How Much Excess Free Fructose (EFF) are we consuming daily?
In fructose malabsorbers, excess-free-fructose levels become elevated in the intestines. In the biochemical pathway thought to give rise to symptoms of Fructositis disease, concentrated fructose interacts with dietary proteins to form fragments known as Advanced Glycation End-products (enFruAGE).
In existing FM research 30% of adults were FM positive after a 25 gram challenge and 10% were FM positive after a 12 gram challenge. By comparing these dosages with daily EFF intake estimates it is easy to see that FM is likely under-recognized and under-diagnosed.
These biomolecules have been studied extensively for their contribution and role in diabetes and aging  but remain unstudied and unmeasured with respect to their potential formation in the intestines of fructose malabsorbers. Yet conditions in the small intestines of fructose malabsorbers appear to be more favorable for their formation. For example, not only is fructose known to be more reactive than glucose because it exists in an open chain form more than does glucose, the alkaline environment of the absorptive upper region of the small intestines is conducive to their formation.
There is no available EFF consumption data that we know of and food labels are not required to disclose EFF content. This makes navigation of food choices for individuals with fructose malabsorption difficult. At present levels of U.S. HFCS consumption, it appears that FM is under recognized and under diagnosed. The following table of daily EFF intake estimates is based on average daily fructose intake calculated by B.P. Marriott, et al. using nationally representative survey data from NHANES for years 1999 - 2004.
The portion of total fructose that is EFF varies based on the dietary source of fructose. For estimation purposes we calculated EFF using two assumptions. One assumption is that 75% of EFF from added sugars is from HFCS that is 60% fructose. The second assumption is that half of EFF from naturally occurring sugars comes from apple juice and juices or drinks with a high apple juice content with 67% fructose. The table is not intended to be a scientific account of EFF consumption. Rather, it is intended to provide an estimation of what EFF consumption might be based the assumptions used. Notably, estimates were based on mean consumption data. Intakes at the 90th percentile were 30% - 40% higher.
Actual EFF intakes vary based upon individual diets. For example, the highest EFF consumption would be among individuals consuming most of their EFF calories from apple juice or fruit drinks with a high apple juice content, the second highest EFF consumption would be among individuals consuming most of their EFF calories from soft drinks sweetened with HFCS that is 60% fructose and 40% glucose. For example, estimates of average daily EFF intake range from 10 g to 25 g for adults who get most all of their fructose calories from HFCS that contains 60% fructose and 40% glucose monomers, and from 16 g to 38 g for adults who get most all of their total fructose calories from AJ or FD with a high AJ content. The lowest EFF consumption would be among individuals getting most of their fructose calories from orange juice since OJ contains very little EFF. According to existing research by Marriott et al, the most significant contributors of dietary EFF are fruit juices and high fructose corn syrup sweetened soft drinks and grains.
Notably, the amount of fructose in popular soft drinks has been challenged by researchers. Independent labs found 65% and 60% fructose in separate studies - not the 55% that is generally recognized as safe (GRAS). These differences may not seem like alot but fructose malabsorption research indicates that 30% of "healthy" adults were FM positive with a 25g EFF challenge. Ten percent were FM positive with a 12g challenge.
See the following table of estimates.
|Age||1Average daily total fructose intake||2Total fructose from Added Sugars||3Total fructose from Naturally Occurring sources||4Daily EFF intake from Added Sugars||5Daily EFF intake from half of Naturally Occurring||6Average Daily total EFF intake|
|1 - 3 y||34||22||12||5||3||8|
|51 and over||41||32||9||8||2||10|
|51 and over||32||24||8||6||2||8|
A comparison of the dosages used in FM research with daily EFF intake estimates support assertions by fructose malabsorption researchers that FM is under-recognized and under-diagnosed. FM research results have been available since the 1980's, but appear to have been overlooked. The ramifications of the ubiquitous use of HFCS and the systemic use of apple juice as a sweetener in fruit juice and fruit drinks are just beginning to be recognized.