What fermentation does to bioavailability and why the same food eaten fermented versus raw is not the same experience
Most people assume that eating well is mainly about what they eat. The food, the ingredients, the quantity. What gets less attention is whether the body can actually access what's in those ingredients.
This is where fermentation introduces something worth understanding. Two people can eat the same vegetable, from the same source, in similar amounts, and their bodies may absorb meaningfully different amounts of what's in it. Not because of genetics alone. Sometimes, it comes down to whether the food was fermented.
Why bioavailability is often the missing part of the conversation
Nutrients in food are not automatically available to the body. A food can contain iron, magnesium, B vitamins, or zinc and still deliver relatively little of it, depending on what else is in that food, how it was prepared, and what the digestive environment looks like at the time.
The term for this is bioavailability: the proportion of a nutrient that actually reaches the bloodstream and becomes usable. Research in the Journal of Food Science has consistently shown that bioavailability can vary significantly depending on food processing methods, including fermentation.
What's often overlooked is that some plant foods contain compounds that actively limit absorption. Phytic acid, found in grains, legumes, and seeds, binds to minerals and carries them out of the body before they can be absorbed. Fermentation, specifically lactic acid fermentation, significantly reduces phytic acid content. A study published in Food Chemistry found that fermentation reduced phytic acid in certain foods by up to 60%, with a corresponding increase in mineral availability.
That's not a small difference.
To understand how fermentation differs across foods and methods, you can also explore different types of fermented foods and their health benefits.
What fermentation actually does to food structure
Fermentation is not just a flavour process. Microbes consume sugars, produce acids, break down proteins, and alter the physical and chemical structure of the food itself.
Some of what changes during fermentation is directly relevant to how nutrients behave:
Phytate reduction
As mentioned, fermentation degrades phytic acid. This matters most for minerals like iron, zinc, and calcium, which phytic acid tends to bind. Raw sauerkraut or traditionally fermented pickles, made through lactic acid fermentation rather than vinegar, go through this transformation. Vinegar-brined alternatives do not.
Protein Breakdown During Fermentation
Fermentation begins breaking down proteins into smaller peptide fragments. This is visible in the texture and flavour of fermented foods - they become softer, more acidic, more complex. But it also means the body encounters proteins that are partially broken down before digestion even begins, which can reduce the work required by digestive enzymes and may improve how those proteins are absorbed and used.
B vitamin synthesis
Certain fermentation microbes produce B vitamins, including B12, folate, and riboflavin, as metabolic by-products. This has been documented across several fermented foods including certain dairy ferments and fermented vegetables. Research published in Nutrients noted that lactic acid bacteria involved in fermentation can synthesise B vitamins that are not present in the raw food at all.
Improved mineral solubility
The acidic environment created by fermentation improves the solubility of certain minerals. In a more acidic food matrix, minerals like iron and calcium are more easily dissolved and therefore more accessible during digestion. This is a different mechanism from phytate reduction, but both work in the same direction.
If you're curious how fermentation changes the actual composition of food over time, this is something we explore in depth at Tabchilli's fermentation workshops, including how the same ingredients behave differently at different stages of fermentation.
Why regularity matters
A single serving of sauerkraut will not restructure how someone's body absorbs nutrients. The shifts described above accumulate with consistent consumption over time, particularly in relation to gut environment. Research in Frontiers in Microbiology has suggested that regular consumption of fermented foods is associated with increased microbial diversity, and a more diverse gut microbiome is associated with more efficient breakdown and extraction of nutrients from food generally.
The gut's microbial community plays an active role in nutrient metabolism. It is not a passive system. What feeds it regularly shapes how it functions.
Tabchilli's unpasteurised fermented foods, from sauerkraut to naturally fermented pickles, are made without heat treatment, which means the live cultures reach the gut intact, rather than processed out before the jar is opened.
Raw versus fermented: they are not the same food
This is the clearest way to put it. Raw cabbage and fermented cabbage share the same origin. The nutrient profile on a basic label may look similar. But the bioavailability of what's in them, the structural form of the proteins, the presence or absence of antinutrients, the microbial content, the pH, all of these differ substantially.
Eating fermented foods regularly is not the same as eating more raw vegetables. They are related but distinct in terms of what they deliver and how the body processes them.
What's also worth noting is that this distinction disappears almost entirely with pasteurisation. Heat treatment stops fermentation, kills live cultures, and largely eliminates the bioavailability advantages that come from the fermentation process. Commercial products labelled as "fermented" are not always raw and live. The process matters as much as the ingredient.
If you want to understand this difference more practically, what to look for, what questions to ask, and how to start including genuinely live fermented foods in daily eating, Tabchilli's vegetable fermentation workshops are built around exactly that kind of hands-on, practical understanding.
Fermented foods are not a quick fix
Fermented foods are not a fix. They are not a supplement, and they do not override an otherwise poorly balanced diet. But within a normal, varied way of eating, they bring something that raw or processed alternatives do not: food that has already been partially transformed, with antinutrients reduced, vitamins added, minerals made more accessible, and proteins partially broken down.
If you want to start experimenting with fermentation at home, Tabchilli's fermentation starters provide a practical way to begin with live cultures.
The same food, eaten fermented versus raw, is genuinely not the same experience for the body. That is not a marketing claim. It is a reasonably well-supported observation from food science research. And it is one of the more practical reasons why fermented foods have been a consistent part of traditional diets across different cultures and centuries.
Sources
● Hotz, C. & Gibson, R.S., Journal of Food Science, 2007 - fermentation and mineral bioavailability in plant-based diets
● Reale, A. et al., Food Chemistry, 2004 - phytic acid degradation during lactic acid fermentation
● LeBlanc, J.G. et al., Nutrients, 2011 - B vitamin production by lactic acid bacteria during fermentation
● Wastyk, H.C. et al., Cell, 2021 - fermented food diet and gut microbiome diversity