By Jeff Chilton, Guest Contributor
Medicinal
mushrooms are fungal organisms sold as health foods, nutritional supplements,
so-called nutraceuticals, and, on occasion, cosmetics ingredients. They are
part of an extensive natural health products category in Asia, where
traditional Chinese medicine has utilized mushroom preparations for thousands
of years. China is the historical site of shiitake mushroom (Lentinula edodes, Marasmiaceae)
cultivation, which is reported to have originated in the 12th century. Today,
China is responsible for 85% of the world’s mushroom production.1
The
estimated worldwide market value of medicinal mushrooms was $6 billion in 1999,
and $18 billion in 2014.2,3 Over the last 25 years the market for
these products has expanded greatly in North America, and, today, just about
every dietary supplement company has one or more mushroom-related formulations
in their product line. In light of this growth trajectory, medicinal mushrooms
are destined to become a much bigger product category.
Category
growth is likely to attract increased scrutiny by the US Food and Drug
Administration (FDA) and other governmental bodies. It is, therefore, more
important than ever to properly define medicinal mushrooms and ensure that
products meet ingredient labeling requirements. This also raises ethical and
liability issues for companies that may be selling products that do not conform
to FDA standards for product authenticity.
It is
well known that different parts of the same plant may contain varying levels of
active compounds. Likewise, depending on the stage of growth or parts used,
fungi may contain different levels of distinct medicinal constituents as well.
This is an important consideration for traditional healers and herbalists, as
well as commercial entities, all of which want to be certain that the medicinal
values and benefits they seek are in fact present. This is also why the FDA
requires the “plant part” to be listed in the Supplement Facts panel for all
botanical (and fungal) ingredients in dietary supplements.
Few
companies realize that medicinal mushrooms as a category encompass more than
just mushrooms. A mushroom is just one stage of these fungal organisms’ life
cycles. Most of the particular fungal organisms that are generally referred to
as medicinal mushrooms belong to a taxonomic grouping called basidiomycetes.
The genera Ophiocordyceps (family:
Ophiocordycipitaceae) and Cordyceps
(family: Cordycipitaceae) are exceptions and belong to the ascomycetes.4
Understanding
the life cycle of a basidiomycete helps to define its respective components. What is commercially referred to as a
medicinal mushroom is actually four distinct parts of a basidiomycete:
mushroom, mycelium, sclerotium, and spore.
It is
fitting to start with the spore, which is the beginning and end of the
basidiomycete life cycle. Similar in function to a seed, fungal spores will
germinate when environmental conditions are favorable. The germinating spore
produces a hypha, a threadlike tube that spreads and branches in every
direction. When multiple spores germinate and their hyphae grow together, a
root-like network called a mycelium is formed.4
Mycelium
is considered the vegetative stage of the basidiomycete.5 In
nature, one rarely sees the mycelium because it is naturally embedded in its
food source, what is often referred to as the “substrate.” Using the secretion
of enzymes to digest its substrate, the mycelium grows in and feeds off of a
diverse menu of dead organic matter, such
as trees, woody debris, fallen leaves, and annual plants of all kinds. Fungal
mycelium is one of nature’'s
premier recyclers and is especially adept at breaking down cellulosic
materials.
When environmental conditions are conducive, a fertile mycelium
will produce a mushroom. The mushroom is defined as a specialized reproductive
structure. A
mushroom can be separated further into parts such as the stem, cap, gills or
pores, and spores, but other than spores, this level of differentiation has not
yet been commercially promoted or supported by consistent scientific analyses.
That may change in the future as more research is conducted on these specific
parts of the mushroom, and certainly companies are free to differentiate using
this subset.
Vegetative
mycelium can also form a dense and often hardened, irregular mass called a
sclerotium. This sclerotium is considered a means for many fungi to survive
environmental extremes such as freezing. When conditions improve, sclerotia
provide food reserves for the production of fruiting bodies. Two important
medicinal basidiomycetes are used in the sclerotial form: chaga (Inonotus obliquus, Hymenochaetaceae) and
poria (Wolfiporia extensa,
Polyporaceae). Although these are commonly called “mushrooms,” they are
classified more accurately as sclerotium or mycelium.
The
mushroom and mycelium are similar in that both are composed of hyphae, but they
are meaningfully different in structure, composition, and function. Mycelium is
the “vegetative body” of a fungal organism, whereas the mushroom is considered
the “fruiting body.”6 Mushroom and mycelium are not synonymous — an
important and necessary distinction. For example, with respect to Ganoderma lucidum (Ganodermataceae), one
can correctly say “reishi mycelium” or “Ganoderma mycelium,” but it is
incorrect to say “reishi mushroom mycelium” since these are separate parts.
Therefore, per existing regulation, it is not permissible for a company to have
a product label that says “reishi mushroom” when the ingredients are primarily
reishi mycelium or reishi spores. So one must be certain of the stage of the
fungal organism that is being sold and label it accordingly.
Since
mycelium is often propagated using grain as a substrate, many basidiomycete
products consist of inoculated grain — what some call a “biomass.” The
overwhelming majority of these products are marketed and labeled as mushrooms.
This is a classic case of mislabeling since there are no mushrooms (in the true
sense of the word, as just noted above) in these products. Furthermore, the
presence of the grain needs to be listed on the label as an ingredient since
these biomass products are not 100% pure mycelium but new and novel products.
For example, it may be necessary to label a product as “reishi mycelium
biomass,” rather than “reishi mycelium,” especially if the amount of mycelium
is less than the residual grain. The actual amount of mycelium in the biomass
can be readily tested by ergosterol analysis, and the grain residue can be
measured by a starch test.7-9 If the grain is not listed as an
ingredient of this mycelium biomass product, it could reasonably be considered
an adulterant.
In
the case of a blend of different basidiomycete stages, proper labeling would
state the percentage of each stage that was included. One could not simply say
mycelium, mushroom, and spore. Some biomass manufacturers claim mushroom
inclusion due to the presence of mushroom primordia. Primordia are not actual
mushrooms, but simply the initial mycelium mass that, over time, becomes a
mushroom.
In 1976,
the FDA issued a statement in its Compliance Policy Guide, Section 585.525:
Mushroom Mycelium – Fitness for Food; Labeling. It states: “Any food in which
mushroom mycelium [sic] is used should be labeled to state that fact. Labeling
should not suggest or imply that the food contains mushrooms.”6 It
could not be clearer.
In
conclusion, proper labeling of medicinal basidiomycete products is an issue
that cannot be ignored. With five primary fungal ingredients in the marketplace
— mushroom, pure mycelium, mycelium on grain biomass, sclerotium, and spore
preparations — proper labeling is more essential than ever for manufacturers to
know what they are selling. Just as important, practitioners and consumers need
to know exactly what they are buying.
Jeff Chilton started growing mushrooms commercially in 1973. In
1983, he co-authored the highly acclaimed book The Mushroom
Cultivator (Agarikon Press, 1983). In the
1980s, he operated a commercial mushroom spawn laboratory, and, in 1989, he
started one of the first medicinal mushroom businesses in North America. His
company, Nammex, sells certified organic basidiomycete raw materials. Contact
Mr. Chilton by email at jeff@nammex.com.
References
- Vikineswary
S, Chang ST. Edible and medicinal mushrooms for sub-health intervention and
prevention of lifestyle diseases. Tech
Monitor. Jul.-Sep. 2013;33-43.
- Wasser
SP, Nevo E, Sokolov D, Reshetnikov S, Timor-Tismenetsky M. Dietary supplements
from medicinal mushrooms: fiversity of types and variety of regulations. Int J Med Mushr. 2000;2:1-19.
- Wasser
SP. Medicinal mushroom science: current perspectives, advances, evidences, and
challenges. Biomed
J. 2014.
doi:10.4103/2319-4170.
- Kendrick B. The Fifth
Kingdom. Sidney, BC, Canada: Mycologue Publications; 2000.
- Snell
W, Dick EA. A Glossary of Mycology.
Cambridge, MA: Harvard University Press; 1971.
- US
Food and Drug Administration. CPG Section 585.525: Mushroom Mycelium – Fitness
for Food; Labeling. Published October 20, 1976. Available at: www.fda.gov/ICECI/ComplianceManuals/CompliancePolicyGuidanceManual/ucm074627.htm. Accessed August
11, 2015.
- Ng
HE, Raj SS, Wong SH, Tey D, Tan HM. Estimation of fungal growth using the
ergosterol assay: a rapid tool in assessing the microbiological status of
grains and feeds. Lett
Appl Microbiol. 2008;46(1):113-118.
- Dalla-Santa HS, Rubel R, Vitola FMD,
et al. Growth parameters of Agaricus brasiliensis mycelium on wheat
grains in solid-state fermentation. Biotechnology.
2012;11(3):144-153.
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Phillips KM, Ruggio DM, Horst RL, et al. Vitamin D and sterol
composition of 10 types of mushrooms from retail suppliers in the United
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