Here's a novel idea: The way fructose is metabolized in the brain may increase food intake and lead to obesity, according to a new review from the US.
The lead researcher, M. Daniel Lane from The Johns Hopkins University School of Medicine, explains: "We feel that these findings may have particular relevance to the massive increase in the use of high fructose sweeteners (both high fructose corn syrup and table sugar) in virtually all sweetened foods, most notably soft drinks".
However Dr Lane added that he did not wish to give the impression that HFCS is the only problem: "since sucrose/table sugar contains only a slightly lower percentage of fructose than HFCS".
Dr Lane said consumption of both HFCS and table sugar in the USA is about 65.8 kg (145 pounds) per year per person. Wow!
I like this, it goes a long way to point the finger to soft drinks, something we have known for quite some time: "I hasten to point out that the situation is probably most critical with the younger population, particularly in the USA, where many children receive enormous amounts of fructose in soft drinks which they consume continuously and acutely. This would be expected to lead to substantial blood levels of fructose, as well as glucose". |
Writing in the journal Biochemical and Biophysical Research Communications, Dr Lane and Seung Hun Cha report that their recent studies have shown that glucose and fructose act quite differently in the brain.
Two other papers published in PNAS in 2007 and 2008 showed that glucose and fructose signal in the brain through the malonyl-CoA signaling pathway and have inverse effects on food intake.
(Fructose is metabolized more rapidly that glucose, and therefore exerts its effects before glucose.)
This is interesting: "As a consequence of this more rapid rate of fructose metabolism ATP [adenosine triphosphate] is depleted and thereby causes the level of AMP [adenosine monophosphate] to rise, which in turn initiates the signaling pathway that leads to an increase in appetite/ food intake".
Now we come to the conflicting view. Commenting on the findings of the study, Dr James Rippe from the Rippe Lifestyle Institute (RLI) says: "While this may be interesting science, it must be approached with extreme caution when attempting to extrapolate this type of information to human nutrition, behavior or health. To speculate, as Lane and Cha do, that the biochemical pathways they describe can lead to over consumption of food and obesity is highly speculative and probably incorrect."
The key word here is "incorrect".
Dr Rippe, who names Pepsico and Tropicana amongst his partners, says that human appetite and eating behaviors are very complex. Well, beat me with a limp lettuce leaf!
"To make the leap from biochemical signaling in the brain to eating behavior is very dangerous and highly speculative. In our research laboratory we showed no difference in either appetite or calories consumed during ad libitum meals following consumption of either High Fructose Corn Syrup or sucrose."
According to Dr Rippe caloric intakes have increased by 24 per cent over the last three decades with fat intakes increasing by 5 per cent, and calories from sweeteners decreasing by 1 per cent. I would dispute this last figure vehemently. Every single report I have read about HFCS marks it as one of the biggest contributor of obesity, worldwide.
As a parting shot, Dr Rippe made a reference to the American Medical Association's 2008 conclusions that: "High Fructose Corn Syrup does not contribute to obesity more than other calorie sweeteners."
He goes on with this lame argument: "the causes of obesity are well known: increased caloric consumption and decreased physical activity. To blame fructose consumption for obesity is not founded on modern scientific evidence and consensus".
I rest my case.
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