Critics of HFCS in particular have repeatedly claimed that it increases fat levels in the liver and muscle tissue, increasing the risk of non-alcoholic fatty liver disease and contributing to insulin resistance, a key factor in the development of type 2 diabetes.
The argument also features heavily in the CSPI's new petition urging the FDA to reassess the GRAS status of sugar and HFCS in beverages.
However, the studies supporting this hypothesis have subjected volunteers “to unrealistically high levels of fructose or had subjects consume fructose independent of glucose, which is just not how fructose is consumed in our daily diet”, said Dr Rippe, director of the Rippe Lifestyle Institute and Professor of biomedical sciences at the University of Central Florida.
“Using real world conditions [in which glucose and fructose are typically consumed together in the form of sucrose or HFCS], we find that HFCS and other caloric sweeteners do not appear to increase liver fat or contribute to insulin resistance.”
The first study of its kind to test effects of HFCS and sucrose on liver fat levels in humans using real world conditions
The new study, published online ahead of print in the Journal of Applied Physiology, Nutrition, and Metabolism, also adds to a growing body of evidence showing that HFCS and table sugar are metabolically equivalent, claimed Dr Rippe, who received a grant from the Corn Refiners Association to conduct it.
“The study’s results are compelling because this is the first study of its kind to test the effects of HFCS and sucrose on liver fat levels in humans using real world conditions.”
There is no significant liver fat infiltration or increase in intramuscular adipose tissue
In the 10-week study, 64 healthy individuals aged 20-60 with a BMI of 23-35 drank low-fat milk sweetened with either HFCS or sucrose, with the added sugar matching the 25th, 50th and 90th percentile population consumption levels of fructose.
They were required to consume one of three different levels of sucrose (which contains 50% glucose and 50% fructose) or HFCS 55 (which contains 55% fructose, 42% glucose and 3% other carbohydrates) at 8%, 18% or 30% of the calories required for weight maintenance. (These consumption levels are equivalent to the 25th, 50th, 90th percentile for fructose consumption respectively.)
The fat content of their livers was measured using unenhanced CT Imaging, while the fat content of their muscle was assessed using magnetic resonance imaging (MRI).
The results showed that “at normal levels of consumption of the most common fructose containing sugars over a 10-week period, there is no significant liver fat infiltration or increase in IMAT [intramuscular adipose tissue]”, said the authors.
“Furthermore, our results demonstrate that there are no differences between HFCS and sucrose related to these two parameters.
“These data suggest that when fructose is consumed as part of a typical diet in normally consumed sweeteners such as sucrose or HFCS, ectopic fat storage in the liver or muscles is not promoted."
Triglyceride levels rose, but remained well within population norms
While there were no changes in total cholesterol, LDL or HDL there was a small increase in triglycerides for the entire cohort (1.11 ± 0.46 vs 1.27 ± 0.73 mmol/L, p<0.05). However, this was comparable among the 6 groups (interaction p>0.05), said the authors.
“While the increases in triglycerides in the current study are not clinically important, this issue remains one of scientific discussion and debate. It should be pointed out that both the pre and post intervention triglyceride levels in the current study are well within population norms.”
Was the study long enough?
However, one possible drawback of the study was that it wasn’t long enough, conceded the authors.
“Our findings must be treated with caution since the duration of the study may not have been long enough to demonstrate accumulation of liver or muscle fat.
“Studies of longer duration utilizing commonly consumed sugars at normal consumption levels are clearly warranted.”
Source: Journal of Applied Physiology, Nutrition, and Metabolism 10.1139/apnm-2012-0322
Title: ‘Consumption of sucrose and high fructose corn syrup does not increase liver fat or ectopic fat deposition in muscles’
Authors: Stephen Bravo, MD; Joshua Lowndes, MA; Stephanie Sinnett, MS RD; Zhiping Fullerton, PhD RD; and James Rippe, MD.