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Review
The Metabolic Effects of Oats Intake in Patients
with Type 2 Diabetes: A Systematic Review
and Meta-Analysis
Qingtao Hou 1, †, Yun Li 2, †, Ling Li 3, Gaiping Cheng 4, Xin Sun 3, Sheyu Li 1 ,* and
Haoming Tian 1,*
Received: 29 September 2015; Accepted: 26 November 2015; Published: 10 December 2015
1Department of Endocrinology and Metabolism, West China Hospital, Sichuan University,
Chengdu 610041, China; qingtao1990@sina.com
2Department of Endocrinology and Metabolism, The Third People’s Hospital of Chengdu,
Chengdu 610031, China; lyhelen37@126.com
3Chinese Evidence-based Medicine Center, West China Hospital, Sichuan University,
Chengdu 610041, China; ebmliling@hotmail.com (L.L.); sunx79@hotmail.com (X.S.)
4Department of Clinical Nutrition, West China Hospital, Sichuan University, Chengdu 610041, China;
hellochgp@163.com
*Correspondence: hmtian999@126.com (H.T.); lisheyu@gmail.com (S.L.); Tel.: +86-189-8060-1303 (H.T.);
+86-131-9487-4843 (S.L.); Fax: +86-28-8542-2982 (H.T. & S.L.)
† These authors contributed equally to this work.
Abstract: The present study aimed to comprehensively assess if oats intake is beneficial for
diabetic patients. The literature search was conducted in PubMed database up to 23 August
2015. Fourteen controlled trials and two uncontrolled observational studies were included.
Compared with the controls, oats intake significantly reduced the concentrations of glycosylated
hemoglobin A1c (HbA1c) (MD, ´0.42%; 95% CI, ´0.61% to ´0.23%), fasting blood glucose (FBG)
(MD, ´0.39 mmol/L; 95% CI, ´0.58 to ´0.19 mmol/L), total cholesterol (TC) (MD, ´0.49 mmol/L;
95% CI, ´0.86 to ´0.12 mmol/L), low-density lipoprotein cholesterol (LDL-C) (MD, ´0.29 mmol/L;
95% CI, ´0.48 to ´0.09 mmol/L). Oatmeal significantly reduced the acute postprandial glucose and
insulin responses compared with the control meal. The present study has revealed a beneficial effect
of oats intake on glucose control and lipid profiles in type 2 diabetic patients. Further investigations
of oats intake in patients with type 1 diabetes and the safety of oats consumption are required.
Keywords: oats; β-glucan; type 2 diabetes mellitus; glycemic control; cholesterol; systematic review;
meta-analysis
1. Introduction
Type 2 diabetes is a common chronic disease with great global health and economic burden.
The prevalence is still increasing due to lifestyle changes, especially in developing countries [1,2].
Diabetic education, nutrition therapy, physical activity, pharmacotherapy and glucose monitoring
are key components of diabetes management. Lifestyle intervention including diet control is
recommended as the fundamental approach for all patients with type 2 diabetes. Diabetic patients are
suggested to consume at least the amount of fibers and whole grains recommended for the general
public, which is 14 g fiber/1000 kcals daily or about 25 g/day for adult women and 38 g/day for
adult men [3]. Dietary fibers promote one or more of the beneficial effects such as laxation, reduction
in blood lipids, modulation of blood glucose due to their non-digestibility in the small intestine and
fermentation in the colon. Oats are a good source of soluble dietary fiber rich in β-glucan, which
is considered as a bioactive component in reducing postprandial glucose and insulin responses,
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Nutrients 2015,7, 10369–10387
improving insulin sensitivity, maintaining glycemic control and regulating blood lipids [4–7]. The
United States Food and Drug Administration (FDA) suggested that the consumption of 3 g or more
per day of β-glucan from oats or barley may reduce the risk of coronary heart disease [8].
A number of studies have reported the beneficial metabolic effects of oats or β-glucan on people
with and without type 2 diabetes [9–12]. A modified diet with β-glucan from oats was reported to
be superior to the American Diabetic Association’s diet in improving metabolic and anthropometric
profiles in well controlled type 2 diabetic patients: larger decreases in glycosylated hemoglobin A1c
(HbA1c), weight and body mass index (BMI); greater increase in high-density lipoprotein cholesterol
(HDL-C) [9]. A high dose of barley β-glucan supplement (6.31 g β-glucan) improved the glucose
and insulin responses when added to a high-carbohydrate food in lean, healthy men without type 2
diabetes [10]. For overweight or obese patients and patients with metabolic syndrome, oats fiber
also improved glucose intolerance and insulin sensitivity [11,12]. However, the European Food
Safety Authority (EFSA) reported that the evidence remained insufficient to prove the relationship
between β-glucan consumption and the long-term maintenance of normal blood glucose level [13].
Accordingly, the aim of this systematic review was to comprehensively evaluate if oats intake is
beneficial for both the short-term glucose response and the long-term glucose control as well as other
metabolic parameters such as lipid and anthropometric profiles in type 2 diabetic patients.
2. Methods
2.1. Literature Search and Study Selection
The electronic database of PubMed was searched for articles published before 23 August 2015
using the keywords “oat”, “oats”, or “oatmeal” and “diabetes”. Medical Subject Heading (MeSH)
was also used during the search when applicable. The references lists of original studies and review
articles investigating the relationship between oats intake and diabetes were screened to make sure
all potentially relevant studies were included.
Studies were included if they met the following criteria: (1) Clinical trials or observational
studies; (2) Participants with type 2 diabetes mellitus; (3) Oats or oatmeal or oats-containing
products as the intervention or exposure; (4) Reporting the changes of blood glucose, insulin, HbA1c,
postprandial glucose and insulin responses, insulin sensitivity or β-cell function. Changes of lipid
profiles, weight and BMI were additional outcomes.
2.2. Data Extraction
All search studies were independently reviewed by two reviewers (Q. T. and Y. L.) and
disagreements were resolved through discussion with a third reviewer (S. L.). The following
information was extracted from each study using a predefined form: first author, year of publication,
country, participant counts, sex, age, subject type, study design, follow-up duration, baseline HbA1c
and diets. The outcomes of interest include glucose and insulin profiles, HbA1c, postprandial insulin
and glucose responses, β-cell function, lipid profiles, weight and BMI.
2.3. Quality Assessment
The modified Jadad scale was used for reporting the quality of randomized controlled trials [14].
The scores range from 0 (very poor) to 7 (very good). The seven-point quality scale includes
items for randomization (described as randomized, 1 point; described randomization method, 2 points
),
randomization concealment (described as randomization concealment, 1 point; described concealment
method, 2 points), blinding (described as blind, 1 point; described blinding method, 2 points),
and follow-up (described the withdrawal in each group, 1 point). Newcastle-Ottawa Scale (NOS)
was used to score the quality of observational studies [15]. The nine-point NOS assigns points for
selection (4 points), comparability (2 points) and outcome (3 points).
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2.4. Statistical Methods and Evidence Assessment
We chose a literal description and a meta-analysis to report the results. The change form baseline
in each diet pattern or the change of the intervention diet relative to the control diet was displayed in
the tables. Statistically significant changes (p< 0.05) were marked with different symbols in the tables.
The meta-analysis was carried out using STATA 12.0, and the changes from baseline of metabolic
parameters were calculated as the mean differences (MD) with their 95% confidence intervals (CIs).
The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system
(GRADEprofiler 3.6.1) was used to rate the quality of evidence.
3. Results
3.1. Search Results
A total of 216 articles were identified (Figure 1). One hundred and sixty-eight articles were
excluded after screening the titles and abstracts and forty-eight potentially eligible articles were
left for full-text assessing. A further thirty-two articles were excluded for the following reasons:
(1) Review articles (n= 4); (2) Participants were not diabetic patients (n= 8); (3) No outcomes
of interest were reported (n= 20). Finally, sixteen articles [9,16–30] were included in this
systematic review.
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3
2.4.StatisticalMethodsandEvidenceAssessment
Wechosealiteraldescriptionandameta‐analysistoreporttheresults.Thechangeformbaseline
ineachdietpatternorthechangeoftheinterventiondietrelativetothecontroldietwasdisplayedin
thetables.Statisticallysignificantchanges(p<0.05)weremarkedwithdifferentsymbolsinthetables.
Themeta‐analysiswascarriedoutusingSTATA12.0,andthechangesfrombaselineofmetabolic
parameterswerecalculatedasthemeandifferences(MD)withtheir95%confidenceintervals(CIs).
TheGradingofRecommendationsAssessment,Development,andEvaluation(GRADE)system
(GRADEprofiler3.6.1)wasusedtoratethequalityofevidence.
3.Results
3.1.SearchResults
Atotalof216articleswereidentified(Figure1).Onehundredandsixty‐eightarticleswere
excludedafterscreeningthetitlesandabstractsandforty‐eightpotentiallyeligiblearticleswereleft
forfull‐textassessing.Afurtherthirty‐twoarticleswereexcludedforthefollowingreasons:(1)
Reviewarticles(n=4);(2)Participantswerenotdiabeticpatients(n=8);(3)Nooutcomesofinterest
werereported(n=20).Finally,sixteenarticles[9,16–30]wereincludedinthissystematicreview.
Figure1.Flowdiagramforstudyidentification.
Fourteencontrolledtrials(4paralleleddesignsand10crossoverdesigns)[9,16–28]andtwo
uncontrolledobservationalstudies[29,30]werefinallyanalyzed.Thecharacteristicsofthestudies
includedinthissystematicreviewareshowninTable1.Thedetaileddietinformationisdisplayed
inTableS1.Eightstudies[17–19,22,26,27,29,30]werecarriedoutinEurope,threestudies[20,24,25]
werecarriedoutinCanada,twoinChina[16,23]andoneinVenezuela[9],USA[21]andMexico[28].
Allthestudiesfocusedontype2diabeticpatients,andthree[9,25,27]ofthemonlystudiedmales.
Thenumberofsubjectsrangedfrom8to260,andthefollow‐updurationrangedfromasingle‐meal
totwelveweeks.Whenweevaluatedthestudyquality,sevenstudies[16–18,21,23,27,28]were
classifiedashigh‐qualitystudies(modifiedJadadscore≥4)andtheremainingseven[9,19,20,22,24–
26]aslow‐qualitystudies(modifiedJadadscore<4)(TableS2).Additionally,thetwoobservational
studiesreceivedaNOSscoreof7[29]and6[30],respectively(TableS3).
Figure 1. Flow diagram for study identification.
Fourteen controlled trials (4 paralleled designs and 10 crossover designs) [9,16–28] and two
uncontrolled observational studies [29,30] were finally analyzed. The characteristics of the studies
included in this systematic review are shown in Table 1. The detailed diet information is displayed
in Table S1. Eight studies [17–19,22,26,27,29,30] were carried out in Europe, three studies [20,24,25]
were carried out in Canada, two in China [16,23] and one in Venezuela [9], USA [21] and Mexico [28].
All the studies focused on type 2 diabetic patients, and three [9,25,27] of them only studied males.
The number of subjects ranged from 8 to 260, and the follow-up duration ranged from a single-meal to
twelve weeks. When we evaluated the study quality, seven studies [16–18,21,23,27,28] were classified
as high-quality studies (modified Jadad score ě4) and the remaining seven [9,19,20,22,24–26] as
low-quality studies (modified Jadad score <4) (Table S2). Additionally, the two observational studies
received a NOS score of 7 [29] and 6 [30], respectively (Table S3).
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Table 1. Baseline characteristics of studies included.
Study Country No. of
Subjects Sex (F %) Age (Year) Subject Type Design Follow-up Duration Baseline
HbA1c (%)
Reyna, 2003 [9] Venezuela 16 Male 45–55 Well controlled T2DM Parallel RCT 4 weeks 8.3
Ma, 2013 [16] China 260 M & F (56.9) 50–65 T2DM, MetS Parallel RCT 30 days 9.9
Liatis, 2009 [17] Greece 46 M & F (43.9) 63 T2DM Parallel RCT 3 weeks 7.1
Cugnet-Anceau, 2009 [18]France &
Sweden 53 M & F (39.6) 30–75 Free-living T2DM Parallel RCT 8 weeks 7.4
Tappy, 1996 [19] Switzerland 8 M & F (12.5) 34–65 T2DM Crossover RCT Single meal 6.4
Jenkins, 2002 [20] Canada 16 M & F (37.5) 46–70 (61 ˘2) T2DM Crossover RCT Single meal 7.4
Rendell, 2005 [21] USA 18 M & F (33.3) 62 ˘3T2DM only under diet
management Crossover RCT Single meal NA
Tapola, 2005 [22] Finland 12 M & F (58.3) 18–75 (66 ˘7) T2DMonly under diet
management Crossover RCT Single meal NA
Yu, 2014 [23] China 30 M & F (56.7) 48–73 (66 ˘6) T2DM without insulin
therapy Crossover RCT Single meal 6.8
Braaten, 1994 [24] Canada 8 M & F (62.5) 59 (50–68) T2DM Non-randomised
crossover trial Single meal 8.3
Pick, 1996 [25] Canada 8 Male 39–57 (46 ˘1) T2DM Crossover RCT 2 consecutive
12-week 7.0
McGeoch, 2013 [26] UK 27 M & F (33.3) 46–71 T2DM under diet and
lifestyle management Crossover RCT 2 consecutive 8-week 6.8
Kabir, 2002 [27] France 13 Male 41–67 (59 ˘2) T2DM Crossover RCT
2 periods of 4 weeks
with a 15-day
washout interval
8.3
Ballesteros, 2015 [28] Mexico 29 M & F (34.5) 54 ˘8 Well controlled T2DM Crossover RCT
2 periods of 5 weeks
with a 3-week
washout interval
6.8
Lammert, 2007 [29] Germany 14 M & F (71.1) 60 ˘10 Uncontrolled T2DM,
insulin resistance, MetS
Uncontrolled
prospective
observational study
2 days & 4 weeks 8.6
Zerm, 2013 [30] Germany 50 M & F (52.0) 65 ˘10
Poorly controlled
T2DM, insulin
resistance, obese
Uncontrolled
retrospective
observational study
2 days 9.6
HbA1c, glycosylated hemoglobin A1c; M, male; F, female; T2DM, type 2 diabetes mellitus; RCT, randomized controlled study; MetS, metabolic syndrome; NA, not available.
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3.2. Glucose Control and Insulin Profiles
Table 2shows the results of nine studies investigating the changes of glucose and insulin levels
after oats interventions or exposures. Eight studies reported HbA1c. Three randomized, parallel
controlled studies [9,16,17] showed a significant reduction from baseline (´0.28% to ´2.22%; p< 0.05)
in the oats intervention group and a significant reduction was observed in subjects who consumed
oats than in the control subjects (MD, ´0.42%; 95% CI, ´0.61% to ´0.23%; p< 0.001) (Figure 2,
Table 3). Among the seven studies reporting fasting blood glucose (FBG), two [16,17] randomized,
parallel controlled studies showed a significant reduction from baseline (´0.72 to ´1.91 mmol/L;
p< 0.05) in the oats intervention group. A significant reduction was observed in subjects who
consumed oats than in the control subjects (MD, ´0.39 mmol/L; 95% CI, ´0.58 to ´0.19 mmol/L;
p< 0.001) (Figure 3, Table 3). One study showed a significantly greater reduction from baseline
following oats intervention compared with the control group of usual care (p< 0.05) [16]. Only one
randomized, parallel controlled study [16] reported the postprandial blood glucose (PBG). It showed
that 50 g and 100 g of organic naked oat with whole germ (ONOG) significantly decreased the
2-h PBG by 3.25 mmol/L (p< 0.05) and 3.70 mmol/L (p< 0.05) from baseline after 30 days of an
oats diet, respectively. Additionally, this reduction from baseline in the 100 g-ONOG group was
statistically greater compared with the 50 g-ONOG group (p< 0.05). Four studies reported fasting
insulin (FINS). Among them, one randomized, parallel controlled study [17] showed a non-significant
reduction from baseline (´3.23 µU/mL; p> 0.05) after three weeks of β-glucan bread intervention
and a non-significant increase from baseline (+3.77 µU/mL; p> 0.05) after white bread intervention.
Although the changes from baseline were not significant within group, the relative changes between
groups were significantly different in this study (p< 0.05). The pooled effect of oats intake on FINS
was only from two studies (MD, ´0.22 µU/mL; 95% CI, ´1.28 to 0.84 µU/mL; p= 0.681) (Figure S1,
Table 3). Two uncontrolled observational studies [29,30] investigated mean blood glucose (MBG) and
mean daily insulin (MDI) changes from baseline after two days of oatmeal consumption in poorly
controlled type 2 diabetic patients with insulin resistance. The MBG decreased by 1.08 to 2.39 mmol/L
(p< 0.05), and the MDI decreased by 36.60 to 62.00 IU/day (p< 0.05) at different time points after the
oatmeal consumption.
Four randomized studies [16,17,26,28] used the homeostasis model assessment (HOMA) of
insulin resistance or β-cell function. Liatis et al. [17] revealed a non-significant decrease in insulin
resistance from baseline (´2.08 µUˆmol/L2;p> 0.05) in the β-glucan bread (3 g/day β-glucan)
group and a non-significant increase from baseline (+1.33 µUˆmol/L2;p> 0.05) in the white
bread group. The relative changes from baseline were significantly different between the two groups
(p< 0.05). Ma et al. [16] found a significant decrease in insulin resistance from baseline (´0.33 µU
ˆmol/L2;p< 0.05) after an intervention of 100 g/day organic naked oat with whole germ (ONOG)
(5.0 g/day β-glucan) based on systematic diet plans and intensive education. Whereas, the decrease
in insulin resistance was not significant in the 50 g-ONOG group (´0.11 µUˆmol/L2;p> 0.05). The
pooled effect of oats intake on HOMA-IR was from two studies (MD, ´0.51 µUˆmol/L2; 95% CI,
´1.05 to 0.02 µUˆmol/L2;p= 0.061) (Figure S2, Table 3). McGeoch et al. [26] and Ballesteros et al. [28]
did not find a diet-related effect on the insulin resistance or β-cell function.
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Table 2. Glucose control and insulin profiles.
Study Comparison FBG
(mmol/L)
PBG
(mmol/L)
FINS
(µU/mL)
PINS
(µU/mL) HbA1c (%) HOMA-IR
(µUˆmol/L2)
HOMA-B
(mU/mmol)
Reyna, 2003 [9] Modified diet V. baseline 0.37 ÓNA NA NA 0.40 Ó§, *NA NA
ADA’s diet V. baseline 0.39 ÓNA NA NA 0.20 Ó§NA NA
Ma, 2013 [16] Usual care V. baseline 0.22 Ó0.01 ÓNA NA 0.22 Ó0.11 ÓNA
Diet V. baseline 1.18 Ó§,a 2.49 Ó§,a NA NA 1.71 Ó§,a 0.27 Ó§NA
50 g-ONOG V. baseline 1.64 Ó§,a 3.25 Ó§,a NA NA 2.21 Ó§,a 0.11 ÓNA
100 g-ONOG V. baseline 1.91 Ó§,a,b 3.70 Ó§,a,b NA NA 2.22 Ó§,a,b 0.33 Ó§,a,c NA
Liatis, 2009 [17]β-glucan bread V. baseline 0.72 Ó§NA 3.23 Ó* NA 0.28 Ó§2.08 Ó* NA
White bread V. baseline 0.07 ÓNA 3.77 ÒNA 0.13 Ó1.33 ÒNA
Cugnet-Anceau, 2009 [18]β-glucan soup V. baseline 0.11 ÒNA NA NA 0.00 ÒNA NA
Control soup V. baseline 0.80 ÒNA NA NA 0.17 ÒNA NA
McGeoch, 2013 [26]Oat-enriched diet
V. habitual diet (baseline) 0.30 ÒNA 0.40 ÓNA 0.10 Ò0.10 Ò5.30 Ó
Standard dietary advice
V. habitual diet (baseline) 0.60 ÒNA 0.00 NA 0.20 Ò0.30 Ò1.00 Ó
Oat-enriched diet
V. standard dietary advice 0.30 ÓNA 0.40 ÓNA 0.10 Ó0.20 Ó4.30 Ó
Kabir, 2002 [27] Low-GIB (GI: 40%) V. baseline 0.30 ÓNA 2.78 ÒNA 0.50 ÓNA NA
High-GIB (GI: 64%) V. baseline 0.30 ÓNA 5.00 ÒNA 0.20 ÓNA NA
Ballesteros, 2015 [28]Oatmeal breakfast
V. egg breakfast 0.20 ÓNA 2.03 ÓNA 0.05 Ò0.60 ÓNA
Lammert, 2007 [29]After 2 days of
oatmeal V. baseline MBG: 2.39 Ó§MDI: 62.00 U/d Ó§NA NA NA
4 weeks after 2 days of
oatmeal V. baseline MBG: 0.94 ÓMDI: 46.80 IU/d Ó§0.40 ÓNA NA
Zerm, 2013 [30]Day 2 after 2 days of
oatmeal V. baseline MBG: 1.08 Ó§MDI: 62.00 U/d Ó§NA NA NA
Day 3 after 2 days of
oatmeal V. baseline MBG: 1.42 Ó§MDI: 36.60 IU/d Ó§NA NA NA
The changes from baseline in each diet pattern or the changes of the intervention diet relative to the control diet are estimated. FBG, fasting blood glucose; PBG, postprandial blood
glucose; FINS, fasting insulin; PINS, postprandial insulin; HbA1c, glycosylated hemoglobin; HOMA-IR, homeostasis model assessment of insulin resistance; HOMA-B, homeostasis
model assessment of β-cell function; ADA, American Diabetes Association; NA, not available; ONOG, organic naked oat with whole germ; GIB, glycemic index breakfast; GI,
glycemic index; MBG, mean blood glucose; MDI, mean daily insulin. §, changes were statistically significant from baseline (p< 0.05); *, changes from baseline were significantly
different between groups (p< 0.05); ap< 0.05, vs. usual care group; bp< 0.05, vs. diet group; cp< 0.05, vs. 50 g-ONOG plus diet group.
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Table 3. Pooled effects of oats intake on metabolic parameters of type 2 diabetic patients.
No. of Subjects Test of Heterogeneity
Variables No. of Studies Intervention Group Control Group MD 95% CI phI2(%) pz
FBG (mmol/L) 6 229 208 ´0.39 ´0.58, ´0.19 0.495 0.0 * <0.001
FINS (µU/mL) 2 36 31 ´0.22 ´1.28, 0.84 0.035 77.5 §0.681
HbA1c (%) 6 229 208 ´0.42 ´0.61, ´0.23 0.300 17.5 * <0.001
HOMA-IR (µUˆmol/L2)2 150 134 ´0.51 ´1.05, 0.02 0.107 61.6 §0.061
TC (mmol/L) 7 237 216 ´0.49 ´0.86, ´0.12 0.016 61.7 §0.010
LDL-C (mmol/L) 5 216 195 ´0.29 ´0.48, ´0.09 0.284 20.5 * 0.004
HDL-C (mmol/L) 6 229 208 ´0.05 ´0.24, 0.14 0.608 0.0 * 0.599
TG (mmol/L) 7 237 216 ´0.16 ´0.34, 0.03 0.351 10.2 * 0.097
Weight (kg) 3 158 142 ´0.10 ´0.33, 0.12 0.505 0.0 * 0.372
BMI (kg/m2)4 187 166 ´0.14 ´0.35, 0.07 0.566 0.0 * 0.205
FBG, fasting blood glucose; FINS, fasting insulin; HbA1c, glycosylated hemoglobin; HOMA-IR, homeostasis model assessment of insulin resistance; TC, total cholesterol; LDL-C,
low-density lipoprotein cholesterol; HDL-C, high-density lipoprotein cholesterol; TG, triglyceride; BMI, body mass index; MD, mean difference; CI, confidence interval. phand I2
were used for heterogeneity assessment by Cochran’s Q test, and ph< 0¨1 or I2> 50% was considered to indicate significant heterogeneity across the studies. pz,pvalue for Z test. *
The fixed-effects model was applied. §The random-effects model was applied.
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Figure2.Resultsofthemeta‐analysiscarriedouttoinvestigatetheeffectofoatsintakeonglycosylated
hemoglobinA1c(HbA1c).Thechangesfrombaseline(Mean±SD)betweenthetwogroupswere
compared.MD,meandifference;CI,confidenceinterval.
Figure3.Resultsofthemeta‐analysiscarriedouttoinvestigatetheeffectofoatintakeonfastingblood
glucose(FBG).Thechangesfrombaseline(Mean±SD)betweenthetwogroupswerecompared.MD,
meandifference;CI,confidenceinterval.
Figure 2. Results of the meta-analysis carried out to investigate the effect of oats intake on glycosylated
hemoglobin A1c (HbA1c). The changes from baseline (Mean ˘SD) between the two groups were
compared. MD, mean difference; CI, confidence interval.
Nutrients2015,7,page–page
8
Figure2.Resultsofthemeta‐analysiscarriedouttoinvestigatetheeffectofoatsintakeonglycosylated
hemoglobinA1c(HbA1c).Thechangesfrombaseline(Mean±SD)betweenthetwogroupswere
compared.MD,meandifference;CI,confidenceinterval.
Figure3.Resultsofthemeta‐analysiscarriedouttoinvestigatetheeffectofoatintakeonfastingblood
glucose(FBG).Thechangesfrombaseline(Mean±SD)betweenthetwogroupswerecompared.MD,
meandifference;CI,confidenceinterval.
Figure 3. Results of the meta-analysis carried out to investigate the effect of oat intake on fasting blood
glucose (FBG). The changes from baseline (Mean ˘SD) between the two groups were compared. MD,
mean difference; CI, confidence interval.
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3.3. Single Meal Responses of Glucose and Insulin
Table 4shows the glucose and insulin responses after oats intake. Six crossover studies [19–24]
compared the glucose or insulin responses between the single oatmeal with different amounts of
β-glucan and the control meal without β-glucan. Compared with the control meal, a single meal of
oatmeal significantly reduced the acute postprandial glucose or insulin responses in all six studies.
Specifically, the area under the curve (AUC) and the peak of glucose after oatmeal was 11.09% to
79.41% smaller (p< 0.05) and 26.38% to 81.82% lower (p< 0.05), respectively. The AUC of insulin was
18.89% to 67.74% smaller (p< 0.05) and the peak of insulin was 32.72% to 83.48% lower (p< 0.05).
Aβ-glucan dosage-dependent reduction in the glucose and insulin responses was observed in one
study [19].
Another three crossover trials [25–27] reported the glucose and insulin responses after a
relatively long term of oatmeal intervention. One study [25] with a follow-up duration of
two consecutive 12-week periods showed the AUCs of glucose and insulin after breakfast were
significantly smaller for the oat bran concentrate bread period than the white bread period (glucose
AUC: 41.98% smaller; insulin AUC: 24.52% smaller; both p< 0.05). The insulin peak after breakfast
was 15.24% lower (p< 0.05) in the oat bran concentrate bread period than in the white bread period.
There were no statistically significant differences in the glucose and insulin responses after lunch
between the two diet periods. One study [26] enrolled 27 type 2 diabetic patients only with diet
and lifestyle managements, and it did not find different diet-related effects on the postprandial
glucose and insulin responses between the oat-enriched diet period and the standard dietary advice
period. Kabir et al. [27] found that the low-glycemic index breakfast (low-GIB) with 3 g of β-glucan
from oats could induce lower acute postprandial glucose and insulin responses compared with the
high-glycemic index breakfast (high-GIB) without β-glucan at both the beginning and the end of a
four-week intervention (p< 0.05). However, there were no significantly chronic changes from baseline
within each group (p> 0.05).
Data from these nine studies illustrated that a single-oatmeal can significantly reduce the acute
postprandial glucose or insulin responses when compared with the control meal. However, the
changes of postprandial glucose or insulin responses after a relatively long period of oat intervention
were heterogeneous when compared with the same period of control food.
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Table 4. Single meal responses of glucose and insulin.
Study Comparison Glucose Response Insulin Response
AUC Peak AUC Peak
Tappy, 1996 [19] 4.0 g V. 0 g β-glucan 4 h: 29.00% Ó33.00% Ó#NA 4 h:33.00% Ó#
6.0 g V. 0 g β-glucan 59.00% Ó#58.00% Ó#NA 38.00% Ó#
8.4 g V. 0 g β-glucan 65.00% Ó#62.00% Ó#NA 41.00% Ó#
Jenkins, 2002 [20] Oat bran cereal (3.7 g β-glucan) V. white bread 3 h: 11.09% Ó#NA NA NA
β-glucan bar (6.2 g β-glucan) V. white bread 55.77% Ó#NA NA NA
β-glucan cereal (7.3 g β-glucan) V. white bread 46.78% Ó#NA NA NA
Rendell, 2005 [21] Prowash (9.9 g β-glucan) V. liquid meal replacer 3 h: 42.36% Ó#59.37% Ó#3 h: 67.74% Ó#83.48% Ó#
Prowash V. oatmeal (3.1 g β-glucan) 58.50% Ó#64.85% Ó#67.74% Ó#72.83% Ó#
Tapola, 2005 [22] Oat bran flour V. 12.5 g glucose load 1 h: 79.41% Ó#; 2 h:
60.17% Ó#81.82% Ó#NA NA
Oat bran crisp V. 12.5 g glucose load 1 h: 49.02% Ó#; 2 h:
21.19% Ó45.45% Ó#NA NA
25 g glucose load + 30 g oat bran flour
V. 25 g glucose load
1 h: 35.00% Ó#; 2 h:
22.00% Ó#34.00% Ó#NA NA
Yu, 2014 [23] SDF liquid (7.5 g β-glucan) V. SDF-free liquid NA 26.38% Ó#NA 32.72% Ó#
Braaten, 1994 [24]Wheat farina with oat gum
(8.8 g β-glucan) V. wheat farina 3 h: 20.35% Ó#26.76% Ó#3 h: 18.89% Ó#NA
Oat bran (8.8 g β-glucan) V. wheat farina 19.95% Ó#26.76% Ó#8.39% Ò#NA
Pick, 1996 [25] Oat bran concentrate bread V. white bread
Total 8 h: 46.06% Ó#;
breakfast (4 h): 41.98% Ó#;
lunch (4 h): 52.07% Ó
breakfast (4 h): 12.99% Ó;
lunch (4 h): 15.27% Ó
Total 8 h: 18.66% Ó;
breakfast (4 h): 24.52% Ó#;
lunch (4 h): 13.61% Ó
breakfast (4 h):
15.24% Ó#; lunch
(4 h): 10.99% Ó
McGeoch, 2013 [26] Oat-enriched diet V. habitual diet (baseline) 3 h: 8.75% Ò§NA 3 h: 3.84% ÒNA
Standard dietary advice V. habitual diet (baseline) 10.92% Ò§NA 3.99% ÒNA
Oat-enriched diet V. standard dietary advice 1.96% ÓNA 0.15% ÒNA
Kabir, 2002 [27] Low-GIB (GI: 40%) V. baseline 3 h: 14.58% Ò6.90% Ò3 h: 10.77% Ó8.00% Ò
High-GIB (GI: 64%) V. baseline 3.66% Ò2.00% Ò0.00% 4.76% Ó
The percentage changes from baseline in each diet pattern or the percentage changes of the intervention diet relative to the control diet are estimated. AUC, area under the curve;
NA, not available; SDF, soluble dietary fiber; GIB, glycemic index breakfast; GI, glycemic index. §, changes were statistically significant from baseline (p< 0.05); # changes were
significantly different between groups.
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3.4. Lipid Profiles
Nine studies assessed the changes of lipid profiles after oats interventions (Table 5). Five
studies [9,16,17,26,29] revealed a significant reduction in total cholesterol (TC) from baseline after
oats interventions, and this reduction ranged from ´0.10 to ´0.80 mmol/L (´2.00 to ´12.80 percent)
(p< 0.05). Moreover, the relative reduction in TC from baseline was significantly greater in the
oats intervention group than that in the control group in two randomized, parallel controlled
studies (p< 0.05) [16,17]. One crossover study [27] showed a significantly different change in TC
between compared periods even though the relative change from baseline within each period was not
significant (low-GIB: ´0.30 mmol/L; high-GIB: +0.20 mmol/L; both p> 0.05). The other two crossover
studies [25,26] showed that the TC level was significantly lower in the oats intervention period than in
the control food period (´0.74 and ´0.20 mmol/L, respectively) (both p< 0.05). Overall, a significant
reduction in TC was observed in subjects who consumed oats than in the control subjects (MD,
´0.49 mmol/L; 95% CI, ´0.86 to ´0.12 mmol/L; p= 0.010) (Figure S3, Table 3). Eight studies reported
the changes of low-density lipoprotein cholesterol (LDL-C), among which three randomized, parallel
controlled studies [9,16,17] indicated a significant reduction from baseline (´0.22 to ´0.66 mmol/L)
(´7.30 to ´15.79 percent) (p< 0.05). One crossover study [25] showed that the concentration of LDL-C
was 0.77 mmol/L lower (p< 0.05) in the oat bran concentrate period than that in the white bread
period. On the whole, oats intake significantly decreased LDL-C values (MD, ´0.29 mmol/L; 95% CI,
´0.48 to ´0.09 mmol/L; p= 0.004) (Figure S4, Table 3). Among the nine studies reporting HDL-C,
two randomized, parallel controlled studies [9,18] indicated a significant increase from baseline (+0.15
and +0.05 mmol/L, respectively) (both p< 0.05) in the oats intervention group. Additionally, the
relative increase from baseline was significantly greater in the oats intervention group than in the
control group in one study (intervention group: +0.15 mmol/L; control group: +0.01 mmol/L) (both
p< 0.05) [9]. However, one randomized parallel controlled study [16] with two oats intervention
groups showed a slight reduction in HDL-C from baseline (´0.06 and ´0.08 mmol/L; both p< 0.05),
while the HDL-C level in the usual care group was almost unaltered. Overall, oats intake did
not significantly affect HDL-C concentrations (MD, ´0.05 mmol/L; 95% CI, ´0.24 to 0.14 mmol/L;
p= 0.599) (Figure S5, Table 3). Nine studies reported triglyceride (TG), two randomized, parallel
controlled studies [16,18] and one uncontrolled observational study [29], which showed a significant
reduction from baseline (´0.12, ´0.53 and ´0.68 mmol/L, respectively) (all p< 0.05) after oats
interventions. Additionally, the relative changes from baseline differed significantly between the oats
intervention group and the control group in two studies (p< 0.05) [16,18]. On the whole, compared
with the control dietary, dietary with oats did not significantly decreased the concentrations of TG
(MD, ´0.16 mmol/L; 95% CI, ´0.34 to 0.03 mmol/L; p= 0.097) (Figure S6, Table 3).
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Table 5. Blood lipids and anthropometry parameters after interventions.
Study Comparison TC (mmol/L) LDL-C (mmol/L) HDL-C (mmol/L) TG (mmol/L) Weight (kg) BMI (kg/m2)
Reyna, 2003 [9] Modified diet V. baseline 0.38 Ó§0.26 Ó§0.15 Ò§,*0.25 Ó3.20 Ó§,* 1.20 Ó§,*
ADA’s diet V. baseline 0.17 Ó0.03 Ó0.01 Ò0.34 Ó1.50 Ó§0.40 Ó§
Ma, 2013 [16] Usual care V. baseline 0.01 Ó0.02 Ò0.01 Ò0.08 Ó0.37 Ó0.14 Ó
Diet V. baseline 0.23 Ó§,a 0.03 Ó0.07 Ó§,a 0.41 Ó§0.86 Ó§0.31 Ó§
50 g-ONOG V. baseline 0.47 Ó§,a,b 0.22 Ó§,a,b 0.06 Ó§,a 0.13 Ó0.79 Ó§0.28 Ó§
100 g-ONOG V. baseline 0.59 Ó§,a,b 0.31 Ó§,a,b 0.08 Ó§,a 0.53 Ó§,a,c 1.17 Ó§,a 0.45 Ó§,a
Liatis, 2009 [17]β-glucan bread V. baseline 0.80 Ó§, * 0.66 Ó§,*0.05 Ó0.21 Ó1.03 Ó§0.38 Ó§
White bread V. baseline 0.12 Ó0.11 Ó0.03 Ó0.06 Ó0.39 Ó0.12 Ó
Cugnet-Anceau, 2009
[18]β-glucan soup V. baseline 0.06 Ó0.05 Ó0.05 Ò§0.12 Ó§,*NA 0.18 Ò
Control soup V. baseline 0.01 Ò0.10 Ó0.03 Ò0.12 Ò§NA 0.36 Ò
Pick, 1996 [25] Oat bran concentrate bread V. white bread 0.74 Ó#0.77 Ó#0.08 Ò0.11 ÓNA NA
McGeoch, 2013 [26] Oat-enriched diet V. habitual diet (baseline) 0.10 Ó§0.10 Ó0.00 0.16 Ò0.30 Ò§0.20 Ò§
Standard dietary advice
V. habitual diet (baseline) 0.10 Ò§0.10 Ò0.10 Ò0.13 Ò0.30 Ó§0.10 Ó§
Oat-enriched diet
V. standard dietary advice 0.20 Ó#0.20 Ó0.10 Ó0.03 Ò0.60 Ò#0.30 Ò#
Kabir, 2002 [27] Low-GIB (GI: 40%) V. baseline 0.30 Ó* NA 0.03 Ò0.10 ÒNA NA
High-GIB (GI: 64%) V. baseline 0.20 ÒNA 0.03 Ó0.20 ÓNA NA
Ballesteros, 2015 [28] Oatmeal breakfast V. egg breakfast 0.10 Ó0.10 Ó0.03 Ó0.05 Ò0.00 0.00
Lammert, 2007 [29] After 2 days of oatmeal V. baseline 0.47 Ó§0.36 Ó0.03 Ó0.68 Ó§NA NA
4 weeks after 2 days of oatmeal V. baseline 0.00 0.13 Ó0.10 Ò0.41 ÓNA NA
The changes from baseline in each diet pattern or the changes of the intervention diet relative to the control diet are estimated. TC, total cholesterol; LDL-C, low-density lipoprotein
cholesterol; HDL-C, high-density lipoprotein cholesterol; TG, triglyceride; BMI, body mass index; ADA, American Diabetes Association; ONOG, organic naked oat with whole germ;
NA, not available; GIB, glycemic index breakfast; GI, glycemic index. §, changes were statistically significant from baseline (p< 0.05); *, changes from baseline were significantly
different between groups (p< 0.05); # changes were significantly different between groups; ap< 0.05, vs. usual care group; bp< 0.05, vs. diet group; cp< 0.05, vs. 50 g-ONOG plus
diet group.
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3.5. Weight and Body Mass Index
There were six studies reporting the changes of weight or BMI. Three randomized, parallel
controlled studies [9,16,17] showed a significant reduction during the follow-up of three to
four weeks. The reduction range of weight and BMI was ´0.32 to ´0.79 kg (p< 0.05) and ´1.20
to ´0.28 kg/m2(p< 0.05), respectively. Only one crossover study [26] found a slight increase
from baseline in weight (+0.60 kg; p< 0.05) and BMI (+0.30 kg/m2;p< 0.05) compared with
those in standard dietary advice within 8-week follow-up. The overall changes of both the weight
(MD, ´0.10 kg; 95% CI, ´0.33 to 0.12 kg; p= 0.372) and BMI (MD, ´0.14 kg/m2; 95% CI, ´0.35 to
0.07 kg/m2;p= 0.205) were not significantly different between the control dietary and the dietary
with oats (Figures S7 and S8, Table 3).
3.6. Quality of Evidence
One critical outcome and nine important outcomes were assessed by the GRADE system.
The detailed information of evidence quality is presented in Table S4.
4. Discussion
The present systematic review of 16 studies has demonstrated a moderately beneficial effect of
oats intake on glycemic control and lipid profiles in patients with type 2 diabetes. To our knowledge,
this is the first systematic review of oats consumption in patients with type 2 diabetes. On the whole,
this review has revealed an improvement of glucose, insulin sensitivity and lipid profiles after oats
consumption. Compared with a control meal, a single meal of oatmeal also showed superiority of
acute glucose and insulin responses.
Among the eight studies investigating HbA1c, three randomized, parallel controlled studies [9,16,17]
showed a significant reduction in HbA1c from baseline in the oats diet group (absolute change:
´0.28%, ´0.40% and ´2.22%, respectively). Ma et al. [16] revealed the greatest beneficial effect of
oats intake on diabetic patients with the following features: First, compared with common oats
products, naked oats maintain the most ingredients and beneficial nutrients of the whole-oat grains,
which indicates naked oats might be better for patients with diabetes. Second, a relatively large
sample size (260 participants) in this study seemed to be more likely to get a positive result. Third,
the baseline glucose level was relatively high (mean HbA1c 9.87%, mean FBG 9.99 mmol/L, mean
PBG 18.77 mmol/L). Forth, a diet with low energy, low fat and high fiber was provided to all the
participants in both the intervention and the control groups, indicating oats consumption might
show its benefits especially when the general energy intake was low. However, Kabir et al. [27]
showed that adding 3 g of β-glucan from oats to a low-glycemic index breakfast with cereal, milk,
bread and butter could not lead to a significant chronic changes (four week-baseline) in FBG, FINS
and HbA1c. It may be due to the fact that the original study mainly aimed to evaluate the effects
of a low-glycemic index breakfast on the glucose and lipid metabolism in type 2 diabetic patients.
Thus, the test meal was focused on the glycemic index of food rather than the ingredients of food
such as oats. Therefore, the results of this study are less meaningful for evaluating the beneficial
effects of oats intake on type 2 diabetes. On the other hand, it suggests that a background diet with
added oats is important for the total effect. The above evidence suggests that adding naked oats
to a calorie-restricted diet might help type 2 diabetic patients to get a more obvious hypoglycemic
effect especially in those with a high level of blood glucose. The amounts of β-glucan were greater
than or equal to 3 g in most oats dietaries of the included studies. Tappy et al. [19] revealed a
dosage-dependent association between the amount of β-glucan in breakfast cereal and the response
of postprandial glucose. Additionally, this inverse liner relationship was more obvious at low doses
of β-glucan (below 6 g). The results of this study were confirmed by previous reports, which also
showed a significant dose-dependent relationship between the hypoglycemic effect and the amount
or the log viscosity of oats [31,32]. These findings will help in deciding the appropriate dose of oats
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or β-glucan included in the whole food system. As the UK Prospective Diabetes Study (UKPDS)
Group revealed, a 1% reduction in HbA1c was associated with a 21% and 14% reduction in the risk
of death related to diabetes and all-cause mortality, respectively [33]. That is to say, the magnitudes
of the statistically significant reduction in HbA1c in the present review would translate to a clinically
significant reduction in the risk of death related to diabetes (´8.82%) and overall mortality (´5.88%).
Compared with the controls, oats intake significantly reduced the concentrations of TC and
LDL-C. The findings in the present review are consistent with previous systematic reviews or
meta-analyses which also showed a significant reduction in TC and LDL-C after oats or oats β-glucan
consumption at the general population level [34–36]. This review also revealed a decreasing tendency
in TG, which was omitted previously [34,36]. This decreasing tendency may partly be explained by
the relatively high baseline level of TG in type 2 diabetic patients in our review. Interestingly, two oats
intervention groups in one study [16] showed a slight reduction from baseline in HDL-C (´0.06 and
´0.08 mmol/L, respectively; both p< 0.05), while two studies [9,18] showed a slight increase in
HDL-C from baseline (+0.15 and +0.05 mmol/L, respectively; both p< 0.05). The slight reduction
in HDL-C in this study may partly be due to the side effect of a low-cholesterol and saturated-fat diet
as the author of the original study discovered [37]. Whether this slight reduction would produce
clinical significance remains to be determined. Some inconsistent results about the effect of oats
intake on HDL-C at the general population level were also reported, Tiwari et al. [35] revealed an
increase in HDL-C after oats intake, while Thies et al. [34] found a non-significant effect of oats intake
on HDL-C. A characteristic pattern of diabetic dyslipidemia, which consists of a mild to marked
elevation of TG and low level of HDL-C [38], may partly account for the discrepancy between the
general population and the diabetic patients. Therefore, further analysis is necessary to confirm the
lipids (especially HDL-C and TG) changes after oats consumption in the diabetic and non-diabetic
people separately. Previous evidence showed that each 1% reduction in TC or LDL-C was associated
with a 2% or 1% reduction in the risk of coronary heart disease, respectively [39]. This means the
effect of oats-containing diets in this review would translate to an additional 4.00 to 25.60% reduction
in coronary heart disease risk due to the lipid benefits from oats intake.
Overall, oats intake was associated with a slight decrease in body weight and BMI, but the
difference was not significant. To be noted, body weight increased slightly following the oat-enriched
diet compared with standard dietary advice in only one study [26], with an excess total energy and
the glycemic load in the oat-enriched dietary plan. It indicated that total energy as well as other
dietary components should be very carefully considered during the assessment of oats consumption
in patients with diabetes.
Oats are classified as a kind of whole grain which is different from other grains. They are
particularly high in soluble fiber, β-glucan and some micronutrients such as magnesium. The unique
components and special physic-chemical properties largely decide the beneficial effects of oats. The
beneficial effects of oats on glycemia and blood lipids are mainly related to oats β-glucan, a soluble
and fermentable fiber, which cannot be decomposed and absorbed in the small intestine but can
be fermented in the colon. The β-glucan is reported to increase the viscosity of food bolus, delay
gastric emptying and lengthen intestinal transit time, slow the absorption of nutrients especially the
carbohydrates, and enhance the satiety [6,40–43]. It was also reported that β-glucan could slow the
appearance of glucose in plasma, resulting in longer-lasting insulin secretion which exert a prolonged
inhibition of endogenous glucose production and lipolysis [44]. Apart from β-glucan, oats are also
a rich source of magnesium, which is an important co-factor for many enzymes including enzymes
involved in the metabolism of glucose and insulin. Additionally, an inverse association between
magnesium in relation to type 2 diabetes was reported [45]. A group of phenolic compounds named
avenanthramides have been found in oats. Avenanthramides are traditionally considered a kind
of antioxidant. Some other important effects of avenanthramides, such as enhanced endothelial
function and anti-inflammatory properties, were reported recently. Thus, avenanthramides as well
as some other antioxidants including vitamin E from oats could synergistically contribute to the
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beneficial effects on diabetes and the subsequent complications such as dyslipidemia, atherosclerosis
and cardio-cerebrovascular diseases [46]. The dosage, chemical structure, molecular weight (MW),
solubility and viscosity are key influential factors for the health effects of oats. Additionally, the above
factors are affected by the variety and growing conditions, the processing and food preparations, and
even the physiological disposition of oats in vivo [7,47]. The mechanisms of lowing cholesterol are
not very clear, but it is suggested that β-glucan can bind with bile acids and increase the intestinal
viscosity, thereby decreasing cholesterol absorption and increasing fecal bile acid excretion [48].
The variety of oats may also be an important source of the heterogeneity among studies included
in the present systematic review.
The argument of oats might be raised due to its potential association with asthma, coeliac
disease, dermatitis and some other allergic conditions. However, another different viewpoint has
indicated that the possible association may result from a wheat contamination which contains gluten.
Gluten is a group of seed storage proteins of cereals. It is also widely used in food manufacturing,
usually as an ingredient and processing aid, due to its viscoelastic properties [49–51]. Pure oats
contain avenins, which are less likely to cause allergies. However, gluten is still added to most
oat breads to produce the needed elasticity and structure of bread [48]. In the current review, we
did not find evidence about the relationship between oats consumption and allergic reactions or
diseases. Caution is still needed to add oats to the diet of wheat hypersensitive patients. It is better
to use pure oats without wheat contamination. The relationship between infant exposure to oats
and the development of type 1 diabetes has been thoroughly discussed recently. Introducing oats
early (<4 months of age) or late (ě6 months of age) in the infancy was reported to be related to the
development of type 1 diabetes [52,53]. The American Academy of Pediatrics also recommended
to introduce solid foods including oats between 4 and 6 months of age [54]. For children with
susceptibility to type 1 diabetes, the introduction of oats would be with great caution. Further
investigation about the safety of oats consumption in diabetic patients is required.
There are several limitations in the present review. Firstly, the limited number of studies included
and the small number of participants involved in each study might not have sufficient power to detect
a definite effect. Secondly, we failed to find evidence of oats consumption in patients with type 1
diabetes, which has a different pathogenesis and clinical feature from type 2 diabetes. Thirdly, the
safety of oats consumption was not assessed due to insufficient data.
5. Conclusions
In conclusion, the present systematic review has revealed a beneficial effect of oats consumption
on glucose and lipid profiles in patients with type 2 diabetes, and could therefore be recommended
to patients. Naked oats, having low calories, might provide more benefits and a recommendation of
3 g or more per day of β-glucan might be beneficial. The effects of oats intake on type 1 diabetes and
the safety of oats consumption should also be investigated in the future.
Supplementary Materials: Supplementary materials can be accessed at: http://www.mdpi.com/
2072-6643/7/12/5536/s1. Table S1: Diets of studies included. Table S2: Methodological quality of studies
included based on modified Jadad scale. Table S3: Methodological quality of studies included based on
Newcastle-Ottawa Scale. Table S4. GRADE evidence profile of the metabolic effects of oats intake in patients
with type 2 diabetes. Figure S1. Results of the meta-analysis carried out to investigate the effect of oat intake
on fasting insulin (FINS). The changes from baseline (Mean ˘SD) between the two groups were compared.
MD, mean difference; CI, confidence interval. Figure S2. Results of the meta-analysis carried out to investigate
the effect of oat intake on homeostasis model assessment-insulin resistance (HOMA-IR). The changes from
baseline (Mean ˘SD) between the two groups were compared. MD, mean difference; CI, confidence interval.
Figure S3. Results of the meta-analysis carried out to investigate the effect of oat intake on total cholesterol (TC).
The changes from baseline (Mean ˘SD) between the two groups were compared. MD, mean difference; CI,
confidence interval. Figure S4. Results of the meta-analysis carried out to investigate the effect of oat intake on
low-density lipoprotein cholesterol (LDL-C). The changes from baseline (Mean ˘SD) between the two groups
were compared. MD, mean difference; CI, confidence interval. Figure S5. Results of the meta-analysis carried
out to investigate the effect of oat intake on high-density lipoprotein cholesterol (HDL-C). The changes from
baseline (Mean ˘SD) between the two groups were compared. MD, mean difference; CI, confidence interval.
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Figure S6. Results of the meta-analysis carried out to investigate the effect of oat intake on triglyceride (TG).
The changes from baseline (Mean ˘SD) between the two groups were compared. MD, mean difference; CI,
confidence interval. Figure S7. Results of the meta-analysis carried out to investigate the effect of oat intake on
weight. The changes from baseline (Mean ˘SD) between the two groups were compared. MD, mean difference;
CI, confidence interval. Figure S8. Results of the meta-analysis carried out to investigate the effect of oat intake
on body mass index (BMI). The changes from baseline (Mean ˘SD) between the two groups were compared.
MD, mean difference; CI, confidence interval
.
Acknowledgments: This study was funded by the National Natural Science Foundation of China (Grant No.
81400811) and Scientific Research Project of Health and Family Planning Commission of Sichuan Province
(Grant No. 150149).
Author Contributions: S. L. and H. T. conceived and designed the study. Q. H. and Y. L. performed data
extraction and drafted the manuscript. Q. H., Y. L., G. C., S. L., and H. T. discussed study findings and clinical
interpretation. L. L. and X. S. provided methodological supervision of the manuscript. L. L., G. C., X. S., S. L.
and H. T. revised the manuscript for publication.
Conflicts of Interest: The authors declare no conflict of interest.
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