Effect of Vitamin D Supplementation on Weight Loss, Glycemic Indices, and Lipid Profile in Obese and Overweight Women: A Clinical Trial Study

Abstract

Introduction
Vitamin D (vit D) deficiency has defined as a health problem worldwide. World Health Organization (WHO) has declared that obesity is an epidemic of the 21st century. Previous studies have shown that obesity may increase the risk of Vit D deficiency. Furthermore, other studies have demonstrated that vit D insufficiency was accompanied with higher risk of type 2 diabetes, cardiovascular diseases, hypertension, and obesity. The aim of this study was to survey the effect of vit D supplementation on weight loss among overweight and obese women aged 20–40 years in Isfahan.

Methods
This double-blind clinical trial was done on 50 overweight and obese women who were divided into two groups, in which one group received vit D supplements and the other group received placebo. Intervention group received vit D with dozes 50,000 IU/w for 6 weeks. The levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), fasting blood sugar (FBS), insulin (ins), homeostasis model assessment of ins resistance (IR), C-reactive protein (CRP), height, weight (WT), waist circumference (WC), hip circumference (HC), and blood pressure (BP) were measured before and after intervention.

Results
After using vit D supplementation for 6 weeks, WT, WC, and body mass index (BMI) were decreased significantly and serum vit D increased significantly compared to control group (P < 0.001). Other factors including TC, TG, LDL-c, HDL-c, FBS, CRP, ins, IR, and waist to hip ratio (WHR) did not change significantly (P > 0.05).

Conclusions
After 6 weeks of intervention, the means of WT, BMI, WC, and HC decreased significantly. Previous studies have shown that vit D deficiency was more prevalence in obese people and there was an inverse association among vit D with BMI and WC. The relationship between vit D and lipid profiles such as glycemic indexes, anthropometric indexes, CRP, and BP is not clear and needs more study in the future.

Full text

1© 2018 International Journal of Preventive Medicine | Published by Wolters Kluwer - Medknow
Introduction
Vitamin D (vit D) deciency is considered
as a health problem worldwide. Nowadays,
vit D deciency has involved more than
half of people worldwide.[1] The prevalence
of vit D deciency in Tehran and Isfahan
was estimated about 81/3% and 70/16%,
respectively.[2] vit D plays an important role
in calcium metabolism, maintenance of the
skeleton, control of cell proliferation and
differentiation, and immunity.[3] Recently,
it has been shown that vit D deciency
has a strong relationship with increased
risk of type 2 diabetes, cardiovascular
disease (CVD) as well as CVD risk
factors such as hypertension and
obesity.[4] Obesity was recognized as an
epidemic of the 21st century by World
Health Organization (WHO)[5] and it is a
serious health problem worldwide.[5,6] Since
Address for correspondence:
Dr. Mohammad Hasan Entezari,
Department of Clinical
Nutrition/Community
Nutrition/Food Science and
Technology, Food Security
Research Center, School of
Nutrition and Food Science,
Isfahan University of Medical
Sciences, Isfahan, Iran.
E‑mail: entezari@hlth.mui.ac.ir
Abstract
Introduction: Vitamin D (vit D) deciency has dened as a health problem worldwide. World
Health Organization (WHO) has declared that obesity is an epidemic of the 21st century. Previous
studies have shown that obesity may increase the risk of Vit D deciency. Furthermore, other studies
have demonstrated that vit D insufciency was accompanied with higher risk of type 2 diabetes,
cardiovascular diseases, hypertension, and obesity. The aim of this study was to survey the effect
of vit D supplementation on weight loss among overweight and obese women aged 20–40 years in
Isfahan. Methods: This double‑blind clinical trial was done on 50 overweight and obese women
who were divided into two groups, in which one group received vit D supplements and the other
group received placebo. Intervention group received vit D with dozes 50,000 IU/w for 6 weeks.
The levels of total cholesterol (TC), triglyceride (TG), low‑density lipoprotein cholesterol (LDL‑c),
high‑density lipoprotein cholesterol (HDL‑c), fasting blood sugar (FBS), insulin (ins), homeostasis
model assessment of ins resistance (IR), C‑reactive protein (CRP), height, weight (WT), waist
circumference (WC), hip circumference (HC), and blood pressure (BP) were measured before and
after intervention. Results: After using vit D supplementation for 6 weeks, WT, WC, and body mass
index (BMI) were decreased signicantly and serum vit D increased signicantly compared to control
group (P < 0.001). Other factors including TC, TG, LDL‑c, HDL‑c, FBS, CRP, ins, IR, and waist to
hip ratio (WHR) did not change signicantly (P > 0.05). Conclusions: After 6 weeks of intervention,
the means of WT, BMI, WC, and HC decreased signicantly. Previous studies have shown that vit
D deciency was more prevalence in obese people and there was an inverse association among vit
D with BMI and WC. The relationship between vit D and lipid proles such as glycemic indexes,
anthropometric indexes, CRP, and BP is not clear and needs more study in the future.
Keywords: Blood pressure, cholesterol, high‑density lipoprotein, low‑density lipoprotein,
triglyceride, Vitamin D supplementation, weight loss, glycemic indices
Effect of Vitamin D Supplementation on Weight Loss, Glycemic Indices,
and Lipid Prole in Obese and Overweight Women: A Clinical Trial Study
Original Article
Zahra Sadat
Khosravi,
Marzieh Kafeshani1,
Parastoo Tavasoli,
Akbar Hassan Zadeh2,
Mohammad Hassan
Entezari1
Departments of Clinical
Nutrition and 1Clinical
Nutrition/Community Nutrition/
Food Science and Technology,
Food Security Research Center,
School of Nutrition and Food
Science, Isfahan University of
Medical Sciences, Isfahan, Iran,
2Department of Epidemiology
and Biostatic, School of Health,
Isfahan University of Medical
Sciences, Isfahan, Iran
How to cite this article: Khosravi ZS, Kafeshani M,
Tavasoli P, Hassan Zadeh A, Entezari MH. Effect
of Vitamin D supplementation on weight loss,
glycemic indices, and lipid prole in obese and
overweight women: A clinical trial study. Int J Prev
Med 2018;9:63.
19th century, the prevalence of obesity has
increased along with changes in diets and
lifestyle factors.[7] WHO estimated that at
least 300 million adults are obese and more
than 1 billion are overweight worldwide.[7,8]
It is proved that 3.4 million of obese and
overweight people are died due to obesity
and comorbidities including hypertension,
type 2 diabetes, stroke, CVD, some type
of cancer such as prostate, breast, ovary,
cervix, colon, and gallbladder every
year.[5,9] In addition, obesity is related
with hypercholesterolemia, osteoarthritis,
gastroesophageal reux, sleep apnea, and
kidney chronic disease.[10] Furthermore, this
issue becomes a general health problem
In Iran. The prevalence of obesity and
overweight was 42% in men and 57% in
women in 2005, and it was anticipated
to reach 54% and 74% among men and
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Khosravi, et al.: Vitamin D supplementation, weight loss, glycemic indices, and lipid prole
International Journal of Preventive Medicine 2018, 9: 632
women, respectively by 2015.[11] A study In Iran showed
that obesity in women are more than twice than men.[12]
In a performed study in Isfahan, all women over than
65 years had abdominal obesity.[13] Lifestyle modication
such as proper exercise is the best and cheapest way for
decreasing the obesity. In addition, diet plays a key role in
weight loss programs.[7] Today’s attention toward the role
of vit D in chronic diseases such as obesity is increasing.
Based on several studies, obese and overweight people
mostly have a lower levels of vit D than those who have
less body fat.[14] Some studies suggested that obesity
increased risk of vit D deciency[15] whereas other studies
shown that insufcient levels of vit D could increase
the risk of type 2 diabetes, CVD, and risks such as
hypertension and obesity.[16] A previous study has shown
that vit D deciency is more common in obese people.
It was seen that there is an inverse association
among vit D with body mass index (BMI) and waist
circumference (WC).[4,17‑20] However, conicting results
had been seen such as a study among Iranian individuals
aged 20–64 years with BMI of 24.2 ± 3.8 (57% female)
which has not shown signicant association between
serum levels of vit D and BMI.[4] In this study, we tried
to perform a comprehensive assessment about the effects
of vit D supplementation and body weight as well as other
anthropometric measurements, BP, lipid prole, glycemic
indices, and C‑reactive protein (CRP) among Iranian
women. Therefore, our main purpose was to examine the
effect of vit D on weight loss in obese and overweight
women aged 20–40 years in Isfahan.
Methods
Subjects
This double‑blind clinical trial study was performed
among overweight and obese women in Isfahan
endocrine and metabolism center, and other participants
were female students of Isfahan University of Medical
Science. Convenient method was used to enroll
participants to the study. The following inclusion criteria
was used to select participants: 20–40 years females,
BMI higher than 25 (obese and overweight), nonsmoking,
no history of diabetes, no hyperthyroids and hypothyroids,
no participation in other weight loss programs, no weight
loss during two past months, regular menstrual cycle,
and no pregnancy. The general questionnaire included
information about demographic characteristics such as
location, education level, marital status and the number
of pregnancy and children. In addition, we asked other
questions about physical activity, the duration and times
of sleep, consumption of supplements, and being on a
special of diet. After giving general overview about this
study, all individuals provided informed written consent.
Study design
The aim of this double‑blind clinical trial study was to
evaluate the effect of vit D supplementation on weight
loss in 20–40 years obese and overweight women in
Isfahan. The enough sample size was 25 person in each
group that calculated according to the following formula
N = (z1+z2)² 2s²/d². In this formula, α was considered
0.05 and β was 80%. Hence, we recruited 75 persons to
compensate potential losses during 6 weeks at follow‑up.
After that, individuals were randomly divided into two
groups (intervention and control) and received vit D
supplements and placebo, respectively. The participants
continued their usual diet during the study. The
intervention follow‑up was 6 weeks that began from May
21, 2013 to July 5, 2013. At the rst visit, we gave 6 pearls
of vit D supplements to intervention group and 6 pearls of
placebo to the controls and we asked them to eat one per
week. Supplements were made in Zahravi pharmaceutical
company, Tabriz, Iran. The dozens of supplements were
50,000 IU and placebo had the same shape, color, and
packaging with given supplement. In addition, at the rst
meeting, food record has been explained to the individuals
and they were asked to prepare it for 3 days including one
weekend and 2 week days. Furthermore, the individuals
were asked to report their physical activity during one
selected week. In addition, participants recorded their
daily amount of sun exposure from sunrise till sunset.
The levels of total cholesterol (TC), triglyceride (TG),
low‑density lipoprotein cholesterol (LDL‑c), high‑density
lipoprotein cholesterol (HDL‑c), fasting blood
sugar (FBS), insulin (ins), homeostasis model assessment
of ins resistance (HOMA‑IR), CRP, vit D, height (ht),
WT, WC, blood pressure (BP), and BMI were measured
at the beginning and the end of study. Furthermore,
anthropometric indicators and BP were measured. ht
was measured by tape without shoes, nearest to the
0.1 cm, and for weight, we used a Beshel model digital
scale (Germany) nearest to the 0.1 kg that individuals
wore light clothing with no shoes. BMI was calculated
with this formula, BMI = weight (kg)/height² (m). BMI
between 24/9 and 29/9 was dened as overweight and
more than 29/9 was dened obese. Individuals’s BP
was measured by trained personnel using a mercury
sphygmomanometer, after 10 min of rest in a sitting
position.
Biochemical analysis
Blood samples were taken in a sitting position following
12–14 h overnight fasting before and after the intervention.
FBS, lipid proles, and CRP were measured by biochemical
autoanalyzer A15 with Biosystem kit (made by Spain).
ELISA method was used to determine concentration of vit
D and ins. In addition, we obtained the ins sensitivity with
using this formula: (fasting ins [micro unit/ml] * fasting
glucose [micro mol/l]/22.5).[8]
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Khosravi, et al.: Vitamin D supplementation, weight loss, glycemic indices, and lipid prole
International Journal of Preventive Medicine 2018, 9: 63 3
Statistical analysis
Normal distributions of all variables were analyzed by the
Kolmogorov–Smirnov test and by evaluating the histogram
curves. All variables had normal distribution. Analyses
were performed with independent t‑test and paired t‑test.
The data were analyzed with SPSS version 20 (IBM,
Armonk, NY, USA). The signicance was considered 0.05.
Independent t‑test and Chi‑square was used to comparison
the general characteristics of participants.
Results
From 75 potentially eligible participants, 6 persons were
excluded due to the personal reasons, 8 persons had
normal serum levels of vit D, and 5 blood specimens
were devastated due to the laboratory personnel mistake.
We could not take blood from 3 participants because
of high weight. Hence, they were eliminated. Finally,
we had 53 individuals that 26 of them were assigned
to intervention group and 27 of them were entered into
control group. The baseline characteristics of 53 obese and
overweight women are shown in Table 1. Anthropometric
variables of participants are presented in Table 2.
According to data, there were no signicantly differences
in baseline anthropometric variables between intervention
and control groups except WC which was signicantly
higher (P = 0.04) in intervention group. The analysis showed
that in intervention group, the means of weight, BMI, and
WC were reduced signicantly (73.2 ± 7.6–71.6 ± 7.7,
28 ± 2.7–27.2 ± 2.8, 90.4 ± 7.2–88 ± 7.5, respectively)
(P < 0.001), but WHR (0.85 ± 0.05–0.84 ± 0.06) did
not change signicantly [Table 2]. As it has shown in
Table 3, there were no differences in means of dietary
energy, macronutrient, and micronutrient such as vit D of
participants between two groups. Biochemical variables
were reported in Table 4. The assessment of biochemical
markers (HDL‑c, LDL‑c, TC, TG, FBS, Ins, HOMA‑IR) in
two groups shown that there were no signicant differences
in all of the biochemical variables (P > 0.05), except for
the vit D that was 21.9 ± 6.5 in intervention and 18.1 ± 4.8
in control groups (P < 0.01). The mean of differences in
anthropometric and laboratory variables were presented
in Table 5. After calculating the mean of differences in
two groups, it was cleared that intervention with the vit
D (P < 0.001) decreased the means of weight (1.6 ± 1.3),
BMI (0.6 ± 0.5), and WC (2.3 ± 1.1) and increased
the mean of vit D (62 ± 29, P < 0.001). Furthermore,
after adjusting for age, the means of the vit D was
signicant (83.49 ± 5.43, 34.2 ± 5.33 P = 0.001).
Discussion
The ndings of this double‑blind clinical trial study in obese
and overweight women aged 20–40 years showed that
supplementation of the vit D with dozes 50,000 IU/w for
6 weeks reduced signicantly the mean of BMI, weight, WC,
and on the other hand, it increased signicantly the level of
vit D in comparison with the control group. However, there
were no signicant effect of the vit D on other factors such
Table 1: Baseline characteristics of the participants†
Parameter Intervention
(n=260)
Control
(n=27)
P*
Age 29.1±9.6 26.9±9.1 0.4
The number of children 1.0±1.3 0.48±0.93 0.06
Job (%)
Homeworker 30.80 25.90 0.54
Student 53.80 66.70
Employee 15.40 7.4
Marital status (%)
Single 53.80 33.3 0.13
Married 46.20 66.70
Education level (%)
Less than high school 3.8 11.10 0.24
High school and higher 46.2 18.50
College education and higher 50.00 70.40
Physical activity (min/week) 874.8±697.1 604.5±643.4 0.14
Sun exposure (min/day) 49.6±40 61.5±49.3 0.34
*P<0.05 is signicant; obtained from independent t‑test and
χ2, †Values are mean±SD. SD=Standard deviation
Table 2: Anthropometric variables of the participants
Variables Intervention
(n=26)
Control
(n=27)
P*,‡
Weight (kg)
Baseline 73.2±7.6 70.3±9 0.02
End 71.6±7.7 70.3±9
P*0.001 0.81
Height 162±7 158.8±6 0.8
BMI (kg/m²)
Baseline 28±2.7 27.8±2.6 0.91
End 27.2±2.8 27.8±2.7 0.4
P*0.001 0.81
WC (cm)
Baseline 90.4±7.2 86±8 0.04
End 88±7.5 86.3±8.5 0.42
P*0.001 0.27
WHR
Baseline 0.85±0.05 0.81±0.05 0.4
End 0.84±0.06 0.82±0.06 0.4
P*0.23 0.44
SBP (mmHg)
Baseline 112.7±8.5 112.5±5 0.9
End 112.3±10 112±6.5 0.8
P*0.8 0.6
DBP (mmHg)
Baseline 80±6.5 78.5±8.5 0.4
End 78±5 76±6 0.2
P*0.15 0.17
*P<0.05 is signicant, †Values are mean±SD, ‡For comparison of
between‑group differences by an independent t‑test. BMI=Body
mass index, WC=Waist circumference, WHR=Waist to hip ratio,
SBP=Systolic blood pressure, DBP=Diastolic blood pressure,
SD=Standard deviation
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Khosravi, et al.: Vitamin D supplementation, weight loss, glycemic indices, and lipid prole
International Journal of Preventive Medicine 2018, 9: 634
as hip circumference (HC), WHR, SBP, diastolic BP (DBP),
lipid proles, glycemic indexes, and CRP. Supplemental
interventions on women aged 20–40 years were our study
target because they were as mothers and had an important
role in prevalence of chronic diseases and therefore health
of society. The result of this study demonstrated that
supplementation of the vit D in obese and overweight
women reduced signicantly the mean of weight, BMI, and
WC. Previous studies had shown that the vit D deciency
is more prevalent in obese people and there was an inverse
association between vit D, BMI, and WC.[3,4,9,11,13‑21] Vashi
et al. showed that 1 kg/m² increase in BMI was associated
with signicantly reduced vit D level (42% ng/ml).[22] In
another study, there was a signicant inverse relationship
after adjusting all confounding that associated with vit
D and BMI.[23] However, conicting results have been
seen[3,17,24] such as a study on Iranian 20–64 years with BMI
24.2 ± 3.8 (57% female) which had not shown signicant
association between the level of vit D and BMI. Probably,
its main reason was BMI, which was 24.2 and in the normal
range. In addition, it could be another reason that only 48%
of individuals had vit D deciency.[17] In some studies,
the inverse association between vit D and WC has been
seen.[22,25] In one of these studies, vit D also had a signicant
association with HC.[25] In Seo’s study only, this association
between vit D and WC has been seen in women.[14]
Our study did not have a signicant effect on FBS, ins, and
HOMA‑IR. A study in 2012 has not found any signicant
effect on FBS and HOMA‑IR with supplementation of
vit D with dozes 1000 IU/d during 1 year.[26] In another
study, there was no signicant relationship between vit
D and HOMA‑IR because of participants were healthy
overweight adults with normal FBS.[3] From this aspect, it
was similar to our study. Furthermore, in several studies,
vit D did not have a relationship with fasting ins, IR,
and fasting glucose.[20,27‑30] Of course in some studies, vit
D had an inverse effect on HOMA‑IR, fasting ins, and
FBS.[16,18] We could not nd any signicant effect of vit
D; this effect may be seen in long‑term studies. In this
study, we could not nd any role of vit D on the lipid
prole such as TG, TC, HDL‑c, and LDL‑c. Result of
this study were approved by previous studies.[31‑33] In
Moghassemi and Marjani’s study of Iran, after 12 weeks
supplementation with the vit D, lipid prole did not
change signicantly.[31] Also, in a randomly clinical trial
on women has not found any changes in lipid prole that
it maybe related to short duration of study and dose
of the vit D.[23] In addition, some studies such as Women
Health Initiative that had longer duration and dose of the
vit D was 200 IU that take it twice a week for 7 years
has not found changes in lipid prole.[33] In several
Table 3: Dietary intake of participants before study†
Nutrient Intervention
(n=26)
Control
(n=27)
P*,‡
Energy (kcal) 2096±6.3 2117±661 0.9
Carbohydrate (g) 292±107 300±157 0.8
Protein (g) 83±36 102.5±89 0.5
Fat (g) 73.5±31 78.5±77 0.3
Saturated fatty acid (g) 20±8 24.5±23 0.4
Polyunsaturated fatty acid (g) 21.5±12 22±15 0.8
Monounsaturated fatty acid (g) 32.2±118 42±214 0.7
Fiber soluble (g) 0.5±0.2 0.8±1.5 0.3
Fiber insoluble (g) 4.5±8 6±12.5 0.5
Calcium (mg) 841±363 899±646 0.7
Vitamin D (Ug) 1.4±1.9 1.3±2 0.93
*P<0.05 is signicant, †Values are mean±SD, ‡For comparison of
between‑group differences by an independent t‑test. SD=Standard
deviation
Table 4: Biochemical variables in participants†
Variable Intervention
(n=26)
Control
(n=27)
P*,‡
HDL‑C (mg/dl)
Baseline 42.8±11.5 48.7±16 0.1
End 42.8±8.7 44.3±10 0.5
P0.1 0.7
LDL‑C (mg/dl)
Baseline 89.5±25 91.4±27 0.8
End 92.7±25.5 87.5±21.2 0.4
P0.3 0.3
TC (mg/dl)
Baseline 184.3±37 188.7±42.5 0.7
End 184±34 176.5±28 0.4
P0.9 0.07
FBS (mg/dl)
Baseline 96.8±12 101±13 0.2
End 90.5±9.5 91.2±12 0.8
P0.01 0.003
TG (mg/dl)
Baseline 118±90 109.5±56 0.7
End 120.5±111 100±48 0.4
P0.8 0.1
Vitamin D (nmol/l)
Baseline 22±6.5 18±5 0.01
End 84±30.5 34±24 0.001
P0.001 0.001
Insulin (mg/dl)
Baseline 10.2±6 9.5±5 0.6
End 13±8 10±6 0.1
P0.09 0.5
HOMA‑IR (mU/l)
Baseline 2.4±1.5 2.4±1.1 0.84
End 2.9±1.9 2.2±1.5 0.16
P0.25 0.7
*P<0.05 is signicant, †Values are mean±SD, ‡For comparison
of between‑group differences by an independent t‑test for
comparison of within‑group differences by an paired t‑test.
TC=Total cholesterol, TG=Triglyceride, LDL‑C=Low‑density
lipoprotein cholesterol, HDL‑C=High‑density lipoprotein
cholesterol, FBS=Fasting blood sugar, SD=Standard deviation,
HOMA‑IR=Homeostasis model assessment of insulin resistance
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Khosravi, et al.: Vitamin D supplementation, weight loss, glycemic indices, and lipid prole
International Journal of Preventive Medicine 2018, 9: 63 5
studies, similar results were obtained.[20,22,26] However,
some studies have found inverse results such as Kim
et al. that after supplementation of the vit D only, HDL‑c
was reduced signicantly.[30] in another study LDL‑c
and TG decreased signicantly[34] but HDL‑c increased
signicantly.[35] In a similar study, after consuming the
supplementation of vit D with dozes 300 IU/d for 3 years,
LDL‑c and TG increased signicantly but TC and HDL‑c
reduced signicantly[36] A meta‑analysis was conducted
on the effects of vit D supplementation on lipid prole.
showed that only LDL was changed signicantly after the
intervention.[25] Overall, there are contradictory results
for the effect of the vit D on lipid proles, so more
investigations are necessary in the future. We have not
seen a signicant relationship between supplementation of
the vit D and BP in our study. A clinical study in Germany
supplementation of the vit D with dozes 100,000 IU did
not cause any changes in BP.[37] In a meta‑analysis that
included 10 interventional studies, after supplementation
of the vit D, no signicant effects was found in systolic
and DBP.[38] As well as several other studies have not
reported the effect of vit D on BP.[26,39,40] Of course, a
study has reported an inverse relationship between vit D
levels and systolic BP in men,[19] but probably, its main
reason was individuals’ age because the aim society in this
study were the individuals with age higher than 65 years
and mostly had a high BP but participants in our study
were individuals with age 20–40 years that mostly had a
normal BP. Another possible reason was the difference in
gender.
We could not nd any effect of the vit D on CRP in our
study. In a study on the healthy population, vit D had no
effect on CRP.[26] Forooghi et al. in Iran have not found
effect of vit D on CRP too.[41] Furthermore, another
studies had similar results. In some studies, an inverse
association has been seen between vit D and CRP. It means
that supplementation of the vit D can reduce CRP.[42,43] In
an interventional study on obese people, CRP increased
signicantly.[16] According to the previous studies, the
reason of the vit D deciency in obesity has not cleared yet
but some mechanisms has proposed these reasons for the
relationship between vit D and obesity: trapped of the vit D
in adipose tissue that makes less bioavailability for convert
to the form of 1,25(OH)2D.[10] In a study vit D deciency
was accompanied with abdominal obesity. Therefore, vit
D is lower in serum of obese people, and therefore, its
bioavailability reduces for these individuals.[16] The role
of vit D in causing IR has not cleared yet. Some studies
have suggested that vit D may have benecial effects
on ins responsiveness by stimulating expression of ins
receptors[44] or regulating calcium homeostasis which
is necessary for intracellular ins‑mediated processes.[45]
As regard to the obesity is the most common cause of
ins‑resistance, the relation between vit D and IR might
be the result of increased body size.[16] We could not nd
the effect of vit D on lipid proles, glycemic indexes,
CRP, and BP in this study. Some studies have reported
these effects which were mostly due to the weight loss
and BMI reduction that improved these factors. The
possible effect of vit D on BP may be related to regulation
the renin–angiotensin system, suppression the spread of
proliferation of vascular smooth muscle cells, improvement
IR, modication extended‑dependent cells to endothelium
and inhibition of anticoagulant activity and hypertrophy of
myocardial cells.[46] Possibility mechanism for the effect
of vit D in CRP reduction is that vit D receptors are in
more than 37 body tissues that effect on these organs by
their receptors and regulate pro‑inammatory mechanisms
and systematic inammation in the body. Vit D receptors
are located in the nucleus of macrophages. Some of these
macrophages produce cytokines, especially Tumor necrosis
factor (TNF)‑α. TNF‑α expression signicantly depends
on the effect of NF‑β. Increased vit D inhibits the protein
expression of NF‑β and reduces the expression of NF‑β and
thus reduces the level of TNF‑α. In addition, vit D binds
to receptors on monocytes and so produce in ammatory
cytokines, CRP and reduces systemic in ammation.[41]
We performed this study as an interventional that gave us
a more acceptable result. We included women aged 20–
40 years that were at risk for vit D de ciency had more
exposure to disease in the future.
Limitations
The short duration of the study and increase in the levels
of the vit D in control group were our limitation. One of
Table 5: The mean of differences in anthropometric and
biochemical variables†
Variable Intervention
(n=26)
Control
(n=27)
P*,‡
Weight (kg) −1.6±1.3 0.05±1 0.001
BMI −0.61±0.5 0.02±0.5 0.001
WC (cm) −2.3±1 0.3±1.5 0.001
WHR 0.01±0.04 −0.0008±0.03 0.22
HDL‑C (mg/dl) 0.003±8 −4.4±12.5 0.13
LDL‑C (mg/dl) 3.17±17.5 −4±19 0.17
TC (mg/dl) −0.3±26 −12.2±33.5 0.15
FBS (mg/dl) −6.35±12 −9.5±15.5 0.4
TG (mg/dl) 2.5±48.5 −9±34.5 0.3
Vitamin D 62±29 15.7±22 0.001
Insulin (mg/dl) 3±8 0.66±6 0.27
HOMA‑IR (mU/l) 0.5±2.1 −0.11±1.5 0.23
SBP (mmHg) −0.5±8 −0.75±7 0.9
DBP (mmHg) −2.3±8 −2.6±9.6 0.9
*P<0.05 is signicant, †Values are mean±SD, ‡For comparison
of between‑group differences by an independent t‑test. TC=Total
cholesterol, TG=Triglyceride, LDL‑C=Low‑density lipoprotein
cholesterol, HDL‑C=High‑density lipoprotein cholesterol,
FBS=Fasting blood sugar, SBP=Systolic blood pressure,
DBP=Diastolic blood pressure, HOMA‑IR=Homeostasis
model assessment of insulin resistance, BMI=Body mass index,
WC=Waist circumference, WHR=Waist to hip ratio
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Khosravi, et al.: Vitamin D supplementation, weight loss, glycemic indices, and lipid prole
International Journal of Preventive Medicine 2018, 9: 636
the possible causes of this increase can be attributed to
the seasons. With the arrival of summer, the amount and
intensity of the sun increases, and spontaneously, levels
of vit D increases. Entrance healthy obese individuals
with normal laboratory indexes may be the reason for not
signicant effects. The authors declared that there is no
conict of interest.
Conclusions
Overall supplementation of the vit D with dozes
50,000 IU/w for 6 weeks in obese and overweight women
aged 20–40 years reduced in the mean of BMI, weight,
and WC signicantly and vit D increased signicantly
compared to the control group.
Financial support and sponsorship
Nil.
Conicts of interest
There are no conicts of interest.
Received: 13 Oct 15 Accepted: 15 Dec 17
Published: 20 Jul 18
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