The digestion of kiwifruit (Actinidia deliciosa) fibre and the effect of kiwifruit on the digestibility of other dietary nutrients

Type of Dietary Fiber Is Associated with Changes in Ileal and Hindgut Microbial Communities in Growing Pigs and Influences In Vitro Ileal and Hindgut Fermentation

BACKGROUND

The degree of ileal organic matter (OM) fermentation appears to be comparable to hindgut fermentation in growing pigs.

OBJECTIVES

This study aimed to determine if dietary fiber sources with known different total gastrointestinal tract (GIT) fermentability in humans affect ileal and hindgut microbial communities and ileal fermentation in growing pigs used as an animal model for human adults.

METHODS

Male pigs (21 kg bodyweight; 9 wk old; PIC Camborough 46 × PIC boar 356L; n = 8/diet) were fed for 42 d a diet containing cellulose (CEL, low fermentability) as the sole fiber source (4.5%) or diets in which half of the CEL was replaced by moderately fermentable fiber, psyllium (PSY), or kiwifruit (KF) fiber. For each diet, terminal jejunal (substrate) and ileal (inoculum) digesta were collected from euthanized animals for in vitro ileal fermentation (2 h). Terminal ileal (substrate) and cecal (inoculum) digesta were used for in vitro hindgut fermentation (24 h). After in vitro fermentations, OM fermentation and short-chain fatty acid (SCFA) production were determined. Ileal digesta and feces were collected for microbial analysis. Data were analyzed by 2-factor ANOVA (diet × GIT region).

RESULTS

In vitro ileal OM fermentation was on average 22% and comparable to hindgut OM fermentation. Ileal and hindgut OM fermentation, SCFA production, and microbial community composition changed (P < 0.05) when CEL was partially replaced by KF or PSY. For instance, pigs fed the PSY diet had 3-fold higher (P ≤ 0.05) number of ileal and fecal bacteria than pigs fed the CEL and KF diets. Pigs fed the CEL diet had 4-fold higher (P ≤ 0.05) hindgut valeric acid production than pigs fed the other diets.

CONCLUSIONS

Ileal fermentation is quantitatively significant. Partial substitution of CEL with more fermentable fibers influences both ileal and hindgut microbial communities and the fermentation in growing pigs.

Classification of organic and ordinary kiwifruit by chemometrics analysis of elemental fingerprint and stable isotopic ratios

Elemental fingerprint, stable isotopic analysis, and chemometrics were combined to identify organic kiwifruit from ordinarily cultivated kiwifruit. Samples of organic (n1 = 78) and ordinary kiwifruit (n2 = 85) were collected from neighboring areas. For elemental fingerprint, the contents of 15 elements in fresh fruits, including Al, Cr, Mg, Pb, Zn, Ca, Cu, Mn, Se, Cd, Fe, Na, Sr, Co, and K, were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Three stable isotopes, including δ¹³ C, δ¹⁵ N, and δ¹⁸ O, were analyzed using an isotope-ratio mass spectrometer (IRMS). Different classification methods including soft independent modeling of class analogy (SIMCA), partial least squares discriminant analysis (PLSDA), and least squares support vector machines (LS-SVM), were used to discriminate the organic and ordinary kiwifruits by fusion of elemental and stable isotopic. As a result, the sensitivity, specificity, and overall accuracy of SIMCA model were 0.885, 0.857, and 0.864, respectively. PLSDA and LS-SVM obtained 0.950 and 0.983 classification accuracy of organic and ordinary kiwifruits, respectively. It was demonstrated that elemental fingerprint and stable isotopic analysis would provide useful chemical information for the identification of organic fruits, and the capacity of these methods could be enhanced by chemometrics. PRACTICAL APPLICATION: The classification of kiwifruit usually relies on the label assigned by the merchant, which is prone to deceive consumers. This research has developed an accurate and effective classification method based on stable isotopes and mineral elements for the identification of ordinary kiwifruit and organic kiwifruit, providing a tool for the quality monitoring of organic food.

Kiwifruit (Actinidia deliciosa), compared with cellulose and psyllium, influences the histology and mucus layer of the gastrointestinal tract in the growing pig

Kiwifruit (KF) fiber, a mixture of soluble and insoluble fibers, elicits mucosal changes in the gastrointestinal tract (GIT). This study aimed to define the nature of these changes in mucosal features throughout the GIT of the growing pig in response to semi-synthetic iso-fiber diets containing cellulose (CEL, low GIT luminal functionality) as the sole fiber source (4.5%), or diets where half of the CEL was replaced by either PSY fiber (PSY husk, high GIT luminal functionality) or KF fiber (consumed as intact fruit). Entire male growing pigs (n = 24, 21 kg bodyweight) received the three diets (n = 8) for 42 d. GIT tissues, digesta, and feces were sampled. The partial replacement of CEL increased (P≤ 0.05) the ileal (KF 22% and PSY 33%) and colonic (PSY 86%) mucus layer thickness, whereas it decreased the rectal crypt depth (KF -26%), and small intestinal (duodenum to ileum) villus length (PSY -17%). The number of duodenal goblet cells was 77% higher (P≤ 0.05) for KF than CEL. Pigs fed the KF-containing diet had greater (P≤ 0.05) apparent ileal organic matter digestibility and apparent total tract organic matter digestibility compared with CEL, but the lowest amount of fermented organic matter in the large intestine. In conclusion, partial substitution of CEL with PSY or KF at a constant, practically-relevant dietary fiber intake, affected several measures of GIT functionality with effects being specific to the added fiber.

Nutritional properties and biological activities of kiwifruit (Actinidia) and kiwifruit products under simulated gastrointestinal in vitro digestion

BACKGROUND

Kiwifruit is one of the most commercialized fruits on the international market, which has notable high nutritional and medicinal value with many health benefits. In addition to being consumed fresh, numerous kiwifruit products are popular, such as kiwifruit juice, vinegar, dried slices, jam, wine, yogurt, and jelly. Although many studies have described the nutritional properties of kiwifruit, investigations on the nutritional properties of kiwifruit products remain limited, especially for kiwifruit products made from raw kiwifruit.

METHODS

Nutritional properties and biological activities of kiwifruit and kiwifruit products, as well as the digestive and absorption characteristics of their nutritional substances, were investigated.

RESULTS

Kiwifruit, juice, wine, and vinegar were observed to be rich in vitamin C (VC) and polyphenol and exhibited high biological activities, whereas dried kiwifruit slices and jam showed higher amounts of mineral elements. During oral digestion, VC and polyphenol showed similar absorption characteristics, while mineral elements exhibited a number of different trends. A good release rate of all nutritional substances was observed during stomach digestion, while the release rate decreased in serum-available, colon-available, and post-colonic fractions. Eating dried slices and jam supplied high amounts of mineral elements, while eating kiwifruit supplied the most comprehensive nutritional substances. The biological activities detected in raw foodstuffs were much higher than those detected after in vitro digestion. Furthermore, kiwifruit and wine showed the highest biological activities, while dried kiwifruit slices showed the lowest biological activities.

CONCLUSION

These results increased our understanding of the nutritional properties of kiwifruit and its products, providing new information and scientific recommendations to consumers for kiwifruit consumption and to producers for kiwifruit production.

Mechanisms underlying effects of kiwifruit on intestinal function shown by MRI in healthy volunteers

BACKGROUND

Chronic constipation affects approximately 17% of the population worldwide and remains an important unmet need since patients are often dissatisfied with treatment. Kiwifruit may offer an alternative to traditional laxatives and have been shown to increase stool volume, frequency and improve consistency.

AIMS

Using non-invasive MRI techniques, we assessed the effect of ingestion of kiwifruit on fluid distribution in the intestines and bowel function.

METHODS

Two period crossover trial of kiwifruit vs control in healthy adults.

INTERVENTION

two kiwifruits twice daily vs isocaloric control (maltodextrin) twice daily, consumed for a total of 3 days. Subjects underwent MRI scanning fasted and at hourly intervals for 7 hours on the third day.

PRIMARY OUTCOME

T1 relaxation time of ascending colon (T1AC) using MRI.

SECONDARY OUTCOMES

Small bowel water content (SBWC), colonic volume, gut transit time, T1 of descending colon, stool frequency and form.

RESULTS

Fourteen volunteers completed the study. T1AC was higher after kiwifruit ingestion (P = 0.029) during the second half of the day (when meal residue would be expected to reach the AC, AUC T1 T240-420 minutes; mean (SD) 137 (39) s*minute with kiwifruit versus 108 (40) s*minute with control. SBWC (P < 0.001), colon volumes (P = 0.004), as well as stool frequency (1.46 ± 0.66 with kiwifruit vs 1.14 ± 0.46 stools per day with control; P = 0.034) and stool form score (Bristol Stool Chart score 4.1 (0.9) with kiwifruit versus 3.4 (0.7) with control; P = 0.011) were markedly increased in participants consuming kiwifruit compared to control.

CONCLUSION

Consumption of kiwifruit in healthy volunteers increases water retention in the small bowel and ascending colon and increases total colonic volume. The data may explain the observed increase in stool frequency and looser stool consistencies, suggesting that kiwifruit could be used as a dietary alternative to laxatives in mild constipation.

Adaptation of intestinal fermentation over time in the growing pig is influenced by the amount of kiwi fruit consumed

The effect of kiwi fruit at two dietary levels on the adaptation of intestinal fermentation over time in the growing pig was studied. A semi-synthetic fibre-free diet and two semi-synthetic diets containing kiwi fruit as a model fibre source (133 or 266 g/kg (DM basis); 28 or 48 g fibre/kg) were formulated and the diets contained titanium dioxide as an indigestible marker. A total of fourteen ileal cannulated pigs (41 kg body weight) were fed the fibre-free diet for 7 d followed by either the low or high kiwi fruit-containing diets (n 7/diet) for a further 44 d. Ileal digesta and faeces were collected at five times throughout the study. Ileal digesta were fermented (in vitro) with a standard pooled human faecal inoculum, while fresh pig faeces were used as inocula to ferment in vitro a standard purified fibre. Observations were normalised for diet DM intake using the marker. The 16S ribosomal RNA gene copy number of ileal and total faecal bacteria were high for the high-kiwi fruit level diet (P<0·05). The ileal bacteria tended to decrease over time (P<0·1), while the faecal bacteria increased (P<0·05), at the same rate for both diets. The amounts of crude protein and insoluble dietary fibre entering the hindgut changed over time similarly for both diets, whereas for starch it changed only for the low kiwi fruit-containing diet (P<0·05). Changes over time were also observed for the predicted hindgut valeric acid production and butyric acid absorption (P<0·05). In conclusion, adaptational changes over time of some characteristics of intestinal fermentation depended on the dietary level of kiwi fruit.