Condition category
Not Applicable
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status
Results overdue

Plain English Summary

Background and study aims
Cocoa flavanols (CF) are a supplement made from cocoa beans. They have several beneficial health effects and can stimulate blood flow to provide the body with sufficient oxygen and nutrients when exercising. After exercise, the body needs to recover. The aim of this study is to find out whether taking this CF supplement can help to improve exercise performance and help recovery from exercise.

Who can participate?
Well-trained male cyclists aged 20 to 35

What does the study involve?
Participants undergo a cycling test on the first occasion. On two separate occasions, participants undergo two 30-min all-out cycling exercises (time trials), 1.5 and 3 hours after taking either CF or a placebo (dummy supplement), with a rest in between. Blood samples are taken at the start of the study and before and after each time trial and tested for several markers.

What are the possible benefits and risks of participating?
The possible benefits include improved performance and recovery from exercise. The study does not involve any risks, as the participants are used to heavy exercise and perform cycling training at least 10 hours per week.

Where is the study run from?
Vrije Universiteit Brussel (Belgium)

When is the study starting and how long is it expected to run for?
March 2015 to July 2015

Who is funding the study?
Vrije Universiteit Brussel (Belgium)

Who is the main contact?
Lieselot Decroix

Trial website

Contact information



Primary contact

Mrs Lieselot Decroix


Contact details

Department of Human Physiology
Pleinlaan 2

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Effect of acute cocoa flavanols intake on exercise-induced oxidative stress, inflammation and nitric oxide production in healthy athletes: a randomized controlled trial


Study hypothesis

It is hypothesized that cocoa flavanol (CF) intake:
1. Will have little or no effect on indirect markers of NO production and exercise performance in healthy, well-trained, subjects
2. Will decrease exercise-induced oxidative stress and inflammation, leading to an improved recovery

Ethics approval

Medical ethics committee UZ Brussel-VUB, 28/01/2015, ref: B.U.N. 143201523265

Study design

Randomized double-blind interventional placebo-controlled cross-over single-centre study

Primary study design


Secondary study design

Randomised cross over trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use contact details to request a participant information sheet


Exercise performance and recovery


Participants perform an incremental cycling test on the first occasion. On two separate occasions, subjects perform two 30-min time trials on an indoor cycle-ergometer, interposed by passive rest, 1.5 and 3 hours after drinking a single dose of either:
1. Chocolate drink with high cocoa flavanol content (900 mg flavanols) (brandname: acticoa)
2. Placebo chocolate drink (13 mg flavanols)
The drinks are matched in caffeine, theobromine, calories, carbohydrates, fat and proteins.

Lactate, glucose, heart rate, rating of perceived exertion (RPE) and power output were measured during the time trials. Blood will be drawn at baseline and before and after each time trial and analyzed for several markers.

Intervention type



Drug names

Primary outcome measure

1. Epicatechin serum concentration
2. Trolox equivalent antioxidative capacity (TEAC)
3. Uric acid (UA) plasma concentration
4. Malonaldehyde (MDA) plasma concentration
5. L-arginine/ADMA plasma concentration
6. Citrulline plasma concentration
7. Interleukin (IL)-1 plasma concentration
8. IL-6 plasma concentration
9. Tumor necrosis factor (TNF)-α plasma concentration
Measured at baseline and before and after each time trial (pre-TT1, post-TT1, pre-TT1, post-TT1) by HPLC, ELISA and spectrophotometry of plasma and serum (blood)

Secondary outcome measures

1. Time trial performance; time to complete a certain predefined workload during time trial 1 (90-120 min after cocoa intake) and during time trial 2 (210-240 min after cocoa intake)
2. Physiological parameters during time trial:
2.1. Lactate concentration, glucose concentration and rate of perceived exertion at start, after 10 min, after 20 min and at the end of each time trial
2.2. Heart rate and power output at start, after 5, 10, 15, 20, 25 mintues and at the end of each time trial

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Age: between 20 years and 35 years
2. No severe head injuries in the past
3. No intake of neurological or psychological medication
4. Healthy
5. No hypertension
6. No cardiovascular disease
7. Cycling training of at least 10 hours per week for the last 2 years

Participant type

Healthy volunteer

Age group




Target number of participants


Participant exclusion criteria

1. Age: younger than 20 years or older than 35 years
2. Severe head injuries in the past
3. Intake of neurological or psychological medication which might alter cognitive function (psychotropic drugs, beta adrenergic blockers, steroids)
4. Hypertension
5. Cardiovascular disease
6. Other diseases which can alter cognitive function (diabetes, depression)

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

Vrije Universiteit Brussel

Sponsor information


Vrije Universiteit Brussel

Sponsor details

Pleinlaan 2

Sponsor type




Funder type


Funder name

Vrije Universiteit Brussel

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

The data will be presented in a peer-reviewed journal.

IPD sharing plan
The datasets generated during and/or analysed during the current study will be available upon request from Lieselot Decroix.

Intention to publish date


Participant level data

Available on request

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes