We get a lot of questions about fermented foods at markets, events and when we hold workshops or talks. One that we recently got inspired me to write this blog, as it's something that we often touch upon but not always in much detail as the answer isn't necessarily straightforward. The question was "are fermented ingredients more nutritious than their raw, unfermented counterparts?"
This is such a great question and one that I really love getting into the nitty gritty with. The range of fermented foods out there and the starting ingredients used varies massively, so this explanation is a general interpretation of fermented foods and might not be applicable to each and every type. Just so you've been warned. Read on to learn whether fermentation actually makes food more nutritious.
1. Pre-digestion
You can think of fermentation as a 'pre-digesting' of our foods, thereby making nutrients more readily available in our body. This can make foods which in their raw state aren't suitable for certain people available to them. For example, milk contains lactose which isn't easily digested by those with lactose intolerance. Because microbes can produce the enzyme needed to break it down (lactase) they reduce the amount of lactose in fermented milk so yoghurt is often well tolerated by those with lactose intolerance.
2. Vitamin production
It's well established through lab studies that microbial fermentation can increase the amount of certain vitamins (mostly B vitamins) found in raw ingredients. However, whether this amount is actually enough to make a difference to us is up for debate still.
3. Fermentation by-products
Certain by-products are produced through fermentation, some of which are thought to be beneficial to us. Bioactive peptides and biogenic amines are by-products of lactic acid fermentation (responsible for dairy ferments, sauerkraut, kimchi and much more) and are thought to provide benefits to cardiovascular, immune and metabolic health. Short chain fatty acids - such as acetate, propionate, and butyrate - are also produced through fermentation of carbohydrates and can have beneficial effects all across our body.
4. Reduction of anti-nutritional factors
Fermentation reduces the amount of anti-nutritional factors in foods which bind to vitamins and minerals meaning they are less available to us. Examples include phytic acid, found in cereals, seeds and nuts, which binds to iron, calcium and zinc, reducing their absorption in our digestive tract.
5. Makes foods edible
The process of fermentation can actually make certain inedible foods edible, thereby broadening the range of foods available to us. An example is the removal of bitter phenolic compounds in raw olives.
6. Enhanced phytonutrient bioavailability
Fermentation enhances the bioavailability of phytonutrients (plant nutrients which can benefit our health). For example, lactic acid fermentation can convert flavanoids into biologically active versions that our body can use.
7. Abundance of live microbes
And then you have the benefits of the living microbes found in fermented foods which can have all kinds of benefits, potentially supporting good gut health. These are often referred to as probiotics, but we caution against thinking of these microbes as the same as those in probiotic pills and supplements. Fermentation-associated microbes are best thought of as probiotic-like, because they haven't been as widely identified and studied as known probiotic strains currently on the market. Read our blog called 'are fermented foods probiotic?' to learn more.
So in summary, fermentation helps to pre-digest our food, enhances the nutritional content by increasing the bioavailability of nutrients and by the production of beneficial fermentation by-products and it increases the amount of 'good' microbes in food. All of this means that yes fermented ingredients are often more nutritious than their non-fermented counterparts. This is without mentioning that they're also often safer and, of course, more delicious!
References
Pessione et al. (2016). Bioactive Molecules Released in Food by Lactic Acid Bacteria: Encrypted Peptides and Biogenic Amines. Front Microbiol. 2016. 7:876. doi: 10.3389/fmicb.2016.00876.
Dimidi et al. (2019). Fermented Foods: Definitions and Characteristics, Impact on the Gut Microbiota and Effects on Gastrointestinal Health and Disease. Nutrients. 11(8):1806. doi: 10.3390/nu11081806.
Leeuwendaal et ak. (2022). Fermented Foods, Health and the Gut Microbiome. Nutrients. 14(7):1527. doi: 10.3390/nu14071527.