アダプトゲン臨床用量 · 300–600mg/day (KSM-66 extract)効果発現時間 · Stress and cortisol effects measured at 60 days; memory effects at 8 weeks (MCI trial)

Ashwagandha (KSM-66)

Name: Ashwagandha (KSM-66) — Human Clinical Effect Matrix
Creator: The Nootropic Lab
License: https://creativecommons.org/licenses/by/4.0/

A 2012 RCT in chronically stressed adults (Chandrasekhar et al., KSM-66 600mg/day, 60 days; extract supplied by its maker Ixoreal Biomed) found serum cortisol fell 27.9% versus 7.9% on placebo and perceived stress fell 44%. A 2024 meta-analysis of 9 RCTs confirmed significant reductions in perceived stress, anxiety and cortisol, though a 2019 crossover trial of a low-dose extract in older overweight men found no cortisol effect. A 2017 RCT (Choudhary et al., 300mg twice daily, 8 weeks) improved memory and executive function — in adults with mild cognitive impairment, not healthy adults. Liver-injury case reports exist, and Denmark banned ashwagandha supplements in 2023.

By The Nootropic Lab editorial teamUpdated 2026年10月9日8 min read✓ Fact-checked

エビデンス確認日: 2026年9月28日

作用機序

Ashwagandha (Withania somnifera) is an Ayurvedic adaptogen. Its withanolides modulate the HPA axis to reduce cortisol, while also inhibiting acetylcholinesterase (preserving acetylcholine) and promoting GABA receptor activity for anxiolytic effects. KSM-66 is the most studied full-spectrum root extract.

臨床エビデンスの概要

ヒト効果マトリクス

Based on human clinical trials only. Animal and in-vitro data excluded.

効果	エビデンス	効果の大きさ	研究数	備考
Cortisol Reduction	strong	大	3	27.9% vs 7.9% serum cortisol drop at 600mg/day (Chandrasekhar 2012) and a significant pooled effect in a 9-RCT meta-analysis; a low-dose crossover trial in older overweight men found no cortisol change, so the effect is dose- and population-dependent.
Anxiety & Stress	strong	大	2	Perceived stress fell 44% vs 5.5% (Chandrasekhar 2012); the 2024 9-RCT meta-analysis found significant reductions on the Perceived Stress and Hamilton Anxiety scales.
Sleep Quality	moderate	中	—	A 90-day RCT (Gopukumar 2021) reported improved sleep-quality (PSQI) scores; sleep is usually a secondary endpoint.
Memory (Mild Cognitive Impairment)	preliminary	中	1	Choudhary 2017 (n=50, 8 weeks) enrolled adults with mild cognitive impairment; its memory and executive-function gains should not be read as a healthy-adult result.

Evidence key: Strong = multiple consistent RCTs · Moderate = smaller/fewer RCTs · Preliminary = early trials or small n · Mixed = conflicting results

実証された効果

Cortisol reduction
Lower perceived stress and anxiety
Memory in mild cognitive impairment (one 8-week RCT)
Sleep quality
Muscle strength and recovery

副作用と注意事項

Generally well tolerated in 8–12 week trials
GI upset in some users
Liver injury: published case reports and case series, including cases scored "probable" on the RUCAM causality scale that resolved after stopping — stop and see a doctor if you notice jaundice or dark urine
Denmark banned ashwagandha food supplements in 2023 because a safe dose could not be established
Contraindicated in thyroid conditions
Avoid during pregnancy

摂取方法

Dosage300–600mg/day (KSM-66)

TimingEvening (1–2 hours before bed) for sleep benefits. Morning for cortisol and stress management. Split dosing (300mg AM + 300mg PM) is used in the most comprehensive trials.

With foodTake with food to minimise GI upset (particularly with 600mg doses). Absorption is not significantly affected by food.

FormsCapsule. Insist on KSM-66 (full-spectrum root extract, 5% withanolides) or Sensoril (leaf + root, 8% withanolides, lower dose needed). Avoid unstandardised ashwagandha with no withanolide percentage stated — active content may be negligible.

スタッキングの推奨

Ashwagandha (KSM-66)と相性の良い成分とその理由。

Rhodiola Rosea

The canonical adaptogen duo. Rhodiola is activating (morning); Ashwagandha is calming (evening). Both target HPA axis dysregulation but through different mechanisms and at different times of day — a perfect day/night pair.

L-Theanine

Both reduce anxiety through distinct mechanisms (HPA axis modulation vs. GABA modulation). L-Theanine provides immediate calm; Ashwagandha provides systemic, longer-term stress reduction. Together they work at multiple timescales.

Phosphatidylserine

Both independently reduce cortisol via different pathways (HPA modulation vs. cortisol receptor sensitivity). The combination may provide additive cortisol reduction under high-stress conditions.

よくある質問

KSM-66 vs Sensoril vs generic ashwagandha — which should I choose?

KSM-66 (5% withanolides from root only) is the extract used in the key stress and cognition trials. Sensoril (8% withanolides from root + leaf, lower dose needed at 125–250mg) has good evidence specifically for stress and sleep. Generic ashwagandha without a stated withanolide percentage is unreliable — you may be paying for starchy root powder with minimal active content. Choose KSM-66 or Sensoril.

Will ashwagandha make me tired during the day?

No — at morning doses, most people experience calm focus, not sedation. The tiredness effect is most pronounced when taken at night, where it reduces sleep latency. Ashwagandha doesn't deplete energy; it reduces the cortisol-driven hyperarousal that causes fatigue. Some people find 600mg in the morning slightly sedating — if so, reduce to 300mg or shift to evening only.

Is ashwagandha safe for long-term use?

Long-term data is missing: most trials run 8–12 weeks, and no controlled safety data beyond about 90 days was found. Published case reports link ashwagandha to liver injury (some scored "probable" on the RUCAM causality scale), and Denmark banned ashwagandha food supplements in 2023 because a safe dose could not be established. Stop and see a doctor if you develop jaundice or dark urine. Avoid if you have thyroid conditions (autoimmune thyroid disease) as withanolides can modulate thyroid hormone levels.

Can ashwagandha increase testosterone?

Two RCTs found increases: 600mg/day for 8 weeks in young men starting resistance training raised testosterone alongside greater strength gains (2015), and a crossover trial in overweight men aged 40–70 found testosterone +14.7% and DHEA-S +18% versus placebo — but no change in cortisol, fatigue or vigour (Lopresti 2019). The magnitude varies by population and extract.

Top stacks containing Ashwagandha (KSM-66)

Hunter Focus

7.7/10

Roar Ambition

Ashwagandha (KSM-66) in Japan

Products in Japan

Hunter Focus7.7/10
No FFC notification found (checked 2026-10-06)Local price: ￥13,500/month

Consumer Affairs Agency (FFC)

Prefecture guides

Regulatory note

本ページは教育目的の編集コンテンツであり、医学的助言を構成するものではありません。日本国内で販売される機能性表示食品（FFC）および特定保健用食品（FOSHU）は、消費者庁への届出または許可を必要とします。届出のない輸入品については、日本の薬機法（旧薬事法）の下で疾病治療を示唆する表現は規制されます。サプリメントを開始する前に、必ず資格のある医療専門家にご相談ください。This page is editorial and not medical advice. Foods with Function Claims (FFC) and Foods for Specified Health Uses (FOSHU) sold in Japan require notification or approval from the Consumer Affairs Agency. Imported products without notification cannot make disease-treatment claims under the Pharmaceuticals and Medical Devices (PMD) Act. Note: In July 2026, the Consumer Affairs Agency (CAA) opened a public comment period (Notice No. 235080088, closes 30 July 2026) on proposed revisions to permitted claim wording for FFC-notified ingredients including DHA, phosphatidylserine, and NMN; compliant claim language may require updating once the final Cabinet Office Order is published. Consult a qualified healthcare professional before starting any supplement.

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