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Nigella Sativa Oil Reduces IL-6 and Fasting Glucose in PCOS but Leaves Insulin Resistance Unchanged
In a 12-week placebo-controlled trial, daily supplementation with 1000 mg of Nigella sativa oil significantly lowered serum IL-6 by an adjusted mean difference of 4.21 units (95% CI −6.34 to −2.08; p < 0.001) and fasting blood glucose by 8.16 mg/dL (95% CI −12.73 to −3.58; p < 0.001) compared with placebo in women with PCOS. Despite these improvements in inflammatory and glycemic markers, no corresponding effects were observed on insulin resistance indices or reproductive hormones.
What Was Studied
The trial examined whether oral Nigella sativa (black seed) oil supplementation could reduce serum interleukin-6 (IL-6) and insulin levels in women diagnosed with polycystic ovary syndrome — a condition characterized by both metabolic dysfunction and chronic low-grade inflammation. The rationale centered on the proposed anti-inflammatory properties of N. sativa oil as a potential adjunctive dietary strategy in PCOS management.
How It Was Studied
This was a randomized, double-blind, placebo-controlled clinical trial enrolling 60 women with confirmed PCOS, equally divided between intervention and placebo arms (n = 30 per group). Participants in the active arm received 1000 mg of N. sativa oil daily for 12 weeks, while the control group received a matched placebo over the same period. Outcomes assessed included serum IL-6, fasting blood glucose, fasting insulin, insulin resistance indices (HOMA-IR and QUICKI), luteinizing hormone, total testosterone, intermenstrual interval, and menstrual duration. Between-group comparisons were performed after adjustment for baseline values.
What Was Observed
- IL-6 was meaningfully lower in the N. sativa group after 12 weeks, with an adjusted mean difference of −4.21 units (95% CI −6.34 to −2.08; p < 0.001), indicating a statistically significant reduction in this key pro-inflammatory cytokine compared with placebo.
- Fasting blood glucose was also significantly reduced in the intervention group, with an adjusted mean difference of −8.16 mg/dL (95% CI −12.73 to −3.58; p < 0.001), suggesting a modest but statistically robust improvement in glycemic status.
- No significant between-group differences were detected for fasting insulin, HOMA-IR, or QUICKI, indicating that despite lower fasting glucose, insulin resistance as measured by these indices was not meaningfully altered over the 12-week period.
- Hormonal markers and menstrual duration remained unchanged between groups, though the intermenstrual interval was significantly shorter in the N. sativa group, suggesting a possible but not fully characterized effect on cycle regularity.
Why This Matters
PCOS affects an estimated 5%–10% of women of reproductive age and involves intertwined inflammatory and metabolic disturbances. The observation that N. sativa oil reduced IL-6 without producing parallel improvements in insulin resistance indices raises substantive questions about the mechanistic relationship between inflammatory signaling and metabolic dysfunction in PCOS. These findings indicate that anti-inflammatory effects from dietary supplementation may not be sufficient alone to reverse insulin resistance within a 12-week window, suggesting these pathways may be partially independent or require longer intervention periods.
How to Read This Result
Given the small sample size of 60 participants, the short 12-week treatment duration, and a study quality signal rated as low, these results should be regarded as preliminary and hypothesis-generating rather than definitive — particularly for outcomes such as insulin resistance and hormonal parameters where statistical power was likely insufficient to detect clinically meaningful differences.
Limitations
The trial enrolled only 60 participants (30 per arm), substantially limiting statistical power to detect differences in secondary outcomes including insulin resistance indices and hormonal measures. The 12-week follow-up may be too short to capture meaningful hormonal or longer-term metabolic changes in a complex endocrine condition. The absence of significant effects on insulin resistance and reproductive hormones constrains broader conclusions about clinical utility. The authors explicitly acknowledge the need for larger, adequately powered trials before firm recommendations can be made.