This case-control study identified four major dietary patterns; "ordinary pattern", "fast food type pattern", "traditional pattern" and "vegetable and dairy pattern". We realized that "ordinary pattern" and "traditional pattern" were significantly increased the risk of NAFLD, while the "vegetable and dairy pattern" has an inverse association with NAFLD in the Ahvaz population. However, we don't find any significant association between the "fast food type pattern" and the risk of NAFLD. Based on our search, this study is the first study investigated the association between dietary patterns and NAFLD in the Ahvaz population.
The "ordinary pattern" is characterized by high intakes of "sweets, oils, fruits, white meats, refined grains, tea and coffee, salt, Biscuits, snacks, and red and organ meats". Most of the food groups in this dietary pattern consist of high amounts of carbohydrates especially refined sugars which enhanced de novo fatty acid synthesis in the liver.
The "fast food type pattern" is characterized by the high consumption of "fast foods, pickles, sauces, soft drinks, snacks, and biscuits". Unlike most studies on this topic that reported a positive relationship between fast food patterns and risk of NAFLD, we don't identify any association between this dietary pattern and NAFLD.
The "traditional pattern" is characterized by high intakes of "condiments, red and organ meats, dairy products, salt, and tea and coffee". This pattern has also a direct association with NAFLD.
The "vegetable and Dairy pattern" is characterized by high intakes of "vegetables, whole grains, legume and nuts, and dairy products. We found that high adherence to this pattern was reduced the risk of NAFLD, perhaps because of high intakes of vitamins and minerals and fiber.
"ordinary pattern" adherence is associated with high intakes of energy-dense foods with relatively high amounts of fat, animal protein, and refined sugars. Some foods in this dietary pattern –including refined grains, white bread, biscuits, and sweets- lead to a rapid increase in postprandial plasma glucose, insulin concentration, and diabetes (30). Such high glycemic index foods cause increase hepatic steatosis, especially in insulin-resistant subjects (31). Jia et al. also reported that a high carbohydrate/sugar pattern was associated with NAFLD in women (18). Moreover, our results are in line with the finding of another study in japan that represented a high carbohydrate diet, especially sweets, resulting in a higher risk of NAFLD (32). However, Chung et al. did not find a relationship between the high carbohydrate diet and the risk of NAFLD (33). Our findings confirm the result of the studies suggesting that a high fruit diet is associated with NAFLD (34, 35). Fruits are rich in simple carbohydrates particularly fructose. Fructose has a role in the pathophysiology of NAFLD. High intake of fructose leads to de novo lipogenesis and lipid accumulation and steatosis in the liver. Moreover, chronic consumption of fructose enhances hepatic inflammation and oxidative stress which are responsible for the progression of the hepatic disease (36).
Some previous studies were suggested that a "fast food pattern" or a "western diet" is associated with NAFLD (5, 19). A western diet, characterized by high intakes of fried foods, red and processed meat, refined grains, snacks, sauces, and soft drinks has been prospectively associated with NAFLD risk in adolescence (19). Kalafati et al. reported similar results about fast food pattern and NAFLD risk with the previous study (5). However, we couldn’t find a significant association between the fast-food pattern and risk of NAFLD but the possible reason for this discrepancy could be due to the differences in dietary patterns between ethnicities, cultural groups, and gender. Also, dietary patterns may vary over time because of personal preferences and the availability of food (9).
Meats like red meat and visceral meat loaded relatively high in the "ordinary pattern" and "traditional pattern". studies that investigated the association between high protein and NAFLD are scarce. Zelber Sagi et al. illustrated that all types of meats were significantly associated with an increased risk for NAFLD (37). one explanation for this association could be that high protein intake is associated with insulin resistance and glucose intolerance and might even increase the incidence of type-2 diabetes (38, 39). Another possible explanation is a higher intake of iron and in particular, heme-iron that may play a role in the pathogenesis of NAFLD by increasing oxidative stress (40). the "traditional pattern" and "ordinary pattern" are high in salt. The findings of the studies about the role of sodium in NAFLD are controversial. A study of a Korean population reported that high salt dietary pattern was associated with an increased risk of NAFLD, while another study in the Chinese population detected no significant association between a high salt dietary pattern and NAFLD (20, 41). More studies are required to clarify this association.
Yang et al. reported an inverse association between a "grain and vegetable pattern" and NAFLD and this association was independent of confounding factors like age, sex, BMI, physical activity (20). Another study in the Lebanese population also showed that a "traditional Lebanese" diet that consists of vegetables and legumes has a negative association with the risk of NAFLD (34). These results confirmed our findings that a dietary pattern rich in vegetables, legume and nuts could reduce the risk of NAFLD. This protective effect against NAFLD might be because of the high fiber content in this pattern.
This study has some possible strengths. This is the first study investigating the association between major dietary patterns and the risk of NAFLD in the Ahvaz population. Potential confounding factors were identified and controlled for in the analysis. Moreover, we used a semi-quantitative FFQ designed for the Iranian population, which result in a better representation of the dietary habits of the participants.
There are some limitations that should be considered. First, because of the case-control design of this study, it cannot confirm a causal relationship between dietary patterns and NAFLD. Second, the overestimation of energy intake because of using a FFQ for data collection is a great risk. Third, recall bias exists because of the self-reporting nature of the questionnaire.