To compare the intakes of dietary fibre (DF) and dietary indigestible fraction (DIF) in the Spanish diet and also to show the limitations of DF values for nutritional and epidemiological studies.Design:
This includes the following: (i) estimation of plant foods consumption in Spanish diet from national food consumption data obtained from annual surveys (6000 households, 700 hotels and restaurants and 200 institutions); (ii) determination of DIF content in plant foods using analytical methods that mimic physiological conditions; (iii) estimation of daily intakes of DIF and DF in the Spanish diet.Results:
DIF intake in the Spanish population was estimated at 41.5 g/person/day. DF intake (18.3 g/person/day) was considerably lower than the amount of carbohydrate necessary to maintain the daily bacterial cell turnover in large intestine ('carbohydrate gap'). The differences between DIF and DF values are a consequence of conceptual and methodological aspects. DIF, as the part of foods reaching the colon, comprises not only DF but also other indigestible compounds such as a fraction of resistant starch, protein, polyphenols and other associated compounds. Analytical conditions are closer to actual physiological conditions in the determination of DIF than in DF analysis.Conclusions:
DF intake underestimates a major part of the dietary substrates that enter the colon. DIF intake more closely matches the amount of substrates needed to maintain a typical human colonic microflora. DIF may be a good alternative to DF for nutritional and epidemiological studies.