Top 5 health benefits of miso
This protein-rich paste made from fermented soybeans is a staple of Asian cuisine. Registered Nutritionist Jo Lewin explains what makes miso a healthy ingredient.
What is miso?
Miso means ‘fermented beans’ in Japanese. A traditional ingredient in Japanese and Chinese diets, miso paste is made from fermented soybeans and grains and contains millions of beneficial bacteria.
There are many different types of miso, with versions linked to regional cuisines, identities and flavours. This protein-rich paste adds the fifth taste, known as ‘umami’, and can be used in all sorts of dishes, including soups or broths, salad dressings, vegetables, stews, glazes and marinades. The length of fermentation time can affect the flavour, ranging from sweet and mild to salty and rich.
Different varieties of miso
Different varieties of miso
The most common type of miso is made from only soybeans, but the variety and ratio of raw ingredients can vary. Some miso pastes are made from cultured wheat or millet, or combinations of different grains and beans. The colour is a fairly good indicator of the strength of flavour. The texture can vary, too. Miso made from a wholegrain is typically saltier than that made from a hulled grain.
White miso (shiro)
Made from soybeans and rice and fermented for no longer than two months. Shiro ('white' in Japanese) is light in colour and sweet to mildly salty. Shiro is a great gateway miso – it's very versatile, providing a bit of oomph to salad dressings or fried vegetables.
Yellow miso (shinsu)
Another mild type that is fermented for slightly longer than white miso. Yellow miso is adaptable in a wide range of recipes.
Red miso (aka)
If a recipe calls for dark miso, you’ll want to use an aka or red miso. Russet in colour, this type is made from a higher proportion of soybeans, fermented for up to three years and saltier and deeper in flavour. Its full flavour is best used in hearty dishes like stews and tomato sauces. Use with caution: its flavour can overpower other ingredients.
Barley miso (mugi)
Made from barley and soybeans, mugi miso usually has a longer fermentation process than most white miso. It has a strong barley aroma, but is still mild and slightly sweet in flavour.
1 tbsp (15g) of miso provides:
- 30kcal / 128kj
- 2.0g protein
- 0.9g fat
- 3.5g carbohydrate
- 0.63mg iron
- 0.49mg zinc
- 5mcg folate
- 1.37g salt
Top 5 health benefits of miso
1. May support gut health
The fermentation process involved in the production of miso promotes levels of beneficial bacteria, known as probiotics. These bacteria are thought to help a range of health issues, including digestion and gut health.
By incorporating a variety of fermented foods in your diet, you may help promote levels of beneficial bacteria and enzymes in the gut, which may in turn improve the balance of gut microbes as well as the function of your digestive system. When buying miso, choose the unpasteurised, live, enzyme-rich product that will need to be stored in the fridge.
2. May promote vitamin levels
Studies in 1997 and 2013 have shown these beneficial bacteria in the gut manufacture vitamins (primarily vitamins K and B12) as a by-product of their metabolism. This means that by improving the balance of your gut microbes through the consumption of fermented foods, an indirect benefit may be enhanced nutritional status.
The process of fermentation also reduces toxins and anti-nutrients, such as phytic acid levels of the soybeans in miso.
3. May reduce the risk of certain cancers
Regular miso consumption is thought to potentially reduce the risk of certain cancers, including breast cancer, especially in post-menopausal women. This is thought to be thanks to the paste’s isoflavone content. Miso is also a rich source of protective antioxidants which may further support its protective role in this area. However, more studies are needed to clarify and confirm these possible benefits.
4. May enhance immune function
Being a rich source of probiotic bacteria, miso may support immune function and help fight infections. Regularly consuming a variety of fermented foods like miso may minimise your need for antibiotic therapy when fighting infection. That said, more studies are needed to assess the benefits of different strains of bacteria, including those most commonly present in miso.
5. May support brain health
Recent advances in our knowledge and understanding of gut-brain connectivity supports a role for diet and in particular the consumption of fermented foods in cognitive health, including anxiety and depression. Although much has been learned, there is still more to discover before we can definitively define the bacterial strains that may be of most value.
Is miso safe for everyone?
Miso is generally safe for most people; however, if you follow a low-salt (sodium) diet, you may wish to limit your intake because miso has high levels.
Soybeans are considered to be goitrogenic. This means if you have a thyroid issue you may be advised to minimise your intake. This is because these foods may interfere with the absorption of iodine, which is needed for the production of thyroid hormones. However, it’s worth bearing in mind that you would need to eat a reasonable amount on a consistent basis for this to be an issue.
Some people may have an allergy to soy protein and may need to avoid miso and other soy-based foods. Those with coeliac disease will need to check labels to ensure the miso product is appropriate for them and made from gluten-free ingredients in a suitably gluten-free environment.
If you are on blood-thinning medication such as warfarin, your GP or dietitian may suggest you monitor vitamin K-rich foods like miso in your diet to ensure you eat similar amounts consistently. If in doubt, consult your GP before making any significant changes to what and how much you eat.
How to select and store
When buying miso, choose the unpasteurised, live, enzyme-rich product that will need to be stored in the fridge. This type is loaded with beneficial microorganisms. After opening, the texture, colour and flavour may change, so keep an eye on it. Some can be kept for quite a long time without any concerns or variations to quality.
Miso makes a delicious marinade:
Miso-glazed tofu steaks with beansprout salad & egg strands
This article was last reviewed on 31st August 2021 by Kerry Torrens.
Kerry Torrens is a qualified Nutritionist (MBANT) with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.
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