I must confess that I’ve always put yeast into the ‘bad-food’ camp. Not that I don’t eat bread, drink red wine or have the odd bit of vegemite when the craving hits. But in term of adding it to a dish as a flavouring or to boost my vitamin/mineral levels, my years of seeing people suffer from candidiasis* has led me to dismiss using nutritional yeast as a dietary supplement/recipe ingredient.
But recently, nutritional yeast has come onto my radar and I decided I needed to find out more about it. Does it have a place in a healthy veggie diet or is it another flavour enhancer that has little – or even a detrimental – effect on health? The more I looked, the more complex the role of yeasts in food and health became. And while there is much more to know, hopefully the below will give you a better understanding about nutritional yeasts and whether they are something you want to make part of your diet. Apologies for the length!
what is a yeast?
Yeasts are microorganisms and part of the fungi family. Most yeasts are unicellular and asexual, and reproduce by mitosis (cell division). Yeasts don’t require sunlight to grow but instead mainly use sugars to reproduce. In labs, yeasts are often grown on potato dextrose, agar or grain extracts like malt. Yeasts can be found naturally on the skins of fruits like grapes, berries, apples and peaches, and they have been used in food and drink production and fermentation since ancient times.
type of yeast used in food/drink production
The main species of yeast used in food and alcohol production is Saccharomyces cerevisiae. In the fermentation process, this species converts carbohydrates into carbon dioxide and alcohols. The carbon dioxide causes things to rise, hence its use in baking, and the alcohol is used in brewing alcoholic drinks.
dead or alive?
To ferment, make bread or create alcohol, yeast needs to be alive. Live baker’s and brewer’s yeasts aren’t so good for you as they can deplete the body of vitamins and minerals, and can exacerbate candidiasis. That said, there are a few live yeasts that can be beneficial like those found in fermented foods and the prebiotic Saccharomyces boulardii, which helps maintain and restore the natural flora in the gastrointestinal tract.
When bread is cooked, the yeast is killed but in some alcohols that haven’t been filtered – like cloudy beers and ciders – there are still some live yeasts present (and can be the reason some people get a sore gut/thrush when drinking these).
Products classed as nutritional yeasts have been deactivated, which means the live yeast is killed, heated and then processed into various forms. This processing prevents any problems that can be caused by a live yeast and leaves behind a product rich in B vitamins, protein and some minerals like potassium. It is important to note that nutritional yeasts do not have Vitamin B12 in them, unless added after production. B12 is a bacteria, not a true vitamin, and is killed when subject to heat/pasturisation.
what is a nutritional yeast?
In many places around the world, ‘nutritional yeast’ is an umbrella term to describe a number of different types of yeasts used as a health supplement or a spread. They have all been deactivated.
nutritional yeast flakes
These flakes are also called savoury yeast flakes, Brufax, nooch or yeshi, depending on where you live. They are produced by culturing Saccharomyces cerevisiae in a nutrient medium for several days – often on sugarcane or beet molasses. Once it is ready, the yeast is killed (deactivated) with heat and then harvested, washed, dried and packaged. The flakes are often used in vegan recipes to create a cheese-like taste.
In Australia, vegemite is a spread made from used brewer’s yeast (before it was a made into a spread it was used to make beer). In the UK, South Africa and New Zealand there is marmite, again made from used brewer’s yeast but with the addition of vitamin B12 (and in NZ a sweetener). There are also yeast extracts called promite, oxo, cenovis, and Vitam-R – all made the same way. Salt is added to a suspension of yeast, which leads to the cells shrivelling up, causing it to self-destruct. The dying yeast cells are then heated and their cell walls are filtered and removed. This removal concentrates the flavours and changes the texture. All are rich sources of some B vitamins (only B12 if added after manufacturing), protein, potassium and minerals, but are very high in salt and contain free glutamic acids, which can mimic the effects of monosodium glutamate (MSG) in some people.
Brewer’s yeast is again a byproduct of the brewing industry and is made in a similar way to nutritional yeast flakes. It also has a very similar nutritional profile but with the unique difference of having a high chromium content. It is often used as a supplement, despite its bitter taste. Avoid brewer’s yeasts that don’t have a bitter taste; it means that the bitterness was removed during manufacturing and with it most of its nutritional value.
This yeast is made from the species Candida utilis and has become a common flavouring in foods like chips (crisps), biscuits and numerous processed foods. It has a similar function to MSG – to add a salty, smoky flavour – and like MSG, can cause problems because of its high free glutamic acid content. Beware of sneaky manufacturers saying ‘MSG-free’ or ‘natural flavouring’ as they are often using Torula yeast instead.
nutritional yeast cautions:
- Inactive yeasts contain free glutamic acid, which mimic the effects caused by MSG
- Nutritional yeasts are best avoided with those suffering from osteoporosis due to their high-phosphorous content
- Even though nutritional yeasts aren’t alive, if you suffer from candidiasis or yeast infections they would be best avoided – especially torula yeast
- Some nutritional yeasts, especially brewer’s yeast, can interact with medications. Those who are on Monoamine Oxidase Inhibator antidepressants (MAOIs) or Type 1 diabetes medication are especially at risk. Check with your health practictioner before supplementing with nutritional yeasts
- There is evidence of high amounts of antibodies against Saccharomyces cerevisiae found in people with Crohn’s disease and ulcerative colitis – which means the body treats its ingestion as an immune attack
- Manufacturers of yeast spreads like vegemite and beer haven’t been ruled out from using genetically modified (GM) ingredients, and as nutritional yeasts are by-products of the brewing industry, they are at risk of containing GM components.
After all this, I believe that while commercial nutritional yeast products do contain a lot of good nutrients, they are highly processed products and there are better food choices containing similar nutrients in a much healthier package.
If you enjoy the flavour of nutritional yeasts and use them in your diet, then do so sparingly. I would caution them being treated as a superfood and used regularly as part of a healthy diet.
If you want good doses of B vitamins, protein and minerals there is nothing better than getting them from foods like organic brown rice, green vegetables, sea vegetables, whole grains, naturally fermented foods and nuts and seeds.
a quick word about fermented foods and drinks
People have been fermenting food and drinks since ancient times in order to preserve them for future use. These foods utilise a mix of bacteria and wild yeasts from the air to ferment and while not technically nutritional yeasts, are a great example of health-affirming yeasts (and bacterias) that are sadly lacking in most western diets. Some examples of fermented foods and drinks are kombucha, kefir, kvass, kimchi, saurkraut, cortido, rejuvelac and sprouted and sour dough breads – plus there are numerous dairy products, grains, vegetables and meats that have been fermented and eaten as part of a traditional diet. Unfortunately, most commercial forms of these products have been pasterised, which means the good bacterias have been killed and won’t have the same health benefits as ones made at home. Lacto-fermentation has been making a comeback and if you’d like more information about it, I found this Nourishing Days post excellent as an introduction to making your own.
*Candidiasis is the term used for people suffering from a chronic overgrowth of the yeast Candida albicans in their body. Small amounts of Candida albicans live on our skin and in our gut and/or vaginal walls quite safely – but it is an opportunistic pathogen and if our gut flora or immune system is compromised (as it can be by using medications like antibiotics, the pill or corticosteroids, or by eating too many processed foods and sugar), candida will proliferate and can cause problems like thrush, athlete’s foot and weaken the immune system. For more information about this common problem, check out Dr William Crook’s informative website http://www.yeastconnection.com/about.html