In Praise of Fungi

Did you know that Japanese mushroom farmers are half as likely to develop stomach cancer as their non-mushroom-growing neighbors? (1)

This may be due to the fact that they regularly eat the mushrooms they cultivate and benefit from the cancer-protective compounds in them.

The best-known medicinal mushrooms are Asian varieties such as oyster mushrooms, maitake, shiitake or the non-edible reishi, but all mushrooms have a mindboggling array of health effects: they are anti-oxidant, anti-diabetic, hypocholesterolemic, anti-tumor, cancer-preventive, anti-inflammatory, immunomodulatory, anti-allergic, nephroprotective, and anti-microbial (phew!).

It’s worth noting that most of the laboratory research on medicinal mushrooms has been carried out using extracts that are much more concentrated than whole mushrooms we might include in our diet.  Nonetheless, dietary mushrooms do appear to have a cancer-protective effect too – including the lowly button mushrooms sold in a supermarket near you!

For instance, researchers at Perth University found that Chinese women eating on average 4 grams of dried button mushrooms daily cut their breast cancer risk by 47% compared to women eating none, while those eating 10 grams of fresh mushrooms daily lowered their risk by 64%. Those who combined mushrooms with regular green tea intake even saw their breast-cancer risk decline by 89% (2).

Button mushrooms contain a fatty acid called conjugated linoleic acid (CLA) that’s thought to protect against breast and prostate cancer by binding onto so-called aromatase enzymes in the cancer cells and lessening their ability to produce estrogen. Since some breast and prostate cancer tumors are dependent upon estrogen for their growth, this blocking of the aromatase enzyme by the mushrooms’ CLA may help prevent or control these types of tumor (3), (4).

A note of caution: raw button mushrooms – which are sometimes included in mixed salads – contain compounds called hydrazines that are thought to be carcinogenic (5). Hydrazines are destroyed by cooking, drying or canning, so it is best to eat mushrooms cooked, and to alternate button mushrooms and other varieties.

And then there are shiitake mushrooms – my personal favorites thanks to their smoky-buttery flavor and velvety texture. In animal and cell studies shiitake extracts have been found to help block tumor growth, sometimes by triggering self-destruction by the cancer cells (apoptosis) (6). More than 100 compounds in shiitake mushrooms – knowns as “mycochemicals” – are thought to work together to accomplish these anti-cancer effects.

Mushrooms also have a gastronomic advantage: their unmistakable “mushroomy” flavor comes from glutamic acid, a natural version of the flavor enhancer monosodium glutamate (MSG). Unlike MSG, the natural occurring glutamic acid does not have a high sodium content. This makes mushrooms a wonderful way of adding a beefy, brothy (“umami”) flavor to stews and sauces, especially meatless ones.

In the recipe that follows, the concentrated flavors of this soup belie its speed of preparation. You can use any mushrooms, but I recommend a mix of shiitake, oyster, porcini and white or brown button mushrooms. Some people like their mushroom soup light, with small bits of mushroom floating in the aromatic broth. If you prefer a thicker soup, add a little flour. Serves 4.

 

Cream of Mushroom Soup (Serves 4) – Recipe from Zest for Life: The Mediterranean Anti-Cancer Diet

½ to 1 oz/10-15g dried porcini or shiitake mushrooms

2 tbsp olive oil

2 large shallots, or 1 small onion, finely chopped

4 whole fresh shiitake mushrooms

15oz/400g fresh mushrooms (e.g. a mixture that includes white and brown button mushrooms, maitake and oyster mushrooms), coarsely chopped

½ tsp thyme

1 tbsp whole grain spelt or wheat flour (optional)

2fl oz/¼ cup/60ml white wine

2 pints/1l vegetable broth

squeeze of lemon juice

salt & freshly ground black pepper

2 tbsp finely chopped parsley

pinch of red pepper flakes or paprika powder

 

Cashew Cream

4.5oz/1 cup/125g unsalted, raw cashew nuts, soaked overnight in water

3.5fl oz/scant 1/2 cup/100ml water

pinch of salt

 

Place dried mushrooms in a bowl and cover with hot water; rehydrate for 15 minutes.

In a heavy cooking pot on low heat, gently warm oil and cook the shallots for 3-4 minutes until translucent. Add the fresh mushrooms and thyme and cook for another 4-5 minutes until the mushrooms are soft and releasing their juices. (For a thicker soup, add flour now and stir well until vegetables are evenly coated.)

With a slotted spoon, remove rehydrated mushrooms from their soaking water, chop coarsely and add to mushroom-shallot mix. Add white wine and vegetable broth. Strain mushroom-soaking water through a cheesecloth to remove any forest grit and add to the mushrooms. Simmer for another 15 minutes.

With a ladle, transfer the soup to a blender in two batches; for a slightly chunky soup, blend the first batch to a fine, creamy texture and the second batch only briefly to preserve some chunks; combine in the cooking pot. Season to taste with salt, pepper and lemon juice.

To prepare the cashew cream, drain soaking water, place nuts and fresh water in a small blender and whizz for about 2 minutes, or until you obtain a smooth, velvety cream. Add more water for a thinner consistency.

Ladle soup into serving bowls, drizzle with Cashew cream and sprinkle with red pepper flakes and chopped parsley. Store any remaining cashew cream in a tightly sealed container in the refrigerator; keeps for up to 3 days.

References

(1)      Monro J, Treatment of cancer with mushroom products. Arch Environ Health. 2003 Aug;58(8):533-7.

(2)      Zhang M, Huang J, Xie X, Holman CD, Dietary intakes of mushrooms and green tea combine to reduce the risk of breast cancer in Chinese women. Int J Cancer. 2009 Mar 15;124(6):1404

(3)      Adams LS, Phung S, Wu X, Ki L, Chen S. White button mushroom (Agaricus bisporus) exhibits antiproliferative and proapoptotic properties and inhibits prostate tumor growth in athymic mice. Nutr Cancer. 2008;60(6):744-56.

(4)      Grube BJ, Eng ET, Kao YC et al. White Button Mushroom Phytochemicals Inhibit Aromatase Activity and Breast Cancer Cell Proliferation. J. Nutr., Dec 2001; 131: 3288 – 3293. 2001.

(5)      Toth B. Hepatocarcinogenesis by hydrazine mycotoxins of edible mushrooms. J Toxicol |Environ Health 1979 Mar-May;5(2-3):193-202.

(6)      Fang N, Li Q, Yu S et al. Inhibition of Growth and Induction of Apoptosis in Human Cancer Cell Lines by an Ethyl Acetate Fraction from Shiitake Mushrooms. The Journal of Alternative & Complementary Medicine, Volume 12, Number 2 (March 2006), pp. 125-132. 2006.