Wild-Gathered Fungi for Health and Rural Livelihoods
Total Page：16
File Type：pdf, Size：1020Kb
Proceedings of the Nutrition Society (2006), 65, 190–197 DOI:10.1079/PNS2006491 g The Authors 2006 Wild-gathered fungi for health and rural livelihoods Miriam de Roma´n1*, Eric Boa1 and Steve Woodward2 1CABI Bioscience, Bakeham Lane, Egham, Surrey TW20 9TY, UK 2School of Biological Sciences, University of Aberdeen, Plant and Soil Science, St Machar Drive, Aberdeen AB24 3UU, UK Fungi are a good source of digestible proteins and fibre, are low in fat and energy and make a useful contribution to vitamin and mineral intake. In terms of current dietary advice, 80 g fungi represent one portion of vegetables. Dried fungi and concentrated extracts are also used as medicines and dietary supplements. Some species show strong anti-tumour and antioxidant activity by enhancing various immune system functions and lowering cholesterol levels. Nevertheless, there are also some safety concerns. Edible species might be mistaken for poi- sonous ones, high heavy-metal concentrations in wild edible fungi (WEF) are a known source of chronic poisoning and the consumption of WEF can contribute markedly to the radiocaesium intake of human subjects. Some regions of Europe have a strong WEF tradition, especially eastern Europe. In the UK the consumption of wild fungi is considered of minor importance. Only one-third of adults consume fungi (cultivated species and WEF) throughout the UK; the average intake of fungi in the UK is estimated to be 0.12 kg fresh weight per capita per year. At least eighty-two species of wild fungi are recorded as being consumed in the UK, although certain species (e.g. chanterelle (Cantharellus cibarius), cep (Boletus edulis), oyster mushroom (Pleurotus ostreatus)) are favoured over others. Although WEF are not essential components in the daily diet, they are a nutritionally-valuable addition to the range of vegetables consumed, and their role in helping to avert food shortages in less-favoured areas should be definitely considered. Wild edible fungi: Medicinal fungi: Nutrition: Safety: Health Wild edible fungi (WEF) are a natural resource with a high WEF is widespread (Yorou & De Kesel, 2001; Kuyper, nutritional and economic value. Although collection is 2002). often regarded as a hobby, recent studies confirm that they The most remarkable WEF species in terms of world are an important source of food and income in both trade are the black truffle (Tuber melanosporum), which is developing and developed countries (Hosford et al. 1997; exported from France, Italy and Spain, the matsutake Wong et al. 2001; Boa, 2004). (Tricholoma matsutake and relatives), which is sent to Attitudes towards WEF are very different around the Japan from the USA, Canada, Mexico, China and neigh- world. According to Boa (2004) about 1200 species bouring countries, and the boletes (Boletus spp.) and of fungi are used in eighty-five different countries for their chanterelles (Cantharellus cibarius), which are widely gastronomic value and/or medicinal properties. China, appreciated. Japan and eastern European countries are particularly In terms of nutrition WEF are rich in protein and have enthusiastic collectors and consumers, and have developed considerable value as a source of dietary fibre because a robust marketing network in order to satisfy the high of both their high fibre content and their unique fibre demand. In northern and western Europe and North composition (Cheung, 1997). Some medicinal species are America WEF have traditionally been mistrusted, although widely used in traditional and alternative medicines to trends vary among countries. In central America some heal a broad range of diseases; Ganoderma lucidum, for wild fungi are revered as sacred objects (Wasson, 1968). example, is especially esteemed in China and Japan Studies in Africa reveal that the knowledge and use of (Molitoris, 2002). Abbreviations: DW, dry weight; WEF, wild edible fungi. *Corresponding author: Dr Miriam de Roma´n, fax + 44 1491 829100, email [email protected] Wild-gathered plants 191 The present paper gives a global perspective on the fungi (Dı´ez & A´ lvarez, 2001). The high concentrations of nutritional and medicinal value of WEF, addresses safety glutamic acid in T. terreum and T. portentosum probably concerns and describes their consumption and role in rural contribute most to their characteristic flavour. Another livelihoods worldwide. possible source of the precursor flavour compounds would be the presence of unsaturated fatty acids, particularly linoleic acid (Dı´ez & A´ lvarez, 2001). Several studies have confirmed that fungi make a The nutritional value of fungi useful contribution to vitamin intake, particularly the B Many studies have been undertaken on the nutritional vitamins and vitamins D and K, and in some cases vita- composition of cultivated edible fungi and WEF (for a mins A and C (Sadler, 2003; Sanmee et al. 2003). Mattila summary of the most informative of these studies, see et al. (1994) have shown that Cantharellus cibarius and Table 1 and for further information, see Mukhiibi, 1973; C. tubaeformis contain high amounts of ergocalciferol Seeger et al. 1983; Coli et al. 1988; Mattila et al. 1994; (128 and 298.2 mg/kg fresh weight respectively), possibly Outila et al. 1999; Vetter, 1999; Ilievska & Petrovska, because in the genus Cantharellus the pileus and gills are 2000; Caglarirmak et al. 2002; Sadler, 2003; Sanmee et al. often more effectively exposed to light than they are in 2003; Yildiz et al. 2005). other species of fungi. The influence of illumination con- In general, edible fungi contain 850–950 g water/kg ditions in determining ergocalciferol content is a factor fresh weight and (g/kg dry weight (DW)) 160–350 protein, that should be taken into account in the case of cultivated 20–60 fat and 280–399 carbohydrate. However, the wide fungi. Outila et al. (1999) have shown that human variety and abundance of minerals are the most character- subjects can easily absorb ergocalciferol from lyophilized istic features of fungi; they are useful sources of Cu, Fe, K, and homogenized Cantharellus tubaeformis. Thus, for Mg, Se, P and Zn in the human diet and are very low in some groups, for example vegetarians or individuals Na. They are a source of unsaturated fatty acids (particu- allergic to fish, fungi can be an important dietary source of larly oleic and linoleic acids), contain high amounts vitamin D. of dietary fibre and are low in energy (1.42–5.46 MJ (340– Fungi rank amongst the vegetables with the lowest Na 1310 kcal)/kg). The proportion of protein, the amino acid content (Seeger et al. 1983). The Na contents of plants index and the quantity of minerals appears to be greater in vary between 200 and 2000 mg/kg, while in some meat and the cap than in the stem (Coli et al. 1988). In terms of meat products Na contents range from 10 000 to current dietary advice, 80 g fresh fungi is equivalent to one 22 000 mg/kg. The fruit bodies of Agaricus species contain portion of vegetables (Sadler, 2003) and a serving (100 g) on average 396 mg Na/kg (Vetter, 2003b), which is of great of fungi guarantees 9 (fresh Agaricus bisporus)–40 (dried nutritional benefit to the consumer. Boletus spp.) % RDA for dietary fibre (Manzi et al. 2001). The nutritional value of fungi can be affected by the The nutritional value of proteins is usually very high in method of preservation. Manzi et al. (2001) have compared the majority of fungi (Ilievska & Petrovska, 2000), and the nutritional value of Agaricus bisporus (fresh, canned fungal proteins are considered to be of equal quality to and deep-frozen), fresh Pleurotus ostreatus and dried those of animal origin (Longvah & Deosthale, 1998). Boletus spp. Cooked dried Boletus spp. were found to have Leo´n-Guzma´n et al. (1997) have shown that the protein the highest nutritional value, although this effect is essen- contents (g/kg) of fresh Amanita rubescens, Boletus frostii, tially a result of insufficient rehydration. On the other Lactarius indigo and Ramaria flava collected in Mexico hand, cooked deep-frozen Agaricus samples have lower are higher (190–350) than those of wheat (132) or milk amounts of protein (19 g/kg) and fat (2.6 g/kg) than fresh (252). Some exceptions exist; in Lentinula edodes or Ter- (protein 20.1 g/kg, fat 4.5 g/kg) or canned (protein mitomyces spp. the protein quality is inferior to that of 20.4 g/kg, fat 4.2 g/kg) Agaricus. It is probable that the grain legumes and cereals, but is still comparable with that structural damage to the cells, occurring during the deep- of many vegetables (Mukhiibi, 1973; Longvah & Deos- freezing process, promotes nutrient loss and causes the thale, 1998). small post-cooking yield (Manzi et al. 2001). Some species, such as Termitomyces umkowaani and Individual species appear to have similar nutrient con- T. sagittaeformis, contain all the essential amino acids centrations in different forest ecosystems (Rudawska & (Botha & Eicker, 1992). Other species lack one or more of Leski, 2005). Sanmee et al. (2003) have found that the the essential amino acids; in T. reticulatus four essential chemical and nutritional composition of WEF collected in amino acids (isoleucine, leucine, methionine and cytosine) sub-tropical forests of Thailand are within the same order are severely limiting (Botha & Eicker, 1992); in Hericium of magnitude as that measured in fungi collected in more erinaceus methionine and tryptophan are absent (Eisenhut temperate regions. et al. 1995). In the fungi analysed by Agrahar-Murugkar & Finally, fungi can also have a role as functional foods, Subbulakshmi (2005) phenylalanine was found to be the known as ‘nutraceuticals’, which are those materials that limiting amino acid and leucine the most abundant amino are beneficial, but not absolutely vital, for the human body acid. Leo´n-Guzma´n et al.