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CHAPTER 1 INTRODUCTION
Synopsis
This chapter briefly examines the relationship of diet to health
and defines the concept of functional foods. A dietary
supplement is considered as an addition to the diet to enhance
health. Foods as medicine underpins the paradigm of functional
foods. The recognition of medicinal mushrooms as functional
foods or as dietary supplements is fully discussed especially in
the concept of Chinese holistic medicine and modern
immunology.
In the developed nations of this world many causes of death or disability such
as coronary heart disease, strokes, diabetes, atherosclerosis, obesity and certain
forms of cancer can, in considerable part, be attributed to diet (Barasi, 1997). Poor
food selection and restricted dietary intake can affect the nutritional status of an
individual at any stage of life and can lead to impairment of long term health.
Increasingly, scientific evidence is supporting the view that diet controls and
modulates many functions of the human body and accordingly participates in the
maintenance of the state of good health or homeostasis necessary to reduce the risk
of many chronic diseases (Carter, 1993). Over the last few decades the science of
nutrition has progressed from being largely epidemiologically based to the greater
understanding of the physiological and genetic mechanisms by which diet and
individual food components influence health and disease. It is indeed a paradox that
nutrition is essential to support life but can also be considered as a causation of
many chronic diseases.
Arising from the
which affects one or more identified functions in the body in a positive manner.
Correspondingly, it can also include foods in which potentially harmful components
have been removed by technological means. The US Academy of Science has
defined functional foods as those that “encompass potentially healthful products”
including “any modified food or food ingredient that may provide a health benefit
beyond the traditional nutrients it contains” (Thomas and Earl, 1994).
Functional foods come in a plethora of name forms, e.g. dietary supplements,
nutra- or nutri-ceuticals, medical foods, vita foods, pharmafoods, phytochemicals,
mycochemicals, biochemopreventatives, designer foods and foods for specific health
uses (Hasler, 1996; Head et al., 1996). Such complex designations could well be an
impediment to their rightful maturation and consumer acceptance (Zeisel, 1999).
There continues to be much confusion over these names especially in the
commercial world. However, the term dietary supplement (DS) is now being more
widely accepted and recognised. The term DS was formally defined by the US
administration in 1994 as a product intended to supplement the diet to enhance
health. A DS includes one or more of the following dietary ingredients: a mineral,
amino acid, vitamin, herb or other botanical; or it is a dietary substance used to
supplement the diet by increasing the total dietary intake and is intended for
ingestion in the form of a capsule, powder, softgel or gel cap and not represented as
a conventional food or as a sole item of a meal or the diet (Dietary Supplement
Health and Education Act, Public Law 103-417, 1994).
However, foods as medicine underpins the paradigm of functional foods.
Functional foods cannot claim to cure diseases but, increasingly, evidence is being
produced that supports the role of some functional foods in disease prevention
(Steinmetz and Potter, 1991). The concept of foods as medicine does not fit easily
2
within the current expertise of either pharmaceutical or food companies and the full
creative development of functional foods may well require new alliances between
these companies with respect to regulatory issues.
Functional food science is now considered as a part of nutritional science in
which the primary objectives are to maintain good health, improve homeostasis and
to create the conditions for disease risk reduction. In this way it should be seen to
be quite distinct from the medical and pharmaceutical sciences where the objectives
are mainly to cure or control diseases (Saris et al. 1998; Diplock et al. 1998). In
many ways conventional medicine seeks to eliminate disease rather than to fortify
the patient. In essence, functional food science aims: 1) to identify beneficial
interactions between the presence or absence of a food component (macronutrient,
micronutrient or so-called non-nutrient) and a specific function or functions in the
body; 2) to understand their mechanisms so as to support hypotheses to be treated
in protocols relevant for human studies. This will require multidisciplinary research
programs containing the expertise of scientific partners including biochemists,
nutritionists, the medical profession and process technologists.
Functional foods are set to play an increasingly important role in national
efforts in developed nations to curtail medical expenditure and also to improve the
dietary habits of the populace. Consumers are becoming increasingly more health
conscious and discerning in the types of foodstuffs that are purchased. It is now not
possible to overlook the critical role that diet, including functional foods, can play in
general health and well-being. Many types of cancer can now be linked to
inappropriate diets. In contrast, regular consumption of fruits and vegetables (now
viewed as classical examples of functional foods) are now considered as essential
ingredients in cancer prevention programmes (Steinmetz and Potter, 1991).
3
Medicinal mushrooms
Mushrooms have long been valued as highly tasty and nutritional foods by
many societies throughout the world (Chang and Miles, 1989). Early civilisations, by
trial and error built up a practical knowledge of those suitable to eat and those to be
avoided, e.g. poisonous or even psychotropic. In many parts of the world, especially
Europe, wild mushrooms are regularly collected and used directly as a main source
of food or added to soups, stews and teas. Mushrooms are considered to be a
good source of digestible proteins with protein content above most vegetables and
somewhat less than most meats and milk. Protein content can vary from 10-40% on
a dry weight basis. Mushrooms contain all the essential amino acids, but can be
limiting in the sulphur-containing amino acids, cystine and methionine (Chang, 1991;
Breene, 1990). Fresh mushrooms contain 3-21% carbohydrates and 3-35% fibre on
a dry weight basis. Thus, a considerable proportion of the carbohydrate of
mushrooms consists of dietary fibre which cannot easily be digested by humans and
whichl function essentially as dietary fibre; in this way the calorific value of most
mushrooms is low. Mushrooms probably contain every mineral present in their
growth substrate including substantial quantities of phosphorous and potassium,
lesser amounts of calcium and iron. Mushrooms appear to be an excellent source
of vitamins especially thiamine (B1), riboflavin (B2), niacin, biotin and ascorbic acid
(VitC). Vitamins A and D are relatively uncommon although several species contain
detectable amounts of ß-carotine and ergosterol which converts to active vitamin D
when exposed to ultraviolet irradiation. While crude fat in mushrooms contains all
the main classes of lipid compounds including free fatty acids, mono-, di- and tri-
glycerides, sterols, sterol esters and phospholipids, levels are generally low, around
2-8% of dry weight (Breene, 1990). Without doubt, edible mushrooms in fresh,
4
cooked or processed forms are a nutritionally sound, tasteful food source for most
people and can be a significant dietary component for vegetarians (Breene, 1990).
In China, the term Yakuzen is generally used for medicinal food dishes of
mushrooms.
However, in the Orient several thousand years ago, there was the recognition
that many edible and certain non-edible mushrooms could have valuable health
benefits (Bensky and Gamble, 1993; Hobbs, 1995). The edible mushrooms which
demonstrate medicinal or functional properties include species of Lentinus
(Lentinula), Auricularia, Hericium, Grifola, Flammulina, Pleurotus and Tremella while
others are known only for their medicinal properties, e.g. Ganoderma and Trametes
(Coriolus) – these are definitely non-edible due to their coarse and hard texture or
bitter taste. The historical evolution of usage of these essentially scarce, forest-
obtained medicinal mushrooms would most certainly not have been as whole
mushrooms but as hot water extracts, concentrates, liquors or powders and used in
health tonics, tinctures, teas, soups and herbal formulae. Nowadays, almost all of
the important medicinal mushrooms have been subjected to large-scale artificial
cultivation, thus removing the historical scarcity factor. This also ensures accuracy
of identification and increased reliability and consistency of medicinal products. Also
many of the edible species of medicinal mushrooms are gaining worldwide popularity
because of their unique flavours, textures and amenability to culinary inclusion.
Indeed, most people in the West who enjoy the unique organoleptic features of the
Shiitake mushroom (Lentinus edodes) are singularly unaware of its possible health
benefits. Regular consumption of whole medicinal, edible mushrooms could
introduce a functional or medicinal contribution within the individual’s diet. The
extent of the health beneficial effect will be dependent on the level and regularity of
5
consumption and the relevance of whole fresh medicinal mushrooms and
concentrates will be discussed in later chapters.
When used for a therapeutic intention the medicinal mushrooms are normally
consumed as powdered concentrates or extracts in hot water, and the extract
concentrated and used as a drink or freeze-dried or spray-dried to form granular
powders which allow easier handling, transportation and consumption (Mizuno et al.
1995). As such, these liquid concentrates or dried, powdered mushrooms contained
in capsules can be considered as dietary supplements or mushroom nutriceuticals
with potential health benefits (Chang and Buswell, 1996). Mushroom nutriceuticals
are usually crude mixtures and should not be confused with pharmaceuticals which
are almost invariably a defined chemical preparation, the specifications for which are
listed in pharmacopoeia. Regular intake of these concentrates is believed to
enhance the immune responses of the human body, thereby increasing resistance to
disease and in some cases causing regression of the disease state (Jong et al.
1991).
These mushroom dietary supplements are used extensively in traditional
Chinese medicine in various combinations, often with other herbal products, to treat
many medical conditions. A limited number of highly purified polysaccharide
compounds derived from certain medicinal mushrooms are now being used,
particularly in Japan, as pharmaceutical grade products and are discussed in later
chapters.
Immune system modulation has long been a feature of Chinese holistic
medicine and is referred to as Fu Zheng therapy. Fu Zheng can be considered as
the Oriental equivalent of Western immunotherapy. Compounds derived from
certain medicinal mushrooms are used extensively in the Orient to increase disease
6
resistance and to normalise body functions. Such extracts are used to treat deficient
principles or qi or ch’i, the ‘vital’ or life energy, blood and yin (fluid) and yang
functionality (especially the kidney).
Cancer and its treatment by conventional therapies as chemotherapy and
radiotherapy are known to have adverse effects on the human immune system.
Cancer immunology has become a rapidly growing field in basic cancer research.
Ways are now being sought to promote host antitumour immune cell activity and to
overcome the ability of the cancer cell to evade immune surveillance (Curt, 1998;
Cassileth, 2000). Immunostimulating agents would possibly be useful adjuncts to
conventional treatments of cancer if they do not interfere with the ability of the
conventional treatment to kill tumour cells. These approaches, like chemo- and
radiotherapy, are designed to cause the destruction of tumour cells but to be much
more tumour-specific than present treatments and, consequently, less harmful to
normal cells.
As will be shown in later Chapters, one of the most noticeable features of
extracts derived from many medicinal mushrooms is their ability to function as
immunomodulators. As such, the physiological constitution of host defence
mechanisms are improved by the intake of these mushroom compounds which
restore homeostasis and enhance resistance to disease. A central premise in
Oriental medicine is to regulate homeostasis of the whole body and to return the
diseased individual to the normal state.
It is interesting to note that several of the medicinal mushrooms and their
concentrates are becoming particularly popular in the US – the movement began
with a drive towards “healthy food” in the 60s-70s; now it is towards “healthy
medicine”. People are interested in the medicinal mushrooms because they appear
7
to have been used with considerable effect for hundreds of years in the Orient while
many modern widely used pharmaceuticals while offering undoubted health benefits
can also in some cases have serious side-effects. Furthermore, it is now
increasingly being recognised that diet is intimately associated with optimal health
and the tenet of Hippocrates c 400 B.C. “Let food be your medicine and medicine be
your food” is fast becoming a truism for many people.
Over the last 2-3 decades scientific and medical studies have been carried
out in Japan, China, Korea and more recently US which have increasingly
demonstrated the potent and unique health enhancing properties of compounds
extracted from a range of medicinal mushrooms. Explanations of how such
compounds function in animal and human systems are now regularly appearing in
peer-reviewed scientific and medical journals.
This review will aim to give a detailed analysis of the history and present state
of knowledge of these organisms, methods of cultivation, range of organisms,
methods of extraction, and detailed examination of medical implications with special
emphasis on immuno-stimulation and cancer treatment. The review will also
examine international regulations related to the use of such compounds (dietary
supplements) with particular emphasis on safety. While the review will concentrate
largely on their applications in the treatment of cancer, a brief overview of the wide
range of other medical uses will also be included.
8
References
Barasi, M. 1997. Human Nutrition: a Health Perspective. Arnold, London.
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Bensky, D. and Gamble, A. 1993. Chinese Materia Medica. 2 Ed., Eastland Press, Seattle.
Breene, W. 1990. Nutritional and medicinal value of speciality mushrooms. Journal of Food
Production 53, 883-894.
Carter, J. 1993. Food: Your Miracle Medicine. Harper Collins Publishers Inc., New York.
Cassileth, B.R. 2000. Complementary therapies; the American experience. Support Case Cancer 8,
16-23.
Chang, S.T. 1991. Cultivated mushrooms. In: Handbook of Applied Mycology, Vol. 3., pp. 221-240.
Marcel Dekker, New York.
Chang, S.T. and Buswell, J.A. 1996. Mushroom nutriceuticals. World Journal of Microbial
Biotechnology 12, 473-476.
Chang, S.T. and Miles, P.G. 1989. Edible Mushrooms and Their Cultivation. CRC Press, Boca
Raton.
Curt, G.A. 1988. Investment in research is a national priority. Oncologist 3, 64-66.
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Dietary Supplements Health and Education Act, 1994. Public Law 103-417, 25 October 1994.
Codified at 42USC 287C-11.
Diplock, A.T., Charleux, J-L. 1998. Functional food science and defense against reactive oxidative
species. British Journal of Nutrition 80 Suppl. 577-612.
Hasler, C.M. 1996. Functional food: the Western perspective. Nutrition Reviews 54, 506-510.
Head, R.J., Record, I.R. and King, R.A. 1996. Functional foods; approaches to definition and
substantiation. Nutrition Reviews 54, 517-520.
Hobbs, C. 1995. Medicinal Mushrooms: An Exploitation of Tradition, Healing and Culture. Botanica
Press, Santa Cruz.
Jong, S.C., Birmingham, J.M. and Pai, S.H. 1991. Immunomodulatory substances of fungal origin.
Sadler, M. and Saltmarsh, M. (eds.) 1998. Functional Foods: The Consumer, the Products and the
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Saris, W.H.M., Asp, N.G.L. et al. 1998. Functional food science and substrate metabolism. British
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