The role of diet in non-alcoholic fatty liver treatment

Fatty liver disease (FLD) is one of the most common chronic liver diseases around the world, and it is divided into two types: alcoholic fatty liver disease (AFLD) and non-alcoholic fatty liver disease (NAFLD) (1). AFLD is a term used to describe a condition in which excessive alcohol consumption impairs liver function (2). NAFLD is caused by the accumulation of too much fat in the liver cells and causes inflammation of the liver and liver fibrosis (3). Patients who consume less than 20 to 30 grams of alcohol per day are diagnosed with NAFLD and those who consume more than this amount with AFLD. AFLD is treated by stopping alcohol consumption(4). In this article, we are going to talk to you about NAFLD and role of diet therapy in NAFLD treatment.

Prevalence and Risk factors and complications of NAFLD

It is estimated that 25% of the world's population suffers from NAFLD(5). NAFLD is more common in adults because these people show more features of its risk factors. However, NAFLD is also detectable in children and adolescents (6). The prevalence of NAFLD is closely related to overweight and central obesity, dyslipidemia, hypertension, insulin resistance, and type 2 diabetes mellitus (7). NAFLD is a complex disease that its risk factors include genetic factors, dietary patterns, and lifestyle (8). If NAFLD is left untreated, it can lead to liver cirrhosis, liver failure, liver cancer, or predispose patients to liver transplants (9). NAFLD is the leading cause of liver transplantation in people over 65 years of age. Cirrhosis from NAFLD develops slowly and often remains silent until clinical signs appear. There are probably 2-3 million patients with cirrhosis from NAFLD in the United States and millions worldwide; still, most are unaware of their disease(10).

How can we prevent NAFLD?

In order to prevent NAFLD, people should be encouraged to have a healthy lifestyle, exercise, and proper nutrition, which play an important role in both the prevention and treatment of NAFLD. If you are overweight and obese, it is recommended to reach your ideal weight. If you have insulin resistance, glycemic control through diet, exercise, and medication is recommended because NAFLD is directly related to obesity and insulin resistance. It is also recommended to consume less refined sugars, especially fructose (11).

What are the treatments for NAFLD?

The number of people with NAFLD is rapidly increasing in the world, and this is increasing the need for new methods to treat this disease (5). Recently, no validated drug has been used to treat NAFLD. New therapies focus on lifestyle modification to achieve the ideal weight. Another method of treating obesity in NAFLD is the use of weight loss drugs, and if these measures are insufficient, obesity surgeries are performed (11).


Lifestyle modification

Lifestyle modification is one of the possible methods to lose weight, including diet and physical exercise, which are very effective for patients suffering from NAFLD (8). Lifestyle modifications that help you lose weight are the standard treatment for NAFLD. Weight loss of 5 to 10 percent of your body weight, can significantly improve NAFLD symptoms. If the dietary restriction is accompanied by physical activity, it will lead to more weight loss (12, 13). Lifestyle modification in NAFLD patients improves the fatty liver and improves atherogenic dyslipidemia, blood pressure levels, and hyperglycemia (8).


Exercise and NAFLD treatment

Studies have shown that any kind of exercise can improve liver function in NAFLD. Houghton and colleagues showed that both aerobic and anaerobic exercise for 12 weeks reduced triglycerides and blood glucose in NAFLD patients. Other studies have shown that moderate-intensity aerobic exercise for 24 weeks improves liver function. Exercise improves NAFLD by reducing fat accumulation, increasing insulin sensitivity and hepatocyte lipoapoptosis, and the inflammatory response. These factors are caused by endoplasmic reticulum stress(ERS) in the liver. ERS performance through exercise depends on conditions such as the type and intensity of exercise, diet, medications, age, and pathology. In general, most studies confirm the positive effect of exercise on NAFLD (14).


Importance of diet in NAFLD treatment

The main goal of diet therapy in NAFLD is to implement a low-calorie diet that is suitable for weight loss. Calorie restriction reduces weight and consequently reduces the accumulation of fat in the liver. The best diet for fatty liver should be tailored to the patient's individual preferences and eating habits. Low carb / high protein diets, in addition to weight loss, also have positive metabolic effects and these diets are effective in treating NAFLD (11).

Many nutritionists recommend the Mediterranean diet in the treatment of NAFLD. This diet improves NAFLD independently of the low calorie diet. The Mediterranean diet consists of the following components:
• Whole grains, legumes, fruits, and vegetables
• Monounsaturated fatty acids such as olive oil
• Limit carbohydrates such as simple sugars and refined carbohydrates
• Limit high-fat dairy and red meat

Compared to a low-fat / high-carbohydrate diet, this diet significantly reduces the fat content of the liver and increases insulin sensitivity (11).


How much carbohydrate should you eat in the NAFLD diet?

Our diets are usually high in carbohydrates, and some studies have shown that fructose intake is associated with increase the risk of NAFLD (15, 16). Low carb diets help deplete intrahepatic triglycerides, reduce weight and improve metabolic parameters in obese patients. When fructose intake exceeds 25% of a person's daily caloric intake, it affects glucose homeostasis and fatty acid metabolism (17). Therefore, high fructose intake can cause complications such as steatosis, obesity, insulin resistance, hepatic fibrosis, and inflammation (18). Therefore you should reduce carb intake in the NAFLD diet.
Another type of carbohydrate that affects NAFLD is dietary fiber. Dietary fiber has beneficial effects on body composition parameters such as reducing body fat percentage, insulin resistance, and waist circumference. These fibers are found in foods containing hemicellulose, cellulose, hydrocolloids, resistant starches, and resistant oligosaccharides. Fibers are divided into soluble fiber and insoluble fiber, and Both have different roles in gastrointestinal health (19, 20). Consumption of fiber in your diet improves NAFLD by reducing calorie intake and stimulating healthy gut microbiota. Studies have shown that consuming dietary fiber in the early stages of NAFLD prevents its progression (21).


Lipids and NAFLD diet

Saturated fats cause oxidative stress and activate pathways that contribute to NAFLD (22). The monounsaturated and polyunsaturated fatty acids found in some foods such as avocados, olive oil, and nuts reduce the accumulation of triglycerides in the liver and improve inflammation (23). Studies have shown that omega-3 supplementation in the fatty liver diet , effectively reduces liver fat but has no effect on liver biochemistry (24, 25).


Proteins intake in NAFLD diet

Studies have shown that a high intake of animal proteins in diet plan, especially red and processed meats, is associated with cardiovascular disease and cancer (26). High intake of animal proteins independent of lifestyle and sociological and metabolic characteristics is associated with NAFLD (27). Animal proteins increase fatty liver index scores, but plant proteins decrease them (28). Processed and red meats are high in saturated fatty acids, cholesterol, iron, nitrates and nitrites, preservatives, and branched-chain amino acids, all of which cause NAFLD (29). Therefore, due to the role of animal protein in NAFLD development, it is recommended that patients with NAFLD reduce consumption of red and processed meat in their diet plan (26).

Can you drink coffee and alcohol in NAFLD?

Coffee consumption in NAFLD diet can reduce the incidence of NAFLD and even prevent its progression. For this purpose, consuming 3 cups per day of coffee is appropriate (30). These effects of coffee are due to the presence of several beneficial nutrients in it that affect glucose metabolism (31).
Evidence has shown that moderate to severe alcohol consumption (≤210 grams per week) in people with obesity and diabetes increase the risk of steatohepatitis, fibrosis, decompensated liver disease, mortality, and liver cancer, so it is recommended to avoid alcohol in these people (32).

Is vitamin D effective in preventing and treating NAFLD?

Vitamin D is a fat-soluble vitamin obtained from sunlight and food sources such as fatty fish or eggs. There are also foods fortified with vitamin D, such as soy milk, mushrooms, and cereals that you can use in your diet plan. Sunlight can provide up to 90% of the vitamin D your body needs. Important forms of vitamin D are calcifediol and calcitriol, which have different hydroxylations. In humans, the primary source of vitamin D is in the skin, which produces vitamin D in cutaneous, and a small amount is obtained through your diet and foods. Calcitriol plays a vital role in metabolic processes by binding to the vitamin D receptor. This form of vitamin D plays an important role in the health of the body. Calcitriol receptors are present in various cells such as adipose tissue, muscle, and liver. Vitamin D reduces inflammation by inactivating inflammatory cytokines, so adequate intake of this vitamin can help reduce weight and prevent fibrosis and inflammation in patients with NAFLD and finally help to NAFLD treatment (8).

Is vitamin E involved in the treatment of NAFLD?

Vitamin E is another fat-soluble vitamin with antioxidant effects that you can use it in your diet plan. Studies have shown that taking vitamin E as a supplement at a dose of 800 IU per day in non-diabetic people improves NAFLD and inflammation. Long-term use of this vitamin as a supplement is not safe. It must be done under the supervision of a doctor or nutritionist (11, 12, 33).

Are nuts Ok to eat at NAFLD diet?

As mentioned above, the Mediterranean diet plays an important role in treating NAFLD, and nuts are one of the important components of this diet. Nuts have beneficial effects on the body because they are high in fiber, which reduces fat, and contain monounsaturated and polyunsaturated fatty acids that help lower cholesterol and insulin resistance. They also have antioxidant properties that reduce oxidative stress and inflammation. In addition, nuts cause weight loss and loss of appetite, all of which are effective in treating NAFLD. But one thing to keep in mind when eating nuts is the presence of aflatoxin, which is a carcinogen, and people with NAFLD are also at risk for liver cancer. Therefore, it is recommended that nuts be eaten fresh and purchased from reputable stores to reduce the risk of aflatoxins (34).


Sorour Taheri Nia, RD

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