Curcumin, an Active Component of Turmeric (Curcuma longa), and Its Effects on Health

Abstract

Turmeric (Curcuma Longa) is a type of herb belonging to ginger family, which is widely grown in southern and south western tropical Asia region. Turmeric, which has an importance place in the cuisines of Iran, Malesia, India, China, Polynesia and Thailand, is often used as spice and has an effect on the nature, color and taste of foods. Turmeric is also known to have been used for centuries in India and China for the medical treatments of such illnesses as dermatologic diseases, infection, stress and depression. Turmeric's effects on health generally are centered upon an orange-yellow colored, lipophilic polyphenol substance called 'curcumin', which is acquired from the rhizomes of the herb. Curcumin is known recently to have antioxidant, anti-inflammatory, anti-cancer effects and, thanks to these effects, to have an important role in prevention and treatment of various illnesses ranging notably from cancer to autoimmune, neurological, cardiovascular diseases and diabetic. Furthermore, it is aimed to increase the biological activity and physiological effects of the curcumin on the body by synthesizing curcumin analogues. This paper reviews the history, chemical and physical features, analogues, metabolites, mechanisms of its physiological activities and effects on health of curcumin.

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Curcumin, an active component of turmeric
(Curcuma longa), and its effects on health
Betül Kocaadam & Nevin Şanlier
To cite this article: Betül Kocaadam & Nevin Şanlier (2017) Curcumin, an active component of
turmeric (Curcuma longa), and its effects on health, Critical Reviews in Food Science and Nutrition,
57:13, 2889-2895, DOI: 10.1080/10408398.2015.1077195
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Curcumin, an active component of turmeric (Curcuma longa), and its effects on health
Bet€
ul Kocaadam and Nevin ¸Sanlier
Faculty of Health Sciences, Nutrition and Dietetics Department, Gazi University, Ankara, Turkey
ABSTRACT
Turmeric (Curcuma longa) is a type of herb belonging to ginger family, which is widely grown in southern
and south western tropical Asia region. Turmeric, which has an importance place in the cuisines of Iran,
Malesia, India, China, Polynesia, and Thailand, is often used as spice and has an effect on the nature, color,
and taste of foods. Turmeric is also known to have been used for centuries in India and China for the
medical treatments of illnesses such as dermatologic diseases, infection, stress, and depression. Turmeric’s
effects on health are generally centered upon an orange-yellow colored, lipophilic polyphenol substance
called “curcumin,”which is acquired from the rhizomes of the herb. Curcumin is known recently to have
antioxidant, anti-inflammatory, anticancer effects and, thanks to these effects, to have an important role in
prevention and treatment of various illnesses ranging notably from cancer to autoimmune, neurological,
cardiovascular diseases, and diabetic. Furthermore, it is aimed to increase the biological activity and
physiological effects of the curcumin on the body by synthesizing curcumin analogues. This article reviews
the history, chemical and physical features, analogues, metabolites, mechanisms of its physiological
activities, and effects on health of curcumin.
KEYWORDS
Turmeric; curcumin; health;
safety
Introduction
Turmeric is acquired from Curcuma long L., a tuberous herba-
ceous perennial plant with yellow flowers and wide leaves,
which is a member of ginger family and grows in tropical cli-
mate (Akpolat et al., 2010; Prasad et al., 2014). Unlike cinna-
mon, turmeric has not any different kinds. On the other hand,
geographical conditions of the region where it grows and the
features of its soil may affect the growth, nutrition composition,
and quality of this plant (Hossain and Ishimine, 2005; Haya-
kawa et al., 2011). While this plant is rather an important spice
in Iran, it is also an important component of curries to which it
gives the yellow color in Malesia, India, China, Polynesia, and
Thailand, and the mustard and sauces in the West (Gupta
et al., 2013a). Turmeric is also used to add flavor and color to
rice, pasta, meat and vegetable dishes, and salads.
It is stated that turmeric has been widely used for medical
treatments of various diseases for at least 2500 years in Asian
countries mostly (Gupta et al., 2013a) and it has many benefits
for prevention and treatment of many diseases in Ayurveda
and traditional Chinese medicine (Deogade and Ghate, 2015).
The importance of turmeric in medical treatment primarily
stems from orange-yellow colored curcumin, the most active
component. Curcumin is a lipophilic polyphenol substance
(Jurenka, 2009), which constitutes the 2–5% of turmeric
powder (Deogade and Ghate, 2015).
With the studies about curcumin, it has been determined
that the chemical structure of this polyphenol substance shows
antioxidant, antimicrobial, anti-inflammatory, antiangiogenic,
antimutagenic, and antiplatelet aggregation properties (Patil
et al., 2009; Shehzad et al., 2013; Prasad et al., 2014; Deogade
and Ghate, 2015). It is stated that, thanks to this properties,
curcumin has a protective and preventive effect against various
diseases such as cancer, autoimmune, neurological, metabolic,
lung, liver, and cardiovascular diseases (CVDs) (Gupta et al.,
2013b; Prasad et al., 2014).
Recently, substantial importance has been put on polyphe-
nol substances due to their effects on various degenerative dis-
eases, especially cancer (Sohrab et al., 2013). Examination of
the effects of curcumin on health, which is also a polyphenol
substance, is highly significant.
Curcumin and its historical process
Curcumin was defined as “substance that gives the yellow
color”by Vogel and Pelletier about 200 years ago. In 1842, it
was purely acquired by Vogel Jr. In the mid-1900, curcumin
was stated to be a biologically active component, to have
antibacterial property, and therefore, to be effective against
Staphylococcus aureus, Salmonella paratyphi, Mycobacterium
tuberculosis, and Trichophyton gypseum types. In 1953,
Srinivasan determined the existence of other components called
curcuminoids as well as curcumin with the analysis of turmeric
through chromatography (Patil et al., 2009; Prasad et al., 2014;
Deogade and Ghate, 2015).
Later, curcumin was said to have a cholesterol-lowering,
antidiabetic, anti-inflammatory, and antioxidant properties and
CONTACT Nevin ¸Sanlier, Professor nevintekgul@gmail.com Gazi University, Faculty of Health Sciences, Nutrition and Dietetics Department, Emniyet Mahallesi,
Muammer Ya¸s ar BostancıCaddesi, No:16, 06500 Be¸sevler/Ankara, Turkey.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/bfsn.
© 2017 Taylor & Francis Group, LLC
CRITICAL REVIEWS IN FOOD SCIENCE AND NUTRITION
2017, VOL. 57, NO. 13, 2889–2895
http://dx.doi.org/10.1080/10408398.2015.1077195

to have an anticancer activity in both in vitro and in vivo mod-
els. Then, with the clinical studies conducted with humans, it
was determined that curcumin was safe and effective. Food and
Drug Administration (FDA) confirmed curcumin as a com-
pound “generally recognized as safe”(Patil et al., 2009; Prasad
et al., 2014).
Chemical and physical characteristic of curcumin
The compound of turmeric contains carbohydrate (69.4%),
protein (6.3%), fat (5.1%), mineral (3.5%), and moisture
(13.1%) (Prasad et al., 2014). The essence of turmeric roots,
pulverized by drying, also contains curcuminoids consisting of
curcumin components. Curcuminoids consist of curcumin
(77%), demethoxycurcumin (DMC; 17%), and bidemethoxy-
curcumin (BDMC; 3%) (Goel et al., 2008). It is stated that even
if studies focus on curcumin, other curcuminoid components
also have biological activities (Shehzad et al., 2010).
Chemical denotation of curcumin is 1,7-bis-(4-hydroxy-3-
methoxyphenyl)-hepta-1,6-diene-3,5-dione or dipheruloylme-
thane; while its chemical formula is C
21
H
20
O
6
(Fig. 1) (Deogade
and Ghate, 2015; Pubchem Open Chemistry Data Base, 2015).
Curcumin is not soluble in water at acidic and neutral pH.
However, it is soluble in acetone, methanol, and ethanol (Goel
et al., 2008; Jurenka, 2009). It is stated that curcumin is sensi-
tive to light and, therefore, it is recommended that biological
samples containing curcumin are to be protected from light
(Prasad et al., 2014).
Curcumin’s natural, synthetic analogues and
metabolites
Due to its insufficient absorption by the body, high metabolism
speed, and high elimination from the body, curcumin has a
limited bioavailability in the body. The low bioavailability of
curcumin limits significantly the therapeutics effects of this
component (Devassy et al., 2015). Now, new methods have
been developed to increase the bioavailability of curcumin. One
of these methods is to use piperine with curcumin. It has been
shown that piperine increases the bioavailability of curcumin
on humans and rats by decreasing glucuronidation of curcumin
(Aggarwal and Harikumar, 2009). Use of liposomal curcumin,
curcumin nanoparticles, and phospholipid complexes are
among other methods. Besides, it is stated that use of structural
analogues of curcumin also increases bioavailability (Shehzad
et al., 2010; Devassy et al., 2015).
It is stated that DMC and BDMC, natural analogues of cur-
cumin, have biological activity like curcumin. A study has
found that inflammatory transcription factor nuclear factor
kappaB (NF-kB) suppression of curcumin is much more effec-
tive than others (curcumin >DMC >BDMC). It is thought
that this result may stem from the important role of methoxy
groups on the phenyl ring of curcumin (Sandur et al., 2007).
DMC and BDMC have been determined to suppress Inos
and COX-2, which are NF-kB onset inflammatory molecules
(Guo et al., 2008). Curcumin and DMC have been shown to be
effective for decreasing AGEs-originated reactive oxygen types
(ROS) in mesangial cells curcumin and DMC have also been
determined to increase significantly the advanced glycosylation
end products (AGEs) decreasing superoxide dismutase activity
and malondialdehyde component in the surface of cell culture.
It is also stated that these two components provide protection
against AGEs-originated apoptosis, and due to these effects,
they may provide protection against diabetic neuropathy (Liu
et al., 2012).
There are many metabolites of curcumin such as dihydro-
curcumin, tetrahydrocurcumin (THC), octahydrocurcumin
(OHC), hexahydrocurcumin (HHC), curcumin glucuronide,
and curcumin sulfate (Prasad et al., 2014). After many
researches on curcumin metabolites, it has been determined
that THC shows antioxidant (Murugan and Pari, 2006), anti-
inflammatory (Lai et al., 2011), and anticancer (Wu et al.,
2011) effects; that HHC has anticancer (Srimuangwong et al.,
2012), antioxidant and anti-inflammatory (Li et al., 2012), and
platelet aggregation epistasis (Dong et al., 2012) properties; that
OHC has anti-inflammatory and antioxidant effects (Somparn
et al., 2007; Prasad et al., 2014).
Furthermore, synthetic derivatives of curcumin can be
acquired with such chemical modifications as phenolic
hydroxyl groups, acylation, alkylation, glycosylation, and
amino acylation (Prasad et al., 2014).
Biological activities and molecular targets of curcumin
and related diseases
In ancient times, curcumin appeared in the Ayurveda medical
treatment methods applied in India, used in treatment of inju-
ries, skin diseases, eye infections, ambustions, and acne
(Hatcher et al., 2008). Curcumin is also an important compo-
nent of traditional treatment methods called Jiawei-Xiaoyao in
China, and it has been used for the treatment of various dis-
eases like dyspepsia, stress, and depression for thousands of
years (Qin et al., 2009). In the last 30 years, curcumin was
shown to have a therapeutic effect against cancer, autoimmune
diseases, metabolic diseases, neurological diseases, CVDs, lung
diseases, liver diseases, and a variety of other inflammatory dis-
eases (Aggarwal and Harikumar, 2009; Kannappan et al., 2011).
Curcumin is thought to be effective on pathogenesis of
molecular targets with the purpose of prevention and treatment
of diseases. It is stated that the modulation of these molecular
targets that have a role in the formation process of the disease
can be achieved. It has been proven, for instance, that tumor
development can be suppressed by suppressing cancer cell sig-
nal pathway (Devassy et al., 2015). Curcumin, with its polyphe-
nol structure, is shown to be able to effectively modulate
Figure 1. Chemical structure of curcumin.
2890 B. KOCAADAM AND N. ¸SANLIER

molecular targets that have a role in the pathogenesis of many
diseases (Fig. 2). Curcumin has been determined to play an
important role regulating cytokines, kinases, enzymes, tran-
scription factors, growth factors, receptors, metastatic, and apo-
ptotic molecules in almost all phases of the development of
many diseases (Shehzad and Lee, 2010; Baliga et al., 2012; Pra-
sad et al., 2014). The fact that its structure is inclined to high-
level methoxylation and low-level hydrogenation and gives cur-
cumin a property that increases free radicals scavenging activ-
ity. It is stated that this structure probably enables curcumin to
have an anticancer, anti-inflammatory, and antioxidant effect
(Devassy et al., 2015)(Fig. 2).
Anticancer effect
Even curcumin has already been shown to have a positive effect
against many diseases; its effect against cancer is the most
under-researched topic (Devassy et al., 2015). Curcumin has
been found to be effective in many phases of cancer develop-
ment, to suppress transformation, beginning, development and
invasion of tumor, angiogenesis, and metastasis. Curcumin has
been determined to suppress the growth of tumor cells via cell
proliferation pathway (cyclin D1, c-myc), cell survival pathway
(Bcl-2, Bcl-xL, cFLIP, XIAP, and cIAP1), caspase activation
pathway (caspase ¡8, ¡3, and ¡9), tumor suppressor pathway
(p53, p21), death receptor pathway (DR4, DR5), and many cell
signal pathways that contain protein kinase pathway (c-Jun
N-terminal kinases (JNK), protein kinase B (PKB), also known
as Akt, and 50adenosine monophosphate-activated protein
kinase (AMPK)) (Ravindran et al., 2009). It is stated that,
thanks to these effects of curcumin, it is effective for decreasing
or preventing various cancer types including multiple myeloma
and colon, pancreas, breast, prostates, and lung cancers (Anand
et al., 2008; Devassy et al., 2015). It is also stated that curcumin
increases the effectiveness of radiotherapy and thus, it may
open a quicker path to treatment (Akpolat et al., 2010).
In a study dealing with monocarbonyl analogue of B63
acquired through some chemical modifications of curcumin’s
structure, this component has been shown to have a higher
antiproliferative effect than curcumin on colon cancer cells. At
the same time, with the use of less B63 (50 mg/kg B63, 100 mg/
kg curcumin), suppression of tumor growth has been achieved
like curcumin (Zheng et al., 2014).
Anti-inflammatory and antioxidant effects
Curcumin has been determined to be an anti-inflammatory and
antioxidant agent (Deogade and Ghate, 2015). It is thought that
curcumin has these properties due to hydroxyl and methoxy
groups (Rahman and Biswas, 2009). Curcumin enables negative
regulation of proinflammatory interleukins (IL-1, ¡2, ¡6, ¡8,
and ¡12), cytokines (tumor necrosis factor-alpha (TNF-a),
monocyte chemoattractant protein-1) by causing down-regula-
tion of janus kinase and signal transducer and activator of tran-
scription (JAK/STAT) signaling pathway. It is also stated that
curcumin regulates the inflammatory response by down-regu-
lating enzymes of inducible nitric oxide synthase (iNOS), cyclo-
oxygenase-2 (COX-2), lipoxygenase, and xanthine oxidase
activity; and thus, it may cause to suppress activation of NF-kB
(Rahman and Biswas, 2009).
Curcumin is stated to show its effectiveness by inhibiting
inflammatory cell proliferation, metastasis, and angiogenesis
through various molecular targets (Shehzad et al., 2013). Large-
scale studies have shown that inflammation changes the signal
pathways; and thus it is related to the increase of inflammatory
biomarkers, lipid peroxides, and free radicals. Acute and chron-
ical inflammation is an important risk factor for cardiovascular,
neurodegenerative, and metabolic diseases, obesity, type 2
Figure 2. Related molecular targets and diseases of curcumin.
CRITICAL REVIEWS IN FOOD SCIENCE AND NUTRITION 2891

diabetes, and some cancer types (Dantzer et al., 2008; Medzhi-
tov, 2008). Curcumin is stated to be effective for the treatment
of various inflammatory diseases such as obesity, diabetes,
CVDs, neurological diseases, and inflammatory bowel disease
(IBD) (Shehzad et al., 2013; Prasad et al., 2014; Deogade and
Ghate, 2015).
Curcumin exhibits strong antioxidant effect through free-
radical-scavenging activity (Deogade and Ghate, 2015). Even
though curcumin shows antioxidant effect, in order to increase
its antioxidant capacity, analogues of curcumin are focused on.
Dolai et al. (2011) showed that the synthetic sugar analogue of
curcumin is a stronger antioxidant. It has been determined that
while curcumin suppresses tau peptides aggregation and amy-
loid-bat micromolar concentrations, sugar-curcumin conju-
gate shows suppressing effect for this aggregation even in
nanomolar levels.
Cardiovascular diseases
Inflammation has been determined to play a great role in devel-
opment of cardiovascular diseases (CVD). Curcumin treatment
is stated to have an anti-inflammatory effect against CVD, by
means of various mechanisms. Curcumin is stated to enable
HO-1 expression by actuating Nrf2-dependent antioxidant
response element. It is also stated that curcumin suppress
TNF-ain vascular and aortic smooth muscle cells; and that it
increases p21 expression through HO-1 (Pae et al., 2007;
Wongcharoen and Phrommintikul, 2009). Curcumin treatment
on animals has been determined to decrease ischemia through
activation of JAK2/STAT3 signal pathway (Duan et al., 2012).
In a study done on rats, it has been proven that applying
50 mg/kg curcumin to rats with salt-sensitivity and hyperten-
sive heart disease develops systolic function and prevents coro-
nary failure (Morimoto et al., 2008). In a study on the
effectiveness of curcumin on cardiovascular risk factors in indi-
viduals with coronary artery disease, it has been determined
that serum triglyceride, LDL and VLDL cholesterol levels
decrease considerably in the group of individuals taking curcu-
min. Even though effects of curcumin on blood lipid profile
have been proven, no considerable effect has been determined
on inflammatory markers (Mirzabeigia et al., 2015). In a study
conducted in Turkey, the consumption prevalence of plant-
based alternative treatments and supplementary foods of indi-
viduals with CVDs was researched; and it was found out that
turmeric is one of the most popular herbal foods. Also, hyper-
tension and hyperlipidemia are found to be the most important
reasons for patients to use alternative products (
_
Ipek et al.,
2013).
Diabetes mellitus
Diabetes mellitus is a health problem affecting liver, heart,
brain, and kidneys. It has been determined that inflammation
is the primary cause of type II diabetes development and that
various inflammatory cytokines, transcription factors, and
enzymes have an important role in the outset and progression
of diabetes (Choudhary et al., 2011; Shehzad et al., 2013).
Ghorbani et al. (2014) pointed out that curcumin has proper-
ties such as decreasing hepatic glucose production, suppressing
inflammatory response stemming from hyperglycemia, increas-
ing GLUT2, GLUT3, and GLUT4 gene expression, increasing
glucose intake of cells, and activating AMPK; and thus, that it
may decrease blood glucose decreasing insulin resistance. They
also stated that, for these reasons, curcumin has an increasing
effect on antihyperglycemic and insulin sensitivity.
One study conducted on type 2 diabetic KK-Ay mice found
that curcumin suppresses the increase in blood glucose level via
peroxisome proliferator-activated receptor-gamma (PPAR-g)
activation (Kuroda et al., 2005). Studies have been conducted
on derivatives of curcumin with the aim of increasing the anti-
diabetic effect of curcumin. For instance, as a result of a study
researching whether a new curcumin derivative (NCD),
acquired by covalent modification of curcumin molecule,
shows hypoglycemic effect on diabetic rats, it has been proven
that NCD decreases plasma glucose level at the rate of 27.5%,
and that it increases plasma insulin up to 66.67%. It is stated
that NCD shows this effect by inducing HO-1 gene (Aziz et al.,
2012; Aziz et al., 2013).
Obesity
Curcumin has been shown to suppress mitogen-activated
protein kinase (MAPK, extracellular signal-regulated kinases
(ERK), JNK, and p38), which is associated with differentiation
of 3T3-L1 cells into adipocytes and activates Wnt/b-catenin
signaling in differentiated adipocytes., which are closely related
to obesity (Ahn et al., 2010). It is stated that curcumin decreases
the macrophage infiltration, leptin, and leptin receptor level
(Ob-R) in the white adipose tissue; that it increases the adipo-
nectin expression in inflammation-related obesity. It is pointed
out that the adiponectin production, which increases due to
effect of curcumin, may have a positive effect against obesity by
decreasing NF-kB activity (Shehzad et al., 2011).
Inflammatory bowel disease
IBD is an immune impairment including Crohn disease and
ulcerative colitis, commonly characterized with digestion sys-
tem chronical inflammation (Shehzad et al., 2013). Studies
indicate that curcumin is useful in prevention and treatment of
IBD (Holt et al., 2005; Ali et al., 2012). Curcumin inhibit the
activity of activated protein-1 (AP-1), STAT proteins, PPAR-g,
b-catenin, COX-2, 5-LOX, and iNOS expression which play a
key role in inflammation (Taylor and Leonard, 2011). There-
fore, it can reduce colitis. It has been proven that curcumin, at
the same time, suppress TLR4-based NF-kB activation; and
thus, it may be effective for recovery of bowel inflammation
(Lubbad et al., 2009; Ali et al., 2012; Baliga et al., 2012).
A pilot study done with Crohn or ulcerative patients by Sus-
kind et al. (2013) indicated that recovery in disease symptoms
is achieved as a result of using curcumin as 500 mg capsules
twice a day during three weeks. Researchers have suggested
that using curcumin as an adjunctive therapy for the individu-
als seeking combination of traditional and alternative treat-
ment. Likewise, Taylor and Leonard (2011) have stated that
curcumin becomes more effective when used with traditional
medicines for the treatment of IBD; and that this combination
is a cheaper alternative method.
Neurodegenerative diseases
Aging is a significant risk factor for neurodegenerative diseases.
It is considered that curcumin may be effective on aging
2892 B. KOCAADAM AND N. ¸SANLIER

mechanisms; thus, it may prevent the changes in the cell pro-
teins which occur due to aging. Therefore, it is indicated that
curcumin may help to maintain protein homeostasis and it
may be effective for prevention of aging-associated diseases
(Monroy et al., 2013). Besides, curcumin has scavenge oxygen
derived free-radical property; and thus, curcumin is stated to
be a potential neuroprotective agent (Nabiuni et al., 2011).
In neurodegenerative diseases such as Alzheimer character-
ized with inflammation and oxidative injury, abnormal protein
development causes such gene mutations as human amyloid
precursor protein or presenile 1 or 2 (Smith et al., 2007). In
Alzheimer disease, curcumin as an antioxidant, anti-inflamma-
tory properties can improve the cognitive functions, and also it
is stated to bring various therapeutic benefits through decreased
b-amyloid plaques and microglia formation, delayed deteriora-
tion of neurons in patients. (Mishra and Palanivelu, 2008).
Parkinson’s disease (PD), one of the most common neuro-
degenerative diseases, is characterized by loss of dopaminergic
neurons in the substantia nigra. The most important biological
effect of curcumin, related to neuroprotection, is its antioxidant
function (Mythri and Srinivas Bharath, 2012). Thus, it protects
substantia nigra neurons, ameliorates dopamine levels in the 6-
OHDA rat model of PD. It is pointed out that curcumin pro-
tects many tyrosine hydroxylase-positive cells in substantia
nigra; and that it maintains the dopamine levels in striatum
probably because of this effect (Zbarsky et al., 2005).
Multiple sclerosis (MS) is a chronic inflammatory autoim-
mune disease, characterized with oligodendrocyte in central
nervous system and degradation of myelin sheath. Curcumin
has been shown to inhibit autoimmune diseases by regulating
inflammatory cytokines and associated JAK-STAT, AP-1, and
NF-kB signaling pathways (Bright, 2007; Tegenge et al., 2014).
Th17 cells are important factor for the pathophysiological pro-
cess of MS. Curcumin suppresses the differentiation and devel-
opment of Th17 cells through the down-regulation of IL-6,
TGF-b,IL-1b, IL-23, and STAT3-phosphorylation (Xie et al.,
2011). Furthermore, it has been determined that curcumin
inhibits channel Kv1.3, which is mainly effective on T(EM)
cells; and at the same time it suppress the cytokine secretion
and proliferation of T(EM) cells which are isolated from MS
patients (Lian et al., 2013).
Skin diseases
The use of curcumin for treatment of skin diseases dates back
to ancient times. Due to its role in treatment of skin diseases in
India, turmeric is used in production of cream and soap in
Ayurveda, the ancient Indian medical system, turmeric is
widely used as an easy treatment method for eye infections,
treat bites, burns, and acne (Hatcher et al., 2008; Akpolat et al.,
2010).
Now, it is indicated that curcumin may be effective against
various skin diseases such as dermatitis, psoriasis, and sclero-
derma. It is pointed out that psoriasis, a chronical skin disease,
which is characterized with hyperproliferation and abnormal
differentiation of keratinocyte, can be treated by curcumin
(Prasad et al., 2014). Curcumin can protect skin by scavenging
free radicals and reducing inflammation through nuclear fac-
tor-kB inhibition and cytokines (Thangapazham et al., 2007). A
study conducted on mice indicates that curcumin diminished
psoriasis-like inflammation by reducing cytokines such as IL-
1band IL-6 (Sun et al., 2013).
Allergy and asthma
Allergy and asthma are proinflammatory diseases, stemming
from inflammatory cytokines (Shehzad et al., 2013). Turmeric
rhizomes have been long used for treatment of allergy and
asthma in Asia, especially in India; for treatment of itching and
other skin diseases in Thailand (Tewtrakul and Subhadhirasa-
kul, 2007; Viswanath and Christy, 2008). Yano et al. (2000)
have indicated that turmeric exhibits antiallergic activity by
suppressing the 48/80-induced histamine release from mast
cells. The hydroxyl groups of curcumin are indicated to
decrease the allergic reactions and to have a positive effect
against asthma by broadening the narrowed air pathway and
increasing the antioxidant capacity (Viswanath and Christy,
2008; Shehzad et al., 2013). Curcumin has been determined to
cause Th2 response down-regulation by decreasing the produc-
tion of IgE antibodies and cytokine, and enabling the formation
of less inflammatory response (Viswanath and Christy, 2008).
The safe dosage and toxicology of curcumin
Curcumin has been confirmed as a “generally recognized as
safe”compound by FDA, and it is stated not to have any toxic
effect. According to Joint FAO/WHO Expert Committee on
Food Additives (JECFA) and European Food Safety Authority
(EFSA) reports, adequate daily intake (ADI) value of curcumin
is 0–3 mg/kg (JECFA, 2004; EFSA, 2014) Lao et al. (2006)
applied 500–12,000 mg curcumin to healthy individuals so as
to examine the maximum tolerance dosage and safety of curcu-
min. As a result, up to 12 g/day intake of curcumin has been
shown to have no harmful effects on individuals. There are
some concerns about the relationship between inhibition of
some enzymes working in drug metabolism, potential DNA
impairment, iron chelation, and curcumin intake. However,
more studies need to be conducted to examine these relation-
ships (Devassy et al., 2015).
Conclusion and suggestions
In conclusion, the effects of curcumin on health are rather
complex as in many other natural products. The results of clini-
cal studies on in vitro, in vivo, and human indicate that curcu-
min may be effective in prevention and treatment of many
diseases, particularly cancer, by affecting various molecular tar-
gets. Safety, active ingredients, interactions, and dosage of the
medicine are highly important in treatment of diseases. For this
reason, the fact that curcumin is a safe natural product and its
cost is lower than drugs may give rise to the thought that curcu-
min can be used in treatment and prevention of diseases.
Because it prevents formation and progression of various dis-
eases, and has positive effects on health, a healthy individual
with a 70 kg body weight can consume 4–10 g turmeric powder
in accordance with JECFA and EFSA’s suggestion that curcu-
min’s ADI value should be 0–3 mg/kg. Oral intake of curcumin
exhibits poor bioavailability, so it limits significantly the thera-
peutic effects of this component. Other structural analogues of
curcumin are more bioavailable and effective, and they could
CRITICAL REVIEWS IN FOOD SCIENCE AND NUTRITION 2893

be designed as to be combined with large and well-controlled
clinical trials. It will be good to conduct more studies in order
to determine the effectiveness of curcumin, its analogues and
metabolites, interaction of drug-food and drug-nutrient more
firmly; to clarify the other possible biological activities; to
develop suggestions; to provide evidence about its relations
with other diseases.
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