Lepidium meyenii, known commonly as maca, is an herbaceous biennial plant of the crucifer family native to the high Andes of Peru around Lake Junin. It is grown for its fleshy hypocotyl (actually a fused hypocotyl and taproot), which is used as a root vegetable, a medicinal herb, and a supposed aphrodisiac. Its Spanish and Quechua names include maca-maca, maino, ayak chichira, and ayak willku.
Botanical characteristics 
The species was first described by Gerhard Walpers in 1843 as Lepidium meyenii. In the 1990s Dr. Gloria Chacon made a further distinction of different species. She considered the widely cultivated natural maca of today to be a newer domesticated species, L. peruvianum. However, most botanists today doubt this distinction and continue to call the cultivated maca L. meyenii. The Latin name recognized by the USDA also continues to be Lepidium meyenii. There is a still ongoing debate about the correct nomenclature, and whether the distinction between meyenii and peruvianum is actually botanically correct or if they are the same species.
The growth habit, size, and proportions of maca are roughly similar to those of the radish and the turnip, to which it is related. The green, fragrant tops are short and lie along the ground. The thin, frilly leaves sprout in a rosette at the soil surface, not growing over 12 to 20 cm in height. The leaves show a dimorphism according to reproductive stage. They are more prominent in the vegetative phase, and are continuously renewed from the center as the outer leaves die. The off-white, self-fertile flowers are borne on a central raceme, and are followed by 4–5 mm siliculate fruits, each containing two small (2-2.5 mm) reddish-gray ovoid seeds. Seeds are the maca’s only means of reproduction. Maca reproduces mainly through self-pollination and is an autogamous species. The genome consists of 2n=8x=64 chromosomes. From experiments with different day lengths it can be concluded that maca is a short-day plant. Some sources consider the maca to be an annual plant, as in favorable years it can complete a life cycle within a year.
Maca is the only member of its genus with a fleshy hypocotyl, which is fused with the taproot to form a rough inverted-pear-shaped body. Maca does vary greatly in the size and shape of the root, which can be triangular, flattened circular, spherical or rectangular, the latter of which forms the largest roots. Maca hypocotyls can be gold or cream, red, purple, blue, black or green. Each is considered a genetically unique variety, as seeds of the parent plants grow to have roots of the same color. Recently, specific phenotypes (in maca, 'phenotype' pertains mainly to root color) have been exclusively propagated to ascertain their different nutritional and therapeutic properties. Cream colored roots are the most widely grown and are favored in Peru for their enhanced sweetness and size. Black maca is considered the strongest in energy and stamina-promoting properties, being both sweet and slightly bitter in taste. Red maca is becoming popular with many people, and has been clinically shown to reduce prostate size in rats.
Growth conditions 
The natural environment of the maca is at 11-12ºS latitude and at an elevation of 3800–4400 m above sea level. At this elevation, temperatures of the growing season vary between -2 to 13 °C in monthly mean minimum or maximum respectively. However temperatures can decline as low as -10 °C and frosts are common. Strong winds and sunlight are also characteristics of the native habitat of the maca. Maca is still today mainly cultivated in Peru and in the high Andes of Bolivia, and to a small extent also in Brazil.
Maca seedlings emerge usually about one month after sowing with the onset of the rainy season in October. In the vegetative phase, until May to June, the lower part of the hypocotyl as well as the upper part of the tap root grows in size. After 260 to 280 days it is formed to the harvestable hypocotyl. If the root is left in the soil, it is dormant for two to three months in the time of the cold, dry season until August. Then it will form a generative shoot on which the seeds ripen five months later. One plant is capable of forming up to thousand tiny seeds of which 1600 weigh approximately one gram. Thus only relatively few plants are needed for propagation. The plants for cultivation are selected for preferred size and color, then placed 50–100 cm deep in pits with alternate layers of grass and soil to protect them from drying out. They are fertilized heavily. The cultivation cycle is strictly linked to seasonality.
Traditionally, land preparation was done by hand. Nowadays, also tractor plowing is used. As maca grows on sites where no other crops can be cultivated, it is often found after long fallows of sheep grazing pastures. Maca croplands are thus traditionally only fertilized with sheep and alpaca manure. However, fertilizer application could prevent soils from depleting in nutrients.
Weeding or pesticide application is usually not necessary as the climate is not suitable for most weeds or pests. Nearly all maca cultivation in Peru is carried out organically, as maca itself is seldom attacked. Maca is sometimes interplanted with potatoes, as it is known to maca farmers that the plant itself naturally repels most root crop pests. The harvest is done manually, with the leaves remaining on the field as livestock feed or organic fertilizer. The yield for a cultivated hectare can reach an estimated 15 tons in fresh hypocotyls resulting in approximately 5 tons of dried material. According to the Ministry of Agriculture of Peru however, average maca yields for 2005 were only 7t/ha, with a great variation between different sites. Although maca has been cultivated outside the Andes, it is not yet clear whether it develops the same active constituents or potency outside of its natural habitat. Hypocotyls grown from Peruvian seeds form with difficulty at low elevations, in greenhouses or in warm climates.
The nutritional value of dried maca root is high, similar to cereal grains such as rice and wheat. The average composition is 60-75% carbohydrates, 10-14% protein, 8.5% dietary fiber, and 2.2% fats. Maca is rich in the dietary minerals calcium and potassium (with low content of sodium), and contains the essential trace elements iron, iodine, copper, manganese, and zinc as well as fatty acids including linolenic acid, palmitic acid, and oleic acids, and 19 amino acids.
In addition to sugars and proteins, maca contains uridine, malic acid and its benzoyl derivative, and the glucosinolates, glucotropaeolin and m-methoxyglucotropaeolin. The methanol extract of maca tuber also contains (1R,3S)-1-methyltetrahydro-carboline-3-carboxylic acid, a molecule which is reported to exert many activities on the central nervous system. Many different alkamides were found in maca.
Further, maca contains selenium and magnesium, and includes polysaccharides. Maca's reported beneficial effects for sexual function could be due to its high concentration of proteins and vital nutrients; maca contains a chemical called p-methoxybenzyl isothiocyanate, which reputedly has aphrodisiac properties.
Uses and preparation 
Maca is mainly grown for the nutritional and health value of its root. The majority of harvested maca are dried. In this form, the hypocotyls can be stored for several years. In Peru, maca is prepared and consumed in various ways, although traditionally it is always cooked. The freshly harvested hypocotyl can be roasted in a pit (called huatia), which is considered a delicacy. Fresh roots are usually available only in the vicinity of the growers. The root can also be mashed and boiled to produce a sweet, thick liquid, dried and mixed with milk to form a porridge. The cooked roots are also used with other vegetables in empanadas, jams or soups. The root can be ground to produce a flour for bread, cakes or pancakes. If fermented, a weak beer called chicha de maca can be produced. In 2010 a US based brewery called Andean Brewing Company, became the first company to produce and commercialize beer made from Maca under the brand KUKA Beer. From the black morphotype a liquor is produced. Also the leaves are edible or may serve as animal fodder. They can be prepared raw in salads or cooked much like Lepidium sativum and Lepidium campestre, to which it is genetically closely related.
The growing demand of the supplement industry has been one of the primary reasons for maca's expanding cultivation in Peru and Bolivia. The prominent product for export is maca flour, which is a baking flour ground from the hard, dried roots. It is called "harina de maca." Maca flour (powder) is a relatively inexpensive bulk commodity, much like wheat flour or potato flour. The supplement industry uses both the dry roots and maca flour for different types of processing and concentrated extracts. An internet query will show dozens of different extracts available, each touting a particular efficaciousness for a traditional use or health claim. Another common form is maca processed by gelatinization. This is an extrusion process which separates and removes the tough fiber from the roots using gentle heat and pressure, as raw maca is difficult to digest due to its thick fibers and goitrogen content. Gelatinization was developed for maca specifically to mimic the activity of cooking, and to allow gentler digestion. Gelatinized maca is employed mainly for therapeutic and supplement purposes, but can also be used like maca flour as a flavor in cooking. Available also is a freeze-dried maca juice, which is squeezed from the macerated fresh root, and subsequently freeze-dried high in the Andes.
Maca has been harvested and used by humans in the Andean Mountains for centuries. Contrary to frequent claims that maca's cultivation was common in what is today Peru, it has been shown that until the late 1980s, maca has only been cultivated in a limited area around Lake Junin, in Central Peru. Historically, maca was often traded for lowland tropical food staples, such as corn, rice, manioc (tapioca roots), quinoa and papaya. It was also used as a form of payment of Spanish imperial taxes. It is cited that maca was eaten by Inca imperial warriors before battles. Their legendary strength was allegedly imparted by the preparatory consumption of copious amounts of maca, fueling formidable warriors. After a city was conquered, the women had to be protected from the Inca warriors, as they became ambitiously virile from eating such quantities of maca. This is of course an appealing endorsement for the masculine angle of maca's recent marketing campaign. Whether or not this often repeated historical use is actually true has yet to be determined. Those who have studied maca's history have not been able to locate formal mention of this particular use.
Health effects 
Maca is consumed as food for humans and livestock, suggesting any risk from consumption is rather minimal. It is considered as safe to eat as any other vegetable food. However, maca does contain glucosinolates, which can cause goiters when high consumption is combined with a diet low in iodine. This being said, darker colored maca roots (red, purple, black) contain significant amounts of natural iodine, a 10-gram serving of dried maca generally containing 52 µg of iodine. Though this is common in other foods with high levels of glucosinolate, it is uncertain if maca consumption can cause or worsen a goiter.[unreliable source?]
Aphrodisiac claims 
Small-scale clinical trials performed in men have suggested that maca extracts can improve semen quality, and boost libido. A small double-blind, randomized, parallel group dose-finding pilot study has shown that Maca root may alleviate SSRI-induced sexual dysfunction. A 12-week randomized, double-blind, placebo-controlled study in 56 subjects found that Maca has no effect on sex hormone levels in men, including LH, FSH, prolactin, 17-OH progesterone, testosterone or estradiol. A recent review states "Randomized clinical trials have shown that maca has favorable effects on energy and mood, may decrease anxiety and improve sexual desire. Maca has also been shown to improve sperm production, sperm motility, and semen volume." In total over 160 studies into the health effect of Maca have been indexed by the United States National Library of Medicine, National Institutes of Health. However, a 2010 review of the extant evidence for the effect of Maca on libido found only tentative support for its aphrodisiac claims.
Marketing potential 
Due to its purported effects on fertility, maca has experienced a major gain of commercial interest as well as research in the last decades. In the 1990s, a quick expansion of cultivated land with maca was observable. As the demand raised rapidly, the producer’s prices increased. However, due to high expectations the production expanded too rapidly and in the year 2000 the prices fell again. Market studies have shown a very low acceptance of the particular maca taste in consumers exposed to it firstly. Apparently the taste is acquired, which creates a barrier for the further propagation of this food as a vegetable. The economic interest lies hence more in the medical application of the root's constituents.
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