The Effect of a 14-Day gymnema sylvestre Intervention to Reduce Sugar Cravings in Adults

Abstract

Gymnemic-acids (GA) block lingual sweet taste receptors, thereby reducing pleasantness and intake of sweet food. Objective: To examine whether a 14-day gymnema-based intervention can reduce sweet foods and discretionary sugar intake in free-living adults. Healthy adults (n = 58) were randomly allocated to either the intervention group (INT) or control group (CON). The intervention comprised of consuming 4 mg of Gymnema sylvestre containing 75% gymnema acids, a fibre and vitamin supplement, and an associated healthy-eating guide for 14 days; participants in the CON group followed the same protocol, replacing the GA with a placebo mint. Amount of chocolate bars eaten and sensory testing were conducted before and after the 14-day intervention (post-GA or placebo dosing on days zero and 15, respectively). Food frequency questionnaires were conducted on days zero, 15 and after a 28-day maintenance period to examine any changes in intake of sweet foods. A range of statistical procedures were used to analyse the data including Chi square, t-test and two-way analysis of variance. Post dosing, INT consumed fewer chocolates (2.65 ± 0.21 bars) at day zero than CON (3.15 ± 0.24 bars; p = 0.02); there were no differences between groups at day 15 (INT = 2.77 ± 0.22 bars; CON = 2.78 ± 0.22 bars; p = 0.81). At both visits, a small substantive effect (r < 0.3) was observed in the change in pleasantness and desire ratings, with INT showing a slight increase while CON showed a small decrease over the 14-day period. No differences were found in the intake of 9 food categories between groups at any timepoint. There were no differences in consumption of low sugar healthy foods between visits, or by group. The 14-day behavioural intervention reduced pleasantness and intake of chocolate in a laboratory setting. There was no habituation to the mint over the 14-day period. This study is the first to investigate the effect of longer-term gymnema acid consumption on sweet food consumption outside of a laboratory setting; further research is needed to assess how long the effect of the 14-day intervention persists.

Full text

Citation: Turner, S.; Diako, C.;
Kruger, R.; Wong, M.; Wood, W.;
Rutherfurd-Markwick, K.; Stice, E.;
Ali, A. The Effect of a 14-Day
gymnema sylvestre Intervention to
Reduce Sugar Cravings in Adults.
Nutrients 2022,14, 5287. https://
doi.org/10.3390/nu14245287
Academic Editor: Emily Sonestedt
Received: 31 October 2022
Accepted: 8 December 2022
Published: 12 December 2022
Publisher’s Note: MDPI stays neutral
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Copyright: © 2022 by the authors.
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4.0/).
nutrients
Article
The Effect of a 14-Day gymnema sylvestre Intervention to
Reduce Sugar Cravings in Adults
Sophie Turner 1, Charles Diako 2, Rozanne Kruger 1, Marie Wong 2, Warrick Wood 1,
Kay Rutherfurd-Markwick 3,4 , Eric Stice 5and Ajmol Ali 1, 4, *
1School of Sport, Nutrition and Exercise, Massey University, Auckland 0632, New Zealand
2School of Food and Advanced Technology, Massey University, Auckland 0632, New Zealand
3School of Health Sciences, Massey University, Auckland 0632, New Zealand
4Centre for Metabolic Health Research, Massey University, Auckland 0632, New Zealand
5Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305-5717, USA
*Correspondence: a.ali@massey.ac.nz; Tel.: +64-9-213-6414
Abstract:
Gymnemic-acids (GA) block lingual sweet taste receptors, thereby reducing pleasantness
and intake of sweet food. Objective: To examine whether a 14-day gymnema-based interven-
tion can reduce sweet foods and discretionary sugar intake in free-living adults. Healthy adults
(n = 58) were randomly allocated to either the intervention group (INT) or control group (CON). The
intervention comprised of consuming 4 mg of Gymnema sylvestre containing 75% gymnema acids, a
fibre and vitamin supplement, and an associated healthy-eating guide for 14 days; participants in the
CON group followed the same protocol, replacing the GA with a placebo mint. Amount of chocolate
bars eaten and sensory testing were conducted before and after the 14-day intervention (post-GA or
placebo dosing on days zero and 15, respectively). Food frequency questionnaires were conducted
on days zero, 15 and after a 28-day maintenance period to examine any changes in intake of sweet
foods. A range of statistical procedures were used to analyse the data including Chi square, t-test
and two-way analysis of variance. Post dosing, INT consumed fewer chocolates (2.65
±
0.21 bars)
at day zero than CON (3.15
±
0.24 bars; p= 0.02); there were no differences between groups at day
15 (INT = 2.77
±
0.22 bars; CON = 2.78
±
0.22 bars; p= 0.81). At both visits, a small substantive effect
(r < 0.3) was observed in the change in pleasantness and desire ratings, with INT showing a slight
increase while CON showed a small decrease over the 14-day period. No differences were found
in the intake of 9 food categories between groups at any timepoint. There were no differences
in consumption of low sugar healthy foods between visits, or by group. The 14-day behavioural
intervention reduced pleasantness and intake of chocolate in a laboratory setting. There was no
habituation to the mint over the 14-day period. This study is the first to investigate the effect of
longer-term gymnema acid consumption on sweet food consumption outside of a laboratory setting;
further research is needed to assess how long the effect of the 14-day intervention persists.
Keywords:
sugar reduction; sensory evaluation; sweet food-food frequency questionnaire; health;
behaviour change; hedonic
1. Introduction
Sugar intake is increasing globally due to changing dietary patterns, such as increased
availability of sweet, highly processed foods [
1
]. Excessive sugar intake has been linked to
dental caries [
2
], metabolic syndrome [
3
], and cardiovascular disease [
4
], with emerging
links to increased cancer risk, particularly for breast cancer [
5
]. Globally, most research in
this area is focused on product reformulation, sugar taxation and food labelling [
6
–
9
], with
few investigations evaluating dietary strategies for reducing excess sugar consumption at
an individual level.
Gymnemic acids isolated from the Gymnema sylvestre (GS) plant native to India has
been reported to exhibit anti-diabetic properties and to normalize blood sugar levels
Nutrients 2022,14, 5287. https://doi.org/10.3390/nu14245287 https://www.mdpi.com/journal/nutrients

Nutrients 2022,14, 5287 2 of 17
by decreasing plasma glucose and increasing insulin secretion [
10
,
11
]. Gymnemic acids
selectively and temporarily suppress taste responses to sweet compounds without affecting
the perception of other taste elements (salty, sour, bitter and umami) [
12
]. Gymnemic
acids bind to taste type 1 receptors (T1R) 2 and 3 on the tongue and palate, preventing
binding of sugar molecules and preventing subsequent firing of the chorda tympani nerve
which sends sweet taste signals to various regions of the brain [
13
–
15
]. The sweet taste
suppression effect of gymnemic acids is transient, generally lasting 30 to 60 min [16].
Recent experiments using formulated gymnema-containing products such as a dissolv-
ing tablet or “lozenge” found that consumption of gymnema in this form acutely reduces
both the intake and pleasantness of confectionary [
17
,
18
]. Furthermore, Turner et al. [
19
]
found that intake of a GS-containing mint significantly reduced intake of high-sugar sweet
foods compared to a placebo and resulted in a decrease in the pleasantness and desir-
ability rating of eating high-sugar sweet foods. Another key finding was that having a
self-reported sweet tooth (relative to non-sweet tooth) resulted in a significant decrease in
pleasantness and desire for more high-sugar sweet food after the GS mint compared to the
placebo mint [
19
]. A small, yet growing body of research has studied the acute effects of
gymnemic acids on pleasantness, desire, and sweet food consumption, however research is
lacking on the effects of the longer-term impact of gymnema-containing products on intake
and enjoyment of sweet foods. To our knowledge, previous studies have only investigated
longer term gymnema consumption on blood glucose levels [
20
,
21
]. Similarly, very little is
known about the effect of gymnema-containing products on sweet food choices outside of
a laboratory environment.
The incentive sensitization model posits that habitual intake of high-sugar foods results
in an elevated response of brain reward regions to cues that are repeatedly associated with
intake of such foods, and that this elevated reward region response to food cues drives
overeating [
22
]. Consistent with this theory, elevated reward region response to high-calorie
food images and cues predicts future weight gain [
23
–
26
]. Critically, a randomized trial
found that an acute dose of GS reduced fMRI-assessed brain reward region response to a
cue that signaled impending tastes of a high-sugar beverage [
27
]. Moreover, GS mint intake
reduced reward region responses to the taste of high-sugar beverages, providing evidence
that GS administration reduces reward region response to food cues. An intervention that
reduces habitual intake of high-sugar foods should theoretically reduce elevated reward
region response to cues for high-sugar foods and reduce future dietary sugar intake.
The primary objective of this study was to assess the effectiveness of a 14-day GS sup-
plementation package in reducing perceived ratings of desire for sweet foods, pleasantness
ratings of sweet foods; the secondary objective was to assess actual consumption of sweet
foods over a 14-day period.
2. Methods
2.1. Study Design
This study used a mixed methods design to examine the effects of a double-blind
randomized control trial on the effectiveness of a 14-day programme to reduce intake of
high sugar, discretionary foods in healthy New Zealand adults. A priori hypotheses and
analyatical data plan were specified before commencement of data collection as per ethics
application requirements. Ethical approval was granted by the Massey University Human
Ethics Committee: Northern (Application NOR 19/52). This trial was registered with
the Australian and New Zealand Clinical Trials Registry (ACTRN12619001558112) from
http://www.anzctr.org.au/ (accessed on 12 November 2019). The results of the qualitative
approach to explore and better understand participants’ experiences with sugar cravings,
and the effects of the 14-day intervention on their relationship with sugar will be reported
elsewhere (manuscript in preparation).
The 14-day programme consisted of (i) a mint (dissolving tablet) to be consumed
three times per day, between meals or when craving sweet foods; (ii) a water-soluble
vitamin and fibre blend to be taken early in the morning and (iii) a guide to healthy

Nutrients 2022,14, 5287 3 of 17
eating. For the intervention (INT) group, the mint contained 4 mg of Gymnema sylvestre
(75% gymnemic acids), the powder contained a prebiotic fibre blend (vitamin D, thiamin,
vitamin B6, vitamin B12, magnesium, zinc and chromium) and the healthy eating guide was
“Eat, Treat, Delete” by Harley Pasternack [
28
]. The vitamin and fibre blend was included
in the intervention due to concerns that consuming the mint would cause participants
to reduce their intake of sweet-tasting foods that provide significant nutritional value
(e.g., fruit, milk or milk products). The CON group consumed an isocaloric placebo
mint and powder and used a healthy eating guide that was a readily available resource
for New Zealand adults published by the Ministry of Health (“Healthy Eating, Active
Living”) [
29
]. Participants completed a daily diary to monitor their adherence to the
programme (indicating if and when they consumed each mint or sachet), with room for
additional comments if they noticed any effects as a result of the programme (e.g., changes
to eating habits, cravings, bowel movements, etc.).
2.2. Participants
Focusing on a mean difference of 0.5 in hedonic scores (sensory test) to be indicative
of significant difference (as the midpoint on the scale between anchors was rounded up
to the nearest whole number for interpretative purposes), the sample size estimate was
52 using 5% significance level, 90% power, and effect size (r) of 0.20. To account for
participant drop out, 61 participants were recruited. Recruitment methods included email
distribution lists to previous study participants, promoting the study on social media, word
of mouth and flyers distributed around Massey University in Auckland, New Zealand.
Potential participants were invited to complete an online screening questionnaire to capture
any exclusionary medical conditions and their preferred chocolate selection from a range of
15 popular choices (Qualtrics, Provo, Utah). An information sheet outlining study protocols
and time commitments was provided should they choose to participate. The inclusion
criteria were healthy people aged 18–45 years living in Auckland. Exclusion critera were
diagnosed diabetes, coeliac disease, gluten intolerance, or having a pacemaker. Those
who satisfied the inclusion/exclusion criteria were emailed to find a suitable appointment
time and to further explain their commitment to take part in the study over a six-week
period. Initially, 129 potential participants completed the screening questionnaire, of which
five were excluded for not meeting the inclusion criteria, one declined to participate and
63 were unable to attend the laboratory sessions. After the first visit, two participants (both
from the CON group) dropped out due to unrelated medical issues; one participant (CON
group) was lost to follow up after the second visit (Figure 1outlines participant recruitment
and follow up). Subsequently, 58 healthy adults (33% men and 67% women) completed
this study (mean age = 29.5 years, BMI = 26.1
±
6.6; Table 1). There were no differences
between participants in the intervention and control groups for any of the variables.
Table 1. Participant characteristics.
Characteristics (Mean ±SD) or n(%) Total
Group
Intervention
Group
Control
Group
Gender n(%) 58 (100) 31 (53.4) 27 (46.6)
Men 19 (32.8) 10 (52.6) 9 (47.4)
Women 39 (67.2) 21 (53.8) 18 (46.2)
Age (years) 29.5 ±7.8 30.5 ±7.4 28.0 ±8.0
Median 27 33 26
Range 18–45 19–44 18–45
BMI (kg/m2) mean ±SD 26.1 ±6.6 25.9 ±7.1 26.3 ±6.2
BMI group n(%)
Underweight 2 (3.4) 2 (6.5) 0 (0)
Normal 33 (56.9) 18 (58.1) 15 (55.6)
Overweight 10 (17.2) 4 (12.9) 6 (22.2)

Nutrients 2022,14, 5287 4 of 17
Table 1. Cont.
Characteristics (Mean ±SD) or n(%) Total
Group
Intervention
Group
Control
Group
Obese 13 (22.4) 7 (22.6) 6 (22.2)
Weight (kg) mean ±SD 73.2 ±19.0 72.5 ±19.6 74.1 ±18.6
Body fat % mean ±SD 29.2 ±11.5 28.1 ±10.6 30.4 ±12.4
Ethnicity * n(%)
M¯
aori 2 (3.5) 1 (3.3) 1 (3.5)
European 34 (59.6) 20 (66.7) 14 (15.9)
Pacific Peoples 2 (3.5) 2 (6.7) 0 (0)
Asian 17 (29.8) 7 (23.3) 10 (37.0)
MELAA #6 (10.5) 3 (10.0) 3 (11.1)
* Participants were able to select multiple ethnic backgrounds and therefore the total is greater than 100%.
#Middle Eastern, Latin American, and African.
Nutrients 2022, 14, x FOR PEER REVIEW 4 of 18
Figure 1. Flowchart of study recruitment and follow up.
Table 1. Participant characteristics.
Characteristics (Mean ± SD) or n (%) Total
Group
Intervention
Group
Control
Group
Gender n (%) 58 (100) 31 (53.4) 27 (46.6)
Men 19 (32.8) 10 (52.6) 9 (47.4)
Women 39 (67.2) 21 (53.8) 18 (46.2)
Age (years) 29.5 ± 7.8 30.5 ± 7.4 28.0 ± 8.0
Median 27 33 26
Range 18–45 19–44 18–45
BMI (kg/m2) mean ± SD 26.1 ± 6.6 25.9 ± 7.1 26.3 ± 6.2
BMI group n (%)
Underweight 2 (3.4) 2 (6.5) 0 (0)
Normal 33 (56.9) 18 (58.1) 15 (55.6)
Overweight 10 (17.2) 4 (12.9) 6 (22.2)
Obese 13 (22.4) 7 (22.6) 6 (22.2)
Weight (kg) mean ± SD 73.2 ± 19.0 72.5 ± 19.6 74.1 ± 18.6
Body fat % mean ± SD 29.2 ± 11.5 28.1 ± 10.6 30.4 ± 12.4
Ethnicity * n (%)
Māori 2 (3.5) 1 (3.3) 1 (3.5)
European 34 (59.6) 20 (66.7) 14 (15.9)
Pacific Peoples 2 (3.5) 2 (6.7) 0 (0)
Asian 17 (29.8) 7 (23.3) 10 (37.0)
MELAA # 6 (10.5) 3 (10.0) 3 (11.1)
Figure 1. Flowchart of study recruitment and follow up.
2.3. Research Design
Participants visited the Human Nutrition Research Unit and sensory research facilities
at Massey University on three separate occasions (each approximately one hour in duration)
between November 2019 and February 2020.
The first and second visits were 14 days apart (days zero and 15), and the third (final)
visit was 28 days after the second visit (day 44). On day zero, participants were again
presented with an information sheet and they provided written informed consent prior to
commencing study activities.
At the first visit all the participants (n = 61) were randomly allocated to one of the
two treatment groups based on a random number generator. The investigation team was
blinded to which group participants were allocated to during the data collection and
data analysis phases of the research. A researcher not involved in this study prepacked

Nutrients 2022,14, 5287 5 of 17
participants’ take-home packages consisting of mints, powder, healthy eating guide and
adherence log book, and labeled them by treatment group.
Post-GA or placebo dosing (day zero), i.e., between day 1 (the day following the initial
laboratory visit) and day 15, participants consumed the products within the appropriate
pack outlined above. Participants were also instructed to return any unused mints and
supplements at their day 15 visit. Fifty-eight participants returned their packaging and had
consumed greater than 90% of the supplied mints and powder supplements.
2.4. Anthropometric Measures
Body composition data was collected using bioelectrical impedance analysis (BIA; In-
Body230 BIA, Biospace Co., Ltd., Seoul, Republic of Korea). A stadiometer (Seka 213, Sweden)
was usedto measure participants’ (double measured) height and entered into the BIA machine.
Participants were instructed not to drink any fluids for the one hour leading up to the sched-
uled visit and to empty their bladder immediately prior to undergoing BIA measurement.
2.5. Sensory Testing
Sensory evaluation was carried out on days zero and 15 in individual booths under
red light to mask the colour of the mints. Forty-five minutes prior to sensory testing, partic-
ipants consumed one standard serving (22 g, 438 kJ) of wholegrain chips (Grainwaves
®
,
Bluebird Foods, Auckland, New Zealand) to reduce and standardize hunger [17].
Participants rated their hunger (on a 100-point VAS) prior to consuming all of a
standardized serving (i.e., manufacturer packaging) of their favourite chocolate (chocolates
varied between 14–18 g; energy varied between 292–370 kJ; Table 2). Scale data were
collected electronically using Compusense Cloud (Guelph, ON, Canada) sensory software
via tablets (iPad, Apple Inc., Cupertino, CA, USA).
Table 2. Participant chocolate selection and nutrition information.
Chocolate Participant Selection
(n) * (%)
Weight
(g)
Energy
(kJ)
Sugar
per Serve (g)
Sugar
per 100 g (g)
Cocoa
Content (%)
Whittaker’s®Almond Gold 15 26 15 360 5.2 34.6 33
Nestle KitKat®8 14 17 370 8.6 50.5 22
Whittaker’s®Creamy Milk 6 10 15 352.5 6.7 44.7 33
Snickers 5 9 18 370 9.3 50.6 25
Whittaker’s
®
Dark Peppermint
5 9 15 342 7.8 52.1 50
Cadbury Crunchie 3 5 15 292 10.3 68.7 26
Cadbury Moro Gold 3 5 17.5 327 7.3 48.6 26
Cadbury Picnic 3 5 15 327 6.8 45.6 27
Cadbury Twirl 3 5 14 316 7.7 55.2 26
Cadbury Flake 2 3 14 313 7.9 56.5 26
Twix®2 3 14.5 308 7.0 48.0 25
Whittaker’s®Peanut Slab 2 3 15 333 7.2 48.0 33
Mars®1 2 18 350 10.5 57.1 25
* Participant section of favorite chocolate in rank order.
Following the chocolate serving, participants rated the pleasantness and their desire
for further chocolate servings. They received the mint and were asked to place it on their
tongue, moving it around their mouth until it dissolved completely. Participants in the
INT group received the gymnema-containing mints (GS mint; “Sweetkick”), and those in
the CON group were given the isocaloric placebo; both provided by Nu Brands Inc. (Los
Angeles, CA, USA). Participants waited 90 s after the complete dissolution of the mint
and then again rated their hunger level, ate a second chocolate serving, then rated the
pleasantness of the chocolate and desire for more servings again.
Hunger, pleasantness and desire for another serving were each assessed using the
100-point VAS. Hunger was rated from “I am not hungry at all” to “I am extremely hungry”,
30 s prior to each serving. Pleasantness, anchored by “Not at all pleasant” and “Very much

Nutrients 2022,14, 5287 6 of 17
pleasant”, was rated immediately following chocolate consumption, as was the desire for
another chocolate serving (“No, not at all” to “Yes, very much”). The first two chocolate
servings (pre-mint and immediately post mint) were compulsory, but for all subsquent
chocolate participants indicated whether they would like another serving of chocolate
(yes/no answer). If participants chose “no”, sensory testing ceased. If participants selected
“yes”, the above procedure was repeated for a maximum of six chocolate servings. This
followed the detailed sensory testing methods described in Turner et al. [19].
2.6. Questionnaires
The sweet-food food frequency questionnaire (SF-FFQ) was developed to capture the
frequency of sweet food and sweetened beverage intake over the past month [
30
]. The
SF-FFQ determines the frequency of participants’ habitual intake of 69 specific sweet-tasting
foods, including both natural sweet-tasting foods and processed sweetened foods within
the following categories: fruits and vegetables (n = 20); dairy-based products (n = 4); cereals
(n = 5); cakes, biscuits, sweet foods (n = 14); desserts (n = 6); spreads and sweeteners (n = 6);
and beverages (n = 15). All items were scored for frequency of use: never, less than once a
month, 2–3 times per month, once per week, 2–4 times per week, 4–6 times per week, once
a day, and twice or more a day.
Eleven further open-ended questions were asked to elicit participants’ favourite foods
(to establish an understanding of whether they prefer sweet or savoury foods), number
of teaspoons of sugar they added to cereal and hot beverages, and whether they snack
between meals. Participants also self-reported whether they considered themselves to have
a “sweet tooth”.
2.7. Data Handling
BMI was calculated using the Quetelet index (weight (kg)/height (m)
2
) and reported
as a continous variable. The Sf-FFQ data was downloaded from Qualtrics as a spreadsheet
(Excel, Microsoft Office 365, Redmond, WA, USA) and checked for completion. The
consumption frequencies of each of the 69 food items were converted to a daily frequency
equivalents (DFE) by allocating proportional values to the frequency of consumption
options calculated with reference to a base value of 1.0 for foods eaten “once a day” [
31
].
DFE scores were reported as mean
±
SD and a mean DFE was calculated for each food
category [
31
,
32
]. All food items were categorised as either everyday foods (to be consumed
regularly every day) or occasional foods (to be consumed irregularly or occasionally). The
“everyday foods” category (n = 20), consisted of foods which should be eaten daily as part
of a balanced diet including fresh fruit, vegetables, unsweetened milk and dairy products,
plain cereals based on the Eating and Activity Guidelines for New Zealand Adults [
33
].
Occasional foods (n = 49) included foods that are high in fat, sodium and sugar, and/or
poor sources of micronutrients and/or highly processed such as dried fruit, sweetened
dairy products, high sugar cereals and spreads which should not be consumed on a regular
basis as part of a balanced diet.
2.8. Statistical Analysis
Chi-square analysis was used to determine significant differences in the number of
participants that declined further servings of the confectionery at each serving point. Average
number of servings received was compared between the CON and INT groups using the
Mann–Whitney U test within visits and the Wilcoxon signed-rank test used to compare
this difference between groups. Data from participants who declined servings of chocolate
after consumption of the mint were treated as missing data. The resulting unbalanced
repeated measures data were analyzed using linear mixed effect model using Restricted
Maximum Likelihood (REML) with Kenward-Roger degrees of freedom correction. The
least square means and standard errors for hunger, pleasantness, and desire ratings for
the INT and CON groups at each of the serving points (servings 1–6) were summarized
to show difference in ratings at each serving point. Standard error was reported to show

Nutrients 2022,14, 5287 7 of 17
the spread of the reported scores relative to the true population mean. Since the data for
serving 2 were collected just after consuming the mint, these results could be regarded as
the immediate effect of the mint consumption. Subsequent analysis focused on servings
1 and 2 comparing changes in ratings before and after consumption of the mint within visits
and between visits. A two-way ANOVA was conducted for demographic variables, sweet
tooth status and mint type to determine their effects on the ratings for hunger, pleasantness
and desire using the SAS proc mixed procedure. Significant differences were established
at p< 0.05. Correlation effect sizes (r) were calculated using the t-statistic and degrees of
freedom from each test. For the repeated measures ANOVA analysis, effect sizes were
calculated using the compute.es package in RStudio (Del Re, 2013). An effect size (r) of
0.1 indicated a small effect, a value of 0.3 indicated a medium effect and a value
≥
0.5
indicated a large effect [
34
]. Data analysis was undertaken using SAS (version 9.4, Cary, NC,
USA), R (RStudio, Boston, MA, USA) and XLSTAT (version 2021.3.1, Addinsoft, Paris, France).
3. Results
3.1. Consumption, Pleasantness and Desire for Eating Sweet Foods
Figure 2A,B show the percentage of participants receiving servings of chocolate at
each of the six chocolate serving times.
Nutrients 2022, 14, x FOR PEER REVIEW 8 of 18
Figure 2. Percentage of participants receiving servings of chocolate at each of the six chocolate serv-
ing times. Participants rated their desire for each serving of chocolate after consuming the previous
serving of chocolate. The first two servings (one before and one after consuming the respective mint)
were compulsory; however, after the second chocolate, participants were able to indicate how much
they would like another serving and then confirm whether they would like another serving. (A)
(Day 0)—pre-intervention; (B) (Day 15)—post-intervention. Numbers in the bars represent percent-
ages of participants who received the serving. Percentages are based on 31 participants in the INT
group and 27 participants in the CON group.
All participants rated their hunger levels, pleasantness and desire for the next choc-
olate serving before serving 1 (before mint) and serving 2 (after mint). After taking the
mint, the number of participants selecting additional servings declined significantly (p <
0.0001), as subsequent servings were optional (servings 3–6).
After GA and placebo dosing on day zero, fewer chocolate bars were consumed by
participants in the INT group (2.65 ± 0.21 bars) than the CON group (3.15 ± 0.24 bars; p =
0.022). However, the same difference was not seen on day 15; after the intervention, there
was no significant difference in the additional number of chocolate bars eaten between
the INT (0.77 ± 0.22 bars) and CON (0.78 ± 0.22 bars; p = 0.800) groups. The CON group
consumed significantly more chocolate at day zero (1.15 ± 0.24 bars) than day 15 (0.78 ±
0.22 bars; p = 0.018), whereas there was no significant difference in the amount of chocolate
eaten compared with the INT group at these two time points (p = 0.49); specifically, 0.65 ±
0.21 bars on day zero and 0.77 ± 0.22 bars on day 15.
The least square means and standard error from repeated measures ANOVA for hun-
ger, pleasantness, and desire for next serving obtained for CON and INT groups at each
serving point for day zero and day 15 are presented in Figures 3 and 4, respectively. No
significant difference was observed between treatment groups and servings for hunger
ratings (Figure 3A). However, significant differences were observed for pleasantness rat-
ings (p < 0.0001; Figure 3B) and desire for next serving ratings (p = 0.0471; Figure 3C).
Serving two consistently showed the largest difference in ratings between the treatment
groups for pleasantness and desire for next-serving ratings. As the data were collected
just after consuming the mint for serving two, these results could be regarded as the im-
mediate effect of the mint consumption; the INT group had significantly lower pleasant-
ness and hunger ratings compared to the CON group (p < 0.05).
Figure 2.
Percentage of participants receiving servings of chocolate at each of the six chocolate serving
times. Participants rated their desire for each serving of chocolate after consuming the previous
serving of chocolate. The first two servings (one before and one after consuming the respective mint)
were compulsory; however, after the second chocolate, participants were able to indicate how much
they would like another serving and then confirm whether they would like another serving. (
A
) (Day
0)—pre-intervention; (
B
) (Day 15)—post-intervention. Numbers in the bars represent percentages of
participants who received the serving. Percentages are based on 31 participants in the INT group and
27 participants in the CON group.
All participants rated their hunger levels, pleasantness and desire for the next chocolate
serving before serving 1 (before mint) and serving 2 (after mint). After taking the mint, the
number of participants selecting additional servings declined significantly (p< 0.0001), as
subsequent servings were optional (servings 3–6).
After GA and placebo dosing on day zero, fewer chocolate bars were consumed by
participants in the INT group (2.65
±
0.21 bars) than the CON group (3.15
±
0.24 bars;
p= 0.022). However, the same difference was not seen on day 15; after the intervention, there

Nutrients 2022,14, 5287 8 of 17
was no significant difference in the additional number of chocolate bars eaten between
the INT (0.77
±
0.22 bars) and CON (0.78
±
0.22 bars; p= 0.800) groups. The CON
group consumed significantly more chocolate at day zero (1.15
±
0.24 bars) than day
15 (0.78
±
0.22 bars; p= 0.018), whereas there was no significant difference in the amount of
chocolate eaten compared with the INT group at these two time points (p= 0.49); specifically,
0.65 ±0.21 bars on day zero and 0.77 ±0.22 bars on day 15.
The least square means and standard error from repeated measures ANOVA for
hunger, pleasantness, and desire for next serving obtained for CON and INT groups at
each serving point for day zero and day 15 are presented in Figures 3and 4, respectively.
No significant difference was observed between treatment groups and servings for hunger
ratings (Figure 3A). However, significant differences were observed for pleasantness ratings
(p< 0.0001; Figure 3B) and desire for next serving ratings (p= 0.0471; Figure 3C). Serving
two consistently showed the largest difference in ratings between the treatment groups
for pleasantness and desire for next-serving ratings. As the data were collected just after
consuming the mint for serving two, these results could be regarded as the immediate
effect of the mint consumption; the INT group had significantly lower pleasantness and
hunger ratings compared to the CON group (p< 0.05).
Nutrients 2022, 14, x FOR PEER REVIEW 9 of 18
Figure 3. Participants’ average ratings for hunger (A), pleasantness of chocolate (B) and desire for
next serving (C) on day 0. Means ± standard error used in the plots represent data from a total of 58,
58, 29, 12, 6 and 5 participants’ ratings at servings 1, 2, 3, 4, 5 and 6, respectively. * Significant differ-
ences at a serving (p < 0.05).
Figure 4. Participants’ ratings for hunger (A), pleasantness of chocolate (B) and desire for next serv-
ing (C) on day 15. Means ± standard error used in the plots represent data from a total of 58, 58, 24,
10, 8 and 3 participants’ ratings at servings 1, 2, 3, 4, 5 and 6, respectively. * Significant differences
at a serving (p < 0.05).
After the 14-day intervention (day 15), hunger ratings across servings remained non-
significant (p = 0.7211) between the treatment groups (Figure 4A) and the levels were com-
parable to those observed on day zero. Pleasantness ratings were significantly different
between INT and CON (p ≤ 0.001). Following the trend observed on day zero, a difference
in the pleasantness rating was observed at serving two with INT reporting a lower rating
than CON (Figure 4B). However, there was no difference (p = 0.60) between the treatment
groups for desire rating at all the serving points; although INT reported a relatively lower
Figure 3.
Participants’ average ratings for hunger (
A
), pleasantness of chocolate (
B
) and desire for
next serving (
C
) on day 0. Means
±
standard error used in the plots represent data from a total of
58, 58, 29, 12, 6 and 5 participants’ ratings at servings 1, 2, 3, 4, 5 and 6, respectively. * Significant
differences at a serving (p< 0.05).
After the 14-day intervention (day 15), hunger ratings across servings remained non-
significant (p= 0.7211) between the treatment groups (Figure 4A) and the levels were
comparable to those observed on day zero. Pleasantness ratings were significantly different
between INT and CON (p
≤
0.001). Following the trend observed on day zero, a difference
in the pleasantness rating was observed at serving two with INT reporting a lower rating
than CON (Figure 4B). However, there was no difference (p= 0.60) between the treatment
groups for desire rating at all the serving points; although INT reported a relatively lower
rating at serving two compared to CON (Figure 4C). Since most of the differences observed
were between servings one and two, subsequent analysis was focused on these two serving
points. Changes in ratings were obtained by subtracting ratings for serving one from
serving two, to reflect the net negative difference (if present).

Nutrients 2022,14, 5287 9 of 17
Nutrients 2022, 14, x FOR PEER REVIEW 9 of 18
Figure 3. Participants’ average ratings for hunger (A), pleasantness of chocolate (B) and desire for
next serving (C) on day 0. Means ± standard error used in the plots represent data from a total of 58,
58, 29, 12, 6 and 5 participants’ ratings at servings 1, 2, 3, 4, 5 and 6, respectively. * Significant differ-
ences at a serving (p < 0.05).
Figure 4. Participants’ ratings for hunger (A), pleasantness of chocolate (B) and desire for next serv-
ing (C) on day 15. Means ± standard error used in the plots represent data from a total of 58, 58, 24,
10, 8 and 3 participants’ ratings at servings 1, 2, 3, 4, 5 and 6, respectively. * Significant differences
at a serving (p < 0.05).
After the 14-day intervention (day 15), hunger ratings across servings remained non-
significant (p = 0.7211) between the treatment groups (Figure 4A) and the levels were com-
parable to those observed on day zero. Pleasantness ratings were significantly different
between INT and CON (p ≤ 0.001). Following the trend observed on day zero, a difference
in the pleasantness rating was observed at serving two with INT reporting a lower rating
than CON (Figure 4B). However, there was no difference (p = 0.60) between the treatment
groups for desire rating at all the serving points; although INT reported a relatively lower
Figure 4.
Participants’ ratings for hunger (
A
), pleasantness of chocolate (
B
) and desire for next serving
(
C
) on day 15. Means
±
standard error used in the plots represent data from a total of 58, 58, 24, 10, 8
and 3 participants’ ratings at servings 1, 2, 3, 4, 5 and 6, respectively. * Significant differences at a
serving (p< 0.05).
Figure 5shows the decrease in pleasantness and desire ratings after the participants
consumed the mint from baseline to end. The INT group had a bigger change (decrease) in
pleasantness ratings than the CON group (Figure 5A). However, there was little change
between day zero and day 15 for both groups which was reflected in a small effect size
(r = 0.11; p= 0.40). The results for desire ratings followed a similar trend as was observed
for pleasantness ratings. The CON group had a slight decrease in desire for next serving
from Day 0 to day 15m, while the intervention group showed a slight increase within the
same time period. The effect size for desire for next rating was twice the effect reported for
the pleasantness ratings (r = 0.22; p= 0.10).
Nutrients 2022, 14, x FOR PEER REVIEW 10 of 18
rating at serving two compared to CON (Figure 4C). Since most of the differences ob-
served were between servings one and two, subsequent analysis was focused on these
two serving points. Changes in ratings were obtained by subtracting ratings for serving
one from serving two, to reflect the net negative difference (if present).
Figure 5 shows the decrease in pleasantness and desire ratings after the participants
consumed the mint from baseline to end. The INT group had a bigger change (decrease)
in pleasantness ratings than the CON group (Figure 5A). However, there was little change
between day zero and day 15 for both groups which was reflected in a small effect size (r
= 0.11; p = 0.40). The results for desire ratings followed a similar trend as was observed for
pleasantness ratings. The CON group had a slight decrease in desire for next serving from
Day 0 to day 15m, while the intervention group showed a slight increase within the same
time period. The effect size for desire for next rating was twice the effect reported for the
pleasantness ratings (r = 0.22; p = 0.10).
Figure 5. Change in ratings between serving 1 (before mint) and serving 2 (post mint) for pleasant-
ness (A) and desire for next serving (B) for day 0 and day15 between treatment groups. Means ±
standard error corresponds to the size of change in rating after taking the mint.
3.2. Effect of Sweet Tooth Status on Consumption, Desire and Pleasantness Ratings
Overall, participants who reported having a “sweet tooth” showed a greater decrease
in pleasantness ratings (p = 0.047, r = 0.27) and desire for further servings of chocolate (p =
0.049, r = 0.26) after consuming the mint (Figure 6A,B) than those who did not self identifiy
as having a “sweet tooth”. Following the 14-day intervention, no significant differences
were observed between the “sweet tooth” and “non-sweet tooth” groups in pleasantness
and desire for more chocolate immediately following consumption of the mint (Figure
6C,D).
Figure 5.
Change in ratings between serving 1 (before mint) and serving 2 (post mint) for pleasantness
(
A
) and desire for next serving (
B
) for day 0 and day15 between treatment groups. Means
±
standard
error corresponds to the size of change in rating after taking the mint.

Nutrients 2022,14, 5287 10 of 17
3.2. Effect of Sweet Tooth Status on Consumption, Desire and Pleasantness Ratings
Overall, participants who reported having a “sweet tooth” showed a greater decrease
in pleasantness ratings (p= 0.047, r = 0.27) and desire for further servings of chocolate
(p= 0.049, r = 0.26) after consuming the mint (Figure 6A,B) than those who did not self
identifiy as having a “sweet tooth”. Following the 14-day intervention, no significant
differences were observed between the “sweet tooth” and “non-sweet tooth” groups in
pleasantness and desire for more chocolate immediately following consumption of the mint
(Figure 6C,D).
Nutrients 2022, 14, x FOR PEER REVIEW 11 of 18
Figure 6. Change in pleasantness and desire ratings based on self-reported sweet tooth status for
day 0 (A,B) and day 15 (C,D).
3.3. Effect of Gymnema sylvestre Consumption on Ad Libitum Sweet Food Consumption (SF-
FFQ)
The calculated daily frequency equivalents (DFE) or daily serves of nine food
categories at day 0, 15 and 44 are presented in Table 3. No significant differences in daily
intake of the same nine food categories were observed between those in the INT and CON
groups during the intervention period (day zero to day 15) or the maintenance period
(day 15 to 44; Table 3; p > 0.05).
Table 3. Daily frequency equivalents (DFE) of sweet food categories by laboratory visit (median and
range).
Food Group Intervention (DFE) Control (DFE)
Day 0 Day 15 Day 44 Day 0 Day 15 Day 44
Fruit 0.59 [0.36, 1.29] # 1.28 [0.68, 2.42] # 1.49 [0.74, 2.35] # 0.46 [0.17, 1.05] # 1.170 [0.50, 2.26] # 1.04 [0.54, 2.25] #
Vegetable 0.30 [0.16, 0.66] 0.27 [0.14, 0.62] 0.27 [0.17, 0.66] 0.27 [0.14, 0.44] 0.28 [0.19, 0.78] 0.32 [0.17, 0.74]
Dairy 0.53 [0.08, 1.53] 0.38 [0.11, 1.03] 0.46 [0.14, 1.42] 0.50 [0.08, 1.14] 0.42 [0.08, 0.85] 0.28 [0.06, 0.85]
Cereal 0.16 [0.03, 0.59] 0.15 [0.03, 0.56] 0.16 [0.03, 0.45] 0.16 [0.03, 0.42] 0.14 [0.03, 0.66] 0.14 [0.03, 0.25]
Spreads 0.23 [0.08, 1.20] 0.17 [0.03, 0.80] 0.16 [0.03, 0.46] 0.34 [0.22, 0.70] 0.33 [0.12, 0.56] 0.22 [0.06, 0.78]
Cakes 1.31 [0.75, 2.03] # 0.70 [0.42, 1.52] # 1.31 [0.75, 1.03] 1.00 [0.62, 1.59] # 0.92 [0.35, 1.25] # 0.95 [0.41, 1.43]
Desserts 0.14 [0.08, 0.33] 0.12 [0.06, 0.22] 0.16 [0.06, 0.25] 0.16 [0.09, 0.30] 0.16 [0.08, 0.42] 0.14 [0.08, 0.44]
Drinks 0.71 [0.32, 1.15] 0.50 [0.17, 1.09] 0.47 [0.23, 1.49] 0.61 [0.33, 1.55] 0.78 [0.25, 1.91] 0.71 [0.36, 1.69]
Occasional foods $ 4.04 [2.22, 6.05] # 2.45 [1.44, 3.87] *# 3.28 [2.01, 5.14] 3.45 [2.77, 4.76] 3.71 [2.37, 4.80] 3.41 [1.80, 4.76]
Everyday foods @ 1.79 [1.23, 3.79] 1.61 [0.84, 3.30] 1.90 [1.31, 3.58] 1.33 [0.81, 3.30] 1.83 [0.99, 2.86] 1.63 [1.06, 2.37]
# Statistically significant result (p < 0.05) within group (Wilcoxon Signed Ranks test). * Significant
result (p < 0.05) between groups (Mann–Whitney test). $ (49 food items combined). @ (20 foods com-
bined).
3.3.1. Occasional Foods
There were no significant differences in the daily intake of 49 “occasional foods” (i.e.,
high-sugar snack foods like sweetened dairy products, high sugar cereals, cakes, desserts
and beverages) between the INT and CON groups during the intervention period (U =
338, p = 0.210) or the maintenance period (U = 289, p = 0.069; Figure 7). However, significant
within-group differences occurred over time. Within the INT group, the occasional foods
intake decreased by 1.6 DFE (p = 0.022) and intake of cakes decreased by 0.61 DFE (p <
Figure 6.
Change in pleasantness and desire ratings based on self-reported sweet tooth status for day
0 (A,B) and day 15 (C,D).
3.3. Effect of Gymnema sylvestre Consumption on Ad Libitum Sweet Food Consumption (SF-FFQ)
The calculated daily frequency equivalents (DFE) or daily serves of nine food cate-
gories at day 0, 15 and 44 are presented in Table 3. No significant differences in daily intake
of the same nine food categories were observed between those in the INT and CON groups
during the intervention period (day zero to day 15) or the maintenance period (day 15 to
44; Table 3;p> 0.05).
Table 3.
Daily frequency equivalents (DFE) of sweet food categories by laboratory visit (median and range).
Food Group Intervention (DFE) Control (DFE)
Day 0 Day 15 Day 44 Day 0 Day 15 Day 44
Fruit 0.59 [0.36, 1.29] #1.28 [0.68, 2.42] #1.49 [0.74, 2.35] #0.46 [0.17, 1.05] #1.170 [0.50, 2.26] #1.04 [0.54, 2.25] #
Vegetable 0.30 [0.16, 0.66] 0.27 [0.14, 0.62] 0.27 [0.17, 0.66] 0.27 [0.14, 0.44] 0.28 [0.19, 0.78] 0.32 [0.17, 0.74]
Dairy 0.53 [0.08, 1.53] 0.38 [0.11, 1.03] 0.46 [0.14, 1.42] 0.50 [0.08, 1.14] 0.42 [0.08, 0.85] 0.28 [0.06, 0.85]
Cereal 0.16 [0.03, 0.59] 0.15 [0.03, 0.56] 0.16 [0.03, 0.45] 0.16 [0.03, 0.42] 0.14 [0.03, 0.66] 0.14 [0.03, 0.25]
Spreads 0.23 [0.08, 1.20] 0.17 [0.03, 0.80] 0.16 [0.03, 0.46] 0.34 [0.22, 0.70] 0.33 [0.12, 0.56] 0.22 [0.06, 0.78]
Cakes 1.31 [0.75, 2.03] #0.70 [0.42, 1.52] #1.31 [0.75, 1.03] 1.00 [0.62, 1.59] #0.92 [0.35, 1.25] #0.95 [0.41, 1.43]
Desserts 0.14 [0.08, 0.33] 0.12 [0.06, 0.22] 0.16 [0.06, 0.25] 0.16 [0.09, 0.30] 0.16 [0.08, 0.42] 0.14 [0.08, 0.44]
Drinks 0.71 [0.32, 1.15] 0.50 [0.17, 1.09] 0.47 [0.23, 1.49] 0.61 [0.33, 1.55] 0.78 [0.25, 1.91] 0.71 [0.36, 1.69]
Occasional foods $4.04 [2.22, 6.05] #2.45 [1.44, 3.87] *#3.28 [2.01, 5.14] 3.45 [2.77, 4.76] 3.71 [2.37, 4.80] 3.41 [1.80, 4.76]
Everyday foods @1.79 [1.23, 3.79] 1.61 [0.84, 3.30] 1.90 [1.31, 3.58] 1.33 [0.81, 3.30] 1.83 [0.99, 2.86] 1.63 [1.06, 2.37]
#
Statistically significant result (p< 0.05) within group (Wilcoxon Signed Ranks test). * Significant result (p< 0.05)
between groups (Mann–Whitney test). $(49 food items combined). @(20 foods combined).
3.3.1. Occasional Foods
There were no significant differences in the daily intake of 49 “occasional foods”
(i.e., high-sugar snack foods like sweetened dairy products, high sugar cereals, cakes,

Nutrients 2022,14, 5287 11 of 17
desserts and beverages) between the INT and CON groups during the intervention period
(U= 338, p= 0.210) or the maintenance period (U= 289, p= 0.069; Figure 7). However, sig-
nificant within-group differences occurred over time. Within the INT group, the occasional
foods intake decreased by 1.6 DFE (p= 0.022) and intake of cakes decreased by 0.61 DFE
(p< 0.001); in the CON group. There was no change in intake of occasional foods (p= 0.694)
but intake of cakes decreased by 0.08 DFE, (p= 0.016; (Table 3).
Nutrients 2022, 14, x FOR PEER REVIEW 12 of 18
0.001); in the CON group. There was no change in intake of occasional foods (p = 0.694)
but intake of cakes decreased by 0.08 DFE, (p = 0.016; (Table 3).
Figure 7. Daily frequency equivalents (DFE) of 49 “occasional” food items using the sweet foods
food frequency questionnaire (Sf-FFQ). Individual dots represent outliers.
3.3.2. Everyday Foods
There were no between-subject or within-subject differences in the median
consumption of 20 everyday foods (i.e., healthy foods like fresh fruit, vegetables,
unsweetened dairy products and plain cereals) between treatment groups at either the
intervention period (U = 381, p = 0.559), or the maintence phase (U = 363,0.522, p = 0.576;
Figure 8).
Figure 8. Daily frequency equivalents (DFE) of 20 “everyday” (healthy) food items using the sweet
foods food frequency questionnaire (Sf-FFQ). Individual dots represent outliers
Figure 7.
Daily frequency equivalents (DFE) of 49 “occasional” food items using the sweet foods
food frequency questionnaire (Sf-FFQ). Individual dots represent outliers.
3.3.2. Everyday Foods
There were no between-subject or within-subject differences in the median consump-
tion of 20 everyday foods (i.e., healthy foods like fresh fruit, vegetables, unsweetened dairy
products and plain cereals) between treatment groups at either the intervention period
(U= 381, p= 0.559), or the maintence phase (U= 363, p= 0.522; Figure 8).
Nutrients 2022, 14, x FOR PEER REVIEW 12 of 18
0.001); in the CON group. There was no change in intake of occasional foods (p = 0.694)
but intake of cakes decreased by 0.08 DFE, (p = 0.016; (Table 3).
Figure 7. Daily frequency equivalents (DFE) of 49 “occasional” food items using the sweet foods
food frequency questionnaire (Sf-FFQ). Individual dots represent outliers.
3.3.2. Everyday Foods
There were no between-subject or within-subject differences in the median
consumption of 20 everyday foods (i.e., healthy foods like fresh fruit, vegetables,
unsweetened dairy products and plain cereals) between treatment groups at either the
intervention period (U = 381, p = 0.559), or the maintence phase (U = 363,0.522, p = 0.576;
Figure 8).
Figure 8. Daily frequency equivalents (DFE) of 20 “everyday” (healthy) food items using the sweet
foods food frequency questionnaire (Sf-FFQ). Individual dots represent outliers
Figure 8.
Daily frequency equivalents (DFE) of 20 “everyday” (healthy) food items using the sweet
foods food frequency questionnaire (Sf-FFQ). Individual dots represent outliers.

Nutrients 2022,14, 5287 12 of 17
3.3.3. Fruit
There were no differences in fruit intake between INT and CON groups between
the intervention period (U= 414.5, p= 0.950) and the maintenance period (U= 370,
p= 0.576). Median daily fruit intake increased over the course of the intervention for
both INT and CON groups (Table 3). Fruit consumption increased by 0.69 serves (116%
increase) per day between days zero and 15 (p< 0.0001) for INT, which was sustained
through the maintenance period (change between days zero to 15, and days 15 to 44 was
not significant, p= 0.086). Within the CON group, there was an increase of 0.71 DFE (153%
increase) between days 0 to 15 (p= 0.001); but a significant decrease (p= 0.049) in fruit
intake over the maintence period (days zero to 15 delta (
∆
) change 0.030 [
−
0.490, 0.530])
compared to the intervention period (∆0.530 [0.060, 1.140]).
4. Discussion
The aim of this study was to examine the effect of a 14-day behaviour intervention
on desire and pleasantness of sweet-tasting foods (chocolate), and whether there was a
reduction in sugar-sweetened food intake. The main findings are: (1) consumption of
the GS-containing mint reduced the amount of chocolate bars eaten (day zero only) and
pleasantness of sweet foods; (2) those who identified as having a “sweet tooth” showed a
greater decrease in pleasantness ratings and reduced desire for further servings of chocolate
after consuming the GS-mint; (3) there was no habituation to the mint after 14 days’ intake.
The current study supports previous research that consumption of a GS mint reduces
ad libitum acute consumption of high sugar sweet foods compared to a placebo, and
reduces the pleasantness of chocolate eaten and subsequent desire for further servings
within a laboratory setting [
18
,
19
,
27
]. Interestingly, this effect was also seen on day 15,
indicating that there was no habituation effect of the GS mint. These novel findings suggest
that the GS-containing mint is still effective at reducing consumption after daily usage for
14 days, when participants are familiar with its sweet taste-altering effects. Although the GS
mint reduced ratings of pleasantness and desire for more chocolate, there was no effect on
hunger, indicating that it is the hedonic properties of the sweet foods that are being affected
rather than the need for energy intake/satiety. Moreover, those who self-identified as
having a “sweet-tooth” showed a greater reduction in pleasantness and desire ratings after
taking the GS mint than those who did not identify as having a “sweet tooth”, consistent
with our previous findings [19].
This study presents novel findings that participants in the CON group reduced their
chocolate consumption, pleasantness and desire for further serves on day 15, but not
on day zero. We hypothesise that this may be an effect of knowingly taking part in a
sugar reduction study. Therefore, all participants increased their awareness of sugar over
this time and those in the CON group (equally wanting to reduce their sugar intake)
made an association between having a mint and eating sugar, suggesting that the wider
behavioural modification regime applied within both groups in the study. Furthermore,
this behavioural effect was observed in both the CON and INT groups, likely due to the fact
that participants were informed that they would be assigned to one of two programmes
that aimed to reduce sugar consumption. Therefore, particiants may have reduced their
intake of sugar-containing foods, in the absence of active taste-altering compounds, simply
because they were in a sugar-reduction study, i.e., a crude measure of behaviour change.
Based on their involvement in the study, it is likely that participants were in the early stages
of behavioural change (contemplation/preparation [
35
], involving a degree of awareness
regarding current dietary patterns and a desire to make change.
Over the course of the study, participants were provided with tools to reduce their
sugar intake and simple guidelines to follow, resulting in small changes within each treat-
ment group. This effect has previously been described among US and Thai college students,
where participants who were contemplating reducing sugar-sweetened beverage reduction
were more aware of their consumption and open to reducing sugar consumption [
36
].
Two focus groups each with INT or with CON participants were conducted at each time

Nutrients 2022,14, 5287 13 of 17
point in this study. Preliminary data from the focus groups for this study (Turner et al.,
unpublished) suggest that the abovementioned behavioural effect from having access to
simple guidelines affecting intake occurred among participants in both groups. Partici-
pants in three of the four focus groups (post day 15) felt that they had taken part in the
intervention, suggesting that the blinding was effective.
Although there were no between-condition differences for occasional food intake we
report the within-condition effects to provide a comprehensive description of the change ob-
served in the trials. A decrease in ad libitum sweet occasional food intake during the interven-
tion period (day zero to day 15)—regardless of being in the INT or CON
groups—indicated an effect from being in the study. Cakes and muffins contribute an es-
timated 4.7% of dietary sugar intake in the diet of New Zealanders [
37
]. Results from an
intensive, multi-component one-year intervention aiming to reduce sugar-sweetened beverage
intake in adolescents, found a reduction in intake and BMI at the end of the intervention,
but no differences after a further one-year follow up [
38
]. The authors suggested that the
intensity of the intervention may have resulted in adopting other health-promoting behaviours
including decreased television viewing which may explain the lack of significance after the
maintenance period [
38
]. In the present study, the intensive 14-day intervention may have
heightened the contemplation of sweet food intake in both treatment groups, resulting in
greater differences in sweet food intake than if they were not participating in the present study.
These findings confirm a previous report that the consumption of the GS mint within a
behaviour modification programme was most effective on those who identified as having a
sweet tooth [
19
]. Future efforts should focus on those with a sweet food preference as this
appears to be the group that experiences the greatest benefit from consuming gymnema-
containing products. Screening tools such as the Sweet Taste Questionnaire (a 12-item
questionnaire to evaluate attitudes, effects and control of eating sweet foods [
39
], or a Sweet
Taste Test assessing response to sucrose would identify this subgroup for future research [
40
].
Short-term, restrictive weight loss diets with strict food consumption rules, e.g., the
palaeolithic diet (restriction of grains, legumes, dairy, salt and refined oil) [
41
], or inter-
mittent fasting (hours of eating are restricted or food intake is reduced on specific days
of the week) [
42
], are popular [
43
,
44
]. These diets can be effective at weight loss and
dietary control in the short term, but long-term data suggests that the level of restriction
is difficult to sustain beyond three to six months [
43
]. Therefore, a long-term restrictive
diet to reduce sugar intake is unlikely to work, however, it may be more effective if ac-
companied by lifestyle strategies. The GS mint used in the current study (“Sweetkick”)
is analogous to the use of nicotine gum or patches to help smokers wean off cigarettes;
however, to our knowledge, the Sweetkick mint does not have addictive properties, unlike
nicotine. Smoking cessation is commonly associated with weight gain, but the Nurses’
Health Study found smoking cessation accompanied by lifestyle modifications such as daily
moderate-vigorous exercise and dietary modification (
≤
2 servings of unprocessed red meat;
≥
5 servings of fruit and vegetables; minimal high sugar treats) resulted in lower weight
gain than those who did not exercise or modify their eating habits [
45
]. A similar impact
may be seen among those who reduce their sugar intake; however, research is lacking in
this area. Ultimately, the GS mint and 14-day programme are not intended to be used
on a long-term basis, but rather as a tool to increase awareness of sugar intake and to
drive changes in habitual intake away from sweet-tasting, energy-dense foods. The World
Health Organisation (WHO) strongly recommends reducing free or added sugar intake to
less than 10% of total energy intake [
46
]. A recent study examining sugar intake in over
100,000 participants (French NutriNet-Santéprospective cohort study) showed that sugar
intake may represent a modifiable risk factor for cancer prevention. Moreover, repeated
24-hr dietary records found significant associations with cancer risk for added sugars,
free sugars, sucrose, sugars from milk-based desserts, dairy products, and sugary drinks;
therefore, any intervention that can reduce sugar intake may offer considerable health bene-
fits [
5
]. The methodology used in the present study focused on the frequency of consuming

Nutrients 2022,14, 5287 14 of 17
selected sweet foods and did not collect data on total dietary intake and therefore, we did
not assess added sugar intake.
The New Zealand Ministry of Health guidelines recommend that adults should con-
sume at least two servings of fruit per day [
47
]. However, the 2020/21 NZ Health Survey
shows that only an estimated 48.2% of adults are achieving this guideline [
48
]. At baseline,
participants in the present study reported consuming only about half a serving of fruit
per day. The study resulted in significantly higher fruit intake in both groups. Seasonality
may have had an effect on fruit intake as fruit consumption is often higher during summer
months than in winter [
49
–
51
]. The study took place between November and February—
summer months in New Zealand—and therefore, fruit consumption in both the INT and
CON groups may have been higher due to seasonal fruit availabilty. A key finding from
this study was that regular consumption of the GS mint did not reduce sweet fruit intake,
which contributed important nutrients as part of an everyday diet. In fact, participants may
have replaced their sweet treats with sweet-tasting, healthy fruit as an alternative; however,
a longitudinal study would be needed to confirm this.
It is worth noting that there was a single case report of an adverse reaction to consum-
ing GS tea thrice daily [
52
]; however, none of our participants complained of any adverse
effects of the dosage regiment we investigated.
Limitations and Future Directions
Participants were given instructions on how to take the Sweetkick mint (“let the mint
fully dissolve on your tongue, moving it around to coat your mouth completely”), however,
we did not monitor their adherence to this instruction. If the mint is not consumed as directed
(e.g., chewed or swallowed), there may be reduced inhibition of sweet taste receptors on
the tongue and therefore participants would retain the ability to taste sweetness. Further
research should monitor the time taken to dissolve the mint to ensure the mint is taken as
directed and all T1R receptors are affected by the product. We provided different healthy
eating guides and sachets to both groups; future studies should examine the individual
effects of the different aspects of the behavioural intervention. Although empty packaging
was collected, no tools were used to confirm that participants ingested the products as
instructed. Future work should involve a biometric measure to confirm consumption,
e.g., inserting riboflavin into the intervention mint [53], or using glucose monitors.
Future research should explore the effect of this intervention in people who consume
high amount of sweet foods, and/or with impaired glucose tolerance that are not yet
taking oral hypoglycaemic agents, as Gymnema sylvestre is also purported to normalise
blood glucose levels [
54
]. Further research is needed to determine how long the effect of
the 14-day intervention persists. This may also assist in determining whether it would
be useful to have a “reinforcement” (or “booster”) period where participants actively re-
engage with the programme after a set period of time to enhance or maintain new sweet
food consumption behaviours. The effect of the intervention on different user groups needs
to be explored further, including (but not limited to) individuals with obesity, pre-diabetes
and/or diabetes, and athletes (who may need to reduce sweet food consumption in non-
competitive periods). Moreover, as sweet food intake can impact reward regions of the
brain [
27
,
55
], research on whether reward region responsivity changes after prolonged GS
use warrants further investigation.
5. Conclusions
This study aimed to examine the effect of a 14-day ‘sugar reset’ behavioural interven-
tion on desire, pleasantness and intake of sweet foods. Consumption of the GS-containing
mint reduced desire, pleasantness and intake for further sweet food. There was no habit-
uation to the GS-mint over the 14-day period (i.e., the mint was just as effective on day
0 as it was on day 15). There was an independent behavioural effect simply by being
part of the 14-day intervention. This is the most comprehensive study in this emerging

Nutrients 2022,14, 5287 15 of 17
research area, and the only work so far to investigate the effect of longer-term gymnema
acid consumption on sweet food consumption outside of a laboratory setting.
Author Contributions:
A.A., S.T., C.D., R.K., M.W., W.W. and K.R.-M. designed the study; A.A.
secured funding; A.A., S.T., C.D., R.K. and E.S. undertook data analysis; S.T. drafted the manuscript;
A.A., S.T., C.D., R.K., M.W., W.W., K.R.-M. and E.S. reviewed and edited the final submission. All
authors have read and agreed to the published version of the manuscript.
Funding:
This work was by funded by Nu Brands Inc. The manufacturers (Nu Brands Inc) only
provided the product used in this study. They did not contribute to the study design, the data
collection, data analysis or manuscript write up.
Institutional Review Board Statement:
The study was conducted in accordance with the Declaration
of Helsinki and approved by Massey University Human Ethics Committee Northern (NOR 19/52;
Date of Approval: 18 November 2019).
Informed Consent Statement:
Informed consent was obtained from all subjects involved in the study.
Data Availability Statement: Data is contained within the article.
Acknowledgments: We would like to thank Nu Brands Inc for funding this project.
Conflicts of Interest: The authors declare no conflict of interest.
Abbreviations
BIA Bioelectric Impendance Analysis
BF% Body fat percentage
DFE Daily frequency equivalent
GS Gymnema sylvestre
GA Gymnemic acids
LMS labelled magnitude scale
SF-FFQ Sweet Food Food Frequency Questionnaire
SSB Sugar Sweetened Beverages
SSP Sugar Sweetened Products
VAS Visual Analogue Scale
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