Psyllium Supplementation in Adolescents Improves Fat
Distribution & Lipid Profile: A Randomized, Participant-
Blinded, Placebo-Controlled, Crossover Trial
Martin de Bock1, Jose ´ G. B. Derraik1, Christine M. Brennan1, Janene B. Biggs1, Greg C. Smith2,
David Cameron-Smith1, Clare R. Wall3, Wayne S. Cutfield1*
1Liggins Institute, University of Auckland, Auckland, New Zealand, 2Department of Molecular Genetics, University of Auckland, Auckland, New Zealand, 3Department of
Nutrition, University of Auckland, Auckland, New Zealand
Aims: We aimed to assess the effects of psyllium supplementation on insulin sensitivity and other parameters of the
metabolic syndrome in an at risk adolescent population.
Methods: This study encompassed a participant-blinded, randomized, placebo-controlled, crossover trial. Subjects were 47
healthy adolescent males aged 15–16 years, recruited from secondary schools in lower socio-economic areas with high rates
of obesity. Participants received 6 g/day of psyllium or placebo for 6 weeks, with a two-week washout before crossing over.
Fasting lipid profiles, ambulatory blood pressure, auxological data, body composition, activity levels, and three-day food
records were collected at baseline and after each 6-week intervention. Insulin sensitivity was measured by the Matsuda
method using glucose and insulin values from an oral glucose tolerance test.
Results: 45 subjects completed the study, and compliance was very high: 87% of participants took .80% of prescribed
capsules. At baseline, 44% of subjects were overweight or obese. 28% had decreased insulin sensitivity, but none had
impaired glucose tolerance. Fibre supplementation led to a 4% reduction in android fat to gynoid fat ratio (p=0.019), as
well as a 0.12 mmol/l (6%) reduction in LDL cholesterol (p=0.042). No associated adverse events were recorded.
Conclusions: Dietary supplementation with 6 g/day of psyllium over 6 weeks improves fat distribution and lipid profile
(parameters of the metabolic syndrome) in an at risk population of adolescent males.
Trial Registration: Australian New Zealand Clinical Trials Registry ACTRN12609000888268
Citation: de Bock M, Derraik JGB, Brennan CM, Biggs JB, Smith GC, et al. (2012) Psyllium Supplementation in Adolescents Improves Fat Distribution & Lipid Profile:
A Randomized, Participant-Blinded, Placebo-Controlled, Crossover Trial. PLoS ONE 7(7): e41735. doi:10.1371/journal.pone.0041735
Editor: Franc ¸ois Blachier, National Institute of Agronomic Research, France
Received April 2, 2012; Accepted June 25, 2012; Published July 27, 2012
Copyright: ? 2012 de Bock et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: Starship Foundation, Australasian Paediatric Endocrine Group, and New Zealand Society for the Study of Diabetes. We also acknowledge the Paykel
Trust for long-term funding of the Maurice & Agnes Paykel Clinical Research Unit at the Liggins Institute. The psyllium suppliers (Douglas Pharmaceuticals) and the
funders had no role in study design, data collection and analysis, decision to publish, or preparation of this manuscript.
Competing Interests: Note that Douglas Pharmaceuticals have provided the capsulated psyllium and placebo for this study, but had no role in study design,
data collection and analysis, decision to publish, or preparation of this manuscript. Thus, this does not alter the authors’ adherence to all the PLoS ONE policies on
sharing data and materials.
* E-mail: firstname.lastname@example.org
The metabolic syndrome encompasses a set of biochemical and
physical parameters that are associated with a greater risk for the
development of type 2 diabetes mellitus and cardiovascular
disease, and all cause mortality . These parameters include
increased central adiposity, and adverse changes in blood pressure,
lipid profile, and insulin sensitivity . The emergence of the
metabolic syndrome in the paediatric population is primarily a
result of dramatic increases in childhood obesity , and tracks
from adolescence into adulthood . Therefore, a range of
initiatives are frequently employed in the attempt to decrease the
incidence of the metabolic syndrome and obesity in childhood.
These are mostly community-based interventions, aiming to foster
increased physical activity and dietary changes. Nutritional
management in particular, varies greatly (from caloric restriction
to changes in macronutrient composition and energy ratio), as
there is a lack of consensus on the optimal approach .
In children, the effects of dietary fibres on parameters of the
metabolic syndrome are not well established. Cross sectional data
have shown that fibre and whole grain consumption in adoles-
cence is associated with increased insulin sensitivity  and a lower
incidence of the metabolic syndrome . However, the majority of
clinical studies have focused on dietary fibre combined with either
exercise and/or other dietary interventions [8,9]. Thus, to our
knowledge, there have been no placebo-controlled clinical trials
investigating the effect of supplementation with dietary fibre alone
on parameters of the metabolic syndrome in adolescents.
PLoS ONE | www.plosone.org1July 2012 | Volume 7 | Issue 7 | e41735
Dietary fibres encompass a broad array of compounds
(primarily of plant origin) with known physiological benefits,
including laxation, and improvements in glucose homeostasis and
cholesterol . The gel-forming water-soluble fibres are those
that appear to have the most beneficial effects on post-prandial
glycemia . Such fibres include the seed husks of psyllium
(Plantago spp., in particular P. ovata), also known as ispaghula,
which is often used to enrich cereals and other food items. Psyllium
husks encompass a mixture of neutral and acid polysaccharides
containing galacturonic acid, with a 70/30 ratio of soluble/
insoluble fibre. Psyllium has been used safely in children and
adolescents, and was shown to improve hypercholesterolemia
[12,13,14]. In this study, we aimed to investigate the effect of
psyllium fibre supplementation alone on insulin sensitivity and
other parameters of the metabolic syndrome in an at risk
Materials and Methods
Ethics approval for this study was provided by the Northern Y
Regional Ethics Committee. Written informed consent was
obtained from participants and caregivers.
Healthy adolescent males aged 15–16 years were recruited from
high schools in Auckland (New Zealand) to participate in the study
(Figure 1). We targeted schools in lower socio-economic areas with
high rates of obesity, in order to select adolescents at greater risk of
developing the metabolic syndrome. Exclusion criteria included
those receiving medications that alter glucose metabolism (e.g.
steroids, stimulants, and insulin), and smokers. Participants
provided written informed consent if they were 16 years and over.
This study was a randomized, participant-blinded, placebo-
controlled, crossover trial. The protocol for this trial and
supporting CONSORT checklist are available as supporting
information (see Checklist S1 and Protocol S1).
Randomization and allocation to trial group were done using
computer random number generation. All participants were
randomized into a 6-week intervention with either 6 g/day of
psyllium (P. ovata) (equating to 6 g of dietary fibre) or 6 g/day of
potato starch placebo (Figure 1). The dose of 6 g/day was adopted
based on review of the existing literature , as well as on the
volume of fibre and placebo each dose would equate to, so as not
to affect compliance with study protocol. After a 2-week washout
period, participants crossed over to receive the opposite in-
tervention for a further six weeks (Figure 1). Both the psyllium and
potato starch were packed as 500 mg capsules (Douglas Pharma-
ceuticals, Auckland, New Zealand). The capsules were blister-
packed to aid compliance, and participants were instructed to
consume the 12 capsules per day with large amounts of water.
Capsules could be consumed all at once or divided in doses, and
with or without food. Adherence to dosing was monitored by
counting non-consumed capsules in returned blister packs at the
end of each 6-week intervention. Participants were advised to
continue their normal eating and exercise patterns during the
All clinical assessments were carried out at the Maurice & Agnes
Paykel Clinical Research Unit (Liggins Institute, University of
Auckland). Subjects were assessed at three time points after an
overnight fast: baseline, end of the first 6-week intervention, and
end of the second 6-week intervention (Figure 1). Height was
measured using a Harpenden stadiometer. Weight and body
composition were assessed using both body mass index (BMI) and
whole-body dual-energy x-ray absorptiometry (Lunar Prodigy
2000, General Electric, Madison, WI, USA). Body composition
data of interest were total percentage body fat and the ratio of
android fat to gynoid fat. Note that android and gynoid fat values
were determined by the manufacturer’s software, based on an
automated sectioning of specific areas of the body . BMI data
were converted to standard deviation scores (BMI SDS) according
to British 1990 standards .
After an overnight fast, blood samples were obtained to assess
metabolic factors. Glucose, triglycerides, cholesterol, HDL, and
LDL concentrations were measured on a Hitachi 902 autoanalyser
(Hitachi High Technologies Corporation, Tokyo, Japan) by
enzymatic colorimetric assay (Roche, Mannheim, Germany) with
an interassay CV of less than 2.5%. Insulin concentrations were
measured using an Abbott AxSYM system (Abbott Laboratories,
Abbott Park, IL, USA) by microparticle enzyme immunoassay
with an interassay CV of 5.4%. Insulin sensitivity was assessed by a
75 g oral glucose tolerance test using the Matsuda method, with
glucose and insulin samples collected at 0, 30, 60, 90, and
120 minutes . The Matsuda method has a strong correlation
with the hyperinsulinemic euglycaemic clamp (r=0.77) , and
excellent reproducibility during multiple measures .
24-hour ambulatory blood pressure was assessed prior to each
clinical assessment. Participants were fitted with a Spacelabs 90207
or 90217 (Spacelabs Medical Inc., Redmond, USA), with each
subject being assigned the same device model for all assessments.
Measurements were performed every 20 minutes from 0700–
2200, and every 30 minutes from 2200–0700. Only profiles with a
total of at least 40 readings over a 24-hr period were included for
Three dietary records were collected at baseline and at clinical
assessment following each 6-week intervention. Each dietary
report encompassed an itemized nutritional intake recorded
during two school days and one weekend day. Nutritional intake
was recorded using standard household measures, as well as the
information from food labels where appropriate. Participants were
instructed by a nutritionist [CRW] on how to fill out the food diary
accurately. A trained investigator [MdB] reviewed all food records
with each participant to address unclear descriptions, errors,
omissions, or doubtful entries. Records were subsequently entered
into Foodworks software (v6.0, Xyris Software, Brisbane, Aus-
tralia) by the trained investigator [MdB]. Accuracy of food record
entry was also externally confirmed by the nutritionist [CRW],
randomly selecting and verifying 10% of all records.
Physical activity was assessed using the Physical Activity
Questionnaire for Adolescents (PAQ-A) (University of Saskatch-
ewan, Saskatoon, Canada). Leisure activities were modified to
reflect those engaged by New Zealand youth. This self-adminis-
tered 7-day recall questionnaire has been validated for use in
Demographic data were also collected on all subjects. Socio-
economic status (SES) was classified using the New Zealand Index
of Deprivation 2006 (NZDep2006) . This uses household
census data reflecting nine aspects of material and social
deprivation to divide New Zealand into tenths (scored 1–10) by
residential address, where a higher score reflects lower SES .
Baseline data associations were assessed using simple linear
regressions, but the association between SES and insulin sensitivity
Psyllium Supplementation Trial in Adolescents
PLoS ONE | www.plosone.org2July 2012 | Volume 7 | Issue 7 | e41735
was examined using non-parametric Spearman’s rank correlation.
Baseline analyses were carried out in Minitab v.16 (Pennsylvania
State University, State College, PA, USA). Crossover trial data
were analysed in SAS v.9.2 (SAS Institute, Cary, NC, USA) using
a linear mixed model design based on repeated measures, which
accounted for treatment sequence (PlaceboRFibre vs FibreR
Placebo), treatment phase (Stage 1 vs Crossover; Figure 1),
ethnicity, SES, as well as participant as a random factor.
Importantly, models also incorporated the baseline value of the
outcome response as a co-variate, to account for the different
starting points for each subject at the beginning of the study. The
Johnson transformation was adopted when necessary to stabilize
the variance. Data are expressed as means 6 SEM.
A total of 47 healthy adolescent males (aged 15.860.1 years at
baseline) met the inclusion criteria and were enrolled in the study.
Randomization order was established prior to recruitment of
subjects, and we aimed for a minimum of 42 subjects (i.e. 21 in
each group) as required by the power calculation to detect a 25%
change in insulin sensitivity . At the point at which we had
enrolled and successfully studied 45 subjects it was obvious that
study failure rates were far lower than anticipated, thus
recruitment was stopped. This explains the uneven ratio of
subjects randomly allocated between groups 1 and 2 (Figure 1).
Subsequently, two participants were lost to follow up, and were
excluded (Figure 1).
All participants were from areas of relatively low SES, with 44%
from the lowest quintile of SES in New Zealand. Subjects were of
Pacific Island (46%), European (37%), Maori (15%), and Indian
(2%) ethnicities. Mean BMI at baseline was 25.860.7 kg/m2, with
24% of subjects obese (BMI $30 kg/m2) and a further 20%
overweight (BMI $25 but ,30 kg/m2); mean percentage body fat
was 23.561.7%. Participants’ compliance with the study was very
high: 87% of participants took more than 80% of prescribed
capsules over the 12 weeks of intervention. No associated adverse
events (including gastrointestinal) were recorded during this study.
Mean pre-study dietary fibre intake was 23.161.7 g/day
(Table 1), with only 37% of subjects meeting the recommended
daily intake of 28 g/day for this age group . As a result, the
addition of 6 g/day of psyllium during the treatment period
equated to a mean individual increase in daily dietary fibre intake
Figure 1. Summary of study’s recruitment process and trial execution. IXindicates timing of assessments.
Psyllium Supplementation Trial in Adolescents
PLoS ONE | www.plosone.org3July 2012 | Volume 7 | Issue 7 | e41735
of 36.464.6%, with an equivalent 50% or more increase recorded
in four subjects. Baseline data demonstrate a high intake of energy
derived from fat, including saturated fat (Table 1).
Insulin sensitivity at baseline was positively associated with
mean daily intake of dietary fibre (r2=0.20; p,0.01; Fig. 2), and
inversely associated with BMI SDS (r2=0.38; p,0.001; Fig. 3).
SES was also correlated with insulin sensitivity (p=0.037), so that
the higher the index of deprivation the lower the Matsuda index
(r=20.31). 28% of subjects were insulin resistant with a baseline
Matsuda score lower than 2.5. BMI SDS was associated with
baseline triglycerides (r2=0.24; p,0.001), total cholesterol
(r2=0.26; p,0.001), LDL (r2=0.26; p,0.001), HDL:LDL ratio
(r2=0.19; p,0.01), but not HDL (r2=0.00; p=0.65) concentra-
Dietary intake among individual participants did not change
significantly throughout the study. Thus, total caloric intake
(p=0.43), total fibre intake (p=0.44), and the percentage of total
calories from saturated fat (p=0.17) at baseline were not different
to the respective intake consumed during placebo and fibre
treatment. In addition, there was also no change in physical
activity levels among groups throughout the study.
Although fibre supplementation did not lead to a reduction in
weight, BMI SDS, or body fat percentage, it did lead to a 4%
reduction in android fat to gynoid fat ratio (p=0.019; Table 2).
Psyllium supplementation also led to a 0.12 mmol/l (6%)
reduction in LDL cholesterol (p=0.042; Table 2). There were
no observed effects on insulin sensitivity, fasting plasma insulin, or
glycemic status (i.e. fasting plasma glucose), irrespective of
ethnicity, baseline fibre intake, or BMI SDS. Ambulatory blood
pressure parameters were similar with placebo and fibre intake,
except nighttime systolic blood pressure that tended to be on
(p=0.073; Table 2).
This is the first randomized, participant-blinded, placebo-
controlled, crossover trial investigating the effects of psyllium
supplementation on parameters of the metabolic syndrome in
adolescents. Our data show that even in the context of a relatively
short intervention, psyllium supplementation improves LDL
cholesterol and android fat to gynoid fat ratio. Conversely, there
was no improvement in insulin sensitivity and HDL, which are
other parameters of the metabolic syndrome. These results have
public health implications as commercial food manufacturers often
use psyllium to fortify products such as cereal and baked goods to
boost their fibre content.
Our study corroborates previous data showing that psyllium has
lipid lowering properties in children and adolescents. The 6%
improvement in LDL cholesterol concentrations we observed is
comparable to other studies that have shown improvements of 0–
23% using psyllium doses ranging from 5–25 g/day [12,13,14,26].
The lipid lowering action of soluble fibres such as psyllium occurs
by binding bile acids and cholesterol, increasing faecal excretion of
bile salts, and reducing cholesterol synthesis via production of
short-chain fatty acids . Importantly for this study, the
reduction of LDL provides evidence that psyllium can be absorbed
in the more palatable capsulated form.
We also observed a reduction in the android to gynoid ratio of
fat distribution with fibre supplementation, which indicates a
decrease in central adiposity. Similarly, a recent large descriptive
study in adolescents showed decreased visceral fat among subjects
with the highest fibre intake . Thus, although we observed no
change in BMI SDS, our findings are important as central obesity
is an independent risk factor for the development of the metabolic
Table 1. Baseline daily dietary parameters among study
Dietary parameterMean ± SEM
Total energy (kJ) 106736560
Energy from fat (%)35.961.2
Energy from saturated fat (%)15.960.7
Energy from carbohydrates (%)43.561.6
Energy from sugars (%)16.261.1
Energy from protein (%)17.061.2
Figure 2. The association between baseline daily dietary fibre
intake (log-transformed) and insulin sensitivity (Matsuda
Figure 3. The association between BMI SDS and insulin
sensitivity (Matsuda index) at baseline.
Psyllium Supplementation Trial in Adolescents
PLoS ONE | www.plosone.org4July 2012 | Volume 7 | Issue 7 | e41735
syndrome and associated cardiovascular disease risk . Possible
explanations for the observed effect in fat distribution include
altered dietary fat lipolysis and subsequent absorption , or
modulation of sex steroids that effect fat distribution .
Importantly, the results could not be explained by changes in
In this study, psyllium supplementation over 6 weeks did not
affect insulin sensitivity. However, previous studies in adults with
type 2 diabetes showed that food supplementation with psyllium
led to improved glucose metabolism, as examined by post-prandial
glucose and insulin excursion [32,33]. This improvement is likely
explained by the solubility and viscosity of psyllium, which
sequesters carbohydrate absorption , and delays gastric
emptying and intestinal transit time . In contrast, our study
investigated the effects of psyllium on insulin sensitivity in the
longer term. Anderson et al. have previously shown that
supplementation with 10.2 g/day of psyllium over three days
improves post-prandial glucose concentrations, but not insulin
sensitivity (measured by euglycaemic hyperinsulinaemic clamp) in
adults with type 2 diabetes . Changes in insulin sensitivity
would require additional physiological properties of psyllium, such
as the production of short-chain fatty acids . Thus, our null
result may be explained by the poor fermentation of psyllium to
produce short-chain fatty acids as compared to other sources of
dietary fibre [36,37]. However, the effects of short-chain fatty
acids on insulin sensitivity are questionable , and these may
even be deleterious in the long-term as observed in animal models
. A further possible explanation (and a weakness of our study)
relates to our chosen method to assess insulin sensitivity; i.e. we
adopted an oral glucose tolerance test rather than the labour-
intensive gold standard euglycaemic hyperinsulinaemic clamp.
One trial examining the effect of resistant starch on insulin
sensitivity detected an improvement using the clamp technique,
but did not demonstrate a difference using the Homeostasis Model
Assessment (HOMA) proxy .
Commercial food producers have capitalised on the broad
benefits of fibre, commonly using psyllium to enrich cereals and
other foods. By definition, fibre encompasses a broad range of
edible plant compounds, which have physiological health benefits
including laxation, lowered cholesterol, and improved glucose
metabolism . However, given that dietary fibre encompasses
such a diverse range of compounds, there is a wide variation in
their physiological effects. The implication is that while psyllium is
a highly soluble and palatable fibre that can easily be added to
food products, it may not deliver all the health benefits associated
with the consumption of different forms of fibre. While we do not
dispute the overall benefits of dietary fibre, it is important that
consumers and food producers become aware that not all forms of
fibre are equal in terms of physiological action.
The adequate intake for dietary fibre for adolescents is 28 g/day
in Australia-New Zealand . Dietary fibre intake in our study
population was poor, as only 37% of participants consumed 28 g/
day or more. Our observation is not unusual, and similar figures
have been obtained for other adolescent populations . These
findings are reason for concern, as a recent cross-sectional study in
adolescents showed that those in the highest quintile of fibre intake
had a three-fold reduction in the incidence of the metabolic
syndrome compared to those in the lowest quintile .
In conclusion, we showed that fibre supplementation using
psyllium improves fat distribution and lipid profile, even after a
relatively short intervention of six weeks. Conversely, psyllium
supplementation did not improve insulin sensitivity. Due to the
enormous burden that cardiovascular diseases have on public
health, our findings have potentially important public health
implications. Continued awareness and promotion of the value of
dietary fibre in the adolescent diet is required. It is possible that
commercial food manufacturers, through fortification of food with
dietary fibre such as psyllium, could play a role in the prevention
of cardiovascular diseases. However, further research is warranted
to investigate the best types of fibre, delivery method, dose, and
length of treatment to determine the appropriate fibre supple-
mentation and associated health benefits.
We would like to thank the LENScience Group (Liggins Institute,
University of Auckland) for forging the relationship between the Liggins
Institute and the secondary schools from which our study population was
Conceived and designed the experiments: MdB WSC. Performed the
experiments: MdB CMB JBB CRW GCS. Analyzed the data: JGBD.
Wrote the paper: MdB JGBD WSC. Provided fundamental input during
analyses and during manuscript writing: DC-S.
Table 2. Outcome measures following a 6-week
supplementation with 6 g/day of psyllium fibre or placebo.
BMI (kg/m2) 26.261.0 26.060.9 0.92
% body fat 23.861.723.461.7 0.95
Android fat to gynoid fat ratio 0.9960.04 0.9560.04 0.019
Ambulatory blood pressure
Daytime diastolic (mmHg)69.860.969.860.90.86
Daytime systolic (mmHg)123.961.5 122.661.30.44
Nighttime diastolic (mmHg)56.222.214.171.124.57
Nighttime systolic (mmHg)109.461.7 106.361.30.073
Diastolic dip (%)19.261.420.361.40.58
Systolic dip (%)11.461.213.661.00.13
Glucose (mmol/l)5.2060.07 5.1160.060.19
LDL (mmol/l) 2.4660.09 2.3260.090.042
HDL (mmol/l)1.1960.04 1.1760.04 0.40
HDL to LDL ratio0.5360.03 0.5460.030.59
Triglycerides (mmol/l)0.9560.06 0.9460.060.99
Insulin sensitivity (Matsuda index)3.8860.33.8560.30.90
Data are means 6 SEM, and p-values refer to results from multivariate models.
Psyllium Supplementation Trial in Adolescents
PLoS ONE | www.plosone.org5July 2012 | Volume 7 | Issue 7 | e41735
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PLoS ONE | www.plosone.org6 July 2012 | Volume 7 | Issue 7 | e41735