Fatty Liver Disease in Children: It's About Sugar, Not Fat!

July 08, 2015
It’s common knowledge that over the last few decades there has been a significant increase in the number of children with obesity in the U.S. One of the complications of obesity is a condition termed metabolic syndrome, which consists of the combination of high cholesterol, blood sugar, blood pressure, and waist circumference. Having metabolic syndrome has long been a well-known risk factor for heart disease, but less known is the relationship between obesity, metabolic syndrome and liver disease.

As a pediatric specialist who treats children with liver diseases, I am often asked to see children with a condition called “fatty liver disease.” In fatty liver disease, fat accumulates within the liver as a direct result of obesity and metabolic syndrome. The curious thing about this type of liver disease, however, is that it is identical to the liver disease seen in alcoholics. Just like alcoholics can develop cirrhosis (where the liver becomes scarred down by fibrotic tissue), children with fatty liver disease can also have liver failure.

To distinguish the difference between the fatty liver disease caused by obesity versus alcohol, the former has been given the medical term, “Non-alcoholic fatty liver disease" (NAFLD).

So how does a child’s liver possibly develop the same damage that alcohol induces in an adult? The answer is fructose. Fructose, a sugar molecule, if consumed in excess amounts, can lead to fat deposition in the liver.

Although fructose is found naturally in fruits and vegetables, it has also become one of the most commonly added sugars in the U.S. diet, in the form of either sucrose (table sugar, which is 50% fructose), high fructose corn syrup, or one of its many other nicknames (eg “evaporated cane juice”, “rice syrup”, “fruit juice concentrate”). With all of the extra, added sources of fructose “hidden” in processed foods, kids are developing NAFLD at increasing rates. In fact, NAFLD is now the most common liver disease in the U.S., affecting about 10% of all children, but a much higher proportion of children with obesity. Among adults in the U.S., NAFLD is one of the top indications for a liver transplant, with the number of children requiring liver transplants also rising steadily.

That being said, fructose, in its natural form (by eating whole, unprocessed fruits and vegetables) is not something that children need to worry about, something specifically discussed further in another blog.

Personally, one of the most unfortunate mistakes I see with children dealing with NAFLD is that they are advised a low-fat diet. Instead, the type of diet that children with NAFLD need to follow is one low in sugar!

My hope is to educate parents that not only does excess sugar intake contribute to well-known diseases like tooth decay and obesity, it can also lead to life-threatening complications of metabolic syndrome, including liver failure. The way I see it, in the same manner that we would be wary of providing alcohol to a child, we also need to be equally cautious when it comes to feeding our kids sugar! After all, the end result to the liver can be the same.