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Kiwifruit and digestive comfort:
In vitro and in vivo supporting evidence
Dr Carlene Starck
Riddet Institute, New Zealand
Kiwifruit and
digestive comfort:
In vitro and in vivo supporting evidence
Carlene Starck, PhD
Riddet Institute
Massey Univ...
Dr Carlos Montoya
Riddet Institute
Dr Sharon Henare
Riddet Institute
Dr Lovedeep Kaur
Riddet Institute
Distinguished Prof ...
1. stomach
2. small
intestine
3. large
intestine
Digestive comfort = digestive health
4. rectum
4-8 hours
18-64 hours
Laxa...
1. stomach
2. small
intestine
3. large
intestine
Optimal laxationEfficient digestion
What does digestive health ‘look like...
Kiwifruit are well-known to promote laxation
Three clinical trials:
As well as the
preliminary results
you just heard abou...
Model systems to investigate the effects of kiwifruit components on digestive health:
Mimics the chemistry of human
digest...
Laxation effects are generally attributed to fibre
High proportion of fibre:
= 2-3 % of fresh weight
green > gold
Both ins...
Water holding capacity
(amount of water bound tightly to the fibre)
Swelling
(volume occupied by fibre)
* Undigested fibre...
Kiwifruit fibre is a prebiotic and is fermented to short-chain fatty acids:
Prebiotics selectively promote the growth of ‘...
Kiwifruit fibre is a prebiotic and is fermented to SCFAs:
Parkar et al (2012) Plant Foods Hum Nutr. 67: 200-207
Kiwifruit ...
Polyphenols in kiwifruit may inhibit pathogenic bacterial growth:
Kiwifruit contain a number of
polyphenols that have been...
Kiwifruit fibre may also stimulate mucin production in the stomach and duodenum:
The mucous layer (complex mixture of muci...
Other components of kiwifruit may also affect mucin production:
actinidin, polyphenols and raphides
Actinidin
- Protease (...
Fibre cannot take all the credit for laxation nor the
additional digestive health benefits of kiwifruit
Actinidin
protease...
Actinidin: History
The presence and activity of a protease in kiwifruit had been known
anecdotally for many years.
 Jelly...
Efficient protein digestion → health and digestive comfort
17
 Meals high in protein can contribute to
gastrointestinal d...
The digestion of food proteins was measured with and without a green kiwifruit extract:
Dietary protein Gastric phase
(sto...
Rats were fed diets containing specific proteins, together with either green (Hayward) or Gold (HORT
16A) kiwifruit.
19
↑
...
The 27Al peak in the stomach chyme of a
selected rat fed a beef muscle-based diet
supplemented with Hayward kiwifruit.
We ...
Dietary
Protein
T ½ (mins) P-value
- Act + Act
Beef muscle 260 144 P < 0.05
Gluten 157 151
P > 0.05
Soy PI 189 159
Whey PI...
 Gastric digestion was increased
significantly when green kiwifruit were
consumed with meat
≈ 50% ↑ in digestion
 Stomac...
10 healthy adult males:
 Aged 21-48 years
 67-106 kg
 BMI 21 – 29
Gearry et al. (unpublished)
6. Human clinical trial
A...
1. stomach
2. small
intestine
3. large
intestine
How does kiwifruit impact digestive comfort?
4. rectum
4-8 hours
18-64 ho...
Actinidin
↑ Protein
digestion
Stomach
Emptying Rate
WHC,
swelling
Bulking
Microbiota
SCFAs
Polyphenols
1. stomach
2. small...
 Kiwifruit is well-known to
promote laxation
 Fibre is only one part of the laxation
story
 Beyond laxation, there are ...
Acknowledgements
The Zespri Scientific Research Strategic Advisory (SRSA) Board especially:
Lynley Drummond
Drummond Food ...
Kiwifruit and Digestive Comfort by Dr Carlene Starck
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Kiwifruit and Digestive Comfort by Dr Carlene Starck

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Dr Carlene Starck, Postdoctoral Research Fellow at Riddet Institute, New Zealand: http://www.kiwifruitsymposium.org/presentations/kiwifruit-and-digestive-comfort-in-vitro-and-in-vivo-supporting-evidence/
Presentation at the 1st International Symposium on Kiwifruit and Health.
Kiwifruit (Actinidia deliciosa) hosts a number of beneficial properties for gut health. In addition to its high fibre content, water holding capacity and levels of the vitamins C and E, its consumption has been reported to provide relief of symptoms of gastrointestinal discomfort.

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Kiwifruit and Digestive Comfort by Dr Carlene Starck

  1. 1. Kiwifruit and digestive comfort: In vitro and in vivo supporting evidence Dr Carlene Starck Riddet Institute, New Zealand
  2. 2. Kiwifruit and digestive comfort: In vitro and in vivo supporting evidence Carlene Starck, PhD Riddet Institute Massey University Palmerston North
  3. 3. Dr Carlos Montoya Riddet Institute Dr Sharon Henare Riddet Institute Dr Lovedeep Kaur Riddet Institute Distinguished Prof Paul Moughan Riddet Institute, Co-director Dr Mike Boland Riddet Institute Assoc Prof Shane Rutherfurd Riddet Institute
  4. 4. 1. stomach 2. small intestine 3. large intestine Digestive comfort = digestive health 4. rectum 4-8 hours 18-64 hours Laxation Functional gut ‘motor’ for optimal transit time Stool characteristics Guttransittime Digestion Enzyme function Microbiota Gut physiology
  5. 5. 1. stomach 2. small intestine 3. large intestine Optimal laxationEfficient digestion What does digestive health ‘look like’? 4. rectum Guttransittime *Optimal transit time - absence of both constipation and diarrhea *Microbiota - healthy composition of gut bacteria and their metabolites (SCFAs) * Healthy mucous layer (gut lining) *Comfort - absence of bloating, pain and excessive flatulence *Soft, bulky stool *Frequent bowel movements How does kiwifruit promote these outcomes?
  6. 6. Kiwifruit are well-known to promote laxation Three clinical trials: As well as the preliminary results you just heard aboutRush et al 2002 Chan et al 2007 Chang et al 2010 What are the mechanisms? And what about digestion?
  7. 7. Model systems to investigate the effects of kiwifruit components on digestive health: Mimics the chemistry of human digestion (37°C): Phase 1. Stomach - Simulated juice with pepsin, pH = 2, 30 mins Phase 2. Small intestine (ileal) - Simulated juice with pancreatin, pH = 8, 120 mins In vitro The growing pig (25-60 kg) Best model of human upper tract digestion Meal-eating omnivore In vivo Rat Easy and inexpensive to raise although digestive system has some differences to human
  8. 8. Laxation effects are generally attributed to fibre High proportion of fibre: = 2-3 % of fresh weight green > gold Both insoluble (eg. cellulose) and soluble (eg. pectin) fibre: - ratio is 3:1 Reduced diffusion and mixing - Metabolic health benefits (Session 3 tomorrow) Hydration properties: - Swelling - High water holding capacity Bacterial fermentation and production of short-chain fatty acids (SCFAs) Undigested fibre increases bulk of stool
  9. 9. Water holding capacity (amount of water bound tightly to the fibre) Swelling (volume occupied by fibre) * Undigested fibre adds bulk to the stool Sims and Munro (2013) Adv Food Nutr Res. 68:81-99 Improve laxation
  10. 10. Kiwifruit fibre is a prebiotic and is fermented to short-chain fatty acids: Prebiotics selectively promote the growth of ‘good’ bacteria in the colon, such as Lactobacilli and Bifidobacteria. The gut microflora have a key role in digestive health through the development and promotion of gastrointestinal motor function. The intestinal microflora ferment dietary fibre to produce a number of important compounds, such as short-chain fatty acids (SCFAs) and polyphenol metabolites.  SCFAs may stimulate the gut ‘motor’ + Important fuel for colon cells and other ‘good’ bacteria.  Polyphenols may inhibit the growth of unwanted bacteria A number of studies have demonstrated an association between gastrointestinal disorders such as IBS and a microbial imbalance in the intestine
  11. 11. Kiwifruit fibre is a prebiotic and is fermented to SCFAs: Parkar et al (2012) Plant Foods Hum Nutr. 67: 200-207 Kiwifruit fibre: - Increases the growth of ‘good’ bacteria (vs negative control) - Fermented for production of SCFAs butyrate, acetate and propionate Butyrate suggested to promote motor function via stimulation of the gut’s nervous system * * *
  12. 12. Polyphenols in kiwifruit may inhibit pathogenic bacterial growth: Kiwifruit contain a number of polyphenols that have been shown to inhibit the growth of pathogenic bacteria in isolation. Salmonella typhimurium A healthy digestive system requires both growth of ‘good’ bacteria as well as the prevention of growth of ‘bad’ bacteria
  13. 13. Kiwifruit fibre may also stimulate mucin production in the stomach and duodenum: The mucous layer (complex mixture of mucins, bacteria + other material) sits on the gut wall between the inside of the gut and the host = is the front line of defence from environmental pathogens. Influence on Muc5AC mRNA: P = 0.067 Increase in Muc1 mRNA: P < 0.05  Growing pigs fed increasing amounts of green kiwifruit (control = 0%)  Measured mucin production and gene expression in: - Stomach - Small Intestine - Colon  Function depends on thickness and the rate it can be replenished (mucin production).  A damaged mucous layer is associated with a number of colonic diseases, such as IBD. Moughan, PJ et al (2013). Adv Food Nutr Res. 68:169-851 Possible mechanisms: Directly: abrasive effect (mucin turnover) Indirectly: gut bacteria play a role in maintaining the mucous layer Further research is currently underway
  14. 14. Other components of kiwifruit may also affect mucin production: actinidin, polyphenols and raphides Actinidin - Protease (enzyme that digests protein) - may enhance the natural proteolytic degradation of the mucous layer → greater production of mucin Like fibre, polyphenols modulate the gut microbiota Raphides – small insoluble needle- shaped calcium oxalate raphide crystals – may have a stimulatory effect on mucin production
  15. 15. Fibre cannot take all the credit for laxation nor the additional digestive health benefits of kiwifruit Actinidin protease Other bioactives ‘KISSPER’ Polyphenols Green kiwifruit (Hayward) contains the protease actinidin (285 units/gDM). Sungold = about 26% of the level in green. Original gold (Hort 16A) = no actinidin. Raphides Preliminary in vitro research suggests a role in contractions of the gut through ion channeling activity. Ciardiello et al. (2008). J Peptide Sci. 14:742-754. Negative control: comparable composition to green kiwifruit minus actinidin
  16. 16. Actinidin: History The presence and activity of a protease in kiwifruit had been known anecdotally for many years.  Jelly (gelatin) would not set if kiwifruit was added.  Kiwifruit placed on meat has a marked tenderising effect. Then: 1959 – Arcus (Otago Medical School)  Presence of a proteolytic enzyme in “Chinese gooseberries” & named it “actinidin” - hydrolyses several proteins (incl. haemoglobin, gelatin and whole milk) 1970s – McDowall (Australia)  Purified the enzyme and showed details of hydrolysis of insulin (as a model protein) 1970s - Massey University  Details of the specificity, mechanism of action and structure of actinidin
  17. 17. Efficient protein digestion → health and digestive comfort 17  Meals high in protein can contribute to gastrointestinal discomfort.  Dietary proteases may assist with efficient protein digestion and therefore may enhance digestive comfort. Does kiwifruit have a role in protein digestion in the stomach and small intestine? Comprehensive series of in vitro and in vivo experiments designed and carried out
  18. 18. The digestion of food proteins was measured with and without a green kiwifruit extract: Dietary protein Gastric phase (stomach) + actinidin Gastric and small intestine + actinidin Casein (main protein in milk)   Meat protein   Soy Protein   Whey protein   Zein (corn)   Gelatin   Gluten and gliadin (main proteins in wheat)   1. In vitro: Actinidin enhances gastric and small intestine protein digestion Casein Casein +Pepsin Casein +Pepsin +Act ‘SDS-PAGE’ Kaur et al. (2010) J. Agric. Food Chem. 58(8): 5068–5073 Kaur et al. (2010) J. Agric. Food Chem. 58(8): 5074–5080 Digestion enhanced compared to no kiwifruit control  No enhancement of digestion compared to no kiwifruit control
  19. 19. Rats were fed diets containing specific proteins, together with either green (Hayward) or Gold (HORT 16A) kiwifruit. 19 ↑ +35% ↑ +60% ↑ +27% ↑ +29% No effect 2. In vivo (rat model): Actinidin-containing kiwifruit enhances gastric protein digestion Rutherfurd et al. (2011) 129(4):1681–1689
  20. 20. The 27Al peak in the stomach chyme of a selected rat fed a beef muscle-based diet supplemented with Hayward kiwifruit. We use ‘Wide-bore Nuclear Magnetic Resonance’ (NMR) for real-time measurement of stomach-emptying. 27Aluminium (natural Al isotope) is fed with the meal and detected at low pH only. 3. In vivo (rat model): Actinidin-containing kiwifruit enhances stomach emptying Photos courtesy Drs C Montoya & J Hindmarsh, Riddet Institute
  21. 21. Dietary Protein T ½ (mins) P-value - Act + Act Beef muscle 260 144 P < 0.05 Gluten 157 151 P > 0.05 Soy PI 189 159 Whey PI 182 185 40 60 80 100 0 25 50 75 100 125 150 Relative27Alconcentration,% Time after feeding (min) Beef muscle (with actinidin) Beef muscle (no actinidin) T1/2 = time required for half the stomach contents to be emptied Smaller T1/2 = faster stomach emptying rate An increase in stomach emptying rate by actinidin may be related to the effects of kiwifruit on gut transit time. Montoya et al. (2014) J Nutr. 144(4):440-6. *
  22. 22.  Gastric digestion was increased significantly when green kiwifruit were consumed with meat ≈ 50% ↑ in digestion  Stomach emptying rate was faster when green kiwifruit were consumed with meat ≈ 20% ↓ in T1/2 Pigs were fed diets containing beef-muscle protein, together with either green (Hayward) or gold (HORT 16A; no actinidin) kiwifruit. 4. In vivo (growing pig model): Actinidin-containing kiwifruit enhances protein digestion and stomach emptying Green KF (+ actinidin) Hort 16A KF (- actinidin) Like human digestive enzymes, actinidin is active at low pH over the time course of normal digestion. Montoya et al. (2014) British Journal of Nutrition. 111: 957-967
  23. 23. 10 healthy adult males:  Aged 21-48 years  67-106 kg  BMI 21 – 29 Gearry et al. (unpublished) 6. Human clinical trial Actinidin contributes to gastric comfort after a high protein meal: Test meals:  400g lean steak +200g Green (+ actinidin)  400g lean steak + 200g Hort16A Gold (- actinidin) Results: For all measures of gastric comfort (pain in upper abdomen, rumbling in stomach, bloating, belching, and flatulence): Green kiwifruit (+ actinidin) → less symptoms reported Reported bloating was significantly less when the subjects ate green kiwifruit (+ actinidin) with their protein meal (p = 0.026)
  24. 24. 1. stomach 2. small intestine 3. large intestine How does kiwifruit impact digestive comfort? 4. rectum 4-8 hours 18-64 hours Laxation Functional gut ‘motor’ for optimal transit time Stool characteristics Guttransittime Digestion Enzyme function Microbiota Gut physiology
  25. 25. Actinidin ↑ Protein digestion Stomach Emptying Rate WHC, swelling Bulking Microbiota SCFAs Polyphenols 1. stomach 2. small intestine 3. large intestine 4. rectum Guttransittime Fibre Mucous layer Raphides Mechanisms underlying benefits of kiwifruit for digestive health and comfort: Supported by experimental evidence Requires further investigation KEY: Component of kiwifruit Mechanism
  26. 26.  Kiwifruit is well-known to promote laxation  Fibre is only one part of the laxation story  Beyond laxation, there are many other digestive health and comfort benefits, including protein digestion, prebiotic activity and mucin production Take Home Message: Cutting-edge in vitro and in vivo evidence shows that kiwifruit enhances digestive health and comfort
  27. 27. Acknowledgements The Zespri Scientific Research Strategic Advisory (SRSA) Board especially: Lynley Drummond Drummond Food Science Advisory Juliet Ansell Zespri Zespri Ltd for supply of fruit and funding.

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