Does Sugar Kill Probiotics

Does Sugar Kill Probiotics & Gut Bacteria? (yogurt, kefir)

If you check the label of probiotic products such as yogurt, you might notice that some contain sugar. Yet you might also be wondering, does sugar affect probiotics? 

To help answer your question, I checked various studies on sugar and bacterial growth – and got surprising results.

Key Highlights:
  • The good bacteria (aka probiotics) feed on sugars. Because sugar is their food, it doesn’t hurt them (most of the time)
  • However, high sugar concentrations can kill many forms of bacteria, including the good ones in probiotics. At these levels, sugar has an antimicrobial effect.
  • Surprisingly, the presence of just a low concentration of sugar can stimulate bacterial growth.

So, why do high sugar concentrations kill off bacteria but low sugar levels promote bacterial growth? Is it good to choose low-sugar probiotics, and can quitting sugar improve your gut health?

Keep reading to get answers to these questions (and more!).

Do Probiotics Need Sugar?

First, let’s answer the question, “Do bacteria feed on sugar?”

The answer is “Yes!” Bacteria feed on sugar. 

However, there’s a big difference between the natural sugars (such as the lactose in milk) that these bacteria feed on and the table sugar (sucrose) that some manufacturers add to their probiotic products.

So that we don’t get confused between these sugars, let’s agree that from this point onwards, the “sugar” we discuss means “table sugar” or “added sugar” (as what you might find on your probiotic product’s label).

Now, why is it that some people think sugar can kill probiotics? Let me explain below.

Does Sugar Kill Gut Bacteria & Probiotics?

No Sugar

Well, it’s either a “yes” or “no.”The simplest answer is that the bacteria that feed on sugar don’t die when given sugar because it’s their food. It would actually have the opposite effect – sugar can help your probiotics (and other forms of bacteria) grow and multiply.

However, it’s important to know that sugar kills gut bacteria when it’s in high concentrations.

That’s the reason why sugar is considered a preservative in various food products, including jam and other sweet goods.

If that’s the case, then would that mean it’s better to choose a product such as probiotic yogurt with sugar in high concentrations or are low-sugar products better?

Well, you have to remember that you need the good bacteria in your probiotics to be alive so they can do their magic in your gut. That means that low-sugar products can be a better choice.

Also, high concentrations of added sugar can prohibit probiotics from colonizing the gut, according to a 2018 study in the Biological Studies journal. So, the low-sugar option is really better.

Why Does a High Sugar Concentration Kill Probiotics?

High sugar levels in a system, such as your gut, can kill probiotics and other bacteria through something called an “osmotic effect.”

Osmosis is simply the movement of water molecules from a solution with higher water concentrations to that with lower water levels.

The water levels are low in a high-sugar concentration. So, the system takes water from something that has a lower sugar concentration – in this situation, it can “forcibly” take water from bacteria to gain equilibrium (to equalize or achieve balance).

Bacteria shrivel and die in the process.

Since probiotics are also bacteria, then they will be affected by the same process – that’s why high sugar concentrations can kill them.

Can You Still Take Probiotic Products That Have Added Sugars?

Don’t be alarmed if the probiotic product you chose contains sugar – these sugar levels aren’t likely to be classified as “too high.”

Human studies on the health benefits of probiotic foods commonly use products with added sugar. Amazingly, health effects are still observed, according to the ISAPP (The International Scientific Association of Probiotics and Prebiotics).

According to Dr. Chris Cifelli, the National Dairy Council’s Vice President of Nutrition Research, in the ISAPP article mentioned above, there isn’t scientific evidence showing that the sugars (added or not) in these products reduce their health benefits.

Of course, you don’t usually consume very large amounts of added sugars (and the products don’t have them). However, regular intake of high-sugar foods can still affect your probiotics because that can hinder them from doing their job of protecting your gut.

What Can Kill Probiotics? (Other Factors)

There are other factors that can kill probiotics. For example, proper storage of probiotic products is very important because high heat and extreme cold (freezing) can easily kill them.

Now, if sugar can kill probiotics through the osmotic effect, can salt kill probiotics in high concentrations, too? The answer might be a “yes” or “no.” We covered that in-depth in this probiotics and salt.

Other interesting questions in this series:


Does Gut Bacteria Feed On Sugar?

Yes. Gut bacteria feed on sugars, such as the natural lactose sugars that you can find in milk.

Do Probiotics Break Down Sugar?

Yes. Probiotics “eat” sugar. They process this “food” and turn the sugars into lactic acid.

Does Sugar Destroy Gut Bacteria?

Regular amounts of sugar aren’t likely to kill your gut bacteria. However, very high concentrations of sugar (such as the levels used in jam and other preserved sweets) can destroy probiotics (and other forms of bacteria).

Does Sugar Interfere With Probiotics?

Yes. Sugar achieves this in several ways:

  • In very high concentrations, osmosis can shrivel the good bacteria and kill them (to forcibly get their water and achieve balance).
  • In very low concentrations, sugar can trigger probiotics or other “healthy” bacteria to turn bad and become pathogenic.
  • Regular consumption of unhealthy sugars can stop your probiotics from working properly and multiplying in your digestive tract.

Does Quitting Sugar Improve Gut Health?

Yes. Based on the 2018 study mentioned above, regular intake of foods with added sugars can be bad for your health. They can even inhibit the growth and colonization of probiotics in your gut.

So, when you quit sugar, you can begin the cleansing and healing process to improve your gut health.

Does Added Sugar Kill Probiotics In Yogurt?

Not really. The sugar levels in yogurt can’t be considered extremely high to cause or trigger the osmotic process. So, it means that these sugars can’t kill the probiotics in yogurt.

Many probiotic yogurts such as Yakult even list sugar as one of their ingredients.

Does Sugar Kill Probiotics In Kefir?

Just like in most food products, sugar isn’t likely to kill the probiotics in kefir unless you pour in a copious or excessive amount of sugar to test your theory.

Do Other Artificial Sweeteners Kill Probiotics?

A 2021 study showed that artificial sweeteners like sucralose, saccharin, and aspartame can promote the growth of pathogenic bacteria. They can even convert healthy, normal gut bacteria to become pathogenic.

However, other studies have also shown that there isn’t evidence that these artificial sweeteners can directly harm and kill the probiotics.

So, while these artificial sweeteners can cause an unbalanced, unhealthy gut, they don’t necessarily destroy the good bacteria.

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