Scientific Background

The most commonly eaten mushroom in Australia is the button mushroom, with the botanical name Agaricus bisporus. There is a good deal of information on the mushroom, especially with regard to its nutrition profile and its potential health benefits. A growing body of research is finding evidence that 100g of mushrooms a day can contribute to your long-term health. An executive summary is provided below, followed by a more in-depth discussion. The scientific references are listed at the end.

Executive summary

You may have thought of mushrooms as something to add another colour or texture to a salad, a complement to eggs and bacon, or to make the occasional soup. Mushrooms offer much more than this. Mushrooms are a very useful source of essential nutrients and could be having a significant effect on your long-term health.

Mushrooms are a vitamin heavyweight. They are the number one source of the essential vitamins riboflavin, niacin, pantothenic acid, biotin, and vitamin D when compared to vegetables, with a normal 100g serve of mushrooms providing more than a quarter of your needs. They also provide a modest amount of folate.

Folate has received a lot of attention through keeping babies free of spinal deformities during pregnancy http://asbha.org.au/index.htm and has also been strongly linked to a lower risk of getting heart disease http://www.heartfoundation.com.au or dementia later in life http://www.alzheimers.org.au/.

In the past, mushrooms have been associated with vitamin B12. The Australian Mushroom Growers Association has just commissioned research by the University of Western Sydney to test mushrooms for their B12 content. We shall give you the results as soon as they are available later in 2008.

Mushrooms also get a range of essential minerals from the ground (known as .substrate.) in which they are grown, such as copper, phosphorus, potassium and selenium. Copper is involved in the production of new red blood cells; phosphorus combines with calcium for strong bones; potassium helps keep our blood pressure healthy; and selenium acts as an antioxidant to protect body cells from damage. A serve of mushrooms will provide about a quarter of your copper and selenium needs.

You probably never though of the mushroom as being a vitamin tonic! For maximum vitamin retention, mushrooms should be stored in the fridge, eaten soon after purchase, consumed raw or quickly cooked.

And the good news doesn’t end there. The fact that mushrooms are very low in kilojoules (or Calories, if you prefer) means that you get the benefit of vitamins and minerals without worrying about your waistline. With no fat, a very low Glycaemic Index (http://www.glycemicindex.com), and being a source of dietary fibre it means that mushrooms are suited to every body

More recently, the scientists have been looking beyond the nutrients in mushrooms. The early research suggests that mushrooms have compounds that can reduce natural bone loss that occurs with osteoporosis. With a few minutes of UV light, the mushroom also becomes a source of vitamin D. Other compounds in mushrooms appear to influence hormones to reduce the risk of both breast cancer and prostrate cancer. If more research confirms these early findings then mushrooms could be providing a health bonus you never considered before.

Finally, remember that we are all being urged to eat more fruit and vegetables – two serves of fruit and five serves of vegetables, to be precise. A serve of vegetables is 75g. With three medium mushrooms being 100 g, mushrooms are a simple way to help meet your daily vegetables needs in one easy, tasty serve.

Some people see mushrooms as a food group of their own. Well, that makes sense, as mushrooms are neither a plant nor an animal as they evolved separately from these two life forms. That probably explains why their nutrition attributes are so unique and they offer benefits not normally associated with fruit and vegetables. A 100 gram serve each day is so easy . breakfast, lunch or dinner, cooked or raw.

Now, lets look at mushrooms and health in more detail.

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1. The vitamins in mushrooms

According to Australian government food tables (NUTTAB 2006), mushrooms are a good source of the B vitamins riboflavin, niacin, folate, pantothenic acid and biotin (see the average figures in table 1 below). The figures are similar for white and brown mushrooms.

Table 1. Average vitamin content of mushrooms

• %RDI = The percentage of the Recommended Dietary Intake each day
• %AI = The percentage of the Adequate Intake each day (as an RDI has not been established)
• mg = milligrams; mcg = micrograms

About one third of your riboflavin (vitamin B2) needs can be obtained from a serve of mushrooms. Riboflavin is also found in milk, yogurt, breakfast cereals and nuts. 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 is also found in protein-rich foods such as meat, poultry, legumes and peanuts. 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.

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 about a quarter of your needs of these two vitamins.

Vitamin B12
There has long been speculation that mushrooms provide vitamin B12, a vitamin normally associated with animal foods. As some vegetarians eat very little animal food, and vegans eat none at all, they have often eaten mushrooms in the hope it would be a viable source of vitamin B12.

In 1987, the Australian Government Analytical Laboratories did an analysis of 33 mushroom samples and found that 100g of mushrooms could provide about 10% of daily B12 needs. It was this finding that generated the expression "Meat for vegetarians".

There has been conjecture that B12 is only present in the micro-organisms on the surface of the mushroom, and it was a type of vitamin B12 that wasn.t absorbed by the body.

The University of Western Sydney will be analysing mushrooms for their B12 content and the results should be available later in 2008. Until we know more, please don.t consider mushrooms as a source of B12.

Vitamin D

Nutrition texts generally state that mushrooms do contain ergosterol, which is converted to ergocalciferol (vitamin D2) by the action of UV light. Scientific papers (eg Mattila 2000, 2001) reveal that mushrooms are the only non-animal based food that has vitamin D. The amounts found in mushrooms will vary, often depending upon how much UV radiation (or sunlight) they have received. On being eaten, the vitamin D2 is then converted to vitamin D3, the active form of the vitamin.

The Mushroom Council in the US also commissioned some research by Dr Mattila in Finland on vitamin D2 levels after exposure to UV light. This work implies that five minutes of UV light exposure brought the vitamin D2 level to around 80-100mcg/100g mushroom. There is a drop in Vitamin D2 levels over time, reinforcing the notion that we should eat mushrooms at their freshest.

Considering that D is only one fifth as effective as D3, then 80 mcg of D2 is the equivalent of 16 mcg of D3, which is well above the 5 mcg/day recommended for young adults and equal to the 15 mcg daily for older adults. Clearly, further studies are required to see if mushrooms can become an effective source of vitamin D2. We will be taking great interest in the ongoing research in this area.

Vitamin D is needed for the absorption of calcium from food, which in turn is needed for healthy bones and teeth. More recently, a low intake of vitamin D has been associated with a greater risk of cancer and, conversely, adequate vitamin D and calcium reducing the risk of cancer in post-menopausal women (Lappe 2007).

There has been a lot of research showing that a good consumption of fruit and vegetables reduces the risk of osteoporosis, but there has been speculation as to the mechanism. A review (Lanham-New 2006) suggested that adequate fruit and vegetable intake reduces bone turnover and calcium loss from the bones.

Certain food components may either stimulate bone formation or reduce bone resorption to slow down age-related bone loss (Muhlbauer 2003). These compounds could be monoterpenes, polyphenolics, the flavonoid rutin, or a combination of other unidentified compounds found widely in plant foods.

A study looked at 24 plant food items and their effect on bone resorption, including mushrooms, and found that many of them can be classified as bone resorption inhibitory food items (BRIFI) ie they reduce bone loss. Herbs had the greatest effect and mushrooms, onions, prunes and oranges were among the next most effective group (Muhlbauer 2003). At this stage it seems that mushrooms could be having a small, but significant, role in human bone health.

2. The minerals in mushrooms

There are many minerals that are essential for a normal healthy body. The most abundant minerals in mushrooms are potassium, copper and selenium. There are lesser amounts of magnesium and phosphorus (table 2).

Up to 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 eg noradrenalin. Other good food sources of copper are shellfish, legumes, cereals, nuts and dark chocolate.

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 used during muscle contraction. Mushrooms are a good source of phosphorus, with higher amounts found in milk, cheese, yogurt, legumes and meat.

Potassium is a natural mineral in 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. Potassium is also abundant in fruit, vegetables and whole grains. 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.

Table 2. Average mineral content of mushrooms

• %RDI = The percentage of the Recommended Dietary Intake each day
• %AI = The percentage of the Adequate Intake each day (as an RDI has not been established)
• mg = milligrams; mcg = micrograms

Sources: Nutrient Reference Values for Australia & New Zealand 2006; NUTTAB 2006

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3. Protein, fat & carbohydrate

The mushroom provides a small amount of protein and negligible carbohydrate (see Table 3). It is naturally low in fat and has no cholesterol (mushrooms and plant foods do not contain cholesterol; cholesterol is only found in animal foods). That makes mushrooms a low kilojoule food.

3.1 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 means that anyone, including people with diabetes, can eat mushrooms without any effect on their blood sugar levels.

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4. Mushrooms and fibre

At 1.5% fibre, mushrooms can be called a reasonable source of fibreAn Adequate Intake of fibre is 25g for women and 30g for men, so a normal serve of 100g mushrooms provides 5-6% of daily fibre needs. The fibre in mushrooms is mainly insoluble. The stage of development of the mushroom does not seem to affect the level of fibre. When mushrooms are cooked and lose some water, the level of fibre rises to 2.7g per 100g (Feeney 2004).

Mushrooms have chitin and glucans as part of their cell walls and some scientists consider these as types of fibre (Beelman 2004). Cellulose is normally the main polysaccharide in plant cells walls, but this has been replaced by chitin in the mushroom. The chitin level is higher the common Agaricus mushroom than found in other types of mushrooms

Dietary fibre has many benefits, but the fibre in mushrooms may have different physiological benefits to those found in most plant foods. About a fifth of the fibre in mushrooms is resistant starch (Dikeman 2005), which resists digestion to become food for the healthy bacteria residing in the large intestine. Hopefully, future research will reveal more about the fibre benefits of mushrooms.

Table 3. Average macronutrients in mushrooms

Source: NUTTAB 2006

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5. Mushrooms and weight control

Weight gain occurs only because the kilojoules eaten are consistently more than the kilojoules burned up each day through physical activity. Therefore, to lose body fat you must consistently eat less kilojoules than you burn. The low carbohydrate diet for weight loss has been popular in recent times. A low carbohydrate diet will result in weight loss, mainly because it is a low kilojoule diet and the degree of weight loss is similar to a low fat healthy eating plan (Eisenstien 2002; Bravata 2003; Stern 2004; Bowman 2004).

For weight control, it is smart to eat a high proportion of low energy dense foods, that is, foods that have a low kilojoule count per 100 grams eg vegetables, fruit and mushrooms (see Table 4).

A preliminary report was presented by Dr Cheskin, Johns Hopkins Bloomberg School of Public Health, at the Experimental Biology Annual Meeting in May 2007 revealing that substituting meat with button mushrooms increased the satiety of the meal. Although the mushroom meal was about 100 calories less than the meat meal, consumers actually ate 379 fewer calories a day over four days. This suggests that mushrooms have a powerful ability to increase the satiety of a meal. Further studies need to be completed over a longer period in a free-living subject group.

Table 4. Energy Density of Example Food

Source: NUTTAB 2006

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6. Mushrooms & antioxidants

For a long time, scientists have known that adequate fruits and vegetables reduce the risk of heart disease, stroke and some cancers, quite possibly through their antioxidant capabilities.

Antioxidants in food help neutralise the free radicals that damage DNA in cells. DNA appears in the nucleus of all cells. If it becomes damaged, then chemicals within the body work to correct the damage before it becomes a cancerous cell. If the antioxidants within the body get overwhelmed then compounds in food give a helping hand.

Mushrooms are a rich source of antioxidants. In an analysis of 30 common vegetables, mushrooms were placed in the top 5 highest antioxidant vegetables. Using three different analytical methods, mushrooms were ranked 5th on average (Pellegrini 2003).

In 2005 it was found that mushrooms are very high in the antioxidant ergothioneine, in amounts many times more than found in wheat germ or chicken liver, previously thought to be the highest sources. This data was presented at the American Chemical Society conference in August 2005 by Dr Robert Beelman and Joy Dubost, Department of Food Science, Pennsylvania State University. Good news for the consumer is that the ergothioneine levels do not decrease with cooking. As ergothioneine is not produced by the body, dietary sources become valuable.

The same researchers also found that button mushrooms were particularly high in phenolic compounds that have been long known for their antioxidant capabilities (Dubost 2007). A serve of mushrooms also provides about a quarter of an adult.s requirements of selenium, an antioxidant mineral.

Put all the news together and it makes mushrooms one of the highest antioxidant foods on the market. It is good sense that mushrooms should regularly feature on the menu.

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7. Mushrooms & immune function

A healthy immune system is a combination of fitness, good nutrition, including eating plenty of fruit and vegetables. With mushrooms offering so many potential health benefits it seems possible that mushrooms could be affecting immune function. There have already been some preliminary reports that mushrooms do indeed boost immune function.

Many of these studies have been on exotic mushrooms, but recently a joint Chinese-US paper studied mice and found that white button mushrooms enhanced the action of natural killer cells in mice (Wu et al 2007). It is not known what intake of mushrooms might have a similar effect in humans.

Other papers were presented to the Experimental Biology meeting in May 2007. A report by Dr S Kuvidibila, Oklahoma State University indicated that mushroom extracts increased defensin production. Defensins are anti-microbial peptides produced by neutrophils and epithelial cells exposed to pathogens. Another report by Dr Cantorna from Pennsylvania State University showed that mushroom extracts given to mice suggested an increased anti-cancer immune response associated with eating mushrooms.

It is still early days, but the results of preliminary studies look promising. (See the Nutrition Research Updates from the Mushroom Council in the US)

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8. Mushrooms & cancer prevention

The mushroom also contains compounds that suppress an enzyme called aromatase (Grube 2001; Chen 2004). 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. Recent research shows that mushroom extracts reduced breast cancer growth (Chen 2006). .Eating 100 grams or even less of mushrooms per day could have an effect on preventing new breast cancers., said lead researcher Dr Shiuan Chen.

Mushrooms also suppress the enzyme 5 alpha reductase that converts testosterone to dihydrotestosterone, which is thought to play a role in the development of prostate cancer and benign prostate enlargement. The use of 5 alpha reductase inhibitors reduces the incidence of prostate cancer. The research on animal cells suggest that mushrooms could have a role in the protection against prostate cancer (Chen 2004).

Mushrooms contain lectins (bio-active proteins), which have been strongly linked to a reduction in the risk of cancer and potentially helpful in the treatment of cancer (De MejíEG 2005). Plant lectins are known to resist digestion and enter the blood stream intact. They can affect the growth and proliferation of cancer cells, including causing their ultimate death. Lectins appear to have anti-tumour and anti-carcinogenic effects that may help cancer treatments in the future.

There have been two reviews of the research on the potential for mushrooms to reduce the risk of cancer and enhance the immune system (Borchers et al 2004; Ziadman et al 2005). Other mushroom components with evidence for reducing cancer risk appear to be the beta-glucans and peptide-bound polypeptides. The glucans stimulate the phagocyte system (eg macrophages and monocytes) that consume alien cells. As selenium has anti-cancer properties, some countries have marketed selenium-enriched mushrooms including Agaricus mushrooms. Even when a cancer is established, compounds found in mushrooms may retard tumour growth.

Much of the research is in the early stages and primarily on extracted compounds from mushrooms. There is only one population study looking at mushroom intake and cancer and that found an inverse relationship between gastric (stomach) cancer and mushroom intake. Overall, it seems that various compounds in mushrooms inhibit cancer growth at a range of stages, so the best advice we can give at this moment is to eat more mushrooms.

Summary
We have learned a lot about the nutrient profile and bioactive compounds found in mushrooms. Mushrooms have high levels of B group vitamins, minerals, fibre and bio-active compounds that could be reducing the risk of breast and prostate cancer. Although no promises can ever be made for a food, the evidence for the health benefits of mushrooms suggests it would be very smart to have mushrooms regularly on the menu.

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References & Bibliography:
• Beelman RB, Royse DJ, Chikthimmah N. Bioactive compounds in Agaricus bisporus of nutritional, medicinal or biological importance. Mushroom Science XVI 2004: 1-16
• Borchers AT, Keen CL, Gershwin ME. Mushrooms, tumors, and immunity: an update. Exp Biol Med 2004; 229: 393-406
• Bowman SA, Spence JT. A comparison of low-carbohydrate vs high carbohydrate diets: energy restriction, nutrient quality and correlation to Body mass Index. J Am Coll Nutr 2002; 21: 268-274
• Bravata DM, Sanders L, Huang J, Krumholz HM, Olkin I, Gardner CD, Bravata DM. Efficacy and safety of low-carbohydrate diets. JAMA 2003; 289: 1837-1850
• Carbohydrates in human nutrition. World Health Organisation, Food & Agriculture Organisation. FAO Food & Nutrition Paper 66; 1998
• Chen S. Anti-cancer activities of white button mushrooms. Mushroom Science XVI 2004: 25-29
• Chen S, Oh S-R, Phung S, Hur G, Ye JJ, Kwok SL, Shrode GE, Belury M, Adams SL, Williams D. Anti-aromatase activity of phytochemicals in white button mushrooms (Agaricus bisporus). Cancer Research 2006; 66 (24): 12026-12034
• Commonwealth of Australia, 2006, Nutrient Reference Values for Australia and New Zealand. National Health & Medical Research Council. Commonwealth of Australia 2006
• De Mejía EG, Prisecaru VI. Lectins as bioactive plant proteins: a potential in cancer treatment. Critical Reviews in Food Science and Nutrition 2005; 45: 425-445
• Dikeman CL, Bauer LL, Flickinger EA, Fahey GC. Effects of stage of maturity and cooking on the chemical composition of selected mushroom varieties. J Agricultural & Food Chemistry 2005; 53: 1130-1138
• Dubost NJ, Ou B, Beelman RB. Quantification of polyphenols and ergothioneine in cultivated mushrooms and correlation to total antioxidant capacity. Food Chemistry 2007 online
• Eisenstein J, Roberts SB, Dallal G, Saltzman E. High-protein weight-loss diets: are they safe and do they work? A review of the experimental and epidemiologic data. Nutn Rev 2002; 60: 189-200
• Feeney MJ. Research identifies & quantifies dietary fibre, carbohydrate components in mushrooms. Mushroom News 2004; 52(9): 26-28
• Grube BJ, Eng ET, Kao YC, Kwon A, Chen S. White button mushroom phytochemicals inhibit aromatase activity and breast cancer proliferation. J Nutr 2001; 131: 3288-3293
• Lanham-New SA. Fruit and vegetables: the unexpected natural answer to the question of osteoporosis prevention. American Journal of Clinical Nutrition 2006; 83: 1254-1255
• Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP. Vitamin D and calcium supplementation reduces cancer risk: results of a randomised trial. American Journal of Clinical Nutrition 2007; 85: 1586-1591
• Mattila P, Ronkainen R, Lehikoinen K, Piironen V. Effect of household cooking on the Vitamin D content in fish, eggs, and wild mushrooms. Journal of Food Composition and Analysis 1999; 12: 153-160
• Mattila P. Suonpää K, Piironeu V. Functional properties of edible mushrooms. Nutrition 2000; 16: 694-696
• Mattila P, Konko K, Eurola M, Pihlava J-M, Astola J, Vahteristo L, Hietaniemi V, Kumpulainen J, Valtonen M, Piironen V. Contents of vitamins, mineral elements, and some phenolic compounds in cultivated mushrooms. J Agric Food Chem 2001; 49: 2343-2348
• Mau JL. Chen PR, Yang JH. Ultraviolet irradiation increased vitamin D2 content in edible mushrooms. J Agric Food Chem 1998; 46: 5269-5272
• Mühlbauer RC, Lozano A, Reinli A, Wetli H. Various selected vegetables, fruits, mushrooms and red wine residue inhibit bone resorption in rats. J Nutr 2003; 133: 3592-3597
• National Food Authority. Code of Practice for nutrient claims in food labels and in advertisements 1995
• Pellegrini N, Serafini M, Colombi B, Del Rio D, Salvatore S, Bianchi M, Brighenti F. Total antioxidant capacity of plant foods, beverages and oils consumed in Italy assessed by three different in vitro assays. J Nutr 2003; 133: 2812-2819
• Stern L, Iqbal N, Seshadri P, Chicano KL, Daily DA, McGrory J, Williams M, Gracely EJ, Samaha FF. The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: one-year follow-up of a randomised trial. Ann Intern Med 2004; 140: 778-785
• Wu D, Pae M, Ren Z, Guo Z, Smith D, Meydani SN. Dietary supplementation with white button mushroom enhances Natural Killer Cell activity in C57BL/6 mice. J of Nutrition 2007; 137: 1472-1477
• Zaidman B, Yassin M, Mahajna J, Wasser S. Medicinal mushroom modulators or molecular targets as cancer therapeutics. Appl Microbiol Biotechnol 2005; 67: 453-468Glenn Cardwell
Monday, July 23, 2007

Glenn Cardwell
Tuesday, September 25th, 2007