Black seed oil: is there any evidence behind the new craze?

I don’t know whether you noticed but everyone seems to be going on about the new wonder SCAM (so-called alternative medicine) ‘BLACK SEED OIL’ (BSO). If you go on the Internet, you’ll find all sorts of health claims for it, e.g.:

• -Reduces Inflammation
• -High in Antioxidants
• -Can Lower Cholesterol
• -Helps to Fight Cancer
• -Can Kill Off Bacteria
• -Balances Blood Sugar
• -Helps to Lower Blood Pressure

Interesting?

I am – as always – doutful. Nonetheless, I had a look at BSO to find out more.

BSO (also known as black caraway, black cumin or kalonji oil) is derived from the tiny black seeds of Nigella sativa (N. sativa) that grows in hot areas like Eastern Europe, Northern African, and Southwestern Asia, etc. The Wikipedia entry states that “despite considerable use of N. sativa in traditional medicine practices in Africa and Asia, there is insufficient high-quality clinical evidence to indicate that consuming the seeds or oil can be used to treat human diseases”.

But Wiki is often not up-to-date, and I therefore looked into Medline. To my surprise, I found research to be extraordinarily active.

Nigella sativa contains several phytochemical compounds, such as thymoquinone, p-cymene, α-thujene, longifolene, β-pinene, α-pinene, and carvacrol. They confer an antioxidant effect to the seeds, leading to a potent anti-inflammatory effect. Particularly, thymoquinone increases the levels of antioxidant enzymes that counter oxidative stress in the liver. Additionally, the essential oil in N. sativa seeds effectively inhibits intestinal parasites and shows moderate activity against some bacteria, including Bacillus subtilis and Staphylococcus aureus. Thymoquinone exhibits minimum inhibitory concentrations (MICs) of 8-16 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA) and exhibits MIC 0.25 µg/mL against drug-resistant mycobacteria. Similarly, quercetin shows a MIC of 2 mg/mL against oral pathogens, such as Streptococcus mutans and Lactobacillus acidophilus. Furthermore, endophytic fungi isolated from N. sativa have demonstrated antibacterial activity. Further mechanisms involve inducing apoptosis, and inhibiting migration and invasion.  N Sativa supplementation significantly decreases serum C-reactive protein, tumor necrosis factor-alpha, and malondialdehyde levels. It also improves total antioxidant capacity and superoxide dismutase  levels.

But these effects do not neccessarily mean that BSO is clinically effective for any condition, particularly in view of its low bioavailability. So, what does the clinical evidence tell us? Here are just 9 of the most recent studies and reviews:

1. This study aimed to investigate the possible beneficial cardioprotective effect of Nigella sativa in pediatric patients with type 1 diabetes mellitus. Sixty children and adolescents with type 1 diabetes were randomized into two groups: group I (n = 30) who received Nigella sativa seed oil 450 mg twice daily after meals for 3 months in addition to insulin, and group II (n = 30) who received insulin alone. Echocardiographic examinations were performed before and after the treatment. The lipid profile, malondialdehyde, nitric oxide, tumor necrosis factor-α, transforming growth factor-β, and troponin I were also measured before and after Nigella sativa treatment. After 3 months of Nigella sativa administration, group I had significantly lower cholesterol and low-density lipoprotein-cholesterol, malondialdehyde, nitric oxide, tumor necrosis factor-α, transforming growth factor-β, and troponin I levels compared with their pretreatment levels and compared with group II. In addition, group I had a significantly higher left ventricular E’/A’ ratio and two-dimensional left ventricular global longitudinal strain (2D-LV GLS) compared with baseline values and compared with group II after treatment. Conclusions: Nigella sativa can improve subclinical left ventricular dysfunction in pediatric patients with type 1 diabetes mellitus.
2. This study evaluated the effects of Nigella sativa L. extract on glycemia among adolescents with PCOS. This secondary analysis used data from a randomized controlled trial conducted between March 2022 and March 2023. One hundred sixteen adolescent girls aged 12-18 years with PCOS were randomized into two groups. The intervention group received 1000 mg/day of Nigella sativa extract for 16 weeks, while the control group received 10 mg/day of medroxyprogesterone for 10 days per menstrual cycle over the same period. Fasting plasma glucose (FPG) and one- and two-hour post-prandial glucose levels were measured at baseline and after the intervention. 103 completed the study (50 in the Nigella sativa group and 53 in the control group). At baseline, there were no significant differences in FPG (p = 0.294), though the control group had higher one-hour (p = 0.002) and two-hour (p = 0.006) post-prandial glucose levels. Post-intervention, significant interaction effects were observed for FPG (p = 0.004) and two-hour post-prandial glucose (p = 0.023), indicating more significant reductions in the Nigella sativa group compared to the control group. Conclusions: Considering the observed effect of Nigella sativa supplementation on FPG and two-hour post-prandial glucose, it may offer a complementary approach to managing glycemia in adolescent PCOS. However, further research is warranted.
3. This systematic review and meta-analysis of randomized controlled trials (RCTs) sought to evaluate the effects of Nigella sativa (N. sativa) consumption on glycemic index in adults. A systematic literature search up to December 2023 was completed in PubMed, Scopus, and Web of Science, to identify eligible RCTs. Random effects models were assessed based on the heterogeneity tests, and pooled data were determined as weighted mean differences with a 95 % confidence interval. Finally, a total of 30 studies were found to be eligible for this meta-analysis. The pooled results using random effects model indicated that N. sativa supplementation significantly reduced FBS (SMD: -1.71; 95 % CI: -2.11, -1.31, p <0.001; I²= 92.7 %, p-heterogeneity <0.001) and HA1c levels (SMD: -2.16; 95 % CI: -3.04, -1.29, p <0.001; I²= 95.7 %, p-heterogeneity <0.001) but not effect on insulin (SMD = 0.48; 95 % CI: -0.53, 1.48, P = 0.353; I²= 96.1 %, p-heterogeneity <0.001), and HOMA-IR (SMD: -0.56; 95 % CI: -1.47, 0.35, p=0.229; I²= 95.0 %, p-heterogeneity <0.001). Conclusion: the evidence supports the consumption of N. sativa to reduce FBS and HA1c levels. Additional research, featuring extended durations and robust study designs, is necessary to determine the ideal dosage and duration of N. sativa supplementation for achieving a positive impact on glycemic markers.
4. In this systematic review, the objective is to assess the effects of Nigella Sativa on parameters that reflect metabolic syndromes, such as lipid profile, blood pressure, blood glucose, and anthropometry indices. Six out of 8 randomised controlled trials (n:776) demonstrated a significant improvement in lipid profile (p <0.05), 5 out of 7 trials (n:701) showed a significant reduction in glycaemic indices (p <0.05), 1 out of 5 trials (n:551) demonstrated significant improvements in blood pressure (p <0.05), and 2 out of 7 trials (n:705) showed a significant reduction in anthropometric measurements (p <0.05). Conclusion: Nigella Sativa has proved to have a significant positive effect on lipid profile and glycaemic index. The results showed in the parameters of blood pressure and anthropometric indices are less convincing, as results were inconsistent across studies. Nigella Sativa can therefore be recommended as an adjunct therapy for metabolic syndrome.
5. This study was designed to investigate the effect of Nigella sativa supplementation on polycystic ovary syndrome (PCOS) symptoms and their severity in adolescents. The current randomized clinical trial was conducted on 114 adolescents with PCOS who were referred to gynecologist offices and clinics in Gonabad, Iran from March 2022 to March 2023. Participants were randomly allocated to the intervention (Nigella sativa 1000 mg/day) and control (10 mg/day medroxyprogesterone from the 14th day of the cycle for 10 nights) groups. The study duration was 16 weeks. Ovarian volume (measured by ultrasound), anthropometric and blood pressure; serum testosterone, dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), luteinizing hormone (LH), hirsutism severity (Ferriman-Gallwey score) levels were evaluated before and after the study. Data from 103 participants (control group = 53, intervention group = 50) were analyzed. The mean age of participants was 17.0 (Interquartile range [IQR]:2.0). The mean difference in hirsutism score changes (p < 0.001), right (p = 0.002), and left (p = 0.010) ovarian volume, serum LH (p < 0.001) and testosterone (p = 0.001) were significantly higher in the intervention group compared to the control group. The frequency of oligomenorrhea, menometrorrhagia, and amenorrhea, were significantly reduced after the study in the intervention group compared to the control group (ps < 0.001). Conclusions: Short-term Nigella sativa supplementation may be effective in reducing ovarian volume and improving hormonal balance, and menstrual irregularities in adolescents with PCOS. Further research and long-term studies are warranted to validate the potential therapeutic effects of Nigella sativa in adolescents with PCOS.
6. This study evaluates the efficacy of a novel mucoadhesive patch containing Nigella sativa 10% extract compared to triamcinolone 0.1% in alleviating symptoms and reducing lesion severity in patients with erosive-atrophic oral lichen planus. A pilot study comprising two groups, each with 10 patients, was conducted. The intervention group received mucoadhesive patches containing N. sativa 10% extract, while the control group received triamcinolone acetonide 0.1% patches. Pain and burning intensity, measured through visual analog scale, and lesion severity based on the Thongprasom scale were assessed weekly for 4 weeks. Descriptive records were kept for side effects and patient satisfaction. Pain and burning intensity decreased in both groups throughout the sessions, with the N. sativa group showing a greater reduction than the triamcinolone group. The reduction in burning intensity within each group was significant (p < .001), and there was a significant difference between groups only in the second session (p = .045). The overall difference between groups was not significant (p > .05). Lesion severity also decreased significantly in both groups (p < .001), with a significant difference between groups observed in the third session (p = .043) and overall throughout the study (p = .006). Conclusion: The use of N. sativa extract in mucoadhesive patches was as effective as corticosteroids in reducing pain, burning, and lesion severity in patients with oral lichen planus, with N. sativa showing superior results in some sessions. Notably, no significant complications were observed with N. sativa use, making it a promising treatment option for lichen planus.
7. This study aimed to explore the impact of N. sativa supplementation on the lipid profile of adult participants. We searched Scopus, Web of Science, PubMed, Cochrane, and Web of Science databases until December 2022. Random effects models were used, and pooled data were determined as standardized mean differences with a 95% confidence interval. The findings of 34 studies with 2278 participants revealed that N. sativa supplementation significantly reduced total cholesterol (TC) (SMD: -1.78; 95% CI: -2.20, -1.37, p < 0.001), triglycerides (TG) (SMD: -1.2725; 95% CI: -1.67, -0.83, p < 0.001), and low-density lipoprotein cholesterol (LDL-C) (SMD: -2.45; 95% CI: -3.06, -1.85; p < 0.001) compared to control groups. However, a significant increase was found in high-density lipoprotein cholesterol (HDL-C) (SMD: 0.79; 95% CI: 0.38, 1.20, p < 0.001). Conclusion: N. sativa has improved effects on TG, LDL-C, TC, and HDL-C levels. Overall, N. sativa may be suggested as an adjuvant anti-hyperlipidemic agent.
8. In this double-blind clinical trial, 70 nulliparous pregnant women referred to Hajar Hospital and Imam Ali clinics of Shahrekord and had missed abortion before the 12-week gestational age were selected and randomly divided into two interventions and control groups. The intervention group received 5 g of Nigella sativa oil alone daily for up to 3 days and the control group received a placebo. In case of nonresponse, 3 days after the last dose of medication or placebo, 800 μg of misoprostol (vaginal) were used. Data were analyzed by SPSS software. The chi-square test, Fisher’s exact test, independent t-test and paired t-test were used for analytical statistics. According to the results, 18 cases (51.4%) in the intervention group and seven cases (20%) in the control group showed complete evacuation of uterine contents which had a significant difference (p < 0.05). The frequency of vagina physical examination and type of hemorrhage did not show any significant difference between the two groups before and after the intervention. After the intervention, human chorionic gonadotropin (HCG) was significantly decreased in the intervention group but did not change in the control group (p < 0.05). The frequency of adverse events in the intervention group was three (8.6%) and in the control group was one (2.9%) which had no significant difference. Conclusion: Nigella sativa improves the outcome of missed abortion by reducing HCG and facilitating cervix dilatation and delivery of uterine contents.
9. This systemaatic review evaluated the role of Nigella spp in managing allergic rhinitis (AR), a comprehensive review through systematic reviews and meta-analyses was conducted. To carry out a meta-analysis of clinical trials that used Nigella spp in treating AR based on current data. A meta-analysis of randomized controlled trials (RCTs) was performed. Various databases, including PubMed, Web of Science, Embase, Science Direct, Springer Link and the Cochrane Library, were searched until October 2023 to obtain RCTs assessing impact of Nigella spp in the control of AR. The current meta-analysis was carried out with a random-effects model. There were 8 studies enrolled, and our meta-analysis findings revealed that, relative to the control group, observation group exhibited the markedly increased total effective rate for allergic rhinitis treatment (odds ratio [OR] = 4.24, 95% confidence interval [CI] (2.57, 7.27), and p < 0.00001); three studies showed that the effect of Nigella spp for nasal symptoms treatment among patients with allergic rhinitis was superior in observation group to control group [mean difference = -2.60, 95% CI (-2.82, -2.38), p < 0.00001]; adverse effects occurred in five studies, all of which were transient, did not require medical intervention, and were not statistically significant between the two groups [OR = 1.01, 95% CI (0.59, 1.73), p = 0.98]. Conclusion: The observation group demonstrated relative safety and had an enhanced effect on allergic rhinitis treatment and total nasal symptom improvement than the control group. The inclusion of fewer studies and the lower quality of trial design might affect the stability of the results. However, the evidence-based findings that Nigella spp for allergic rhinitis treatment is more accurate should be validated in future large-scale, multicenter, and well-designed RCTs.

Yes, I know: the evidence is not perfect for any of the indications. In addition, there is a problem with low bioavailability. And I am suspicious of any SCAM that seems to be effective for an incredibly long list of conditions.

At the same time, I have to admit that, collectively, the research on BSO is impressive. As BSO has been used for centuries (as a spice etc.), serious adverse effects seem unlikely. The evidence regarding its effectiveness might not be fully convincing but, in my book, it is encouraging.