Scientific Name(s): Lepidium meyenii Walp.
Common Name(s): Ayak chichira, Ayuk willku, Maino, Peruvian ginseng
The genus Lepidium belongs to the family Brassicaceae, which includes approximately 175 species. The aerial part of maca has 12 to 20 leaves, and the foliage forms a mat-like, creeping system of stems that grows close to the soil. The underground portion of the plant, known as the hypocotyl, is a storage organ and is the part that is used commercially. The hypocotyl can be a variety of colors, such as red, purple, cream, yellow, or black, and is 10 to 14 cm long and 3 to 5 cm wide; a cold climate seems to be critical for its formation or growth.1 Maca is cultivated in a narrow, high-altitude zone of the Andes Mountains in Peru, particularly near Carhuamayo and Junin.2 Maca has one of the highest frost tolerances of any cultivated plant, allowing it to grow at altitudes of 3,800 to 4,800 m above sea level in the puna and suni ecosystems, where only alpine grasses and bitter potatoes can survive.3, 4 Maca and several related wild species are also found in the Bolivian Andes.5 Although traditionally cultivated as a vegetable crop, its medicinal use has recently become more prominent in Peru. Maca is related to the common garden cress, Lepidium sativum L.
Maca was domesticated at least 1,300 to 2,000 years ago1 and used as an important food by native Andean people because of its high nutritional value as well as to enhance fertility and sexual performance.6 Throughout the Inca empire, maca consumption was limited to the privileged classes and often given as a prize to warriors.7 Indigenous people used maca to treat numerous conditions including anemia, tuberculosis, sterility, and fatigue. Because of its claimed anabolic and aphrodisiac effects, maca is often referred to as the "ginseng of the Andes" or "Peruvian ginseng."1, 8, 9 Although its efficacy is not proven, some athletes have used maca as an alternative to anabolic steroids.10 Ethnobotanical studies document the use of maca for depression, cancer, as well as menstrual and sexual disorders.11 Other studies document its use for regulation of hormonal secretion, immunostimulation, and memory improvement.8
The tuberous hypocotyl of the plant or root may be eaten raw or cooked, and dried and stored for years without serious deterioration. The root has a tangy taste and an aroma similar to that of butterscotch. The dried roots may be mixed with honey or fruits to prepare juices, gelatins, jams, and alcoholic beverages. In South America, the roots are used to make porridge (known as mazamorra), jam, and pudding. In Peru, the roots are made into a sweet, fragrant drink called maca chichi. Flour may be added to the roots to prepare bread and cookies. A maca coffee is made from toasted and grounded hypocotyl roots. Ground hypocotyl is sold as a nutraceutical under several commercial names and purported to enhance fertility and act as an aphrodisiac in men, women, and livestock.1, 8
The root of maca is the primary medicinal component, containing up to 80% water.1 The following is a brief review of studies on the chemical components of the plant species.
Glucosinolates and isothiocyanates
Glucosinolates and isothiocyanates have anticancer activity and may be responsible for some of the activity in the plant species. The aromatic isothiocyanates may be associated with aphrodisiac activity.1, 3, 9
Phenolic and saccharide compounds
Maca roots contain several amino acids, trace minerals, vitamins, sterols, protein, fiber, and fatty acids.1, 9 The macaenes and macamides have been determined in several commercial products. Macamides may inhibit cannabinoids and act as competitive ligands.1, 13, 14
Other species of Lepidium have been analyzed. L. sativum contains many glucosinolates, and in vitro assays document tumorigenesis inhibition and bactericidal, antiviral, and fungicidal activity.15, 16 An alkaloid, lepidine, has been isolated from the seeds of L. sativum.17 Evomonoside, a cardiac glycoside, has been isolated in substantial yield from the seeds of Lepidium apetalum, a Korean species.18 Several flavones and flavonoid glycosides have also been isolated from the genus Lepidium.19
Uses and Pharmacology
Numerous animal and human studies on the aphrodisiac and fertility-enhancing properties of maca are found in the scientific literature. The exact mechanism of action remains to be elucidated. One study established that maca does not directly modulate androgen receptors.11
Oral administration of a purified lipid extract from L. meyenii enhanced the sexual function of mice and rats; this was evidenced by an increase in the number of complete copulatory events in a 3-hour period of sperm-positive female mice and a decrease in a latent period of erection in male rats with erectile dysfunction.20
Hexane, chloroform, and methanol maca extracts administered to rats decreased intromission latency, intercopulatory interval and increased intromission frequency and copulatory efficacy (P < 0.05). Overall, the maca hexane extract was most effective.21
The effect of chronic and acute administration of pulverized maca root was studied on the sexual performance parameters in male rats. Both chronic and acute treatment of maca decreased first mount, first intromission, ejaculation, and postejaculation.10 Another similar study found that chronic administration of maca did not increase locomotion or anxiety, and after 21 days of treatment had no effect on sexual behavior.22
Maca improved sexual desire in 57 healthy men (21 to 56 years of age) treated with 1.5 to 3 g/day of gelatinized maca root (500 or 1,000 mg 3 times a day) in a 12-week, double-blind, placebo-controlled, randomized, parallel trial. A dose-response effect was not demonstrated with the 3 versus 1.5 g dose. The improvement of sexual desire was independent of any changes in mood, serum testosterone, or estradiol levels.23
Another clinical trial (n=50) reported improvements in erectile dysfunction in both placebo and maca (2,400 mg daily) study groups over 12 weeks. A larger effect size was reported for maca-treated participants.24 A smaller study (n=16) reported a dose-dependent effect, with 1,500 mg daily not effective, but 3,000 mg daily as effective in selective-serotonin reuptake inhibitor (SSRI)-associated sexual dysfunction in men.25
In women, maca (3.5 g/day for 6 weeks) reportedly reduced psychological symptoms including depression and sexual dysfunction in a small clinical study (n=14). No significant changes were found for somatic or vasomotor scores.26 Similar findings on depression were reported in a study in a Chinese population (n=29).27
Sex steroid hormones
Blood levels of progesterone in female mice and blood levels of testosterone in male mice were increased during administration of maca. However, maca administration did not affect levels of blood 17-beta-estradiol or the rate of embryo implantation in female mice.28
Maca administered to male rats exposed to a high altitude of 4,340 m prevented altitude-induced reductions in body weight and epididymal sperm count. The mechanism of action may be associated with maca acting on stage VIII and stages IX through XI of the seminiferous cycle. Stage VIII is associated with the release of spermatozoa to the lumen of the seminiferous tubules. Stages IX through XI are associated with the first mitosis of spermatogonia A.29 A similar study by the same author found that oral administration of an aqueous maca extract to normal adult male rats for 14 days increased spermatogenesis, acting on stages IX through XI.30
One study examined the effect on spermatogenesis in rats after short-term (7 days) and long-term (42 days) treatment with red, yellow, and black ecotypes of maca. Yellow and red maca increased stage VIII after 7 days, but black maca increased stages II through VI and VIII. The biological response of black maca on sperm counts and epididymal sperm motility was much more pronounced. The same results were found after 42 days of treatment.2 Black maca improved sperm counts in the epididymis within 1 day; this regulatory mechanism may be associated with the testes rather than an actual increase in sperm.31
Administration of aqueous yellow maca extract to female mice increased female fertility and litter size. Treatment with the extract also increased uterine weight in ovariectomized animals. The effects of maca on litter size and uterine weight may be caused by a progestin versus estrogenic effect, because maca contains other sterols besides the phytoestrogen sitosterol.32
Maca increased seminal volume, sperm count per ejaculum, motile sperm count, and sperm motility in 9 healthy men (24 to 44 years of age) treated over 4 months with gelatinized maca root 1,500 or 3,000 mg/day. Serum hormone levels of luteinizing hormone, follicle stimulating hormone, prolactin, testosterone, and estradiol were not modified with maca treatment. Because serum testosterone levels were not affected, the mechanism of action may be associated with augmentation of bioavailable testosterone or testosterone receptor binding. Maca may also act via an androgen-independent mechanism because the weight of the seminal vesicle was not influenced by maca.33 A 12-week, double-blind, placebo-controlled, randomized, parallel study of 56 healthy men (21 to 56 years of age) administered gelatinized maca root 1,500 or 3,000 mg/day had similar results.34
A small study in postmenopausal women (n=14) reported no effect of maca (3.5 g/day for 6 weeks) on serum concentrations of estradiol, follicle-stimulating hormone, luteinizing hormone, or sex hormone-binding globulin.26 Similar findings were reported in a study in a Chinese population (n=29), which additionally reported no effect of maca on lipid profiles and serum cytokines but there was a decrease in diastolic blood pressure.27
Other pharmacological effects
Maca protects cells from oxidative stress and is capable of scavenging free radicals.14, 35 Maca decreased the levels of very low density lipoproteins (VLDL); low density lipoproteins; total cholesterol; and the level of triacylglycerols in the plasma, VLDL, and liver in rats. Maca and rosiglitazone improved glucose tolerance and lowered glucose levels in blood.36
A study in high altitude-living Peruvian adults reported an association of maca consumption with lower serum interleukin-6 levels (as a marker of oxidative stress) and low chronic mountain sickness scores.37
In vitro studies/animal data include antiviral effects (eg, influenza).38
Learning and depression
Studies in rodents suggest that maca exerts antidepressant actions. The mechanism proposed for the observed effects includes the effect of phytoestrogens,39 monoamine neurotransmission,40 and the activation of noradrenergic and dopaminergic systems.41
Maca improved bone mass and restored the trabecular network in lumbar vertebrae in ovariectomized rats. Calcium, magnesium, and silica are useful in bone calcium loss in menopausal women and each are found in maca.42
Red maca reduced ventral prostate size in normal and testosterone enanthate-treated rats. The mechanism of action may be associated with the activity of glucosinolates on androgen receptors43; other studies have challenged this mechanism associated with glucosinolates.44
A recent study showed that finasteride reduced prostate and seminal vesicle weight, whereas red maca only reduced prostate weight. The results suggest that red maca may exert its effects at a level after 5-alpha reductase conversion of testosterone to dihydrotestosterone. Red maca reverses androgen action in the prostate organ and does not affect serum testosterone levels.45
Maca is available commercially in several dosage forms including powder, liquid, tablets, and capsules. Most commercial Web sites recommend a daily dose of 1 dried maca extract 450 mg capsule 3 times daily taken orally with food.
A small study (n=16) reported a dose-dependent effect, with 1,500 mg maca daily not effective, but 3,000 mg maca daily as effective in SSRI-associated sexual dysfunction in men.25
Doses of 3.5 g maca daily for 6 weeks have been used in postmenopausal women.26
Pregnancy / Lactation
Avoid use during pregnancy and lactation due to lack of safety and efficacy data.
There is no evidence of adverse reactions to maca. Maca has been reported to have a low degree of acute oral toxicity in animals and low cellular toxicity in vitro.48
No adverse reactions were reported in an animal study with rats fed maca extract in doses up to 5 g/kg, equivalent to an intake of 770 g of hypocotyls in a 70 kg man.49
The presence of substantial amounts of a cardiac glycoside in the related species, L. apetalum18 is cause for concern. Cardioactive substances have also been detected in L. sativum.50 However, dried maca roots have been consumed for many years without reports of cardiotoxicity. Lepidium virginicum was inactive in a screen for genotoxicity.51
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