Professor YOSHIMOTO Hiroaki

Japan is the land of mushrooms, where the greatest range in the world can be found, with many adorning our meals. Japan is not the only country where a wide variety of both wild and cultivated safe mushrooms are available, is it? Mushrooms are not just ingredients; since ancient times, attention has also been paid to their health benefits. However, the health effects are not only immediate but significant in enhancing health when eaten daily.

In this four-part series, I will explain what we can do now to prepare for next season, with a primary focus on health effects. Start incorporating mushrooms into your meals today to help prepare your body for winter. Please note that the mushroom effects I will introduce in this series are merely complementary to any medical care. If you have any symptoms requiring treatment, please follow the directions of your doctor.

Preparing for winter in autumn
In my previous article, I focused on the rapid environmental changes of autumn, namely the changes in temperature, humidity, air pressure and daylight hours, and how to deal with them. Winter is a time when these changes come to a halt and it is in winter that it is necessary to address this stagnation.

All animal classes have species that hibernate. From mammals such as bears and insects such as rhinoceros beetles, all sorts of animals become inactive and sleep through winter, which means they adopt a strategy of pausing all activities to survive the season. Microorganisms, including mushrooms, and plants also become dormant in order to deal with the low temperature and dryness. This, however, is not something humans do.

We need the foresight to prepare for winter, when everything stagnates, in autumn. Bodily changes we need to be mindful of in the stagnant winter include cardiovascular issues like hypertension and mood disorders such as depression, namely those that affect the central nervous system. In this article, I will explain the hypertension and central nervous system mechanism.

 It is known that blood pressure rises in winter. This is caused by exposure to cold temperatures and cold air stimulating the sympathetic nervous system and constricting the blood vessels. Additionally, the increase in the salt content of meals in winter is also said to be a factor. There is a lot of research verifying the effect of mushrooms on high blood pressure with various mushrooms showing this effect. The latest literature reviewing the effect of mushrooms on hypertension cites button mushrooms, oyster mushrooms, shiitake, maitake (hen-of-the-woods), reishi, bunashimeji (beech) mushrooms, chanterelles, cauliflower mushrooms, and enoki mushrooms.

The Ministry of Health, Labour and Welfare’s e-healthnet website says that it is crucial to limit the intake of dietary salt. In addition to reducing salt intake, potassium intake is also important for sodium excretion and mushrooms are high in potassium. This is shown in Table 1. Matsutake mushrooms are expensive so if we sideline them, we can see that shimeji mushrooms have the highest potassium content and are accessible.

Although it is crucial to reduce sodium in meals in winter, doing so diminishes flavour and leaves dishes lacking. To get around this, you can for example add more ingredients to miso soup or make the stock richer. If you use a lot of mushrooms in cooking, their umami components enhance the broth, making for a satisfying dish even with reduced salt.

Shorter daylight hours in winter mean reduced secretion of serotonin, a neurotransmitter in the brain that stabilises mood. This can cause depressed mood and other depressive states. Feeling melancholy in winter evenings is not just a matter of mood; it is thought to be caused by stress from environmental changes affecting the central nervous system. The cold also means the sympathetic nervous system dominates, upsetting the balance with the parasympathetic nervous system and thus promoting depressed mood. On top of this, we tend to become more sleep deprived and overworked around the New Year period so we need to be extra careful. Although the season is in a state of stagnation, it may be a characteristic of winter that we become emotionally restless. Everything I talked about in part one of this series about boosting health, improving sleep, and increasing physical strength for summer is also effective for getting ready for winter.

Hearing of mushroom’s effect on the central nervous system, some people that have dabbled in biology may wonder if the components of mushrooms reach the brain. To confirm this, my group conducted experiments on mice using almond mushrooms. When we marked a hot water almond mushroom extract with a radioactive substance and administered it orally to mice, we demonstrated that a number of mushroom components absorbed in the digestive tract are transported to the brain and specifically bind to H3 receptors in the brain. Further, because it is known that poisonous mushrooms have hallucinogenic and other effects on the central nervous system, it is clear that mushroom components reach the brain.

So, are mushrooms effective on depressive states? The answer is yes. Some psychedelic mushrooms contain psilocybin, a component similar to serotonin. This component is being used in clinical trials in the United States for treatment-resistant depression. However, as mushrooms containing psilocybin are scheduled narcotics, growing and consuming them is prohibited by law so these are not a realistic option.

In this regard, the edible mushroom Lion’s mane has been reported to contain hericenones and erinacines, which are nerve growth factor stimulators. Nagano et al (2010) conducted randomised double-blind controlled trials on 30 middle-aged women using Lion’s mane cookies and placebo cookies (not containing Lion’s mane). The results showed that the Center for Epidemiologic Studies Depression Scale (CES-D) and indeterminate complaint index (ICI) improved significantly. The items that improved were listlessness, palpitations, concentration, irritability, and anxiety. It is believed that energy and anxiety are related to neurotransmitters in the brain such as serotonin, which suggests that it may be possible to address seasonal affective depression. It is worth mentioning that the trial participants consumed 2g of dried Lion’s mane daily. This is equivalent to about 20g of fresh Lion’s mane, an amount that can readily be consumed on a daily basis.

It has long been told over the generations that mushrooms, as a form of traditional medicine, help blood pressure. On the other hand, research findings showing mushrooms to be effective on depression and anxiety are the latest scientific achievement. They say that “alcohol is the best of all medicines”, but I would rather shout from the rooftops that “mushrooms are the best of all medicines”. The potential of mushrooms is limitless. So this autumn, be sure to enhance your meals with mushrooms to prepare for the long winter nights ahead.