]
Aloe vera has commonly been used in the treatment
of skin problems. Aloe vera products for topical
use are derived from a clear, viscous liquid that appears
when the leaves of the plant are cut, and this liquid is frequently an ingredient in cosmetics and alternative
medicine products.[,] These products are claimed to
be effective in the treatment of many dermal and mucosal
problems such as wounds, burns, frostbite, xerosis,
psoriasis, eczema, genital herpes, aphthous stomatitis,
and seborrheic dermatitis.[,] However, studies
have not found adequate evidence to support claims of
effectiveness of Aloe vera treatment. Although some
studies have demonstrated promising results in treating
burns and abrasions in particular, they have not
proven Aloe vera to be superior to standard treatment
for these conditions.[,] Aloe vera products for oral
consumption include capsules made of Aloe leaves,
dried latex, and Aloe vera juice.[] These products are
utilized especially in the treatment of constipation because
of a laxative effect. However, the US Food and
Drug Administration (FDA) has stated that use of aloe
as a laxative is not safe. Moreover, the FDA required
aloe laxative products to be removed from all sales points in the United States in 2002.[,] In recent
years, Aloe vera has frequently been claimed to have
an effect on cancer. In particular, topical use is alleged
to be effective in the prevention and treatment of skin
irritation after radiotherapy; however, clinical studies
do not support these claims.[,–]
Laboratory Studies on the Effects of Aloe Vera on
Cancer
In laboratory studies, Aloe vera has been shown to
have some anti-oxidant, anti-inflammatory, immunomodulatory,
and anti-cancer properties.[–] The
immunomodulatory properties of Aloe vera, which
contains many active components, are attributed to
acemannan, while its anti-proliferative properties are
attributed to the components anthracene and anthraquinone.[,]
In a study published in 2014, Aloe emodin, an anthraquinone
component in Aloe vera, inhibited the
proliferation and increased the radiosensitivity of HeLa
cervical cancer cell lines.[] In a laboratory study on
hepatocellular cancer cell lines, it also inhibited cell
proliferation and induced cell apoptosis.[] In a study
on breast cancer cell lines, it once again suppressed
proliferation,[] and in another study on colon cancer
cell lines, it induced apoptosis through the activation
of caspase-6.[] Similarly, there are also studies showing
that Aloe emodin inhibited cell growth in cell lines
of lung cancer, leukemia, and neuroectodermal cancer.[–] In another study, Aloin, another anthraquinone
component in aloe, inhibited angiogenesis
through suppression of vascular endothelial growth
factor (VEGF).[] In an in vitro study carried out on
neuroblastoma cells, Aloe vera was found to decrease
neuroblastoma cell proliferation by suppressing cyclin
D2 transcription.[] In a study on prostate cancer
cell cultures (PC3), Aloe emodin was found to inhibit
prostate cancer cell proliferation by acting through
mammalian target of rapamycin complex 2 (mTORC2)
(Table 1).[]
Table 1: Selected laboratory and clinical studies
Clinical Studies on the Effects of Aloe Vera on Cancer
Despite some positive results obtained from a few studies
on the anti-cancer potential of Aloe vera, such results
are not adequate to be reflected in clinical practice.
The most highlighted and advocated effect of Aloe
vera is the prevention and treatment of skin irritation
caused by radiotherapy.[] Clinical studies have produced
inconsistent results and have not verified this effect. In a Phase III study carried out on 225 breast
cancer patients treated with postoperative adjuvant
radiotherapy, it was stated that Aloe vera provided
no significant benefit to skin problems caused by radiotherapy.[] Another study combining 2 separate
Phase III randomized clinical studies had similar findings
regarding the effect of Aloe vera.[] Comparable
results were also obtained in a review compilation of 7
clinical studies.[] In another study that enrolled 57
patients with head and neck cancer, Aloe vera was observed
to delay the onset of radiotherapy-induced skin
lesions and reduce their intensity; however, it was ineffective
in the prevention of lesions or reducing their
incidence.[]
In a study that involved the evaluation of the use of
Aloe vera in conjunction with chemotherapy, a subset
of 240 patients with metastatic tumor was given chemotherapy
alone, while the rest also received 10 mg
daily oral dose of Aloe vera. Tumor regression rate and
3-year survival rate were found to be significantly higher
in the group given chemotherapy plus Aloe vera.[]
In a small epidemiological study, lung cancer incidence
was observed to be lower in those using Aloe vera orally
on a regular basis; however, the study was not of a
level that results might be considered promising.[]
In a systematic compilation published in 2011, the
prevention of oral mucositis due to chemotherapy
by using Aloe vera was studied. Despite some positive
results, researchers noted that this effect might be
specific to a certain chemotherapeutic agent or type
of cancer and emphasized the need for well-designed
studies with subgroup analyses.[] In a preliminary
study carried out on 20 patients with oral submucous
fibrosis, Aloe vera gel provided a benefit in reducing
the symptoms.[] In another study that enrolled 58
patients with head and neck cancer, the oral administration
of Aloe vera made no contribution in terms of
reducing symptoms or increasing quality of life (Table
1).[]
Potential Side Effects of Aloe Vera
Although many proponents of alternative medicine
claim that Aloe vera has no side effects, it is an herbal
treatment about which many toxicity cases have been
reported.[] Moreover, Aloe vera administered by injection
resulted in death in 4 reported cases.[,]
In a case reported in the literature, a 56-year-old
female patient with reticular lichen planus lesion in
her mouth declined use of corticosteroid and turned
to alternative medicine procedures that included the consumption of Aloe vera juice. Although she used this
product for a period of 11 months, there was no improvement
in oral lichen planus, and in fact, hypothyroidism
developed as well.[] In another case where
Aloe vera was used in conjunction with chemotherapy,
serious hypokalemia developed.[] In a study published
in 2010, 3 cases of toxic hepatitis due to use of
Aloe vera were reported.[] There are many other cases
of toxic hepatitis associated with Aloe vera reported
in the literature.[,] There are also cases in which
it delayed recovery of postoperative wounds,[] and
caused the development of Henoch-Schonlein purpura.[]
Abdominal cramps, diarrhea and related electrolyte
disorders due to the oral administration of Aloe
vera have been reported. In some preliminary studies,
Aloe vera was stated to have a blood sugar reducing
effect, and diabetic patients using or considering using
Aloe vera were warned about the risk of possible hyperglycemia.
The National Center for Complementary
and Integrative Health (NCCIH) states that there is not
adequate scientific evidence supporting the use of Aloe
vera for any health problem.[]
In a study conducted by the US National Toxicology
Program (NTP), the carcinogenic potential of the oral
administration of Aloe vera in mice was investigated. The results indicated that long-term exposure to Aloe
vera might be carcinogenic.[] Another study carried
out on mice showed that Aloe vera taken orally is likely
to trigger colon cancer;[] and another study showed
that Aloe vera may increase skin cancer induced by ultraviolet
rays.[]
In the literature, there is also evidence regarding
drug interactions with Aloe vera. A laboratory study
showed that the plant juice of Aloe vera inhibits the
CYP3A4 and CYP2D6 enzymes which may affect the
intracellular concentration of drugs metabolized by
these enzymes.[] It has been stated that use of Aloe
vera might increase the effects of antiarrhythmics, cardiac
glycosides, diuretics, and steroid drugs.[] In 1
instance, a possible sevoflurane-Aloe vera interaction
may be responsible for a women losing approximately
5 liters of blood during surgery.[]
