The role of dietary fructose in the development of obesity and fatty liver diseases remains controversial, with previous studies indicating that the problems resulted from fructose and a diet too high in calories. However, a new study conducted in an animal model at Wake Forest Baptist Medical Center showed that fructose rapidly caused liver damage even without weight gain.
Fructose can damage the liver, according to a new study showing how dietary fructose causes liver damage in an animal model. The role of dietary fructose in the development of obesity and fatty liver diseases remains controversial, with previous studies indicating that the problems resulted from fructose and a diet too high in calories. One of the limitations of the study was that it only tested for fructose and not dextrose. Fructose and dextrose are simple sugars found naturally in plants.
A new study conducted in an animal model at Wake Forest Baptist Medical Center showed that fructose rapidly caused liver damage even without weight gain. The researchers found that over the six-week study period liver damage more than doubled in the animals fed a high-fructose diet as compared to those in the control group. The study is published in the June 19, 2013 online edition of the American Journal of Clinical Nutrition.
“Is a calorie a calorie? Are they all created equal? Based on this study, we would say not,” explains Kylie Kavanagh, D.V.M., in the June 19, 2013 news release, “Dietary fructose causes liver damage in animal model, study finds.”Kavanagh is an assistant professor of pathology-comparative medicine at Wake Forest Baptist and lead author of the study.
In a previous trial which is referenced in the current journal article, Kavanagh’s team studied monkeys who were allowed to eat as much as they wanted of low-fat food with added fructose for seven years, as compared to a control group fed a low-fructose, low-fat diet for the same time period
Not surprisingly, the animals allowed to eat as much as they wanted of the high-fructose diet gained 50 percent more weight than the control group. They developed diabetes at three times the rate of the control group and also developed hepatic steatosis, or non-alcoholic fatty liver disease. The big question for the researchers was what caused the liver damage. Was it because the animals got fat from eating too much, or was it something else?
To answer that question, this study was designed to prevent weight gain. Ten middle-aged, normal weight monkeys who had never eaten fructose were divided into two groups based on comparable body shapes and waist circumference. Over six weeks, one group was fed a calorie-controlled diet consisting of 24 percent fructose, while the control group was fed a calorie-controlled diet with only a negligible amount of fructose, approximately 0.5 percent.
The study’s high-fructose diet was made from fructose mixed with eggs, butter, flour, and pork fat
Both diets had the same amount of fat, carbohydrate and protein, but the sources were different, Kavanagh said. The high-fructose group’s diet was made from flour, butter, pork fat, eggs and fructose (the main ingredient in corn syrup), similar to what many people eat, while the control group’s diet was made from healthy complex carbohydrates and soy protein.
Every week the research team weighed both groups and measured their waist circumference, then adjusted the amount of food provided to prevent weight gain. At the end of the study, the researchers measured biomarkers of liver damage through blood samples and examined what type of bacteria was in the intestine through fecal samples and intestinal biopsies.
“What surprised us the most was how quickly the liver was affected and how extensive the damage was, especially without weight gain as a factor,” Kavanagh says in the news release. “Six weeks in monkeys is roughly equivalent to three months in humans.”
Intestinal bacteria migrated to the liver more rapidly where they caused damaged in the high-fructose group
In the high-fructose group, the researchers found that the type of intestinal bacteria hadn’t changed, but that they were migrating to the liver more rapidly and causing damage there. It appears that something about the high fructose levels was causing the intestines to be less protective than normal, and consequently allowing the bacteria to leak out at a 30 percent higher rate, Kavanagh said.
One of the limitations of the study was that it only tested for fructose and not dextrose. Fructose and dextrose are simple sugars found naturally in plants. “We studied fructose because it is the most commonly added sugar in the American diet, but based on our study findings, we can’t say conclusively that fructose caused the liver damage,” Kavanagh says in the news release. “What we can say is that high added sugars caused bacteria to exit the intestines, go into the blood stream and damage the liver. The liver damage began even in the absence of weight gain. This could have clinical implications because most doctors and scientists have thought that it was the fat in and around tissues in the body that caused the health problems.” The Wake Forest Baptist team plans to begin a new study using the same controls but testing for both fructose and dextrose over a longer time frame.
The study Wake Forest School of Medicine and grants RR019963, OD010965 and AG033641 from the National Institutes of Health supported the study. Co-authors are Ashley Wylie and Kelly Tucker, B.S., of Wake Forest Baptist; John Culler, D.V.M., Ph.D., of North Carolina State University; Timothy Hamp, B.S., Anthony Fodor, Ph.D., and Raad Gharaibeh, Ph.D., of the University of North Carolina at Charlotte.
If you eat too much fructose, you may get high blood pressure
In another study, researchers found that instead of lowering your consumption of fructose, there’s a drug made to lower high blood pressure caused by eating too much fructose from beverages and foods sweetened with lots of fructose. See the article, “Medical News: Allopurinol Lowers Fructose-Triggered Hypertension.” After all, fructose keeps you from feeling full when you should be feeling satiated. You feel hungry and tend to eat more, say studies. See, “Fructose changes brain to cause overeating, scientists say – CBS.”
What can you do to help your health before you reach the stage where you are on the road to taking drugs to solve a problem that could have been solved by eating fewer foods loaded with fructose? Also see the Jan. 26, 2009 article, “Much High Fructose Corn Syrup Contaminated With Mercury, New Study.”
That study revealed according to the article, “Mercury was found in nearly 50 percent of tested samples of commercial high fructose corn syrup (HFCS), according to the article published January 26, 2009 in the scientific journal, Environmental Health. A separate study by the Institute for Agriculture and Trade Policy (IATP) detected mercury in nearly one-third of 55 popular brandname food and beverage products where HFCS is the first or second highest labeled ingredient-including products by Quaker, Hershey’s, Kraft and Smucker’s.”
Also see the article, ” Mercury from chlor-alkali plants: measured concentrations in food product sugar.” A pilot study was conducted to determine whether high fructose corn syrup contains mercury, a toxic metal historically used as an anti-microbial.
See the study in Alternative Medicine Review, June, 2009 by R. Dufault, LeBlanc B., Schnoll R. This article by lead researcher Renee Dufault, a former U.S. Environmental Protection Agency (EPA) scientist, along with several co-authors well known to environmental medicine, was recently published in the online journal, Environmental Health.
Mercury cell chlor-alkali products are used to produce thousands of other products including food ingredients such as citric acid, sodium benzoate, and high fructose corn syrup. High fructose corn syrup is used in food products to enhance shelf life. A pilot study was conducted to determine if high fructose corn syrup contains mercury, a toxic metal historically used as an anti-microbial agent.
High fructose corn syrup samples were collected from three different manufacturers and analyzed for total mercury
The samples were found to contain levels of mercury ranging from below a detection limit of 0.005 to 0.570 micrograms mercury per gram of high fructose corn syrup. See the articles, Raw Agave Syrup Nectar: Not as healthy as you may think. Nutrition, and also check out the article, Agave syrup’s benefits are in debate – Los Angeles Times. Agave syrup is mainly fructose and glucose though ratios vary from 56% to 92% fructose depending on the agave variety.
Average daily consumption of high fructose corn syrup is about 50 grams per person in the United States. With respect to total mercury exposure, it may be necessary to account for this source of mercury in the diet of children and sensitive populations.
Read the abstract of the study, “Mercury from chlor-alkali plants: measured concentrations in food product sugar.” But of course, too much salt if you’re salt-sensitive, also could raise your blood pressure. An old adage of biologists is to remind people that to give rats high blood pressure in lab studies, the scientists fed the lab animals excess sugar. See, “Development of sugar-induced blood pressure elevation after uninephrectomy in a resistant rat strain.”
Certain rat strains acutely increase blood pressure (BP) when given diets high in salt (sodium). Prior results showed that “salt-sensitive” rat strains, at least the ones studied, also increase blood pressure in response to sugar loading. That study’s conclusions focused on observing sugar-induced blood pressure elevation that was similar to salt-induced blood pressure elevation in a normally resistant rat strain. Scientists wrote in the study’s abstract that “the rise of blood pressure may be caused by a circulating factor.”