|Date: 11-30-2016||HC# 111621-557|
Mahdavi R, Namazi N, Alizadeh M, Farajnia S. Nigella sativa oil with a calorie-restricted diet can improve biomarkers of systemic inflammation in obese women: A randomized double-blind, placebo-controlled clinical trial. J Clin Lipidol. September-October 2016;10(5):1203-1211.
Obesity and inflammation are linked, and losing weight can help reduce inflammation. Black cumin (Nigella sativa, Ranunculaceae) is a commonly used plant in the Middle East that is traditionally used to treat conditions associated with inflammation and metabolic disorders, including rheumatoid arthritis, diabetes, and dyslipidemia. Thymoquinone (TQ), one of the bioactive compounds in black cumin, is presumed by these authors to be primarily responsible for black cumin's anti-inflammatory, antioxidant, and antihyperglycemic properties. Since TQ is fat-soluble, the authors used black cumin oil, rather than an aqueous product, in the first clinical trial to investigate the effects of black cumin combined with a weight-reduction diet on inflammatory markers (interleukin-6 [IL-6], tumor necrosis factor-alpha [TNF-α], and high-sensitivity C-reactive protein [hs-CRP]) in obese women.
In this double-blind, placebo-controlled, randomized, clinical trial, women aged 25-50 years with a body mass index (BMI) > 30 and < 35 kg/m2 were recruited at the obesity clinic affiliated with Tabriz University of Medical Sciences, Iran, from April through July 2014. Exclusion criteria included a history of diabetes or any of a variety of chronic illnesses, current or recent infectious disease, recent (≤ 1 month) use of antibiotics, pregnancy, smoking, use of alcohol, use of drugs with blood-thinning effects or any herbal or antioxidant supplements, current dieting, and use of anti-obesity drugs within 6 months. Subjects were randomly divided into 2 groups based on age and BMI using block randomization. All the subjects received an individualized calorie-restricted diet that provided 500 kcal less than their calculated resting energy expenditure and contained 30% calories from fat, 15% from protein, and 55% from carbohydrate; subjects were also advised of healthy food choices. Dietary intakes and compliance were estimated using 24-hour dietary recall on 1 weekend day and 2 weekdays, apparently before and after the study period.
For 8 weeks, the intervention group received black cumin oil (3 g/day) in soft gel capsules (1 g/capsule, taken 30 minutes before each main meal). The placebo group received similar amounts of sunflower (Helianthus annuus, Asteraceae) oil as a placebo. Black cumin and sunflower oil were prepared by Dana Company (Tabriz, Iran); capsules were identical in size and color. Black cumin oil was prepared using a previously published cold-press procedure, which had a 30% yield. Gas chromatography-mass spectrometry was used to determine fatty acid concentrations in both oils. The oils were roughly similar in fatty acid content, and both contained ~57% linoleic acid. In the black cumin oil, TQ was measured at 1.25 mg/100 mg, corresponding to a total daily dose of 37.5 mg. Serum levels of IL-6, TNF-α, and hs-CRP were measured after overnight fasting at baseline and end of trial. Primary outcomes were the effects of black cumin oil supplementation in the context of a low-calorie diet on weight, dietary antioxidant intake, and inflammatory markers (IL-6, TNF-α, and hs-CRP). Secondary outcomes were effects on energy, macronutrient, and fiber intakes. In some analyses, results were adjusted by analysis of covariance for weight changes; energy, macronutrient, dietary antioxidant, and fiber intake changes; and baseline values.
Ninety subjects were recruited, and 84 subjects completed the trial. Two subjects in the black cumin group were excluded—1 due to pregnancy and 1 because of stomach ache. Four subjects were excluded from the placebo group (3 subjects due to lack of adherence and 1 due to stomach ache). Subjects were excluded if they took < 95% of the supplements. However, data analysis was performed on an intention-to-treat basis, with all 90 included. Subjects reported no adverse side effects other than mild gastrointestinal problems.
At baseline, there were no significant differences in body weight or BMI between the 2 groups. After the intervention, weight decreased significantly compared to baseline in both groups (−6.0% for the black cumin group vs. −3.5% for the placebo group; both P < 0.01), as did BMI (−3.9% and −1.5%, respectively; both P < 0.01). Weight loss was significantly greater in the black cumin group compared to placebo (P = 0.03), while the reduction in BMI was not significantly greater. Total energy, carbohydrate, and fat intakes decreased significantly in both groups compared to baseline (P < 0.01 for all except P = 0.04 for fat intake in the placebo group). Reduction of energy intake in the black cumin group was greater than in the placebo group at the end of the trial but not significantly so (−782 vs. −530 kcal/day; P = 0.1).
At the end of the trial, there were no significant differences in intakes of specific macronutrients (adjusted for baseline values), antioxidant vitamins and minerals, or fiber. At baseline, TNF-α, hs-CRP, and IL-6 concentrations did not differ significantly between groups. End-of-trial comparison revealed that TNF-α levels decreased more in the black cumin group as compared to placebo (−40.8% vs. −16.1%; P = 0.04), as did hs-CRP (−54.5% vs. −21.4%; P = 0.01); changes from baseline were significant only in the black cumin group, both at P < 0.01. However, declines in IL-6 (−8.6% vs. −2.4%) were small and not statistically significant.
Eight weeks of supplementation with black cumin oil in combination with a calorie-restricted diet led to a significant decrease in body weight, TNF-α, and hs-CRP compared to placebo in obese women, indicating that black cumin oil may help manage weight and inflammation. The mechanisms of action of black cumin are not well understood. The findings of this study suggest that the anti-inflammatory effects of black cumin and a weight-reduction diet may interact synergistically. The researchers of this study recommend that future trials try a crossover design, consider including a purified TQ treatment arm or measuring serum levels of TQ and its metabolites, and, lastly, evaluate different dosages and forms of black cumin both alone and in conjunction with a weight-reduction diet. They also note that this study is limited by its relatively short duration and use of only female subjects; future studies should ideally be longer and include both sexes.—Alexis Collins, MA, M