The Effect of Formulation of Curcuminoids on Their Metabolism by Human Colonic Microbiota

Turmeric (Curcuma longa L.) is the only edible plant recognized as a dietary source of curcuminoids, among which curcumin, demethoxycurcumin (DMC) and bis-demethoxycurcumin (Bis-DMC) are the most representative ones. Curcumin shows a very low systemic bioavailability and for this reason, several technologies have been adopted to improve it. These technologies generally improve curcuminoid absorption in the small intestine, however, no data are available about the effect of curcuminoid formulation on colonic biotransformation. The present study aims at investigating the human colonic metabolism of curcuminoids, prepared with two different technologies, using an in vitro model. Unformulated curcuminoid and lecithin-curcuminoid botanical extracts were fermented using an in vitro fecal model and colonic catabolites were identified and quantified by uHPLC-MSⁿ. Native compounds, mainly curcumin, DMC and bis-DMC, were metabolized by colonic microbiota within the 24-h incubation. The degradation of curcuminoids led to the formation of specific curcuminoid metabolites, among which higher concentrations of bis(demethyl)-tetrahydrocurcumin and bis(demethyl)-hexahydrocurcumin were found after lecithin-extract fermentation compared to the concentration detected after unformulated extract. In conclusion, both curcumin-based botanical extracts can be considered important sources of curcuminoids, although the lecithin-formulated extract led to a higher production of curcuminoid catabolites. Moreover, a new curcuminoid catabolite, namely bis(demethyl)-hexahydrocurcumin, has been putatively identified, opening new perspectives in the investigation of curcuminoid bioavailability and their potential metabolite bioactivity.

Pasta Structure Affects Mastication, Bolus Properties, and Postprandial Glucose and Insulin Metabolism in Healthy Adults

Background

Structure and protein–starch interactions in pasta products can be responsible for lower postprandial glycemic responses compared with other cereal foods.

Objectives

We tested the effect on postprandial glucose metabolism induced by 2 pasta products, couscous, and bread, through their structural changes during mastication and simulated gastric digestion.

Methods

Two randomized controlled trials (n = 30/trial) in healthy, normal-weight adults (mean BMI of 23.9 kg/m² (study 1) and 23.0 kg/m² (study 2)) evaluated postprandial glucose metabolism modulation to portions of durum wheat semolina spaghetti, penne, couscous, and bread each containing 50 g available carbohydrate. A mastication trial involving 26 normal-weight adults was conducted to investigate mastication processes and changes in particle size distribution and microstructure (light microscopy) of boluses after mastication and in vitro gastric digestion.

Results

Both pasta products resulted in lower areas under the 2-h curve for blood glucose (−40% for spaghetti and −22% for penne compared with couscous; −41% for spaghetti and −30% for penne compared with bread), compared with the other grain products (P < 0.05). Pasta products required more chews (spaghetti: 34 ± 18; penne: 38 ± 20; bread: 27 ± 13; couscous: 24 ± 17) and longer oral processing (spaghetti: 21 ± 13 s; penne: 23 ± 14 s; bread: 18 ± 9 s; couscous: 14 ± 10 s) compared with bread or couscous (P < 0.01). Pastas contained more large particles (46–67% of total particle area) compared with bread (0–30%) and couscous (1%) after mastication and in vitro gastric digestion. After in vitro gastric digestion, pasta samples still contained large areas of nonhydrolyzed starch embedded within the protein network; the protein in bread and couscous was almost entirely digested, and the starch was hydrolyzed.

Conclusions

Preservation of the pasta structure during mastication and gastric digestion explains slower starch hydrolysis and, consequently, lower postprandial glycemia compared with bread or couscous prepared from the same durum wheat semolina flour in healthy adults.

The postprandial in vivo trials were registered at clinicaltrials.gov as NCT03098017 and NCT03104686.

The importance of glycemic index on post-prandial glycaemia in the context of mixed meals: A randomized controlled trial on pasta and rice

BACKGROUND AND AIMS

Post-prandial glycemic response (PPGR) depends on the intrinsic characteristic of the carbohydrate-rich foods as well as on the amount and type of other nutrients. This study aimed to explore whether the addition of condiments can affect the difference in PPGR between a low and a medium-high Glycemic Index (GI) food.

METHODS AND RESULTS

Spaghetti (S) and rice ® were consumed plain and after adding tomato sauce and extra virgin olive oil (TEVOO), or pesto sauce (P). The GI of R (63 ± 3) was statistically higher than that of S (44 ± 7) (p = 0.003). The Incremental Area Under the Curve (IAUC) for R was significantly greater than S (124.2 ± 12.1 and 82.1 ± 12.9 mmol∗min/L respectively) (p = 0.016) for blood glucose but not for insulin (1192.6 ± 183.6 and 905.2 ± 208.9 mU∗min/L, respectively) (p = 0.076). There were no significant differences after the addition of either TEVOO or P. The postprandial peaks of blood glucose and insulin for R (6.7 ± 0.3 mmol/L and 36.4 ± 4.9 mU/L, respectively) were significantly higher compared to S (6.0 ± 0.2 mmol/L and 26.7 ± 3.6 mU/L, respectively) (p = 0.033 and p = 0.025). The postprandial peak for insulin remained significantly higher with P (36.8 ± 3.7 and 28.6 ± 2.9 mU/L for R + P and S + P, p = 0.045) but not with EVOO (p = 0.963). Postprandial peaks for blood glucose were not significantly different with condiment.

CONCLUSIONS

The differences in PPGR were significant between spaghetti and rice consumed plain, they reduced or disappeared with fat adding, depending on the type of condiment used. REGISTRATION NUMBER: (www.clinicaltrial.gov):NCT03104712.

A nutritional evaluation of various typical Italian breakfast products: a comparison of macronutrient composition and glycaemic index values

Breakfast foods with lower glycaemic responses are associated with better body weight control. Glycaemic index (GI) values of some commonly consumed breakfast foods in Italy were determined and compared, along with macronutrients. Cakes/pastries were low-medium GI (44-60), with high-sugar and saturated fat and low-fibre. Generally, mueslis and breads were medium GI (62-66 and 59-76, respectively) with higher fibre and lower saturated fat and sugar. The addition of spreads to bread lowered GI (47-66) but increased sugar and saturated fat.