Following prospective analyses using data from a population-based study, we observed a trend of decreasing incident CKD risk with increasing intakes of a lacto-vegetarian dietary pattern among adults. In addition, participants who were in the highest tertile of the high fat, high sugar dietary pattern had a significant 49% increased odds of having incident CKD, independent of diabetes and hypertension.
In accordance with the our findings which lacto-vegetarian dietary pattern decreased risk of CKD, a study of diabetic patients from a cohort in Taiwan showed that extracted dietary pattern named fish and vegetable dietary pattern was independently associated with decreased adjusted means of creatinine levels . A cross-sectional study from the Multi-Ethnic Study of Atherosclerosis (MESA) found that a dietary pattern including high intakes of whole grains, fruit, vegetables, and low-fat dairy foods was inversely associated with urinary albumin-to-creatinine ratio and the odds of microalbuminuria among adults without CVD, diabetes or microalbuminuria . However unlike our findings, a study conducted on female nurses, aged 30–55 years, from the Nurses’ Health Study showed that higher adherence to the prudent dietary pattern (high intake of fruits, vegetables, legumes, fish, poultry, and whole grains) was not significantly associated with kidney function decline .
In previous studies we observed that both DASH diet and Mediterranean diet recommending foods and nutrients similar to the lacto-vegetarian dietary pattern characterized by high intakes of fruit, vegetables, low-fat dairy, and whole grains and low intakes of processed meat, have been shown to improve kidney function and decrease the risk of kidney damage [3, 4, 6, 24,25,26]. Several components of the DASH-style diet including fruits, whole grains, and nuts and legumes have also been associated with the decreased risk of CKD . Higher compliance to the dietary pattern which is similar to the DASH diet could mediate decreased risk of CKD by modifying several cardio-metabolic risk factors, e.g. improved plasma lipid profiles, blood pressure, insulin sensitivity, oxidative stress, inflammation, and endothelial dysfunction [27,28,29]. Besides, the favorable effect of the lacto-vegetarian dietary pattern on kidney function has been illustrated by higher intakes of calcium, vitamin C, potassium, and magnesium, increases intakes of potassium and magnesium were associated with the lower dietary acid load. Recent studies suggest that dietary acid increment has an undesirable effect on kidney function . Whereas, higher intakes of vegetables and fruits as main component of lacto-vegetarian dietary pattern had an inverse association with CKD [10, 11, 31]. Low-fat dairy, loaded in the lacto-vegetarian dietary pattern was inversely associated with ACR . The amino acid and fatty acid composition of dairy foods in comparison with non-dairy might justify the different directions of associations. Furthermore, milk proteins, vitamin D, magnesium, and calcium may also contribute to these associations [32, 33].
Compared with participants in the lowest tertile of the high fat, high sugar dietary pattern, those in the highest one had 49% higher odds of incident CKD. Similar to our findings, the previous study among women from the Nurses Health Study showed the highest quartile of the Western dietary pattern (characterized by high intakes meat, processed meat, saturated fat, and sweets) compared with the lowest quartile has a 77% increased rapid eGFR decline after 11 years of follow-up . Consistently, Shi et al. observed that a modern dietary pattern (high intake of fruit, soy milk, egg, milk and deep fried products) was associated with 50% decreased risk of CKD . In this regard, studies found that higher consumption of red and processed meats, sugar-sweetened beverages, and sodium, which in combination were known as the Western dietary pattern, have been positively associated with CKD [11, 31, 34]. The Western dietary pattern is correlated positively with inflammatory markers such as CRP, interleukin 6, and E-selectin ; apparently these mediators may explain the direct association of the Western dietary pattern with kidney function impairment in those consuming more fat and meat .
From population-based studies that used factor analysis to identify dietary pattern, mostly two major dietary patterns were distinguished. The Prudent pattern is characterized by higher intakes of fruits, vegetables, legumes, whole grains, and sometimes poultry, and fish, whereas the Western pattern is characterized by higher intakes of saturated fats and processed and artificially sweetened foods, and salt. The former is consistently shown to have significant relation with lower risk of coronary heart disease, type 2 diabetes, and colorectal cancer, whereas the latter significantly elevated the risk of these diseases [36,37,38]. In the current study, the lacto-vegetarian dietary pattern was closely similar to the prudent pattern and the high fat, high sugar dietary pattern was consistent with western dietary pattern. In addition, it seemed that higher adherence to the lacto-vegetarian dietary pattern was accompanied by a healthier lifestyle including a decrease in smoking, BMI, and prevalence of diabetes and hypertension. In contrast, higher adherence to the high fat, high sugar dietary pattern was associated with increased smoking, BMI, and increased prevalence of hypertension. In this regard, previous studies extracting dietary pattern mostly described a healthy dietary pattern and high fat, high sugar dietary pattern. Nutrition transition of Iran as a subsequent issue of economic growth, urbanization, and industrialization push people toward the high fat, high sugar dietary pattern. Fast foods, sugar-sweetened beverage, and meat products high in saturated fat, sugar, and salt became more common in Iran.
Our findings revealed that there was no significant association between the traditional Iranian dietary pattern and incidence of CKD. Shi et al. observed that a traditional Southern dietary pattern (high intake of rice, pork, and vegetables, and low intake of wheat) was associated with 4.5-fold increased odds of prevalence of CKD. Netletton et al. illustrated that a dietary pattern which is similar to ours, high intakes of legumes, tomatoes, refined grains, high-fat dairy, and red meat was positively associated with albumin to creatinine ratio (ACR) . The traditional dietary pattern of the Iranian population is identified mainly by high consumption of refined grain, egg, tea, potato, red meat, pickles, hydrogenated fat, and sugar as seen in previous studies, which used factor analysis to extract Iranian population dietary pattern [39,40,41,42,43,44,45]. In Iranian traditional dietary pattern, unhealthy food groups such as refined grains (white rice and bread), potatoes, and red meat were highly loaded; however, the presence of some healthy foods like legumes also loaded in this dietary pattern which could interact with other foods in the pattern to modulate consequent kidney dysfunction.
Although the association of major patterns identified through factor analyses with kidney function has been examined in several studies among American , European , and Chinese  populations, there is a lack of evidence in Iranian ones. Dietary patterns are likely to vary according to ethnic groups and cultures. It is thus necessary to replicate the results in diverse populations.
Limitations of this investigation need to be mentioned; first, as in most epidemiologic studies, our definition of CKD is based on a limited number of isolated creatinine measurements that were not repeated within three months to confirm a chronic reduction in GFR. Besides, although using creatinine estimated eGFR has a limitation because serum creatinine varied day-to-day (15.5–19.6%), most epidemiologic studies used serum creatinine for the definition of the CKD as it is cheap, technically simple and therefore easily applied for a large population measurements [5, 34]. Second, despite controlling for various confounders in our analysis, residual confounding due to unknown or unmeasured confounders such as socioeconomic factors cannot be excluded. However, the study’s noteworthy strengths, unlike previous studies, the current study provided data based on habitual dietary intakes in a population-based sample of participants, therefore, increasing the generalizability of its results.