Maca Root (Lepidium meyenii) | Supplementopedia

Overview

Maca root (Lepidium meyenii), a cruciferous biennial plant native to the high Andes of Peru (2 500–4 500 m), is cultivated for its fleshy subterranean taproot, which has been used for centuries as a nutritional and medicinal food. Modern dietary supplements exploit the root’s dense profile of glucosinolates, polyphenols, and unique alkylamides (macamides) to support energy, hormonal balance, and metabolic function.

Benefits

Research on standardized maca extracts (typically 1–3 g/day) demonstrates several reproducible benefits:

Sexual health: Randomized trials show modest improvements in libido and erectile function, likely mediated by hormone‑modulating and vasodilatory actions.
Mood & cognition: Double‑blind trials report reduced fatigue and improved scores on the Profile of Mood States and short‑term memory tasks, possibly linked to antioxidant and neuro‑protective properties.
Physical performance: Meta‑analyses of endurance athletes indicate modest increases in VO₂max and reduced perceived exertion after 8–12 weeks of supplementation.
Metabolic health: Small RCTs demonstrate modest reductions in fasting glucose and improved insulin sensitivity in overweight adults, likely via modulation of adipokines and glucose‑transport pathways.
Bone health: Animal studies indicate that maca’s calcium‑binding phytochemicals can attenuate bone loss, though human data remain limited.

How It Works

Maca’s bioactivity stems principally from alkylamides (e.g., maca‑1, maca‑2), glucosinolates, and polyphenols.

Alkylamides: Bind to the GABA‑A receptor complex, enhancing inhibitory neurotransmission and reducing stress‑related cortisol spikes, which underlies mood‑enhancing effects.
Glucosinolates: Undergo hydrolysis by myrosinase (or gut microbiota) to produce isothiocyanates, potent Nrf2 activators that up-regulate antioxidant enzymes (HO‑1, NQO1) and mitigate oxidative stress.
Polyphenols: (e.g., quercetin, kaempferol) act as free‑radical scavengers and modulate MAPK/ERK pathways, supporting neuro‑plasticity.
Hormonal Modulation: Maca modulates the hypothalamic–pituitary–gonadal axis: alkylamides stimulate luteinizing hormone (LH) and follicle‑stimulating hormone (FSH) secretion, supporting testosterone and estrogen synthesis.
Metabolic Effects: The combined actions enhance mitochondrial ATP production, improve oxygen utilization, and support glucose uptake via AMPK activation, explaining the reported benefits on energy, performance, and metabolic regulation.

Dosage

Clinical studies most commonly employ 1.5–3 g of dried, powdered maca or an equivalent 300–600 mg of standardized extract (≈ 5–10 % total alkylamides) per day, divided into two doses with meals to improve absorption and minimize gastrointestinal discomfort.

Energy/fatigue: 2 g/day (split 1 g morning, 1 g evening) for 8–12 weeks is typical.
Sexual‑health: 2–3 g/day, often taken in the morning to coincide with natural circadian hormone peaks.
Sport‑performance: 2 g/day throughout training cycles.
Loading Phase: A “loading” phase (3 g/day for 2 weeks) followed by a maintenance phase (1–1.5 g/day) is sometimes recommended, though evidence for superiority is lacking.
Thyroid Considerations: Individuals with thyroid dysfunction should avoid doses >3 g/day without medical supervision.

Safety & Side Effects

Maca is generally well‑tolerated; mild adverse events (bloating, gas, or headache) occur in <5 % of users, typically at doses >3 g/day. Because maca contains goitrin‑related glucosinolates, high chronic intake may interfere with thyroid hormone synthesis, especially in iodine‑deficient individuals, potentially worsening hypothyroidism. Contra‑indications include:

Thyroid disorders: (especially untreated hypothyroidism or hyperthyroidism; monitor TSH if >2 g/day).
Pregnancy & lactation: Limited safety data; precautionary avoidance or use ≤1.5 g/day after consulting a clinician.
Hormone‑sensitive conditions: (e.g., estrogen‑dependent cancers) – caution due to potential mild estrogenic activity.
Interactions: No clinically relevant interactions have been documented, but theoretical additive effects with antihypertensives or anticoagulants (via platelet‑modulating polyphenols) may occur; monitoring is advisable.

Chemistry

Maca is a complex plant matrix; its principal bioactives are:

Alkylamides: (e.g., N‑(3‑hydroxy‑5‑methoxy‑phenyl)‑2‑methyl‑2‑butenamide) – C₁₁H₁₇NO₂, MW 191 g/mol; they contain a fatty‑acid‑derived amide backbone with a phenyl‑substituted side chain.
Glucosinolates: (e.g., glucobrassicin) – C₁₂H₁₅NO₆S, MW 389 g/mol; characterized by a β‑D‑glucose–sulfonate conjugated to a 4‑hydroxy‑3‑methoxy‑phenyl group.
Polyphenols: (quercetin, C₁₅H₁₀O₇, MW 302 g/mol) with multiple hydroxyl groups conferring antioxidant capacity.

The root’s proximate composition includes 12–18 % carbohydrate (primarily fructose), 5–8 % protein, and 2–3 % lipids (rich in fatty acids such as linoleic and oleic acids). The overall IUPAC name for the primary alkylamide is (2‑E‑1‑(3‑hydroxy‑5‑methoxyphenyl)‑2‑methylbut-1‑en-1‑yl)‑N‑phenyl‑acetamide, reflecting its unique amide‑linked phenyl structure.

Sources & Quality

Maca is cultivated almost exclusively in Peru’s high‑altitude regions (Junín, Pasco, and Huancayo provinces) where the thin, cool climate fosters high glucosinolate and alkylamide concentrations.

Harvesting: Commercially, roots are harvested at 6–9 months, washed, sliced or ground, and dried at ≤45 °C to preserve heat‑labile compounds.
Extraction: Standardized extracts are obtained via aqueous‑ethanol (70 %) extraction followed by spray‑drying; the final product is standardized to 5–10 % total alkylamides (often measured by HPLC).
Quality Considerations:
- Geographic traceability: Certified Peruvian origin and altitude (>3 500 m) are linked to higher phytochemical content.
- Processing method: Low‑temperature drying and minimal exposure to light/oxygen preserve glucosinolates and polyphenols.
- Third‑party testing: for heavy metals (Pb, Cd, As) and pesticide residues is essential, as soil contamination can occur in high-altitude mining regions.
Product Selection: Choosing products with a “standardized to X % alkylamides” label and independent certifications (e.g., USDA Organic, GMP) ensures consistent potency and safety.