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 2010 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

You may never have thought of the mushroom as a vitamin supplement, but you can be assured that a serve of mushrooms provides a healthy ‘dose’ of the essential B group vitamins riboflavin (B2), niacin (B3), pantothenic acid and biotin.

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

• mg = milligrams; mcg = micrograms
• RDI = Recommended Dietary Intake (covers the daily needs of a nutrient)
• source: NUTTAB 2010 Online

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 in mushrooms 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.