Review of Black Cumin for Metabolic Disorders

Black cumin (Nigella sativa, Ranunculaceae) seed is popular in the Middle East and Southeast Asia for treating diabetes, dyslipidemia, hypertension, and obesity. However, clinical evidence is inconclusive. The purpose of this systematic review was to evaluate the clinical and biochemical effects of black cumin on lipid profiles, glycemic factors, blood pressure, and anthropometric indices (weight, body mass index [BMI], and waist circumference), all of which are parameters of metabolic syndrome.

The following databases were searched from inception through June 2014: PubMed, Google Scholar, Thomson Reuters Web of Science, and Cochrane. The following medical subject headings (MeSH) and title/abstract (tiab) search terms were used: (“Nigella sativa” [MeSH] OR “black seed” [tiab] OR “black cumin” [tiab] OR “Kalonji” [tiab]) AND “Triglycerides” [MeSH] OR “Cholesterol” [MeSH] OR “Lipoproteins, LDL” [MeSH] OR “Lipoproteins, HDL” [MeSH] OR “Blood glucose” [MeSH] OR “Hemoglobin A, Glycosylated” [MeSH] OR “Blood pressure” [MeSH] OR “Body mass index” [MeSH] OR “Waist circumference” [MeSH]). The inclusion criteria were (1) published in English, (2) the effect of black cumin on clinical or biochemical parameters, and (3) clinical trial. The exclusion criteria were (1) animal studies, (2) review studies, (3) the effect of black cumin on unrelated blood or clinical parameters, (4) the effect of black cumin combined with other plants or exercise, and (5) duplicated studies.

A total of 515 articles were located, and 18 studies (with a total of 1531 subjects) met the inclusion/exclusion criteria. The studies were highly heterogeneous: five studies were randomized, double-blind, controlled studies; five studies had no control group, and eight studies were randomized controlled studies. Included patients were aged 18-65 years and had diabetes (n = 5 studies), metabolic syndrome (n = 7 studies), hyperlipidemia (n = 4 studies), hypertension/coronary disease (n = 2 studies), obesity (n = 1 study), or were healthy subjects (n = 4 studies). All treatments were oral and doses ranged from 200 mg/day to 5 g/day of seed extract (n = 2 studies), seed oil (n = 8 studies), or seed powder (n = 13 studies). Treatment duration ranged from two weeks to six months.

Table 1 summarizes the study findings. The authors note significant findings; however, they do not report whether the changes are compared with baseline or control. In Table 1, the column titled “overall effect” indicates which parameters had more evidence in favor of a significant improvement.

Table 1: Summary of Number of Studies with Significant Improvements in Measured Parameters

Number of Studies
Parameters Significant improvement No significant effect Overall effect (Yes/No)
Triglycerides 7 10 No
Total cholesterol 10 4 Yes
Low-density lipoprotein (LDL) cholesterol 11 3 Yes
High-density lipoprotein (HDL) cholesterol 6 10 No
Fasting blood sugar 13 3 Yes
Glycosylated hemoglobin 4 Yes
Blood pressure 4 5 No
Weight 2 6 No
BMI 2 6 No
Waist circumference 1 5 No

Based on the number of studies demonstrating a significant improvement, the evidence weighs more in favor of black cumin improving total cholesterol, LDL, fasting blood sugar, and glycosylated hemoglobin. Evidence does not support an effect of black cumin on blood pressure or anthropometric indices. A total of 10 studies evaluated safety. Two studies that treated subjects with 5 mL/day black cumin seed oil reported mild nausea that resolved after one week of treatment. Eight studies measured liver and kidney function and reported no adverse effects.

The authors conclude that black cumin should be “a complementary treatment protocol for many diseases, especially metabolic disorders.” However, even though the evidence leans more favorably in the direction of a benefit for some parameters, the heterogeneity of the studies must be taken into consideration. It would have been advantageous if the researchers conducted a meta-analysis to provide more scientific rigor to their analysis and conclusions. Recommendations for the effective dose or preparation cannot be gleaned from this analysis. More research is needed if black cumin is to be recommended as a treatment for patients with symptoms of metabolic syndrome.

Resource:

Mohtashami A, Entezari MH. Effects of Nigella sativa supplementation on blood parameters and anthropometric indices in adults: A systematic review of clinical trials. J Res Med Sci. 2016;21:3. doi: 10.4103/1735-1995.175154.

 

Review on the Effectiveness of Aloe Vera for Oral Diseases

The succulent leaves of the aloe vera (Aloe vera, Xanthorrhoeaceae) plant have been used medicinally for hundreds of years. The clear gel, or mucilage, found inside the leaves, is well known for having wound-healing, anti-inflammatory, antioxidant, antitumor, and analgesic properties. These attributes could potentially help in treating oral ailments. The aim of this systematic review was to accumulate and assess clinical trials evaluating the effectiveness of aloe vera preparations in treating various oral diseases.

Studies on aloe vera were eligible if they were randomized, controlled, single- or double-blind, cross-sectional, or case-controlled trials published as full papers in English. PubMed (Medline), Scopus, Cochrane Database, Embase, and ScienceDirect were searched from July 1998 to December 2015. Search terms included “herbs,” “Ayurveda,” and “oral mucosa.” The Jadad scale (a scale ranging from 0 to 5, where the higher number indicates higher trial quality) was used to assess quality.

In total, 15 articles met the inclusion criteria. Only six trials achieved a Jadad score of 4/5; the rest scored between 0 and 3. Most studies were carried out in hospital clinics in countries such as Iran, Spain, India, the United States, and Saudi Arabia. Study populations ranged from 20 to 110 patients with clinically diagnosed oral mucosal lesions. Five of the 15 studies focused on patients with oral lichen planus (OLP). Two studies examined efficacy on oral submucous fibrosis (OSMF) in patients. The remaining studies investigated the effects of aloe vera on burning mouth syndrome, radiation-induced mucositis, Candida-associated denture stomatitis, xerostomia, and minor recurrent aphthous/stomatitis. All studies demonstrated a low risk of bias using the Cochrane Risk of Bias Tool. Blinding bias was low among all studies except one on Candida-associated denture stomatitis. Randomization sequence bias was high in seven studies.

Most studies showed statistically significant results for efficacy of aloe vera in treatment of oral lesions. There were no withdrawals due to adverse effects of aloe vera in any of the clinical trials. This review found aloe vera was most beneficial in patients with OLP. All five studies in patients with OLP demonstrated a low risk of bias and proved aloe vera effectively reduced lesion-associated pain and burning sensation, leading to partial or complete remission of symptoms. Studies conducted in patients with OSMF showed aloe vera to be effective in all stages of OSMF, particularly mild-stage OSMF clinically and early-stage OSMF histopathologically. Pain and burning sensations were significantly reduced in OSMF studies, and other outcome measures (mouth opening, cheek flexibility, tongue protrusion) were promising. The overall quality of OSMF studies was good with low risk of bias. Four trials in patients with aphthous stomatitis were reviewed, consisting of 319 patients. The overall quality of these studies was good. Lesion healing improved and there was significant remission of pain, erythema, and lesion size. Aloe vera was found to be less beneficial in patients with radiation-induced mucositis, as it was not effective in improving tolerance to head and neck radiotherapy, decreasing mucositis, or decreasing soreness; however, quality-of-life measures were improved in the patients receiving aloe vera. In the single Candida study reviewed, aloe vera had an anticandidal oral effect surpassed by that of Triphala, an Ayurvedic combination remedy.

Lack of randomization, lack of double-blinding, and a lack of description for withdrawals, dropouts, and methods to generate the sequence of randomization were all prevalent limitations that excluded trials from this review. The studies included demonstrated aloe vera has a wide spectrum of properties and uses and is a promising agent in treating oral lesions. However, based on this review, aloe vera may be better suited to OLP, OSMF, and aphthous stomatitis lesions versus those induced by radiation or Candida. For aloe vera to be more seriously considered for clinical treatment of oral lesions, future clinical trials should strive to meet more rigorous standards.

Resource:

Nair GR, Naidu GS, Jain S, Nagi R, Makkad RS, Jha A. Clinical effectiveness of aloe vera in the management of oral mucosal diseases – A systematic review. J Clin Diagn Res. August 1, 2016;10(8): ZE01-ZE07. doi: 10.7860/JCDR/2016/18142.8222.