Fructose Sweeteners: University Of California Study Shows That Excessive Fructose Intake May Cause Leaky Gut Which In Turn Leads To Fatty Liver Disease
: Contrary to previous fallacies, researchers from the University of California-San Diego School of Medicine report that fructose adversely affects the liver only after it reaches the intestines, where the sugar disrupts the epithelial barrier protecting internal organs from bacterial toxins in the gut. The researchers say that developing treatments that prevent intestinal barrier disruption could protect the liver from non-alcoholic fatty liver disease or NAFLD, a condition that affects one in three Americans.
The study findings were published in the journal: Nature Metabolism. https://www.nature.com/articles/s42255-020-0261-2
In United States, excessive consumption of fructose, a sweetener ubiquitous in the typical American diet typically results in non-alcoholic fatty liver disease (NAFLD), of which is incidence rate is phenomenally high in the country.
Senior author Dr Michael Karin, Ph.D., Distinguished Professor of Pharmacology and Pathology at UC San Diego School of Medicine told Thailand Medical News, "NAFLD is the most common cause of chronic liver disease in the world. It can progress to more serious conditions, such as cirrhosis, liver cancer, liver failure and death. These findings point to an approach that could prevent liver damage from occurring in the first place."
It has been reported that fructose consumption in the U.S. has skyrocketed since the 1970s and the introduction of high fructose corn syrup (HFCS), a cheaper sugar substitute that is broadly used in processed and packaged foods, from cereals and baked goods to soft drinks.
Numerous studies in animals and humans have linked increased high fructose corn syrup or HFCS consumption with the nation's obesity epidemic and numerous inflammatory conditions, such as diabetes, heart disease and cancer. The U.S. FDA, however, currently regulates it similar to other sweeteners, such as sucrose or honey, and advises only moderation of intake.
The recent research, however, defines a specific role and risk for HFCS in the development of fatty liver disease.
Dr Karin adds, "The ability of fructose, which is plentiful in dried figs and dates, to induce fatty liver was known to the ancient Egyptians, who fed ducks and geese dried fruit to make their version of foie gras.”
She further added, "With the advent of modern biochemistry and metabolic analysis, it became obvious that fructose is two to three times more potent than glucose in increasing liver fat, a condition that triggers NAFLD. And the increased consumption of soft drinks containing HFCS corresponds with the explosive growth in NAFLD incidence."
Typically, fructose is broken down in the human digestive tract by an enzyme called fructokinase, which is produced both by the liver and the gut.
Utilizing mouse models, researchers found that excessive fructose metabolism in intestinal cells reduces production of proteins that maintain the gut barrier ie a layer of tightly packed epithelial cells covered with mucus that prevent bacteria and microbial products, such as endotoxins, from leaking
out of the intestines and into the blood.
The study's first author Dr Jelena Todoric, MD, Ph.D., a visiting scholar in Karin's lab said, "Thus, by deteriorating the barrier and increasing its permeability, excessive fructose consumption can result in a chronic inflammatory condition called endotoxemia, which has been documented in both experimental animals and pediatric NAFLD patients."
In the research, Dr Karin, Dr Todoric and colleagues from universities and institutions around the world, found that leaked endotoxins reaching the liver provoked increased production of inflammatory cytokines and stimulated the conversion of fructose and glucose into fatty acid deposits.
Dr Karin, "It is very clear that fructose does its dirty work in the intestine and if intestinal barrier deterioration is prevented, the fructose does little harm to the liver."
The researchers noted that feeding mice with high amounts of fructose and fat results in particularly severe adverse health effects.
Dr Karin said, "That is a condition that mimics the 95th percentile of relative fructose intake by American adolescents, who get up to 21.5 percent of their daily calories from fructose, often in combination with calorie-dense foods like hamburgers and French fries."
Significantly, the study team found that when fructose intake was reduced below a certain threshold, no adverse effects were observed in mice, suggesting only excessive and long-term fructose consumption represents a health risk. Moderate fructose intake through normal consumption of fruits is well-tolerated.
Dr Karin stressed, "Unfortunately, many processed foods contain HFCS and most people cannot estimate how much fructose they actually consume.”
She added, “Although education and increased awareness are the best solutions to this problem, for those individuals who had progressed to the severe form of NAFLD known as nonalcoholic steatohepatitis, these findings offer some hope of a future therapy based on gut barrier restoration."
Fructose, or fruit sugar, is a simple ketonic monosaccharide found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into blood during digestion.
Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847. The name "fructose" was coined in 1857 by the English chemist William Allen Miller.
Pure, dry fructose is a sweet, white, odorless, crystalline solid, and is the most water-soluble of all the sugars. Fructose is found in honey, tree and vine fruits, flowers, berries, and most root vegetables.
Commercially, fructose is derived from sugar cane, sugar beets, and maize. High-fructose corn syrup is a mixture of glucose and fructose as monosaccharides. Sucrose is a compound with one molecule of glucose covalently linked to one molecule of fructose. All forms of fructose, including fruits and juices, are commonly added to foods and drinks for palatability and taste enhancement, and for browning of some foods, such as baked goods.
About 920,000 t
onnes of crystalline fructose are produced annually!
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