# Can Walnut Serve as a Magic Bullet for the Management of Non-Alcoholic Fatty Liver Disease?
## 1 Introduction  
Nuts are natural food sources and are globally one of the most popular snacks or ingredients of a healthy diet. Walnut has a distinct composition compared with that of other nuts [1]. It is an excellent source of essential fatty acids such \(\alpha\)-linolenic acid and oleic acid [2] and contains high levels of polyphenols, such as gallic acid, (+)-catechin, chlorogenic acid, and ellagic acid [3], in addition to being rich in fiber, and vitamins such as \(\gamma\)-tocopherol, folate, and vitamin B 6. Walnut also contains minerals such as copper, chromium, iron, and zinc and plant compounds such as phytic acid and melatonin. Furthermore, walnut is a healthy source of vegetable proteins. Thus, walnut is a natural functional food and the incorporation of walnut into the human diet is highly desirable for the prevention of chronic diseases such as cardiovascular disease, type 2 diabetes mellitus (T2 DM), cancer, and neurocognitive disorder [4]. Walnuts, including their roots and leaves, have been traditionally used as herbal medicines for treating various conditions such as infectious disease, abdominal pain, skin disease and rheumatic pain [5, 6]. Interestingly, in folk medicine, walnuts have also been used for treating liver injury, even though the efficacy remains uncertain [7].  
Non-alcoholic fatty liver disease (NAFLD) is a disease whose prevalence is increasing in adults and children globally; its prevalence parallels that of obesity [8; 9]. NAFLD is a broad spectrum disease whose manifestation range from simple steatosis and steatohepatitis to liver cirrhosis and liver cancer [10]. It is characterized by the excessive fat deposition in the hepatocytes, suggesting that NAFLD is a metabolic disease associated with dyslipidemia. However, NAFLD is not a simple metabolic liver disorder and is associated with various extra-hepatic diseases, including cardiovascular disease, chronic renal disease, and cancers as well as metabolic comorbidity with obesity, T2 DM, and hyperlipidemia, which are interconnected as metabolic syndrome [11]. Although hepatic fat accumulation can be promoted by multiple metabolic and environmental factors, NAFLD is considered to be a nutritional disease. Lipid metabolism in the liver is a complex process involving digestion and absorption of foods and nutrients to obtain energy and maintain metabolic homeostasis.  
Unfortunately, although NAFLD is the most common liver disease, no specific medications are available for NAFLD except those that target NAFLD-accompanying conditions such as dyslipidemia, obesity, high blood glucose or high blood pressure. Thus, lifestyle change such as diet control and exercise are recommendations for etiology-based therapy. In this respect, the management of NAFLD with walnuts or walnut-enriched diets can be an effective strategy because healthy components of walnut can target all candidate mechanisms underlying NAFLD development and progression.  
The present review addressed the effects of walnut on NAFLD based on the pathophysiological mechanisms by which walnut and walnut components exert preventive effects with respect to the development and progression of NAFLD.