An explorative study of in vivo digestive starch characteristics and postprandial glucose kinetics of wholemeal wheat bread.
BACKGROUND
Based on in vitro measurements, it is assumed that starch in wholemeal bread is rapidly digestible, which is considered to be less desirable for health.


OBJECTIVE
To evaluate the in vitro prediction, we characterized starch digestion of wholemeal wheat bread (WB) and postprandial glucose kinetics in healthy volunteers.


METHODS
In a crossover study 4 healthy men ingested either intrinsically (13)C-enriched WB (133 g) or glucose (55 g) in water. Plasma glucose and insulin concentrations were monitored during 6 h postprandially. Using a primed continuous infusion of D-[6,6-(2)H(2)] glucose, the rate of systemic appearance of glucose was estimated (reflecting glucose influx) and the endogenous glucose production calculated.


RESULTS
The glucose influx rate after WB was comparable with that after glucose in the early postprandial phase (0-2 h) (P = 0.396) and higher in the late postprandial phase (2-4 h) (P = 0.005). Despite the same initial glucose influx rate the 0-2 h incremental area under the curve (IAUC) of insulin after WB was 41% lower than after glucose (P = 0.037). Paradoxically endogenous glucose production after WB was significantly more suppressed than after glucose (0-2 h IAUC: P = 0.015, 2-4 h IAUC: P = 0.018).


CONCLUSIONS
Starch in WB seems to be partly rapidly and partly slowly digestible. Postprandial insulin response and endogenous glucose production after WB ingestion might not solely be determined by the digestive characteristics of starch; other components of WB seem to affect glucose homeostasis. In vitro measurements might not always predict in vivo starch digestion precisely.
Dept of Medical Biomics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. m.g.priebe@med.umcg.nl
Marion G
MG
Priebe
Renate E
RE
Wachters-Hagedoorn
Janneke A J
JA
Heimweg
Alexandra
A
Small
Tom
T
Preston
Henk
H
Elzinga
Frans
F
Stellaard
Roel J
RJ
Vonk
D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism*; D001939:Bread; D002247:Carbon Isotopes; D018592:Cross-Over Studies; D003903:Deuterium; D004063:Digestion; D038321:Glycemic Index; D006801:Humans; D007328:Insulin / Q000097:blood*; D008297:Male; D019518:Postprandial Period; D013213:Starch / Q000008:administration & dosage / Q000493:pharmacokinetics*; D014908:Triticum / Q000737:chemistry*; D055815:Young Adult
D001786:Blood Glucose; D002247:Carbon Isotopes; D007328:Insulin; D013213:Starch; D003903:Deuterium