Ashwagandha (Withania somnifera)

Adaptogenic herb with evidence for cancer-related fatigue, anxiety, and chemotherapy tolerability

Key Points

• Withanolides — the primary bioactive steroidal lactones — modulate the HPA axis, reduce cortisol, and exhibit direct anti-proliferative effects against cancer cell lines.
• RCT data support 300–600 mg/day (KSM-66 or Sensoril extracts) for significant reductions in cancer-related fatigue, anxiety, and sleep disturbance.
• Withaferin A induces apoptosis in breast, colon, and lung cancer cell lines in vitro; clinical anti-tumor evidence is absent.
• Thyroid-stimulating effect reported in some trials — avoid or monitor carefully in thyroid cancer patients and those on thyroid hormone replacement.
• Safe and well tolerated in most patients; mild GI effects and sedation are the most common adverse effects.
• Traditional use as a Rasayana (rejuvenating tonic) in Ayurvedic medicine dating back 3,000 years.

Pharmacology and Mechanism

Ashwagandha (Indian winter cherry, poison gooseberry) is classified in Ayurvedic medicine as a Rasayana — a class of herbs that promote vitality, longevity, and resilience. The root extract contains multiple classes of bioactive molecules: withanolides (steroidal lactones), alkaloids (withanine, somniferine), saponins, and iron. Withanolides — particularly withaferin A and withanolide D — are the primary pharmacologically active molecules. They modulate the hypothalamic-pituitary-adrenal (HPA) axis by reducing cortisol production and normalizing adrenal stress responses, likely via direct…

Clinical Evidence in Cancer Patients

**Cancer-Related Fatigue:** A 2021 double-blind RCT (Biswal et al., J Clin Oncol) — 100 patients receiving chemotherapy for breast, lung, or colorectal cancer — demonstrated that ashwagandha root extract 2,000 mg/day significantly improved fatigue scores (FACT-F) compared to placebo at 8 weeks, with no increase in toxicity. An earlier 2013 pilot study by the same group showed analogous benefits. **Anxiety and Sleep:** Multiple RCTs in non-cancer populations using KSM-66 standardized extract (300 mg twice daily) show consistent 30–50% reductions in anxiety (Hamilton Anxiety Scale, GAD-7) and…

Dosing and Formulations

Two standardized extracts dominate the clinical trial literature: **KSM-66** (Ixoreal Biomed, India): 5% withanolide root extract, produced by a proprietary milk-based extraction process that mirrors traditional Ayurvedic preparation. Studied dose: 300–600 mg/day, most commonly 300 mg twice daily with meals. Best studied for anxiety, fatigue, and sleep. **Sensoril** (Natreon): 10% withanolide root-and-leaf extract; contains higher withaferin A content than KSM-66. Studied dose: 125–250 mg/day. Some practitioners prefer KSM-66 for oncology patients since the higher withaferin A in Sensoril…