How to eat more fermented foods

• As foods ferment, microbes (like bacteria or yeast) transform it, changing its flavor, texture, and sometimes nutritional value.

• Some studies suggest that fermented foods may support gut health and reduce inflammation for some people, but results vary between types.

• If you’re new to fermented foods, start with small portions and build up gradually to avoid digestive upset.

• When choosing products, watch out for high sugar and salt content, and be cautious if pregnant, immunocompromised, or histamine-sensitive.

Fermented foods are having a moment, from kimchi and kombucha to kefir and miso. And it’s easy to see why: they can add big flavor to meals, and may support gut health too.

At ZOE, we’re interested in fermented foods because they’re one way to bring more variety into your diet, and variety is one of the strongest signals we see for a healthier gut microbiome.

In this article, we’ll cover what fermented foods are, what science can (and can’t) tell us about their benefits, the best fermented foods to try, and the simplest ways to fit them into everyday meals. 

We’ll also include some common mistakes to avoid when introducing fermented foods.

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What are fermented foods?

Fermentation is a process in which microbes (such as bacteria or yeast) break down parts of a food over time. This can change its taste, texture, and nutritional profile.

Depending on the product and how it’s made, fermentation can:

• create organic acids (which can give foods a tangy flavor)

• reduce bitterness or increase savory “umami” notes

• help preserve foods

• sometimes increase certain vitamins or make nutrients easier to absorb

Some fermented foods do contain live cultures (often those that are not heat-treated after fermentation), but many do not. For example:

• Pasteurized or heat-treated products usually don’t contain live microbes.

• Baked products (like sourdough bread) don’t typically contain live microbes by the time you eat them.

What are the benefits of fermented foods?

Fermented foods are popular for a mix of reasons. Some studies suggest they may influence the gut microbiome and the immune system. 

For example, in a small randomized trial, a diet rich in fermented foods was associated with increased microbiome diversity and reduced inflammatory markers during the intervention period. 

And in ZOE’s Fermentation study, people who added up to three extra portions of fermented foods per day for 2 weeks reported improvements in bloating, hunger, energy, and mood (especially those with obesity). 

However, these outcomes were self-reported, and the study didn’t directly measure changes in the microbiome.

Just as importantly, fermented foods can make healthy eating easier in everyday life: Their tangy, salty, savory flavors can make meals more satisfying when used like a condiment, and many options are nutritious in their own right. 

Also, the fermentation process can “pre-digest” certain compounds, making micronutrients like iron and magnesium easier for your body to absorb.

Which fermented foods should you try first?

Below are some of the easiest fermented foods to add to your diet. We’ve included some simple ways to use them if you’re short on time.

Yogurt and kefir

If you want one staple fermented food, yogurt or kefir is often the simplest place to start. 

Try it for breakfast with berries, nuts, and seeds, or blend kefir into a smoothie with frozen fruit and veg. 

Kefir also works great as a mayo alternative mixed with lemon, garlic, and herbs for a savory dressing.

Sauerkraut and kimchi

Think of these as veggie-packed flavor boosters. Add a spoonful to eggs, tofu scramble, or avocado toast, or even as a topper to grain bowls, salads, tacos, or sandwiches. 

Miso

Miso is an easy way to add “umami” depth to everyday cooking. 

Stir it into soups, whisk it into salad dressings (miso, lemon, and olive oil), or add it to sauces for noodles or roasted vegetables. 

Tempeh

Tempeh is a fermented soy food that’s best thought of as a nutritious protein (rather than a source of live microbes, since it’s usually cooked). 

You can slice and pan-fry it for stir-fries, crumble it into tacos or bolognese-style sauces, or marinate and roast it for salads.

Kombucha

Kombucha is a fizzy, fermented drink made from sweetened tea (usually black or green tea) and can be a nice occasional swap for fizzy drinks. 

Sometimes manufacturers hide added sugars in the ingredient list by using different names, like cane syrup or agave nectar. For a full list of terms manufacturers use for sugar, check this article.

Sourdough

Sourdough is made using fermentation, but because it’s baked, it won’t contain live microbes by the time you eat it. 

It can still be a satisfying bread choice, especially when paired with fiber-rich toppings like beans, eggs, or vegetables.

Find Tim Spector's favorite sourdough bread recipe here.

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How to start with fermented foods

If you’re new to fermented foods, start small: try 1–2 teaspoons of kimchi or kraut per day, or a small serving of yogurt or kefir, then increase gradually over 1–2 weeks. 

This is important because a sudden increase in live microbes and organic acids from these foods can increase gas production and lead to bloating, cramping, or looser stools in some people. 

You should also rotate different types of ferments to see what you like most, and focus on adding fermented foods to meals you already enjoy.

Common mistakes to avoid when introducing fermented foods

Mistake 1: Assuming all fermented foods contain live cultures

Many fermented foods are heat-treated, pasteurized, or cooked. If you want live microbes, look for “live” or “active cultures” and choose refrigerated products where possible.

Mistake 2: Going from zero to huge portions

A sudden jump can cause bloating or digestive changes, especially if you’re not used to these foods. Start small and build up.

Mistake 3: Choosing very sugary options

Some kombuchas and flavored yogurts can contain lots of added sugar. Choose plain versions and add fruit yourself when you can.

Mistake 4: Forgetting sodium

Kimchi, sauerkraut, pickles, and miso can be high in salt. Small amounts can still fit into a healthy diet, but if you have high blood pressure or are watching salt intake, portion size matters.

Who should be cautious when introducing fermented foods?

Fermented foods are safe for most people, but those with histamine sensitivity should be aware that some products are high in histamine and may trigger symptoms. 

If you have digestive conditions, such as irritable bowel syndrome (IBS) or are prone to acid reflux, you may find that very acidic or spicy options like kimchi cause uncomfortable digestive symptoms. 

Finally, anyone with high blood pressure should choose lower-salt options and keep portions modest.

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Summary

Fermented foods like yogurt, kefir, kimchi, sauerkraut, miso, and kombucha are made when microbes break down parts of the food, changing its flavor and sometimes its nutritional content. 

But not all fermented foods are probiotic. Pasteurized, heat-treated, or cooked options (like most sourdough) usually don’t contain live cultures.

Some studies suggest fermented foods may support gut health and inflammation, and they can be an easy way to add flavor and variety to meals. 

If you’re new to them, start with small portions and build up gradually to avoid bloating, and watch for high sugar (some kombuchas and yogurts) and high salt (kimchi, kraut, miso).

FAQs

Are fermented foods the same as probiotics?

No, fermented foods are made using microbes, but some are pasteurized, heat-treated, or cooked, which can mean they don’t contain live microbes by the time you eat them. 

Probiotic foods contain live microbes in a sufficient amount to potentially benefit health.

How much should I eat per day?

At ZOE, we recommend 3 portions a day, but if you’re new to fermented foods, start with a small serving (like 1–2 teaspoons of kimchi/kraut or a small portion of yogurt/kefir) and increase gradually over a few weeks if you tolerate it.

Do I need to eat fermented foods every day?

Not necessarily. Some people like a small daily habit (like yogurt at breakfast). Others prefer rotating fermented foods a few times per week. 

Consistency can help you build a habit, but variety also matters.

What’s the difference between pickled and fermented?

Pickled foods are preserved in an acidic solution (often vinegar). Fermented foods are transformed by microbes over time. 

Some pickles are both pickled and fermented, but many vinegar pickles are not fermented.