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Comparative guide · 6 min read

Maca vs Ashwagandha — libido, stress, and hormones compared

Updated 2026-05-14 · Reviewed by SupplementScore editors · No sponsorships

Maca and ashwagandha get marketed similarly — "hormonal support, adaptogen, libido" — but the evidence breakdown is different. Maca has small-trial evidence specifically for libido in both sexes (including SSRI-induced sexual dysfunction) without measurable effects on sex hormones. Ashwagandha has stronger evidence for cortisol-driven stress, sleep quality, and modest testosterone effects in untrained men — but a real thyroid-disease caveat that most users don't know.

Quick verdict

GoalBetter choiceWhy
Libido (men and women, including SSRI-induced)MacaSmall RCTs show libido improvement at 1.5–3 g/day without measurable hormone changes.
Subjective stress / cortisol reductionAshwagandha (KSM-66)Multiple RCTs at 300–600 mg/day show subjective stress and cortisol reductions.
Sleep qualityAshwagandhaModest improvements in PSQI scores; not in maca's evidence base.
Testosterone in untrained menAshwagandha (modest)Small studies show ~10–15% increases in young untrained men over 8 weeks; effect attenuates with training.
Menopausal symptomsMaca (modest)Small trials show improvement in subjective menopausal symptoms; effect modest.
Use in autoimmune or treated thyroid diseaseMaca (preferred)Ashwagandha can raise free T4 and lower TSH — relevant in hypothyroidism on levothyroxine and contraindicated in hyperthyroidism.

How they actually work

Maca (Lepidium meyenii) — Andean root with unclear mechanism

Maca is a cruciferous root traditionally cultivated in the Peruvian Andes. The proposed bioactives include macamides (long-chain fatty acid amides), glucosinolates, and macaenes — but the mechanism of any libido effect remains unclear in the literature. Pharmacological studies have not identified a clear hormonal or neurotransmitter target. Despite marketing claims, properly designed trials in maca have consistently failed to show changes in serum testosterone, estradiol, LH, FSH, or DHEA. The libido signal appears to be present but mechanism-mysterious.

Ashwagandha (Withania somnifera) — withanolide-driven adaptogen

Ashwagandha's bioactives are the withanolides (most prominently withaferin A and withanolide D), present at varying concentrations across cultivars and extraction methods. The most-studied branded forms are KSM-66 (5% withanolides, root-only) and Shoden/Sensoril (higher withanolide concentration). The pharmacology includes mild GABA modulation, HPA-axis attenuation (lower cortisol), and direct effects on thyroid hormone synthesis and conversion. The thyroid effect is the under-discussed clinically important one.

Libido — maca's only clean win

Three small placebo-controlled trials of maca (Gonzales 2002, Stone 2009, Dording 2008/2015) show libido improvements in healthy men, healthy women, and SSRI-treated patients with SSRI-induced sexual dysfunction. Effects are modest, doses range 1.5–3 g/day of gelatinised maca root, and the libido effect is not accompanied by hormonal changes. Ashwagandha has secondary libido signals but they're more in the context of stress reduction than direct.

Stress and sleep — ashwagandha's strongest lane

Multiple RCTs of KSM-66 at 300–600 mg/day or Shoden at 240 mg/day show reductions in Perceived Stress Scale scores, salivary or serum cortisol, and improvements in PSQI sleep quality. Effect sizes are modest but consistent. Maca does not have this evidence base.

The ashwagandha thyroid issue

Ashwagandha at 600 mg/day for 8 weeks has been shown to lower TSH and raise free T4 — direction-consistent with mild thyroid stimulation. This is a problem in: (1) hyperthyroidism / Graves' disease, where it should be avoided; (2) treated hypothyroidism on levothyroxine, where it can produce iatrogenic hyperthyroidism by stacking; (3) subclinical hyperthyroidism. The thyroid effect is dose-dependent and partially reversible on discontinuation, but it's the most clinically important caveat that most consumer ashwagandha labels do not disclose. Pregnancy and lactation are also avoidance categories.

Practical rule. For libido (men or women, including SSRI-induced): maca 1.5–3 g/day gelatinised root, 8–12 weeks. For stress/sleep without thyroid disease: ashwagandha (KSM-66 root extract) 300–600 mg/day for 8–12 weeks. For users with hypothyroidism, hyperthyroidism, pregnancy, or autoimmune disease: skip ashwagandha and consider maca, magnesium glycinate, glycine, or saffron instead.

Dose, form, and timing

Maca: 1.5–3 g/day gelatinised root (cooked or extracted form is the studied one — raw maca root has thiocyanate content). Powder or capsule. Effect onset is gradual — judge at 6–8 weeks.

Ashwagandha: KSM-66 300–600 mg/day, or Shoden 240 mg/day. Take with a meal. Evening dose tends to favor sleep benefit; morning dose tends to favor stress reduction across the day.

Safety

Maca: well-tolerated. GI complaints uncommon. The cruciferous-vegetable thiocyanate content makes raw maca a theoretical concern in users with iodine-deficient hypothyroidism (uncommon in iodine-replete countries); gelatinised maca avoids this.

Ashwagandha: well-tolerated for most users. Sedation (often welcomed). Hepatotoxicity has been reported in case series (rare). Thyroid effects above. Avoid in pregnancy, lactation, untreated hyperthyroidism, and in users on levothyroxine without endocrinologist input.

What to skip

"Black maca for testosterone" — color of maca root does not predictably alter hormonal effects, and there is no good RCT evidence that black maca uniquely improves testosterone. "Adrenal complex" products bundling ashwagandha + licorice + tyrosine + B vitamins at subtherapeutic doses. Untested raw ashwagandha bulk root from unverified sources — heavy metal contamination has been documented.

What we'd actually buy

For libido use: gelatinised maca root 2 g/day, third-party tested. For stress/sleep use without thyroid disease: KSM-66 ashwagandha 600 mg/day, taken with dinner. For users with any thyroid concern, autoimmune disease, or pregnancy: skip ashwagandha. Re-evaluate after 8–12 weeks.

Sources

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