Impact of Dark Chocolate Consumption on Glucose Levels of People With Diabetes
Phase: NA
Conditions: Type 2 Diabetes, Type 1 Diabetes
Sponsor: University of British Columbia

 
 
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Faculty of Health and Social Development 
School of Health and Exercise Sciences 
3333 University Way 
Kelowna, BC  V1V 1W5 
Title: Impact of dark chocolate consumption on glucose levels of people with diabetes 
 
Research Question: Does dark impact blood glucose levels in people with 
diabetes? 
 
Objectives 
1) To determine whether a dark chocolate sweetened with stevia, erythritol, 
and inulin compared to a standard dark chocolate bar impacts blood 
glucose levels in individuals with diabetes (T1D and T2D);  
2) to understand and manage glucose levels in people with diabetes after 
consumption of different blends of chocolate. 
 
Hypothesis: 
a) A dark chocolate sweetened with stevia, erythritol, and inulin, compared 
to a standard dark chocolate bar will not impact blood glucose levels in 
individuals with diabetes (T1D and T2D) 
 
 
Background Information 
 
Diabetes is a growing concern in the world with an estimated 9.3% of adults, ages 
20-79, with it in 2019, type 2 diabetes accounting for 90% of this total (1). In 
Canada, approximately 7.5% of adults have type 2 diabetes, 4.7% diagnosed and 
2.8% undetected (2). Furthermore, an estimated 12.4% of adults in Canada have 
prediabetes, with 5-10% of those becoming diabetic each year (2). In order to 
prevent this, interventions aimed at weight loss, dietary change, and increased 
physical activity have been found to be effective (3). Additionally, a common 
recommendation for individuals with type 2 diabetes is to limit sugars and sweets 
as it may cause a high blood glucose response (4). 
In diabetes, the postprandial phase is characterized by a rapid and large increase 
in blood glucose levels, and the possibility that these postprandial “hyperglycemic 
spikes” may be relevant to the pathophysiology of late diabetes complications is 
recently receiving much attention (5). 
Postprandial hyperglycemia is a major component of glucose toxicity at the cellular 
and tissue level. Acute elevations of glucose after nutrient ingestion are associated 
with a variety of glucose-mediated tissue defects, including oxidative stress, lipid 
peroxidation, and advanced glycation end products (AGEs) formation leading to 
endothelial dysfunction and inflammation (6). This state not only initiates the 
development of early microvascular and macrovascular complications, but it also 
can contribute to a rapid progression to diabetes by causing glucose toxicity in 
muscle and pancreatic beta cells. The effects of hyperglycemia are often 
irreversible and lead to cell dysfunction.  

 
 
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Faculty of Health and Social Development 
School of Health and Exercise Sciences 
3333 University Way 
Kelowna, BC  V1V 1W5 
Therefore, strategies aiming at the specific reduction of postprandial 
hyperglycemia must be utilized to minimize clinical damages (7). 
Chocolate is often avoided due to the sugar content, however, high‐polyphenol 
chocolate has a beneficial effect on hyperglycaemia. (8) In a study looking at 
consumption of isocaloric doses of dark, milk, and white chocolate, blood glucose 
levels were higher 30 minutes after ingestion of the white and milk chocolate 
compared to the dark chocolate (9). This offers potential for individuals with 
diabetes to consume chocolate products depending on sugar and cocoa content. 
Daily consumption of flavonoid-rich chocolate have shown improved fasting 
plasma glucose levels and insulin resistance, three times greater than in milk 
chocolate (10). It has also been shown that a 15-day administration of polyphenol-
rich dark chocolate decreased blood pressure and increased insulin sensitivity in 
healthy subjects (11). Similar results after 4-week consumption of polyphenol-rich 
dark chocolate; improved fasting glucose and decreased insulin resistance (12). 
By consuming high-quality cocoa products such as dark chocolate, insulin function 
could be improved, blood sugar better controlled, and possibly, the incidence of 
prediabetes is lowered (13). Therefore, it appears that the health benefits from 
chocolate are predominantly from the dark chocolate form. 
The sugar-free chocolate from Ross Chocolates is formulated with a blend of 
inulin, erythritol, and stevia. These alternatives to sugar are not expected to cause 
a significant change in blood glucose levels following consumption. A study 
evaluating the consumption of sucrose, fructose, and isomalt-sweetened 
chocolates in type 2 diabetes patients found that while the sucrose and fructose-
sweetened chocolates induced a similar glycemic effect, the isomalt-sweetened 
chocolate produced a lower glycemic effect (14). Therefore, since it has never 
been tested scientifically before, it would be novel and beneficial to assess if Ross 
Chocolates’ blend of sweeteners would lead to a lower or null glucose spike in 
people with diabetes. Confirmation of this key piece of evidence could open the 
door for longer term studies easing concern over sugar-free dark chocolate 
postprandial hyperglycemia.  
 
Research Method 
 
Twenty (N=20) individuals at University of British Columbia with physician 
diagnosed T1D (N=10) or T2D (N=10) (HbA1c 6.5-8.5%), between the ages of 18-
75 years, with a BMI between 25-40 kg/m2 will be recruited through online social 
media and newspaper advertising.  
Inclusion criteria will be: i) physician-diagnosed T1D or T2D of ≥1 year; ii) current 
HbA1c of 6.5-8.5%; iii) BMI: 25-40 kg/m2; iv) blood pressure of <160/99 mm Hg 
assessed according to guidelines; v) non-smoking; vi) not on hormone 

 
 
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Faculty of Health and Social Development 
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3333 University Way 
Kelowna, BC  V1V 1W5 
replacement therapy, corticosteroids, or anti-inflammatory medications; and vii) 
18–75 years old. Exclusion criteria will include i) 
Are taking more than 2 
glucose lowering medications; ii) Are ongoing medical treatment for diseases 
such as cancer, auto-immune or inflammatory disease, liver or kidney disorders;  
iii) Have allergy, intolerance or aversion to cocoa, stevia, erythritol, inulin, or any 
other dietary restrictions (e.g., vegan) that will prevent them from following the 
standardized study diets; iv) Are unable to follow remote guidance by internet or 
smartphone; v) Are unable to follow the controlled diet instructions; vi) Are unable 
to read or communicate in English. 
 
 
Based on our previous studies ~55% of males and ~70% of females with T1D or 
T2D who volunteer will meet these eligibility criteria so we anticipate no recruitment 
issues. We will allow statins and anti-hypertensive medications if on a stable dose 
for 3 months because the majority of T2D patients are on at least one of these 
medications; excluding them would leave a small pool for recruitment and limit the 
generalizability of our findings. Interested participants will provide their e-mail to 
establish direct and individual communication with research team. 
 
A double-blinded crossover pilot trial is proposed. Eligible participants will 
complete 2 experimental trials separated by approximately 2-7 days, consuming 
no-sugar dark chocolate from Ross Chocolates and a conventional dark chocolate 
bar.  
 
Due to COVID-19 breakout, this study is proposed to be done remotely since 
participants belong to risk group and will probably maintain in quarantine for 
unpredictable time. Information and guidance for the trial will be done by email, 
telephone calls and Zoom meeting. RedCap-UBC will be used to manage 
information and deliver questionnaires. Participants will be recruited after 
completing an online Eligibility questionnaire. 
Participants will receive in their homes a box containing a OneTouch Verio IQ® kit 
Blood glucose monitoring system (OneTouch Verio IQ® meter, lancing device, 
sterile lancets, carrying case), glucose strips,  alcohol swabs, 1 bar of Ross dark 
chocolate (34g each) and 1 bar of a conventional dark chocolate (34g each) and 
instructions on how to proceed during each trial. Chocolate bars will be identical 
and wrapped equally and labeled as A and B, by Ross Chocolates (prepared in 
the same mold and packaged identically) who are not involved in any other aspects 
of the study,  allowing for blinding of research team and participants. Participants 
will complete two experimental trials: 1) consumption of 1 bar (34g) of Ross dark 
chocolate 2) consumption of 1 bar (34g) of conventional dark chocolate. The order 
of the bars will be randomized so there will be an equal chance of getting bar A or 
bar B first (similar to drawing a name out of a hat or flipping a coin). Participants 
will be advised to perform both trials on the exact same time of day, in the morning 
after an overnight fast, refraining from diabetic medications. They will be asked to 
register glucose levels before and after eating the chocolates. A OneTouch Verio 

 
 
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Faculty of Health and Social Development 
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3333 University Way 
Kelowna, BC  V1V 1W5 
IQ®  meter will be used to measure blood glucose. Time points will be as follows: 
before consumption, 15 min after, 30min after, 45min after, 60min after, 90min 
after, 120min after. Values will be registered on a Glucose Form and stored on the 
meter and sent to research team by email.  Participants will then be asked to 
Complete Taste Test Questionnaire sent by RedCap link through e-mail. 
 
Study Timeline:  
 
 
 
Baseline Contact 
 
On the initial contact, by a FIRST email, participants will be informed of the study and 
asked to complete a Health Screening Questionnaire and sign electronically an Informed 
Consent. After confirmation of eligibility and given consent, participants will receive a 
SECOND email with information on the study kit and asked to inform Research team when 
kit arrives. The kit will contain:  
 
- 
Study Welcoming, Instructions and Responsibilities 
- 
Glucose levels form 
- 
OneTouch Verio IQ® kit Blood glucose monitoring system (OneTouch Verio IQ® 
meter, lancing device, sterile lancets, carrying case) 
- 
Glucose strips 
- 
Alcohol swabs 
- 
1 bar of dark chocolate A (34g each) 
- 
1 bar of dark chocolate B (34g each) 
 
Once participants confirm study kit was received, they will get a THIRD email suggesting 
to start the protocol. 
Participants will choose 2 different days, one for Day 1 and one for Day 2 (2-7 days 
apart from each other) and perform the following protocol: 
 
 
Day 1 
 
 Measure glucose levels before chocolate consumption and write down value on 
Glucose levels form 
 Consume 1 bar of dark chocolate (A or B) according to instructions from 
Research team after randomization 

 
 
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Faculty of Health and Social Development 
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3333 University Way 
Kelowna, BC  V1V 1W5 
 Measure glucose levels after consumption (15 min, 30 min, 45 min, 60 min, 90 
min, 120 min) and write down values on Glucose levels form 
 Complete Taste Test Questionnaire sent to participant’s e-mail 
Day 2  
 Measure glucose levels before chocolate consumption and write down value on 
Glucose levels form 
 Consume 1 bar of dark chocolate (A or B) according to instructions from 
Research team after randomization 
 Measure glucose levels after consumption (15 min, 30 min, 45 min, 60 min, 90 
min, 120 min) and write down values on Glucose levels form 
 Complete Taste Test Questionnaire sent to participant’s e-mail 
 Send photo of Glucose levels form by email  
A Zoom meeting will be scheduled to guide participants with procedures in study 
if necessary. 
 
Statistical Analysis 
Changes in blood glucose across time between conditions will be analyzed with a 
linear mixed effects model including time, condition, and their interaction as fixed 
effects and participant ID and baseline glucose values as random effects. Area 
under the curve and incremental AUC will be calculated and analyzed by paired t-
test.  
 
Sample size 
Sample size calculation for a within-between interaction with alpha of 0.05, power 
of 80%, and an expected moderate effect size (f=0.25) reveals a sample size of 
12 is needed to detect a significant difference. To preserve power and enable 
potential sub-analyses of type 1 vs. type 2 diabetes we will aim to recruit 20 
participants for this preliminary study.   
 
Significance 
The results of this study will help determine whether by consuming a dark 
chocolate bar sweetened with stevia, erythritol, and inulin will cause a blood 
glucose spike in people with diabetes (T1D and T2D). This information will provide 
high quality scientific evidence which will allow individuals with diabetes more food 
choices, helping them manage diabetes better.  
 
 
OUTCOMES MEASUREMENTS AND METHODS 
 
The primary outcome measure is plasma glucose levels following consumption of 
the dark chocolate bars. The taste of the chocolates will also be evaluated. 
 
Glucose Monitoring 

 
 
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Faculty of Health and Social Development 
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3333 University Way 
Kelowna, BC  V1V 1W5 
A glucose monitoring device (OneTouch Verio IQ® kit Blood glucose monitoring 
system) will be used to measure blood glucose levels before and after 
consumption of chocolates. Following consumption, measurements will be taken 
15 min after, 30 min after, 45 min after, 60 min after, 90 min after, and 120 min 
after. Values will be registered on a form,  stored on the meter and sent to research 
team by email. All to be done at home with no displacement. 
 
Taste Test Questionnaire 
Questionnaire is included as attachments and will be sent as link from the RedCap 
platform. 
 
Protection of Human Subjects 
 
All participants will be given a unique study code, with all data and information 
gathered connected with this code. Only the PI will have access to the master list 
linking the codes with participant names. Participant information and data will be 
either stored in a locked filing cabinet, or on an internal UBC network drive 
accessed only through a dedicated LAN internet connection on a password 
protected computer in the PIs laboratory with Salto passcard access only to the 
members of the research lab.  
REDCap will be used as project management, storage of information, sending 
questionnaires and processing results.  The REDCap platform is a secure web 
application for building and managing research data collection instruments. The 
platform is specifically designed to support online or offline data capture for 
research studies. The REDCap platform runs on server infrastructure physically 
located in BC, Canada, at the UBC University Data Centre (UDC).  
   
 
POTENTIAL PROBLEMS AND ALTERNATIVE STRATEGIES 
Diet compliance: Since the study involves a minor modification to diet, we do not 
anticipate that any adverse events due to the interventions will be seen. 
 
Blood sampling:  
When compared to traditional wet blood and plasma collection using venipuncture, 
capillary blood sampling is safer and easier, so much so that nearly anyone can 
perform the procedure, mainly diabetes patients who are used to doing finger 
pricks for glucose levels.  However, risks associated with the process of finger-
stick blood draws are minimized by usage of sterile and disposable material as 
well as hygiene procedures. Participants will receive their own kit with sterile 
material and instructions on procedure. 
 
Protection of personal data: All participants will be given a unique study code, with 
all data and information gathered connected with this code. Only the PI will have 
access to the master list linking the codes with participant names. Participant 
information and data will be either stored in a locked filing cabernet, or on an 

 
 
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Faculty of Health and Social Development 
School of Health and Exercise Sciences 
3333 University Way 
Kelowna, BC  V1V 1W5 
internal UBC network drive accessed only through a dedicated LAN internet 
connection on a password protected computer in the PIs laboratory with Salto 
passcard access only to the members of the research lab.    
 
REDCap will be used as project management, storage of information, sending 
questionnaires and processing results.  The REDCap platform is a secure web 
application for building and managing research data collection instruments. The 
platform is specifically designed to support online or offline data capture for 
research studies. The REDCap platform runs on server infrastructure physically 
located in BC, Canada, at the UBC University Data Centre (UDC).  
 
Informed consent and ethics: Prior to beginning the study Informed consent will 
be obtained from participants and they will be informed they can withdraw at any 
time. They will be informed that this study is partially funded by Ross Chocolates 
through a Mitacs Accelerate Grant. Ross Chocolates is a for-profit company that 
may stand to benefit commercially from research on how its sugar-free chocolate 
impacts blood sugar levels. 
 
References 
(1) 
Saeedi, P., Petersohn, I., Salpea, P., Malanda, B., Karuranga, S., Unwin, N., … Williams, R. 
(2019). Global and regional diabetes prevalence estimates for 2019 and projections for 2030 and 2045: 
Results from the International Diabetes Federation Diabetes Atlas, 9th edition. Diabetes Research and 
Clinical Practice, 157, 107843. doi: 10.1016/j.diabres.2019.107843 
(2) 
Hosseini, Zeinab, et al. "Type 2 diabetes prevalence among Canadian adults--dietary habits and 
sociodemographic risk factors." Applied Physiology, Nutrition, and Metabolism, vol. 44, no. 10, 2019, p. 
1099+. Gale OneFile: Health and Medicine, https://link-gale 
com.ezproxy.library.ubc.ca/apps/doc/A603404292/HRCA?u=ubcolumbia&sid=HRCA&xid=f24562d2. 
Accessed 9 June 2020. 
(3) 
Lindström, J., Peltonen, M., Eriksson, J. G., Ilanne-Parikka, P., Aunola, S., Keinänen-
Kiukaanniemi, S., . Tuomilehto, J. (2012). Improved lifestyle and decreased diabetes risk over 13 years: 
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284-293. doi:10.1007/s00125-012-2752-5 
(4) 
Basic meal planning. (n.d.). Retrieved June 8, 2020, from https://www.diabetes.ca/managing-my-
diabetes/tools---resources/basic-meal-planning 
(5) Ceriello, A. (2005). Postprandial hyperglycemia and diabetes complications: is it time to treat?. 
Diabetes, 54(1), 1-7. 
(6)  Gavin, J. R. Pathophysiologic mechanisms of postprandial hyperglycemia. American Journal of 
Cardiology vol. 88 4–8 (2001). 
(7) Rendell, M. S. & Jovanovic, L. Targeting postprandial hyperglycemia. Metabolism: Clinical and 
Experimental vol. 55 1263–1281 (2006). 
(8) 
Mellor, D. D., Madden, L. A., Smith, K. A., Kilpatrick, E. S., & Atkin, S. L. (2013). High-
polyphenol chocolate reduces endothelial dysfunction and oxidative stress during acute transient 
hyperglycaemia in Type 2 diabetes: A pilot randomized controlled trial. Diabetic Medicine, 30(4), 478-483. 
doi:10.1111/dme.12030 

 
 
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3333 University Way 
Kelowna, BC  V1V 1W5 
(9) 
Marsh CE, Green DJ, Naylor LH & Guelfi KJ. (2017). Consumption of dark chocolate attenuates 
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(10) 
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Almoosawi, S., Tsang, C., Ostertag, L. M., Fyfe, L., & Al-Dujaili, E. A. (2012). Differential effect 
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(13) Al-Dujaili, E., Tsang, C., & Almoosawi, S. (2013). Polyphenol-rich dark chocolate in treatment of 
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Gee, J. M., Cooke, D., Wortley, G. M., Zumbe, A., & Johnson, I. T. (1991). Effects of 
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