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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
The effects of kiwifruit supplementation on neutrophil and sperm function in young adult males low in vitamin C: implications for immunity and fertility
Scientific title
The effects of kiwifruit supplementation on neutrophil and sperm function in young adult males low in vitamin C: implications for immunity and fertility
Secondary ID [1] 283128 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Immunity 289978 0
Fertility 289979 0
Condition category
Condition code
Inflammatory and Immune System 290353 290353 0 0
Normal development and function of the immune system
Reproductive Health and Childbirth 290354 290354 0 0
Fertility including in vitro fertilisation
Diet and Nutrition 290369 290369 0 0
Other diet and nutrition disorders

Study type
Description of intervention(s) / exposure
Participants will be supplemented with two export-grade gold kiwifruit/day for four weeks. Compliance will be monitored by measuring plasma vitamin C levels every week.

An extension period will comprise supplementation with 250 mg/d vitamin C tablets for two months. Compliance will be determined by counting remaining tablets.
Intervention code [1] 287849 0
Other interventions
Comparator / control treatment
No control group
Control group

Primary outcome [1] 290385 0
Neutrophil function:
- apoptosis quantified by double staining of cells with propidium iodide and Annexin V-FITC, and fluorescence-activated cell sorting (FACS)
- bacterial killing by neutrophils cocultured with S. aureus and measuring loss of bacterial colony-forming units using the fluorescent membrane potential dye DiOC2
- neutrophil chemotaxis assayed using Falcon Fluoroblok inserts and a fluorescence plate reader
- neutrophil extracellular traps production measured using the membrane impermeable DNA binding dye Syntox Green and fluorescence microscopy
Timepoint [1] 290385 0
pre- and post-intervention (4 weeks)
Primary outcome [2] 290386 0
Sperm function:
- WHO fertility criteria e.g. volume, count, motility, vitality
- metabolic activity of mitochondria measured using a Seahorse XF extracellular analyser
- oxidative stress determined by oxidative state of peroxiredoxins measured using SDS-PAGE and western blotting
- sperm chromatin structure assay measured using FACS
Timepoint [2] 290386 0
Pre-intervention, post-intervention (4 weeks) and post vitamin C tablet supplementation period (3 months)
Primary outcome [3] 290387 0
Vitamin C content of plasma, neutrophils and semen measured using HPLC with electrochemical detection
Timepoint [3] 290387 0
Pre-intervention and post-intervention (4 weeks) for plasma, neutrophil and semen vitamin C levels, and post vitamin C tablet supplementation period (3 months) for plasma and seminal vitamin C levels only
Secondary outcome [1] 304391 0
General health (SF-36 questionnaire)
Timepoint [1] 304391 0
Pre- and post-intervention (4 weeks)
Secondary outcome [2] 304436 0
Urate and allantoin content of plasma and semen measured using UHPLC with stable isotope dilution mass spectrometry
Timepoint [2] 304436 0
Pre- and post-intervention (4 weeks)
Secondary outcome [3] 304437 0
Myeloperoxidase content of plasma and semen measured using ELISA
Timepoint [3] 304437 0
Pre- and post-intervention (4 weeks)

Key inclusion criteria
Male aged 18-35 years
Plasma vitamin C <50 umol/L
Residing in Christchurch for the duration of the study
Minimum age
18 Years
Maximum age
35 Years
Can healthy volunteers participate?
Key exclusion criteria
allergy/intollerance to kiwifruit
recent smoker (within previous year)
taking vitamin C supplements (within past 3 months)
taking prescription medication (within past 3 months)
excessive alcohol consumption (>21 std drinks/week)
high fruit and vegetable consumption (>5 servings/d)
diabetes mellitus
bleeding disorgers
fainting due to fear of needles

Study design
Purpose of the study
Educational / counselling / training
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Who is / are masked / blinded?

Intervention assignment
Other design features
Type of endpoint(s)
Statistical methods / analysis

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment outside Australia
Country [1] 5354 0
New Zealand
State/province [1] 5354 0

Funding & Sponsors
Funding source category [1] 287879 0
Government body
Name [1] 287879 0
Ministry of Business, Innovation & Employment (MBIE)
Address [1] 287879 0
33 Bowen Street, Wellington 6011
Country [1] 287879 0
New Zealand
Funding source category [2] 287880 0
Commercial sector/Industry
Name [2] 287880 0
Zespri International Ltd
Address [2] 287880 0
PO Box 4043
400 Maunganui Road
Mount Maunganui 3149
Country [2] 287880 0
New Zealand
Primary sponsor type
University of Otago, Christchurch
PO Box 4345
2 Riccarton Avenue
Christchurch 8140
New Zealand
Secondary sponsor category [1] 286606 0
Name [1] 286606 0
Address [1] 286606 0
Country [1] 286606 0

Ethics approval
Ethics application status
Ethics committee name [1] 296204 0
Health and Disability Ethics Committees
Ethics committee address [1] 296204 0
C/- MEDSAFE, Level 6, Deloitte House
10 Brandon Street
PO Box 5013
Ethics committee country [1] 296204 0
New Zealand
Date submitted for ethics approval [1] 296204 0
Approval date [1] 296204 0
Ethics approval number [1] 296204 0

Brief summary
Vitamin C is an essential nutrient which is not produced in humans and consequently must be obtained through dietary sources. Vitamin C is required in all body tissues for optimal activity of a number of essential biosynthetic and regulatory enzymes. We are particularly interested in the role that vitamin C may play in immunity and fertility, through enhancement of white blood cell (neutrophil) and sperm function.

Kiwifruit are an outstanding commonly available source of vitamin C. We have recently carried out human intervention studies investigating the bioavailability of kiwifruit-derived vitamin C. We found that two kiwifruit per day were required to saturate plasma and thus provide “optimal” vitamin C levels. Neutrophil and seminal vitamin C levels were also increased significantly with two kiwifruit per day. Furthermore, we have shown that kiwifruit-derived vitamin C has equivalent bioavailability to synthetic vitamin C supplements.

The aim of our current study is to investigate the effects of kiwifruit-derived vitamin C on neutrophil and sperm function. We will supplement young men low in vitamin C with two kiwifruit per day for one month and measure neutrophil and sperm function before and after intervention. Specifically, we will determine the effects of the intervention on neutrophil cell death, bacterial killing, formation of extracellular traps and neutrophil chemotaxis. We will also determine the effects of the intervention on specific sperm parameters such as viability, motility, agglutination, mitochondrial function, markers of oxidative stress, and chromatin structure. The vitamin C status of the participants’ blood plasma will be monitored weekly for the duration of the study.

Overall, the proposed study will provide valuable information as to how vitamin C affects neutrophil and sperm function and thus potentially impact on immunity and fertility.
Trial website
Trial related presentations / publications
Enhanced human neutrophil vitamin C status, chemotaxis and oxidant generation following dietary supplementation with vitamin C-rich SunGold kiwifruit.
Bozonet SM, Carr AC, Pullar JM, Vissers MC.
Nutrients. 2015 Apr 9;7(4):2574-88. doi: 10.3390/nu7042574.
Public notes

Principal investigator
Name 42594 0
Prof Margreet Vissers
Address 42594 0
University of Otago, Christchurch
2 Riccarton Avenue
PO Box 4345
Christchurch 8140
Country 42594 0
New Zealand
Phone 42594 0
64 3 364 1524
Fax 42594 0
Email 42594 0
Contact person for public queries
Name 42595 0
Dr Anitra Carr
Address 42595 0
University of Otago, Christchurch
2 Riccarton Avenue
PO Box 4345
Christchurch 8140
Country 42595 0
New Zealand
Phone 42595 0
64 3 364 0649
Fax 42595 0
Email 42595 0
Contact person for scientific queries
Name 42596 0
Dr Anitra Carr
Address 42596 0
University of Otago, Christchurch
2 Riccarton Avenue
PO Box 4345
Christchurch 8140
Country 42596 0
New Zealand
Phone 42596 0
64 3 364 0649
Fax 42596 0
Email 42596 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary