Vitamin D is known as the "sunshine vitamin" because your body requires sunlight to synthesize the nutrient. According to the September 2010 issue of "Digestive Diseases and Sciences," vitamin D deficiency is universal among patients with chronic liver disease. While a fatty liver is not necessarily dangerous, there are some suggestions that vitamin D supplementation and sunlight exposure may help prevent its progression into a more serious liver disease.
Fatty Liver Disease
According to researchers reporting in the July 2008 issue of the "Journal of Hepatology," you may have fatty liver disease and not be aware of it because symptoms arise only in advanced cases. There are two types: alcoholic and nonalcoholic. Nonalcoholic Fatty Liver Disease, or NAFLD, is caused by obesity, diabetes and high cholesterol levels and is characterized by fat build-up in the liver, which in most cases is not harmful. In some instances, NAFLD can lead to cirrhosis and irreparable liver damage; however, cirrhosis is most often associated with Alcoholic Fatty Liver Disease, also known as AFLD.
Symptoms
The UCSF Medical Center website explains that studies are underway to determine how NAFLD progresses into cirrhosis, and that it occurs in about 20 percent of cases. NAFLD typically shows up as an abnormality in liver function tests in people who otherwise feel well. Incidence is rising along with increasing rates of obesity, and if you're obese and over age 50, it may benefit you to be tested. Symptoms typically don't manifest until cirrhosis has set in. They include fatigue, confusion, fluid retention in the abdomen or legs and the passage of tarry black stools suggesting internal bleeding.
Animal Studies
The December 2010 issue of the "Journal of Hepatology" reported that Non-Alcoholic Steatohepatitis, or NASH, is a severe form of NAFLD likely to develop into cirrhosis. To investigate the impact of vitamin D in its progression, the researchers induced four groups of rats to develop NASH through unhealthy diets. Two groups served as controls for six and 12 weeks, and two were treated with phototherapy and vitamin D supplementation for six and 12 weeks. The researchers found that both supplementation and phototherapy protected against NASH, although the mechanisms by which they provided protection differed.
Human Studies
Researchers reporting in the September 2007 issue of "Nutrition, Metabolism and Cardiovascular Disease" explain that you run an additional risk of developing NAFLD if you don't get enough sunlight. The researchers compared the winter serum levels of vitamin D in patients with biopsy-proven NAFLD against those of healthy controls matched for age, sex and body mass index. While being obese and over age 50 are known NAFLD risk factors, the researchers discovered that NAFLD patients also had significantly lower levels of vitamin D than controls, and that the lower their levels, the more severe their liver disease.
References
- "Digestive Diseases and Sciences"; Prevalence of Vitamin D Deficiency in Chronic Liver Disease"; J. Arteh et al; September 2010
- "Journal of Hepatology"; Increased Overall Mortality and Liver-related Mortality in Non-alcoholic Fatty Liver Disease; Janus Ong; July 2008
- UCSF Medical Center: NAFLD
- "Journal of Hepatology"; Impact of Artificial Sunlight Therapy on the Progress of Non-Alcoholic Liver Disease in Rats; Toshiaki Nakano et al; December 2010
- "Nutrition, Metabolism and Cardiovascular Diseases"; Resource Associations Between Serum 25-Hydroxyvitamin D3 Concentrations and Liver Histology in Patients With Non-alcoholic Fatty Liver Disease; Giovanni Targher et al; September 2007
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