Nonalcoholic Fatty Liver Disease (NAFLD) and Nonalcoholic Steatohepatitis (NASH)
A functioning liver is vital to human life. Your liver filters harmful substances out of your blood, and it converts the food you eat and drink into nutrients your body uses. It is the second-largest organ in the human body, after skin. A liver with too much fat--over 5% to 10% of the liver’s weight--is considered a fatty liver.
While fatty livers are often linked to use of alcohol, some people have fatty livers without consuming excessive alcohol. People who do not drink a lot and have fatty livers are considered to have nonalcoholic fatty liver disease (NAFLD). This condition can develop in people who are overweight, or have diabetes. It may also be caused by rapid weight loss and unhealthy eating habits.
Various studies estimate that about 20% to 30% of all adults have fatty livers. This includes 50% of patients with diabetes, and roughly 80% of people who are obese.1 However, some people with no risk factors also develop NAFLD.
Some people with the condition have livers that become swollen and scarred. This is called nonalcoholic steatohepatitis (NASH), and it affects about 2% to 5% of people in the United States.3
Scarring, or cirrhosis, involves permanent liver damage and is a very serious condition. It can lead to liver cancer and even liver failure.2 NASH is diagnosed more often in women than men, and in the United States it is one of the major causes of cirrhosis. As many as 25% of people with NASH may have cirrhosis.2 The highest-risk groups for NAFLD and NASH are Hispanics and people with diabetes.4 Diagnoses of these liver diseases have increased dramatically in the United States over the past 20 years, possibly due to the epidemics of obesity, high blood cholesterol levels and diabetes.3
Symptoms of NAFLD and NASH
Many people with NAFLD have no symptoms. However, symptoms can include:
- Severe tiredness
- Generally feeling bad (malaise)
- Full, uncomfortable feeling in the upper abdomen
- Unexplained weight loss
- Nausea with or without vomiting
- Abdominal pain and swelling (ascites)
- Swelling in the legs (edema)
- Blood in stools or bowel movements
- Jaundice (yellowed skin and white of the eyes) or discolored skin
- Bleeding from the gums or nosebleeds
- Red, spidery blood vessels just under the skin surface.
In addition, some children who have NAFLD have dark, velvety patches on their hands, armpits and necks. This skin discoloration, called acanthosis nigricans, indicates an increased risk for type 2 diabetes.
Symptoms of NASH indicate a more serious condition, and should be checked immediately. The symptoms are:
- Severe abdominal pain
- Abdominal bloating or swelling
- Mental status or behavior change (for example, confusion, delirium, hallucinations, delusions, and reduced awareness or alertness)
- Change in consciousness or alertness (for example, passing out or being unresponsive)
- Severe tiredness
- Vomiting blood or black material (resembles coffee grounds)
- Sudden behavioral changes
Diagnosis of NAFLD and NASH
Blood tests are used to check liver enzymes, which are high when a person has NAFLD. After ruling out other liver diseases with more tests, a diagnosis of NAFLD can be confirmed with an ultrasound of the liver.2 Samples of liver tissue can be taken in a biopsy to distinguish between NAFLD and NASH. If the biopsy indicates inflammation, fatty liver and scarring, NASH will be diagnosed.
Treatment for NAFLD or NASH
There are no treatments specifically for NAFLD or NASH. However, there is evidence that diet plays an important role in controlling or reversing the symptoms of NAFLD.1 Unbalanced diets are strongly associated with NAFLD.
Doctors recommend a healthy diet low in saturated fat, trans fat, sugar (including sugary drinks) and meat. They recommend switching to polyunsaturated fat from plant oils, and consuming more omega-3 fatty acids from fish.1 It’s also important to lose weight if needed and exercise regularly. Other recommendations include avoiding alcohol consumption and not taking unnecessary medicines. Some benefit may be gained from taking dietary supplements such as vitamins D and E (both of which are antioxidants), but these benefits have yet to be proven in clinical studies.1,3
If NAFLD progresses to NASH, the liver may begin scarring. Development of scar tissue, or fibrosis, has to be controlled to avoid the complications of cirrhosis, including liver cancer or liver failure. If scar tissue and fat buildup in the liver can be slowed or stopped, these diseases can be prevented.
Experimental treatments include antioxidants, such as vitamins D and E, betaine, and selenium. These agents reduce the oxidative stress that seems to build up inside the livers of people with NASH. But their ability to effectively treat the disease has not yet been proven.Clinical studies are currently examining whether diabetes medicines can help treat NASH. Most people with NASH are insulin sensitive, which means that their insulin is unable to effectively control their blood sugar and fatty acid levels in their bloodstream. Some diabetes drugs, including metformin, rosiglitazone and pioglitazone, may help the body become more sensitive to insulin and also prevent liver damage in people with NASH.3
- Zelber-Sagi S, Ratziu V, Oren R. Nutrition and physical activity in NAFLD: an overview of the epidemiological evidence. World J Gastroenterol 2011 August 7; 17(29):3377-89.
- National Digestive Diseases Information Clearinghouse (NDDIC): Nonalcoholic steatohepatitis
- Williams C, Stengel J, Asike M, Torres D, Shaw J, Contreras M, Landt C, Harrison S. Prevalence of Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis Among a Largely Middle-Aged Population Utilizing Ultrasound and Liver Biopsy: A Prospective Study. Gastroenterology. 2011 Jan:140(1);124-31 (abstract).
- American College of Gastroenterology: Nonalcoholic fatty liver disease (NAFLD)
- American Association for the Study of Liver Diseases (AASLD): New practice guideline developed for nonalcoholic fatty liver disease
- Chalasani N, Younossi Z, Lavine J, Diehl A, Brunt E, Cusi K, Charlton M, Sanyal A, American Gastroenterological Association; American Association for the Study of Liver Diseases; American College of Gastroenterology. Gastroenterology. 2012 Jun;142(7):1592-609.Erratum in Gastroenterology 2012 Aug;143(2):503.
- Welsh J, Karpen S, Vos M. Increasing prevalence of nonalcoholic fatty liver disease among United States adolescents, 1988-1994 to 2007-2010 (abstract). J Pediatr doi:10.1016/j.jpeds.2012.08.043.
- eMedicine Health: Fatty liver disease (NAFLD, NASH)
- Zelber-Sagi S, Ratziu V, Oren R. Nutrition and physical activity in NAFLD: an overview of the epidemiological evidence. World J Gastroenterol. 2011 Aug 7;17(29):3377-89.