The hunger-suppressing effects of functional fibres have been called into doubt after a new study revealed foods containing ingredients like inulin and corn fibre do not increase feelings of fullness in the short term.
The small-scale study – published in the Journal of the Academy of Nutrition and Dietetics – investigated the hunger and satiety effects of chocolate bars containing one of four functional fibres: oligofructose, inulin, soluble corn fibre, and resistant wheat starch – all of which are commonly used in food products.
Despite the large body of evidence to support the role of fibre in increasing satiety and reducing food intake, the research, led by Joanne Slavin, from the University of Minnesota, USA, suggests that fibre-enriched foods may in fact not increase satiety. The team revealed that intake of 10 grams of the functional fibre in the form of a chocolate bar played ‘a limited role’ in short term (acute) satiety and energy intake in the new study.
“Our findings suggest a limited role for the four functional fibres tested in short-term satiety or food intake,” said Slavin and her colleagues, who revealed that the study data suggests that any ability to affect satiety and food intake may not be immediate for the types of fibre studied.
However, the authors said that dietary fibres are ‘diverse’ and have various physical and chemical properties that may affect how they are processed in, and interact with, the human gut. Such variations may influence physiologic effects, they suggested, adding that “one fibre type may not elicit the physiologic effects of another, such as inducing a feeling of satiation.”
In the study, Slavin and her team recruited 22 women, all of whom consumed five different chocolate crisp bars on separate days; four of the bars had one of four added fibres, while the fifth one had no extra fibre.
The women had one bar in the evening and then a bar for breakfast the next morning. They then had lunch at the research lab, where they rated their fullness and hunger on a standard scale. After that, they used diaries to record their food intake for the rest of the day.
The team noted that ‘as expected’, oligofructose, inulin, and soluble corn fibre were all fermented in the colon, while the resistant starch was not. “This was demonstrated by significant increases in breath hydrogen excretion,” they explained.
However, Slavin and her colleagues found that there were no differences in the women’s hunger ratings or food intake with the fibre-rich bars versus the low-fibre one.
“Functional fibres incorporated into chocolate bars at high fibre doses produce greater gastrointestinal symptoms than control, but do not alter satiety, hunger, or food intake compared with control in the short term.”
However, Slavin added that the findings do not mean fibre-enriched foods are bad: “The health benefits of increased fibre consumption are well established; therefore, functional fibres that can be easily added to traditionally low-fibre foods do warrant additional long-term study in the context of appetite control as well as the promotion of health.”
Source: Journal of the Academy of Nutrition and Dietetics
Published online ahead of print, doi: 10.1016/j.jand.2012.05.022
“Fermentable Fibers do not Affect Satiety or Food Intake by Women Who do not Practice Restrained Eating”
Authors: Melinda Karalus, Michelle Clark, Kathryn A. Greaves, William Thomas, Zata Vickers, Megumi Kuyama, Joanne Slavin