Non-alcoholic Fatty Liver Disease (NAFLD)

NAFLD is recognized as a major health burden and has become one of the most common causes of liver disease worldwide. Excessive fat deposition in the liver is seen in about thirty percent of the adult general population and now seen in young children. The prevalence over the last two decades has grown proportionally with the rise in obesity, sedentary lifestyles, unhealthy dietary patterns, and metabolic syndrome (insulin resistance, hyperlipidemia and hypertension). (1,2)

Currently there is no drug therapy and the only treatment is a combination of dietary modifications and increased physical activity although various insulin-sensitising medications appear promising. Weight-loss alone by dietary changes has been shown to lead to improvement quite quickly (around 6 weeks) and has become the cornerstone of treatment. Moreover, research has shown that the key foods to focus on are eliminating refined carbohydrates in favour of complex options, reducing saturated fats such as those from animal origin and trans fats from processed foods, and simple sugars especially fructose and sucrose. (2)

The development of NAFLD is considered to be through a “two hit” process starting with a habitual diet that is high in fats and refined carbohydrates which effect insulin. The second hit is increased oxidative stress and a pro-inflammatory effect by the immune system as a result of the poor quality of dietary composition. (3) The nutritionist regards this as high energy nutrients and low micronutrient intake.

Currently the only established treatment is the use of diet to reduce weight, improve glycaemic control (fluctuating blood sugar levels), change blood lipid levels and reduce cardio-vascular risk. This is all sounds good advice but it also needs to be substantiated with scientific research and be more applicable to the patient. In addition, increased physical activity greatly reduces liver fat and improves insulin sensitivity.

Dietary Changes

Studies of dietary intake in patients with NAFLD show they consume high caloric diets especially carbohydrates and increased consumption of sweetened drinks. Soft drinks are the leading source of added sugar worldwide and have strong links with a number of metabolic diseases. Musso et al noted that high protein intake was associated with NAFLD which also increases the intake of saturated fats. (4,5)

Caloric restriction is one way to approach weight loss, however Browning et al showed that short term carbohydrate restriction is more effective at reducing fats in the liver than caloric restriction. The mechanism behind this is that insulin resistance is a key factor in NAFLD and increased fat breakdown from fat tissue, increases free fatty acids which are retained in the liver causing steatosis. This also increases the need for oxidation in the mitochondria cell which becomes overloaded and an ongoing inflammatory cycle begins revving up metabolic risk. Low carbohydrate diets reduce the involvement of insulin, allows the body to liberate stored fats and sets the energy cycle up to oxidise them for energy in the mitochondria and use fat for energy, which finally leaves the body as carbon and oxygen through breathing. (7, 8)

The composition of dietary lipids has been well studied. Keto diets are currently very popular, low carb/high fat, however Westerbacka et al demonstrated that high fat diets even though calories were average and controlled (1200kcals) in postmenopausal women, caused increased triglycerides in the liver. A well-managed fat intake is recommended especially alongside other metabolic disease conditions and fatty liver.  Specific types of fat play an important role in NAFLD in addition to the total fat intake. The amounts of saturated to polyunsaturated is difficult to determine but all are required for health. Taking away all animal fat is not advisable as it is required by the body, while of the polyunsaturated (PUFA), omega 3 fatty acids are still regarded as key to good health. PUFA are extracted from seeds, nuts, grains, olives, avocado (plant based) while omega 3 fatty acids are from oily fish, walnuts and flaxseed. It is difficult to get enough of these as they are an acquired taste for many people but go hand in hand with reduced inflammation, decreased insulin, triglycerides and leptin levels. Omega 3 fatty acids help lower LDL cholesterol by binding it and taking it to liver for oxidation.

Oxidation plays a very important role in fatty acid degradation and foods high in anti-oxidants are nuts and seeds, fruits and vegetables, green tea, and supplements such as glycine, CoQ10, Resveratrol, alpha-lipoic acid and acetyl cysteine. They all play a part in supporting the liver, oxidizing fat and energy production.

The exact effect of protein on NAFLD is not clear, however studies have shown a significant association with red meat consumption. (10)

Physical activity

Hallsworth et al found that exercise alone (8 weeks, 3 times per week, lasting 45 – 60 minutes) had a positive effect on liver enzymes used as predictors of the presence of NAFLD. And the results of most studies have shown similar outcomes probably alongside weight loss of 5-10%. Exercise intensity also shows a positive association and maybe more important and effective than duration of exercise. Whatever the form of exercise, strategies to promote activity are effective to motivate patients, especially where large weight loss cannot be easily pursued.(11)

Also studies is rapid weight loss through very restricted diets and intense exercise. This has shown to cause inflammation and an increase in the progression of fatty acid breakdown from fatty tissue overloading the transportation of fats to the liver.

Diet and lifestyle changes that lead to weight loss and the reduced delivery of fatty acids to an already overburdened the liver are the likely treatment plan for NAFLD. Based on available data, weight loss of between 5-10% (avoid rapid weight loss) is optimal and the benefits of a healthy diet go far beyond weight reduction. Reducing saturated/trans fats and increasing PUFA and omega 3’s  (1g/d fish oil), reduce added sugar and especially highly concentrated fructose corn syrup found in sodas, sweetened sauces and fruit juice. Eating less red meat and increasing fish consumption is recommended and helping cleanse the body by adding fibre from fresh raw fruit and vegetables

Nutrition counceling with a multidisciplinary team including nutrition, and physical activity supervisors is the preferable method in the management of NAFLD.

References:

  1. Nseir W, Hellou E and Assy N (2014) Role of diet and lifestyle changes in non-alcoholic fatty liver disease. World J Gastroenterol; 20(28);9338-9344.
  2. Papandreou D and Andreou E (2015) Role of diet on non-alcolic fatty liver disease: An updated narrative review. World J Hepatology; 7(3): 575-582.
  3. Mirmiran P et al (2017) Relationship between diet and non-alcoholic fatty liver disease: A review article. Iran J Public Health; 46(8);1007-1017.
  4. Abid A et al (2009) Soft drink consumption is associated with fatty liver disease independent of metabolic syndrome. J Hepat; 51: 918-924.
  5. Browning JD et al (2011) Short-term weight loss and hepatic triglyceride reduction: evidence of a metabolic advantage with dietary carbohydrate restriction. Am J Clin Nutr; 93:1048-1052.
  6. Musso G et al (2003) Dietary habits and their relations to insulin resistance and post prandial lipedema in nonalcoholic steatohepatitis. Hepatology; 37: 909-916.
  7. Marchesini G at al (1999) Association of nonalcoholic fatty liver disease with insulin resistance. Am J Med; 107:450-455.
  8. Merrman R and Brown A (2014) When somebodt loses weight, where does the fat go?. BMJ 2014;349:g7257.
  9. Westerbacka J etal (2005) Dietary fat content modifies liver fat in overweight nondiabetic subjects. J Clin Endocrinol Metab. 90; 2804-2809.
  10. Shi L et al (2012) The prevalence of nonalcoholic fatty liver disease and its association with lifestyle/dietary habits among university faculty and staff in Chengdu. Biomed Environ Sci; 25: 383-391.
  11. Halsworth K et al (2011) Resistance exercise reduces liver fat and its mediators in nonalcoholic fatty liver disease independent of weight loss. Gut;60:1278-1283.