Growing & Environmental Considerations for Maca
Maca’s native growing location is 3500–5000 meters above sea level in Peru’s high, harsh-weathered Andean plateaus, specifically the Junín and Pasco provinces (1–5). Though it is also grown in Bolivia and northwestern Argentina (6–8). Due to its rising consumer demand in China, it has also begun to be cultivated in select areas of western China with high altitudes, such as the Yunnan and Pamirs regions (2800–3500 m) (9) as well as Tibet (above 3000 m) (10,11).
As described by Meissner et al. the shape of maca cultivated in Peru and China are distinctly different with Peruvian maca being cylindrical elongated and pointed root whereas the Chinese maca is disfigured appearing as a “ginseng-type root”. These shape differences may be a result of: (12)
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injury from transplantation from greenhouses to outdoor
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commercial plantation sites
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invasion by nematodes or microbial and/or fungal soil infections from the relatively lower altitude and less UV radiation to disinfect soil
The maca cultivated in non-native locations exhibit different characteristics since the growing environment can significantly affect the plant phenotype and composition (3).
Compositional Differences in Maca Grown in Peru and China
Geng et al. used mass spectral fingerprinting, metabolomic analysis, and genetic sequencing to assess 71 maca samples (39 commercial maca supplements from 11 different companies, 31 unprocessed maca tubers from Peru and China, and a maca non-tuber historical sample from Peru) (7). There were compositional differences between the maca samples originating from these two different countries of origin such as higher glucosinolates in Chinese maca and higher alkaloids in Peruvian maca. While there were also differences in the colors of maca studied, Geng et al. stated that the origin of maca had a greater significance to the compositional differences over the color (7). Similarly, another study utilizing quantitative analysis concluded that geographical origin, rather than color, had a more critical role in the macamide content of maca (13).
Altitude and Soil
It has been reported that the location, including the altitude and soil where maca is grown can have a significant impact on the quality and active ingredient profile of maca, with Chinese maca being different from native Peruvian maca (14). Even within Peru, there are phytochemical differences between maca sourced from different altitudes and the two primary locations where it is grown (15,16).
For example, when maca is cultivated at altitudes under 3500 m, one of its phytochemical classes, macamides, is reduced (17). Whereas purple and red maca, typically grown in higher elevations (4,300 meters), had higher glucosinolate concentrations compared to black and yellow maca (15).
In one study, samples of yellow, violet, lead (gray), and pink maca from two locations in Peru were collected from land that had never been cultivated for maca and land that had been previously cultivated two to three years earlier (18). Significant differences in the metabolites existed, leaving the authors to conclude that the planting site, and all of its accompanying aspects such as the soil, microclimate, and hydration conditions, is the “major determining factor” in the concentration of metabolites in maca, perhaps even more than the actual color, which corresponded to Geng et al. findings (7).
As described by Minich, et al (19)
Maca is often planted in the same area in rotation with other crops, although expansion has been needed into other regions within Peru due to increasing demand. As a result of repeat planting, there can be changes in the composition of the soil, the soil microbes, and even the maca phytomicrobiome, which could each conceivably alter the quality of maca and its sensory properties such as flavor. Evaluation of maca from newly cultivated terrains suggests improved sensory quality. Therefore, best practices are to allow for crop rotation over 4–10 years or more. Traditional Andean farming practices recommend crop rotation for up to seven years to help reduce pests. Commercial plantations are rotated on an average of three years due to the depletion of nutrients in the soil.
Of concern, the American Botanical Council has reported a potential toxic feature of Chinese maca due to the use of pesticides and herbicides on the soil and plant to accommodate for the difference in altitude relative to the Andean highlands as well as chemical contamination in the agricultural settings in parts of China, especially the Yunnan province (19).
Read the American Botanical Council Herbalgram report:
Maca Madness: Chinese Herb Smugglers Create Chaos in the Peruvian Andes
Post-Harvesting Practices
The post-harvesting practices for maca have been described by Minich et al (19):
Finally, the post-harvesting practices (e.g., mechanical breakdown, fermentation, drying) of maca also impact its active constituents. The traditional drying methods have been documented to be superior to oven-drying in commercial operations. The traditional open-field drying methods take about two to three months and include the climate changes that naturally occur in the Andes mountains, such as freeze–thaw cycles and intense ultraviolet (UV) radiation. Compared to fresh maca hypocotyls, this process can alter the profiles in glucosinolates, free fatty acids, and amides. While some of these practices have been detailed in the scientific literature, there is a lack of research identifying the best procedures to optimize actives in each color of maca.
Processing and Storage Methods
The processing and storage methods of maca have been described by Minich et al (19):
Often, maca hypocotyls are subject to gelatinization due to their relatively high starch content. Gelatinization involves an extrusion process incorporating short-term high pressure, temperature, and moisture after drying and pulverization into a powder. The result is a more digestible end product with bioavailable actives, which may be favorable for select populations such as those following a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) or those with digestive issues. In addition to digestibility, gelatinization may help to reduce the content of goitrogens, a class of compounds commonly found in a variety of plants, including legumes, cruciferous vegetables, and maca that are known to interfere with thyroid hormone activity. Goitrogens can be inactivated through methods that involve moisture and heat. While gelatinization has benefits, it can also result in a more hygroscopic product that is less stable.
Moderate pressure within a specific temperature range would provide ideal conditions for myrosinase, the enzyme that can degrade glucosinolates into its many metabolites. Raw maca may be about 20% higher in glucosinolates compared with the gelatinized format, and storage of maca tubers in the Andean highlands for up to seven years has not been known to result in significant losses of glucosinolates (only a 9–12% loss). Therefore, manufacturing the product closer to when it is required would be a better practice due to the balance of the raw versus gelatinization issues that can arise. Manufacturing practices for maca products need to be attentive to these details to ensure a more efficacious, reproducible product. Moreover, each color of maca may require specific handling based on the actives they are known to contain.
It is worthwhile to consider the effect of storage on the microbial contamination of maca hypocotyls. Meissner et al. evaluated the microbial contamination of four colors of maca hypocotyls. Yellow hypocotyls had the highest Gram-positive aerobic Bacillus strains, whereas the black maca had no detectable or low microbial levels of Gram-positive cocci strain colonies. Therefore, due to compositional differences, there may be storage requirements for each color of maca to maintain its microbial integrity over time.
Summary
Research has extensively explored the impact multiple environmental factors have on maca’s composition including:
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The location where maca is grown
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The altitude it is grown
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The soil it is grown on
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Post-harvesting practices
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Processing methods
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Storage methods
Healthcare professionals and consumers would be wise to diligently understand each of these factors when choosing a maca supplement.
Author: Mona Fahoum, ND
Reviewer: Kim Ross, DCN
Last Updated: March 25, 2024
References
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