The Toxic Truth

Too much fructose can damage your liver, just like too much alcohol

There is growing scientific consensus that one of the most common types of sugar, fructose, can be toxic to the liver, just like alcohol.1,2

Fructose is the sugar that makes fruit taste sweet. For most people, there's nothing wrong with eating fructose in its natural state, in fruit. 

But today, manufacturers extract and concentrate the fructose from corn, beets and sugarcane, removing the fiber and nutrients in the process. Getting frequent, high doses of fructose throughout the day, without fiber to slow it down, is more than our bodies were designed to handle.

31%of American adults and13%of kids suffer from non-alcoholic fatty liver disease (NAFLD).

Nearly all added sugars contain significant amounts of fructose.3 Typical formulations of high-fructose corn syrup contain upwards of 50% fructose, depending on processing methods. Table sugar and even sweeteners that sound healthy, like organic cane sugar, are 50% fructose.

What's unique about fructose is that, unlike any other sugar, it's processed in the liver. Small amounts of fructose, meted out slowly, are not a problem for your liver. Think of eating an apple - its sweetness comes with a lot of chewing that takes time. The apple's fiber slows down its processing in the gut.

But when we consume large amounts of fructose in added sugar, particularly in liquid form on an empty stomach, it slams the liver with more than it can handle. 

As with alcohol, a little added fructose, consumed with fiber-rich foods, is OK. It's only when we frequently consume large quantities, in concentrated form, that fructose becomes a health hazard.

Liver damage is a looming health issue

For a long time, doctors mainly worried about life-threatening liver disease in alcoholics. But since 1980, there has been growing concern about two new conditions linked to fructose consumption from added sugar, as well as to obesity and other unhealthy dietary additives, such as trans-fats:

 - Non-alcoholic fatty liver disease (NAFLD): This is characterized by excess fat build-up in the liver.

 - Non-alcoholic steatohepatitis (NASH): This is characterized by fatty liver, inflammation and "steatosis," which is essentially scarring as the liver tries to heal its injuries. That scarring gradually cuts off vital blood flow to the liver. 

About one-quarter of NASH patients will progress on to non-alcoholic liver cirrhosis,4,5 which requires a liver transplant or else it can lead to death.

Since 1980, the incidence of NAFLD and NASH has doubled, along with the rise of fructose consumption. Approximately 6 million individuals in the United States are estimated to have progressed to NASH and some 600,000 to NASH-related cirrhosis. Eating a lot of trans-fats, being overweight and not exercising also can contribute to NASH. Most people with NASH also have Type II diabetes.

What is alarming is that NASH is now the third-leading reason for liver transplantation in America.6 And it will become the most common if recent trends continue. Rates of NASH have doubled in America during the past 20 years alongside a dramatic increase in sugar consumption.

Estimates vary, but conservatively, 31% of American adults and 13% of kids suffer from NAFLD.7,8,9,10

How do you know if you have a liver problem?

You should be concerned if you or your kids have a "sugar belly" or belly fat. If your waist is larger than your hips, you should ask your doctor for a blood test that checks for triglyceride levels.

A sugar belly occurs when the liver detects more fructose than can be used by the body for energy. That excess fructose is broken down by the liver and transformed into fat globules (triglycerides), some of which are exported into the bloodstream and selectively deposited around your midsection and internal organs. Just as people who drink too much get a "beer belly," those who eat or drink too much fructose can get a "sugar belly."

Fat cells that accumulate around your midsection send out disruptive hormonal messages that upset your body's normal chemical balance.11,12 Scientists are actively studying how these hormonal imbalances become implicated in a wide variety of diseases, including heart disease, stroke, diabetes, cancer and Alzheimer's disease.

Why am I only hearing about this now?

Scientific evidence on fructose and the liver is relatively new, but it is a major area of laboratory and clinical research in our best universities and medical centers.

The goal of SugarScience is to bring you the latest research, getting the most critical information out of universities and into public awareness as quickly as possible. Getting you the news on fructose toxicity could change your health and the health of your kids. It's a good example of why we're here.

  • [1]Leung, T.M., & Nieto, N. (2013, February). CYP2E1 and oxidant stress in alcoholic and non-alcoholic fatty liver disease. Journal of Hepatology , 58(2), 395-398.
  • [2]Lustig, R.H., Schmidt, L.A., & Brindis, C.D. (2012, February 2). Public health: The toxic truth about sugar. Nature , 487(5), 27-29. doi:10.1038/482027a. Retrieved from
  • [3]Ng, S.W., Slining, M.M., & Popkin, B.M. (2012). Use of caloric and noncaloric sweeteners in US consumer packaged foods, 2005-2009. Journal of the Academy of Nutrition and Dietetics , 112(11), 1828-1834.e1821-1826.
  • [4]Powell, E.E., Cooksley, W.G., Hanson, R., Searle, J., Halliday, J.W., & Powell, L.W. (1990). The Natural History of Nonalcoholic Steatohepatitis: A Follow-up Study of Forty-two Patients for Up to 21 Years. Hepatology , 11(1).
  • [5]Farrell, G.C., & Larter, C.Z. (2006, February). Nonalcoholic fatty liver disease: from steatosis to cirrhosis. Hepatology , 43(2, Suppl 1), S99-S112.
  • [6]Charlton, M.R., Burns, J.M., Pedersen, R.A., Watt, K.D., Heimbach, J.K., & Dierkhising, R.A. (2011, October). Frequency and outcomes of liver transplantation for nonalcoholic steatohepatitis in the United States. Gastroenterology , 141(4), 1249-1253.
  • [7]Lazo, M., & Clark, J. (2008). The Epidemiology of Nonalcoholic Fatty Liver Disease: A Global Perspective.. Seminars in Liver Disease , 28(4), 339-50. doi:10.1055/s-0028-1091978
  • [8]Browning, J.D., Szczepaniak, L.S., Dobbins, R., Nuremberg, P., Horton, J.D., Cohen, J.C., & Hobbs, H.H. (2004, November 24). Prevalence of hepatic steatosis in an urban population in the United States: Impact of ethnicity. Hepatology , 40(6), 1387-1395. doi:10.1002/hep.20466. Retrieved from
  • [9]Schwimmer, J.B., Deutsch, R., Kahen, T., Lavine, J.E., Stanley, C., & Behling, C. (2006, October 1). Prevalence of Fatty Liver in Children and Adolescents. Pediatrics , 118(4), 1388-1393. doi:10.1542/peds.2006-1212. Retrieved from
  • [10]Lindbäck, S.M., Gabbert, C., Johnson, B.L., Smorodinsky, E., Sirlin, C.B., Garcia, N., & Schwimmer, J.B. (2010). Pediatric Nonalcoholic Fatty Liver Disease: A Comprehensive Review. Advances in Pediatrics , 57(1), 85-140. doi:10.1016/j.yapd.2010.08.006
  • [11]McGown, C., Birerdinc, A., & Younossi, Z.M. (2014, February 18). Host genetic variants in obesity-related nonalcoholic fatty liver disease. Clinics in liver disease , 18(1), 249-67. doi:10.1016/j.cld.2013.09.017. Retrieved from
  • [12]Kershaw, E.E., & Flier, J.S. (2004, June). Adipose tissue as an endocrine organ. The Journal of clinical endocrinology and metabolism , 89(6), 2548-56.

non-alcoholic fatty liver disease

(also called NAFLD) Fatty liver that is not caused by drinking too much alcohol. Too much alcohol drinking can cause fatty liver diseases and steatohepatitis. NAFLD happens to people who are overweight, have diabetes, high cholesterol or high triglycerides in their blood. Rapid changes in weight can also cause NAFLD. It can happen to even those without any of the things listed above. It is common, up to 31% of adults in the United States have NAFLD.

SugarScience Glossary

non-alcoholic fatty liver disease

(also called NAFLD) Fatty liver that is not caused by drinking too much alcohol. Too much alcohol drinking can cause fatty liver diseases and steatohepatitis. NAFLD happens to people who are overweight, have diabetes, high cholesterol or high triglycerides in their blood. Rapid changes in weight can also cause NAFLD. It can happen to even those without any of the things listed above. It is common, up to 31% of adults in the United States have NAFLD.

SugarScience Glossary

High-Fructose Corn Syrup

(HFCS) A concentrated form of liquid sugar which may contain a wide range of fructose concentrations. Most commonly it contains either 42% or 55% fructose, but may contain up to 90% fructose.

SugarScience Glossary

Table sugar

Sucrose, also called granulated sugar, is two simple sugars stuck together in a single molecule. Sucrose is made of one fructose and one glucose molecule. On this website, one level teaspoon of table sugar weighs 4.2 grams and has 16.8 calories.

SugarScience Glossary

Heart disease

A broad term for a group of chronic diseases of the heart, these diseases include problems with blood supply to heart muscle, problems with heart valves and the electrical system of the heart. Another term you will see used to mean the same thing is cardiovascular disease.

SugarScience Glossary

Non-alcoholic steatohepatitis

(also called NASH) A more dangerous type of fatty liver than NAFLD. There is inflammation in NASH. Inflammation damages the liver with NASH over time. Healthy liver cells die, scar tissue forms, and the liver may stop working. NASH is a step toward cirrhosis. These changes occur over a period of years.

SugarScience Glossary

Liver disease

A broad term meaning any bodily process in which the liver is injured or does not work as it is supposed to. In this website we focus on liver diseases in which the diet hurts the liver

SugarScience Glossary

Added sugar

Any sugar added in preparation of foods, either at the table, in the kitchen or in the processing plant. This may include sucrose, high fructose corn syrup and others.

SugarScience Glossary

Diabetes mellitus

Usually shortened to just diabetes. Sometimes called sugar diabetes. Look at Type 1 Diabetes and Type 2 Diabetes for more information

SugarScience Glossary

Fatty liver

An abnormal condition in which too much fat is stored in the liver. "Too much fat" means more than one tenth of the liver is made of fat.

SugarScience Glossary



SugarScience Glossary


Poisonous, capable of causing damage

SugarScience Glossary


The most common type of fat in our body and in our food. We can eat triglycerides, our bodies can make triglyceride, and our livers can turn excess sugar into triglycerides. If we do not burn triglycerides as fuel, they are stored as fat in the liver and elsewhere in the body.

SugarScience Glossary


An abnormal condition in which healthy liver is replaced by scar tissue. In cirrhosis, the liver no longer works well to digest food or protect us from toxins. Eventually, liver failure will occur when most normal parts of the liver have been replaced by scar tissue. The only treatment is liver transplant.

SugarScience Glossary


Abnormal, uncontrolled cell growth in a part of the body, many types. Another of the chronic diseases.

SugarScience Glossary


Sugars are chemicals made of carbon, hydrogen, and oxygen found which taste sweet and are found in food. They are an important part of what we eat and drink and of our bodies. On this site, sugar is used to mean simple sugars (monosaccharides) like fructose or glucose, and disaccharides like table sugar (sucrose). Sucrose is two simple sugars stuck together for example (see Table sugar). Sugars are a type of carbohydrate. Carbohydrates are energy sources for our bodies Sugars enter the blood stream very quickly after being eaten.

SugarScience Glossary


Rapid loss of blood supply to a portion of the brain causing brain damage. This may lead to difficulty with memory, thought, speech, sensation, and movement. Stroke is usually due to blockage of blood vessels in the neck or brain. It is more common as people age, and is associated with high blood pressure, heart disease and diabetes.

SugarScience Glossary


Abnormal storage of fat in cells of an organ. When this happens, the organ gets bigger and becomes paler in color.

SugarScience Glossary


One of the three major groups of nutrients we eat. Much of this website is related to problems associated with too much fat storage in the body. Each gram of fat produces 9 calories of energy if burned by the body as fuel. Fat can be stored in many places in the body. We generally think of fat as under the skin (subcutaneous), but the fat that may be most damaging to us is the fat stored in the liver and around the organs of the abdomen (intrahepatic and visceral or abdominal or intra-abdominal)

SugarScience Glossary


A sugar that we eat. Also called fruit sugar. Most fructose comes in sucrose (table sugar, cane sugar, beet sugar), or from high-fructose corn syrup.

SugarScience Glossary


The largest internal organ. It weighs about three to four pounds and is located under the lower edge of the ribs on the right side. It helps us digest our food and remove toxins from our blood. "Hepat" in a word means liver, so an "hepato-toxin" is a liver poison or something that can cause damage to the liver

SugarScience Glossary


The human body uses special cells and chemicals to fight against injury, poisons or diseases. These cells and chemicals can be seen or measured and when they are present that is called inflammation. Too much inflammation can cause damage to the body and is a part of what happens in many diseases, like cancer and heart disease to name only two.

SugarScience Glossary

SugarScience Facts

Alzheimer's disease, cognitive decline and memory loss: Excess sugar consumption was linked to deficiencies in memory and overall cognitive health.

SugarScience Facts

Today, 31% of American adults and 13% of kids suffer from non-alcoholic fatty liver disease (NAFLD).

SugarScience Facts

Too much fructose in added sugar can damage your liver just like too much alcohol.

SugarScience Facts

MetS, linked to sugar overconsumption, is a strong predictor of heart disease.

SugarScience Facts

Fructose is in many of the foods we eat and makes up about half of table sugar and high-fructose corn syrup.

SugarScience Facts

Too much added sugar from soda and sports drinks overloads critical organs, which can lead to diseases.

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