The Effect of Wholegrain on Appetite: Short- and Long-Term Effects and the Potential Role of Colonic Fermentation

Research output: Book/ReportPh.D. thesisResearch

  • Sabine Ibrügger
Background:
Wholegrain consumption is suggested to improve short-term appetite sensation. This may occur immediately after wholegrain intake but also after a second meal. The latter may potentially be mediated by short-chain fatty acids (SCFA) that are generated during colonic fermentation of wholegrain components. Little is, however, known how regular wholegrain intake influences appetite sensation. Hypothetically, an increase in satiety-inducing gut hormones, due to steady colonic fermentation upon regular wholegrain intake, may lead to an improvement of the overall appetite sensation. In the long run, regular wholegrain intake may also reduce body weight due to reoccurring short- and long-term effects on appetite.

Aim:
This PhD thesis investigates the effects of selected wholegrain products on appetite after a second meal, as well as the effects of sustained wholegrain intake on overall appetite sensation with special attention to the role of colonic fermentation. Further, the impact of regular wholegrain intake on body weight is investigated.

Methods:
In a second meal study we studied the effects of two coarse wholegrain rye evening meals on subjective appetite after a standardized breakfast and on ad libitum energy intake at lunch at the subsequent day compared to white wheat bread. In a human intervention study we investigated the effects of 8-week ad libitum consumption of a mixed wholegrain diet on appetite after a standardized, non-wholegrain breakfast, on ad libitum energy intake at a subsequent lunch, and on body weight compared to 8-week refined grain consumption. Furthermore, in a crosssectional study we studied the associations between habitual wholegrain intake and appetite after a standardized, non-wholegrain breakfast, ad libitum energy intake at lunch and body weight. In the three studies we approximated colonic fermentation by measuring the excretion of hydrogen in the breath. Moreover, we determined the production of SCFA in an in vitro fermentation of wholegrain rye products.

Results:
Consumption of coarse wholegrain rye evening meals reduced ad libitum energy intake at lunch at the subsequent day compared to white wheat bread whereas subjective appetite was not changed. On the other side, we did not find effects on subjective appetite after a standardized, non-wholegrain breakfast and on ad libitum energy intake at lunch after 8-week wholegrain consumption, whereas body weight was decreased. The cross-sectional data indicate that greater habitual wholegrain intake is associated with increased appetite after a standardized, nonwholegrain breakfast, while it was not associated with ad libitum energy intake. Further, habitual wholegrain intake was negatively related to BMI in men. Breath hydrogen excretion was increased at the next day following consumption of coarse wholegrain rye evening meals. Also, SCFA concentration increased after in vitro fermentation of wholegrain rye products. In contrast, 8-week wholegrain intake did not affect basal breath hydrogen excretion and habitual wholegrain intake was even negatively associated with breath hydrogen excretion.

Conclusion:
Consumption of coarse wholegrain rye products may reduce energy intake at a later meal, which may potentially be mediated by colonic fermentation. It is, however, not clear whether effects are due to wholegrain per se or rather due to cereal type or structure. Regular wholegrain intake does not seem to improve overall appetite sensation; in contrast, it may even increase appetite after energy-dense meals. Regular wholegrain intake does not seem to increase basal colonic fermentation. However, this may be owing to methodological limitations. Furthermore, sustained wholegrain intake may reduce body weight, although the effect size may be rather small in the long run.
Original languageEnglish
Place of PublicationCopenhagen
PublisherDepartment of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen
Number of pages133
ISBN (Print)978-87-7611-829-7
Publication statusPublished - 2015

ID: 130279601