DKD. Smoking is a known risk factor for DKD, and nicotine in it will increase the expression of proteinuria and fibronectin in diabetic mice.49 This suggests that current smoking may weaken the protective effect of a healthy diet on the kidneys, thereby offsetting the potential benefits of a healthy diet. It is worth noting, however, that some limitations in the research should also come into consideration. Since this work is a cross-sectional analysis, we can only identify the relationship between variables rather than establish causality. Secondly, according to the KDIGO guidelines, CKD is defined as persistent abnormalities in renal structure or function (eGFR <60mL/min/1.73m2 and/or urinary albumin/creatinine ratio ≥30mg/g) that persist for ≥3 months.50 In this study, we only evaluated renal function based on a single measurement of eGFR and urinary albumin/creatinine ratio. The transient renal dysfunction may increase the risk of overestimating the prevalence of DKD. Thirdly, this study excluded a large number of samples due to missing covariate information from some participants, which may lead to selection bias and affect the representativeness of the results. Fourthly, all participants are drawn from the NHANES program, which may limit the generalizability of our findings when applied to other populations. Fifthly, despite our efforts to adjust potential confounders in the analysis process to minimize their impact on the results, we cannot entirely exclude the impact of other potential confounders such as environmental factors (air quality and water quality), metabolic levels, as well as genetic structures. In the present study, our main focus was on the impact of HEI-2020 scores on the prevalence of DKD. Unfortunately, we did not delve into an in-depth analysis regarding whether the long-term prognosis of patients with DKD would change. Future studies can dig out the impact of HEI-2020 scores on the outcomes of DKD patients.

This study revealed a negative correlation between HEI-2020 scores and DKD prevalence among T2D patients. Additionally, dairy products, complete protein foods, and total vegetables offer significant health benefits in reducing the prevalence of DKD. These findings underscore the importance of dietary management in T2D patients, suggesting that personalized dietary strategies could facilitate the health of such individuals and mitigate the risk of DKD.

Conceptualization: Chunping Dong, Hui Li, Jing Li; Data curation: Hui Li; Formal analysis: Chunping Dong, Shan Gao; Investigation: Jing Li; Methodology: Chunping Dong; Project administration: Chunping Dong; Resources: Hui Li; Software: Yuan Qiao; Supervision: Hui Li; Validation: Shan Gao; Visualization: Shan Gao; Writing – original draft: Chunping Dong, Hui Li, Jing Li; Writing – review & editing: Yuan Qiao, Shan Gao.

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The data and materials in the current study are available from the corresponding author on reasonable request.