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Nutrition & health Surprises from the mushroom The common button mushroom (Agaricus bisporus) is now so popular that it is consumed by 86% of Australian households each year, and 55% of households every week. Those that love their mushrooms eat them at least three times a week. Their increasing popularity has seen mushroom consumption increase five-fold since 1980, with mushrooms now the third highest selling fresh produce item at the supermarkets. Below is a summary of what we know about the health benefits of the mushroom, followed by a more detailed description and a list of the scientific references. Executive summary
The mushroom is not a plant
First, it is important to understand that the mushroom is not a plant as it evolved at a different time to plants (Carroll 2001). This helps to explain why a mushroom’s nutrition profile is different to plant foods like fruit and vegetables. We still want people to eat their vegetables, but the evidence is mounting that having mushrooms in the diet complements vegetables and offers unique health benefits. By regularly being one of the five daily vegetable serves in the Go for 2 & 5 campaign, mushrooms enhance fruit and vegetable’s ability to keep the doctor away and disease at bay.
The mushroom is bursting with flavour
The unique taste and texture of the mushroom makes it a favourite with meat eaters and vegetarians alike. The rich flavour comes from the natural glutamates present in the mushroom. Glutamate is also produced by the body, used as a neurotransmitter in the brain by half of all nerve cells.
The glutamate level of the mushroom increases as the mushroom matures from a button to a flat mushroom. The natural glutamates are not MSG. Fresh and powdered mushroom can be added to soups, casseroles and stews for extra flavour. Including mushrooms in a dish means you can dispense with the salt shaker. See the Fact Sheet on umami for much more information and references.
The macronutrients in mushrooms The mushroom has more protein than most vegetables and a carbohydrate content similar to zucchini and tomatoes (see Table 1). Cholesterol-free and with virtually no fat, the mushroom is a very low kilojoule food. A serve of mushrooms is 100g, which is equivalent to three button mushrooms or one flat mushroom.
Table 1. Macronutrient profile/100g fresh mushrooms
Source: NUTTAB 2006 Online
The mushroom is also an abundant source of essential vitamins and minerals (see Table 2), surprising many health professionals with its nutrient diversity and density. A serve of mushrooms provide over 20% of the Recommended Dietary Intakes (RDI), or daily needs, for each of the B vitamins riboflavin, niacin, pantothenic acid, biotin, and the minerals selenium and copper, while also providing an appreciable amount of folate and bioactive compounds. Mushrooms exposed to light quickly generate vitamin D to levels that meet daily needs. No vegetable can match the nutrient profile of the mushroom.
The vitamins in mushrooms About one third of your riboflavin (vitamin B2) needs can be obtained from a serve of mushrooms (see Table 2). Riboflavin is involved in the release of energy from carbohydrate, protein and fat. It is uncommon to see mushrooms listed as a source of niacin (vitamin B3), yet it can provide a quarter of our daily needs. Niacin can also be made in the body from the amino acid tryptophan. The role of niacin in the body is closely related to that of riboflavin as it is involved in cell respiration and the metabolism of carbohydrate, fat and protein. Table 2. B vitamins, minerals & other important compounds in mushrooms
Pantothenic acid is involved in more than 100 different steps in making neurotransmitters, hormones and haemoglobin, while biotin is also involved in the normal metabolism including the production of glucose. Both vitamins work primarily as co-enzymes, compounds that allow enzymes to function properly. A serve of mushrooms will provide around 20% of your daily needs of these two vitamins.
Vitamin B12 There has long been speculation about whether or not mushrooms provide vitamin B12, a vitamin normally associated with animal foods. In 1987, the Australian Government Analytical Laboratories found appreciable amounts of B12 in mushrooms. Based on this analysis, the mushroom industry then included B12 as a nutrient in their promotional material and advertising. The B12 level was disputed by some nutrition professionals who believed that only animal sources can provide B12, while others wanted to know whether the B12 claimed to be found was bio-available. In early 2009, researchers at the University of Western Sydney completed ground-breaking research on the B12 content of Australian button mushrooms (Koyyalamudi 2009). Their detailed experiments on mushrooms of all sizes and stages of growth from around Australia conclusively proved that: A. Mushrooms do have B12 present. It is on both the surface of the mushroom and in the flesh of the mushroom. The majority of B12 is in the surface of the cup of the mushroom. B. The B12 present is bio-available, in exactly the same form as B12 in beef liver and fish. C. The amount of B12 in mushrooms varies from crop to crop. One serve will provide about 2-4% of the RDI. However, that level may be an important amount over a lifetime for a vegan who loves their mushrooms. Vitamin D Vitamin D has sparked a lot of interest this century, as adequate vitamin D has been linked to a number of benefits beyond healthy bones and the prevention of rickets and osteoporosis, such as a decreased risk of heart disease, type 2 diabetes, hypertension and colorectal cancer (Lee 2008; Wang 2008; Dobnig 2008; Holick 2010). In November 2010 the Institute of Medicine in the US raised the daily requirement levels. The levels are expected to rise in Australia too when the RDIs are next reviewed. The adult RDI for vitamin D ranges from 5-15 mcg, with more being needed by older people. Compare that to the typical vitamin D dietary intake of 2-3 mcg daily by adults (Nowson 2002). The common dietary form of vitamin D in Australia is cholecalciferol (vitamin D3) available from table margarine, canned fish and eggs (Shrapnel 2006). Both vitamin D2 and D3 are offered as supplemental vitamin D in Australia. Mushrooms too, are a source of vitamin D. It is quite natural for ergocalciferol (vitamin D2) to be found in mushrooms. Wild mushrooms, through the action of sunlight, convert their abundant ergosterol to ergocalciferol. Wild mushrooms in Europe commonly have 2-40 mcg vitamin D/100g (Mattila 1994; Mattila 2002; Teichmann 2007). There is a small amount of vitamin D in cultivated mushrooms as they don’t need light to grow. Farmers generally don’t subject their mushrooms to light other than during growing operations and harvesting. However, if these mushrooms are exposed to a short burst of ultraviolet light they generate in excess of the daily recommended intake for vitamin D. Vitamin D-enhanced mushrooms are now available in supermarkets in Australia, the US and Canada, providing at least the daily allowance of vitamin D in a single serve. Farmers mimic nature by passing the mushrooms under a UV light with the same spectrum as sunlight. A few seconds is all it takes for the D2 conversion process to be activated. Following research at the University if Western Sydney showing that UV light boosts the vitamin D levels in mushrooms, the Australian mushroom industry refined the US technique to their growing system so consumers in Australia have had D-enhanced mushrooms since September 2011 (Koyyalamudi 2009; Koyyalamudi 2011). The vitamin D in mushrooms is easy to absorb (Outila 1999; Jasinghe 2005; Koyyalamudi 2009). There is at least an 85% retention of vitamin D in wild mushrooms after frying for five minutes (Mattila 1999). Furthermore, there is very little loss of vitamin D2 when the mushrooms are refrigerated for eight days (Koyyalamudi 2009) or even three months (Mattila 1999). This means that mushrooms can be a very useful source of vitamin D to the consumer, whether eaten raw or cooked. Vitamin D-enhanced mushrooms will become a simple and delicious way for Australians to get 100% of their daily vitamin D needs, especially if they are unable to get adequate sun exposure during the day. The minerals in mushrooms About a quarter of your Copper requirements are found in a serve of mushroom. Copper is very important in the production of red blood cells and it’s also a component of antioxidant enzymes naturally produced by the body, such as superoxide dismutase. It is also involved in energy production, and the making of tendons and neurotransmitters, such as noradrenalin. A serve of mushrooms will provide 10% of your daily Phosphorus needs. The main role of phosphorus is, in combination with calcium, to form the structure of teeth and bones. The other roles of phosphorus include energy metabolism and being a critical part of ATP, the high-energy molecule needed for muscle contraction. Potassium is a natural mineral in mushrooms and plant foods and it plays a major role in maintaining fluid and electrolyte balance. A serve of mushrooms will give you around 10% of your potassium needs. A diet with plenty of potassium appears to both prevent and help correct high blood pressure. This, in turn, helps to prevent strokes. Selenium is one of the body’s antioxidants nutrients helping to prevent free radical formation, and a serve of mushrooms can provide about a quarter of your daily needs. A lack of selenium has been implicated in the cause of both heart disease and some cancers. The mushroom has more selenium than found in vegetables. The fibre in mushrooms A serve of mushrooms provides around 1.5g of fibre, which is about 5-6% of the daily fibre needs of an adult. When mushrooms are cooked and lose some water, the level of fibre rises to 2.7g per 100g. The fibre in mushrooms is mainly insoluble. Mushrooms have chitin and glucans as part of their cell walls (Beelman 2004; Wu et al 2004). Cellulose is normally the main polysaccharide in plant cells walls, but chitin plays a similar role in the mushroom. Dietary fibre has many benefits, but the fibre in mushrooms may have different physiological benefits to those found in plant foods. Chitin in particular has been associated with maintaining healthy blood cholesterol levels. Around 15% of the total dietary fibre in mushrooms is resistant starch type 1 (Dikeman 2005), which can act as a prebiotic by resisting digestion to become food for the healthy bacteria residing in the large intestine. Glycaemic Index (GI)
You may have heard of the Glycaemic Index (GI), which is the measure of the blood glucose response to carbohydrate-containing foods. It gives an indication of the rate at which the carbohydrate in food is digested and absorbed into the blood. The GI of mushrooms is so low it can’t be measured realistically in humans. In fact, to get a GI measurement for mushrooms, you would need to eat over 12 kg in less than 10 minutes! The very low GI of mushrooms means that anyone, including people with diabetes, can eat them without any effect on their blood glucose levels. An Australian animal study showed that mushrooms can be having a positive effect on both blood glucose and blood lipids, possibly due to the fibre content (Jeong 2010).
Mushrooms & antioxidants Mushrooms have a powerful antioxidant capacity. Compared to 30 common vegetables, using three different analytical methods, mushrooms were placed in the top five for antioxidant capacity (Pellegrini 2003). Subsequent studies have confirmed the antioxidant potential of button mushrooms (Dubost 2007; Savoie 2008). Mushrooms are very high in ergothioneine, an intracellular antioxidant first identified in 1909. Analysis shows that ergothioneine is in mushrooms, meats (especially liver and kidney), egg yolk, oat bran, wheat germ (but not the endosperm) and some beans and onion (Ey 2007). It was not found in other vegetables and fruit. Ergothioniene levels are high in red blood cells, bone marrow and semen. It is believed that ergothioneine protects the haemoglobin in red blood cells, and protects monocytes against oxidation (Gründemann 2005). Ergothioneine is not made by the body so it can only be obtained from the diet. The best indication that ergothioniene is essential to humans was the discovery in 2005 that the body has a specific ergothioniene transporter (Gründemann 2005). Cells that have the transporter will actively accumulate and retain ergothioneine, while those without the transporter cannot obtain ergothioneine. Ergothioneine is concentrated in the mitochondria and other cells exposed to oxidative stress and involved in the inflammatory response. When cells are deprived of the transporter there is increased mitochondrial DNA damage, protein oxidation and lipid peroxidation (Paul 2010). Oxidative damage to mitochondrial DNA is linked to neuro-degenerative diseases, especially Parkinson’s Disease. Ergothioneine accumulates in the endothelial cells of blood vessels and appears to protect against atherosclerosis, at least with in vitro tests (Martin 2010). A study determining the ergothioneine levels in different mushrooms found that both white and brown button mushrooms were rich in ergothioneine and that the levels did not diminish during cooking (Dubost 2006). Mushrooms helping the waistline Foods with a low energy density like fruits, vegetables and mushrooms have the ability to fill people up, avoiding an over-consumption of food. The mushroom, one of the lowest energy dense foods around, appears to have an additional benefit for the weight watcher: it has the ability to dampen the appetite, certainly over the short-term. When meat dishes were substituted with button mushrooms, the satiety of the meal was enhanced (Cheskin 2008). Although the mushroom meal was 420 kJ (100 Calories) less than the meat meal, consumers actually ate 1555 fewer kilojoules (370 Calories) each day over four days. This suggests that mushrooms have a powerful ability to increase the satiety of a meal. The same research group is now looking at the effect of mushroom consumption on appetite over 12 months, rather than just days, to see if the effect is sustained. The mushroom is ideally suited for weight control because it is filling, is low in fat, low in kilojoules and low in energy density (Table 3).
Table 3. Energy Density of Example Foods
Source: NUTTAB 2006
Mushrooms & immune function With mushrooms offering so many nutritional and antioxidant benefits the next step was to check the mushrooms effect on the broader human physiology. Preliminary reports indicate that mushrooms do indeed boost immune function. Many of these studies have focused on exotic mushrooms, but a recent paper found that white button mushrooms enhanced the action of natural killer cells in mice (Wu 2007), reduced the severity of arthritis in mice (Chandra 2011) and stimulated the production of anti-microbial peptides (Kuvibidila 2010). Another report from Pennsylvania State University showed that mushroom extracts given to mice decreased inflammation and increased the anti-cancer immune response (Yu 2009). Mushrooms & cancer prevention The mushroom has been linked to cancer prevention for some time. The mushroom contains compounds that suppress two enzymes called aromatase and 5-alpha-reductase (Grube 2001; Chen 2006). Aromatase converts androgen to estrogen, which in turn can promote the development of breast cancer, especially in post-menopausal women. Currently aromatase inhibitors are being used in the treatment of estrogen-dependent breast cancer. Aromatase has been found in other cancers, such as ovarian, uterine and prostate cancers and there is speculation that aromatase inhibitors may have a significant role in preventing such cancers (Hong 2006). The enzyme 5-alpha-reductase converts testosterone to dihydro-testosterone and is thought to play a role in the development of prostate cancer and benign prostate enlargement. Research on animal cells in vivo suggest that mushrooms could have a role in protecting men against prostate cancer (Chen 2004). The same team found that button mushrooms reduced prostate tumour size and tumour proliferation, and increased tumour cell death, in mice (Adams 2008). There have been two reviews of research on the potential for mushrooms to reduce the risk of cancer by enhancing the immune system (Borchers 2008; Ziadman et al 2005). The two mushroom components with the most supporting evidence appear to be the beta-glucans and peptide-bound polypeptides. The glucans stimulate the phagocyte system (eg macrophages and monocytes) that consume alien cells. Mushrooms also contain lectins (bio-active proteins), and other compounds that have been strongly linked to a reduction in the risk of cancer and could potentially be helpful in the treatment of cancer (De Mejía 2005, Jedinak 2008). Australian researchers from the University of Western Australia recently studied women in China and found a strong association between mushroom consumption and a decreased risk of breast cancer (Zhang 2009). They undertook a diet and lifestyle interview with 1009 Chinese women with breast cancer and 1009 matched controls. Compared to those having no mushrooms, women eating 10g or more of mushrooms each day reduced their risk of breast cancer by over 60%. This protection was further enhanced if the women also consumed a cup of green tea (1g dried leaves). The effect was seen in both pre- and post-menopausal women. The most common mushroom consumed was the common button mushroom Agaricus bisporus. Two other studies have also shown a link between mushroom eaters and a much lower risk of breast cancer, in the order of 50-60% compared to women who don’t eat mushrooms (Hong 2008, Shin 2010). Because three studies show a similar effect, it has stimulated more human research to see if breast cancer risk reduction in women is specifically due to compounds in mushrooms. Is the mushroom a superfood? The term “superfood” is used a lot by the media, possibly too frequently, yet there is no formal definition of the term. If there were such a definition, a superfood might have the following characteristics:
Judging against these characteristics, it is indisputable that the mushroom is quite an exceptional food! The mushroom is:
There is no doubt that the mushroom is a food that punches well above its weight. References:
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