Reviewed: Salem AM, Bamosa AO, Qutub HO, et al. Effect of Nigella sativa supplementation on lung function and inflammatory mediators in partly controlled asthma: a randomized controlled trial. Ann Saudi Med. 2017;37(1):64-67.

Asthma is an incurable condition caused by chronic inflammation in the lungs. The goal of treatment is to control or reduce the severity of exacerbations. Nigella (Nigella sativa, Ranunculaceae) seeds have anti-inflammatory, immunomodulatory, and antioxidant properties. Preliminary studies suggest that nigella may be beneficial for patients with asthma, but many of these studies have had weak designs. The purpose of this single-blind, randomized, placebo-controlled study was to evaluate the effects of nigella on various clinical measures and indicators of airway inflammation and airway constriction in patients with partly controlled asthma.

Asthma is an incurable condition caused by chronic inflammation in the lungs. The goal of treatment is to control or reduce the severity of exacerbations. Nigella (Nigella sativa, Ranunculaceae) seeds have anti-inflammatory, immunomodulatory, and antioxidant properties. Preliminary studies suggest that nigella may be beneficial for patients with asthma, but many of these studies have had weak designs. The purpose of this single-blind, randomized, placebo-controlled study was to evaluate the effects of nigella on various clinical measures and indicators of airway inflammation and airway constriction in patients with partly controlled asthma. 

Patients (N = 76, aged 18-65 years) with asthma according to the criteria of the US National Institutes of Health were recruited from the pulmonary outpatient clinic at the University of Dammam in Saudi Arabia. Included patients had partly controlled asthma according to Global Initiative for Asthma guidelines, were nonsmokers, had been on daily maintenance therapy with inhaled corticosteroids for at least three months, and were not taking any other asthma medications except for short-acting β-agonists. The study excluded patients who used additional asthma medications (e.g., leukotriene modifiers or oral steroids), had a severe exacerbation or hospitalization for asthma within one month prior to or during the study period, had a chronic disease, took less than 90% of the assigned study medication, or were pregnant or lactating.

Patients were randomly assigned to receive 1 g or 2 g of ground nigella seeds taken as either one 500-mg capsule twice daily or two 500-mg capsules twice daily (Bio Extracts Pvt Ltd.; Colombo, Sri Lanka) or placebo (520 mg of charcoal powder; Arkopharma Laboratories; Carros, France) for 12 weeks. Patients were also required to continue with their regular maintenance inhaler therapy. Most patients were taking 400 mcg of budesonide (a conventional corticosteroid asthma medication) once daily, and the remainder were taking 250 mcg of fluticasone propionate (a conventional drug used to treat non-allergic nasal symptoms) twice daily.

Control of asthma symptoms was assessed at six weeks and 12 weeks with the following measures: (1) the Asthma Control Test (ACT), which is used to assess daytime and nocturnal symptoms, activity limitations, rescue inhaler use/need, exacerbation frequency, and baseline lung function; (2) recording of moderate or severe exacerbations as defined by the American Thoracic Society and European Respiratory Society criteria; (3) spirometry to measure forced vital capacity, forced expiratory flow (FEF25-75%), and predicted values of forced expiratory volume at one second (FEV1% predicted); (4) peak expiratory flow (PEF) measured twice per day at home before medicine was taken; (5) measurement of fractional exhaled nitric oxide (FeNO); and (6) bloodwork to measure total levels of immunoglobulin E (IgE) and cytokines (interleukin [IL]-4, IL-10, IL-17, interferon-gamma [IFN-γ], and eotaxin). 

At baseline, all three groups were similar in pulmonary function tests and all parameters. Treatment with placebo had no significant effect on any measured parameter. At 12 weeks, both nigella groups experienced significant increases in cytokine IFN-γ (P = .05 for both groups). There were no significant changes in any other cytokine measured. Compared with baseline, 1 g of nigella (but not the 2-g dose) significantly reduced FeNO at 12 weeks (P < .05). Compared with baseline, 2 g of nigella significantly reduced IgE at 12 weeks (P < .01). Both nigella groups had significantly higher ACT scores compared with baseline (P < .001 for both groups) and compared with placebo (P < .01 for both groups) at six weeks and 12 weeks.

For pulmonary function tests, FEV1% predicted was significantly improved compared with baseline in patients treated with 2 g of nigella at six and 12 weeks (P < .05 for both time points). FEF25-75% predicted was significantly improved compared with baseline in patients treated with 2 g of nigella for six weeks (P < .01). Compared with placebo, the 1-g nigella groups had significant improvement in PEF variability at six and 12 weeks (P < .01 for both). The 2-g group experienced significant improvement in PEF variability only at 12 weeks (P < .05), compared to placebo.

Since nigella is a popular and traditionally used spice in India, the Mediterranean region, and other areas, it is not surprising that it was well-tolerated and that no adverse effects were reported.

The authors conclude that adding nigella to regular maintenance inhaler therapy can improve overall control and decrease exacerbations in patients with partly controlled asthma. The authors state that this is the first study to demonstrate that nigella can significantly decrease FeNO (a marker of inflammation underlying the pathogenesis of asthma) in patients with asthma. However, this effect was observed only with the 1-g dose. The authors do not hypothesize why the 2-g dose did not have the same effect. The improvements in function, as measured by the ACT, correspond with the decreases in FeNO seen in the 1-g group. IFN-γ is known to suppress inflammation in patients with asthma, and in this study there was a significant increase in IFN-γ with both doses of nigella. Prolonged inflammation can result in remodeling (structural changes) of lung tissue, and the authors point out that nigella may help reduce the severity of remodeling. The authors hypothesize that nigella may work by reducing pulmonary inflammation, which may ultimately prevent progression of bronchial remodeling. The authors were unable to receive consent for obtaining bronchoalveolar lavage or induced sputum samples to measure inflammatory cells directly.

One of the advantages of the study was the robust randomization scheme. One limitation of this study was that it was single-blind (i.e., the patients were blinded but not the researchers) rather than double-blind, which could have introduced bias into the data.

—Heather S. Oliff, PhD

Editor’s note: For more information on nigella, the reader is directed to the herb profile on Nigella sativa in HerbalGram issue 114.