Our Livers may Look More Alike than our Faces
When listening to news reports of conflict among different groups within the world, one can lose sight of the fact that humans share so much in common. 99.9% of our genome is identical. Despite the apparent aggression among some people/groups, there is less than 0.1% difference among persons on the planet. We may look different – hair and eye color, body shape, skin color. We may adopt different beliefs and cultures – religions, languages, clothing. But truly, we share so much in common.
When each of us eats, our liver coordinates the use of every bite (after digestion and absorption from the gut). The liver is responsible for repackaging every bite of fat, carbohydrate, and protein into appropriate building blocks. The liver packages and sends nutrients into the blood to circulate to cells of the body (brain, muscle, fat, etc) or the liver stores them. Excess storage in the liver increases the fat content of the liver.
Wulan and colleagues studied the response of the liver to overfeeding with a high-fat diet. Ten South Asian men and 10 Caucasian men (healthy, 20-40y men matched for body fat) were put on a maintenance diet for 3 days. Liver fat content was measured and then they were overfed (50% more calories than they needed) a high-fat diet (60% of calories from fat) for 3 days, followed by another liver fat measurement. Overfeeding significantly increased liver fat content in all men. The liver response to overfeeding did not differ between the South Asian and Caucasian men.
A healthy liver should be relatively fat-free because it sends lipids elsewhere in the body to be a fuel source, used to make cell membranes, or stored in fat tissues. The accumulation of fat in the liver, non-alcoholic fatty liver disease (NAFLD), is an early sign of liver dysfunction.
The prevalence of NAFLD in young children is increasing due to the rise of the obesity epidemic. New research finds NAFLD is an independent risk factor for all-cause, cardiovascular (CVD) and non-cardiovascular mortality.
Two nutrients may play a role in NAFLD. Because oxidative stress plays a role in its pathology, viitamin E supplementation has improved outcomes in patients with more advanced liver disease. Data in children, however, have been slightly mixed.
The vitamin D receptor (VDR) and serum 25(OH)D levels have been linked with NAFLD. Since the liver metabolizes vitamin D, it isn’t known if vitamin D status affects NAFLD or vice versa but lower serum 25(OH)D levels have been associated with NAFLD.
Bottom line: The best advice for maintaining a healthy liver is to avoid overeating and to regularly consume recommended amounts of essential vitamins.
Wulan SN, Schrauwen-Hinderling VB, Westerterp KR, Plasqui G. Liver fat accumulation in response to overfeeding a high-fat diet: a comparison between South Asian and Caucasian men. 2015 Nutr Metab doi: 10.1186/s12986-015-0015-4
Tao K, Shi K-H, Wu J-X, Zhan H-Y. Nonalcoholic fatty liver disease is a potential risk factor for cardiovascular diseases. 2014 Nutr Metab Cardiovas Dis doi: 10.10.1016/j.numecd.2013.04.012
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Barchetta I, Carotti S, Labbadia G, Gentilucci UV, Muda AO, Angelico F, Silecchia G, Leonetti F, Fraoli A, Picardi A, Morini S, Cavallo MG. Liver vitamin D receptor, CYP2R1, and CYP27A1 expression: relationship with liver histology and vitamin D3 levels in patients with nonalcoholic steatohepatitis or heaptitis C virus. 2012 Hepatol doi: 10.1002/hep.25930
Jablonski KL, Jovanovich A, Holmen J, Tagher G, McFann K, Kendrick J, Chonchol M. Low 25-hydroxyvitamin D level is independently associated with non-alcoholic fatty liver disease. 2012 Nutr Metab Cardiovasc Dis doi: 10.1016/j.numecd.2012.12.006