Are you sensitive to fermented foods? Here’s why your body reacts

Fermented foods can have many positive effects on gut flora and health. But what happens when the sauerkraut that’s supposed to be good for you instead gives you stomach cramps or a headache? Does that mean your gut needs time to adjust, or is your body trying to tell you something else?

Fermentation is a completely natural process in which microorganisms, such as bacteria and yeast, transform substances in food. This process can change both the flavor and nutritional content of food, as well as how it affects digestion and gut health. 

Examples of fermented foods include:

• Sauerkraut and kimchi
• Kefir and yogurt with live cultures
• Kombucha
• Miso and tempeh
• Fermented vegetables, such as carrots

One benefit of fermented foods is that they can help promote a more diverse gut flora. Many fermented foods contain live bacteria, and some of these can help break down substances in food or produce compounds that are beneficial for the gut. Fermentation can also make food easier to digest and help the body absorb certain nutrients.

But despite all their benefits, fermented foods aren’t necessarily suitable for everyone.

Why can’t everyone tolerate sauerkraut?

There are several possible explanations, and it’s not always the bacteria that are responsible.

Fermentation changes the carbohydrates in food. When white cabbage is fermented to make sauerkraut, for example, bacteria can convert the fructose in the cabbage into mannitol, a sugar alcohol that some people have trouble absorbing in the gut. Mannitol can then draw in water, while gut bacteria produce gas as they break it down. This can cause bloating, stomach cramps, or loose stools, especially in people with IBS or a sensitive stomach.

Histamine and other substances produced during fermentation. Some bacteria can produce histamine as food ferments. For people who are sensitive to histamine, this can lead to headaches, flushing, itching, a rapid heartbeat, or digestive problems. Histamine levels can also vary quite a lot between different fermented products.

A sensitive gut. If you have IBS or often react to certain foods, your gut may be especially sensitive to gas and distension. In that case, even a small amount of fermented food can cause noticeable symptoms.

This doesn’t necessarily mean anything is wrong with your gut flora. Sometimes it simply means the food contains something your body has trouble handling.

Is it normal to react at first?

You may experience a little extra gas or temporary bloating when you start eating fermented foods. But it’s important to distinguish between mild discomfort that goes away and symptoms that recur or get worse.

If you get severe stomach cramps, diarrhea, a headache, or other noticeable reactions every time you eat sauerkraut (or another fermented food), it may be a good idea to reduce the amount or avoid it altogether. Especially if you react to a very small serving.

How to try fermented foods, step by step

Curious about trying fermented foods, but unsure how your stomach will react? Take it slowly and see how it goes.

1. Start with a teaspoon. Try a little sauerkraut alongside your usual meal, for example. You don’t need to start with a full serving.
   
   
2. Give your body time to respond. Pay attention to how you feel for the rest of the day and into the next day. Does your stomach feel normal, or do you get gas, stomach pain, loose stools, or other symptoms?
   
   
3. Is it going well? Increase the amount slowly. For example, try two teaspoons after a few days. Only keep increasing the amount if it feels good.
   
   
4. A little gassy? Stick to the same amount or reduce it. Mild discomfort that goes away quickly doesn’t have to be a cause for concern, but there’s no point in pushing your body.
   
   
5. Noticeable or recurring symptoms? Take a break or stop. If you like, you can try another fermented food at a later time. Reacting to sauerkraut, for example, doesn’t necessarily mean you’ll react to tempeh or kefir.

Try one new food at a time. That makes it easier to tell what you’re reacting to.

If you have severe or recurring symptoms, it may be a good idea to seek medical advice to find out what’s causing them. If your throat swells or you have difficulty breathing, seek emergency help.

How much fermented food do you really need?

There’s no established amount you “need” to have a healthy gut. The most important thing to remember is that fermented food is just one of several ways to support your gut. Fiber from vegetables, fruit, legumes, and whole grains also nourishes the microorganisms in your gut.

So if your stomach doesn’t agree with sauerkraut or pickled carrots in particular, you don’t need to force yourself to eat them. Explore your options and start slowly if you’re curious, pay attention to how your body actually responds, and choose foods that work for you.