The “Healthy” Drink That May Spike Your Blood Sugar

When you grab a bottle of kefir off the supermarket shelf, it’s easy to assume it’s an all-around win for your health. But depending on the type you grab, it may affect your blood sugar more than you realize—especially if you opt for flavored kefir. 

While there’s plenty of research to show that plain kefir is nutritious and rich in gut-healthy probiotics, many sweetened kefirs contain added sugar. Like anything else with added sugar, this can adversely impact your blood sugar, especially if you’re drinking lots of it.

Dietitians agree! Read on to learn what they want you to know about how sweetened flavored kefir can impact your blood sugar, plus tips to enjoy kefir without the blood sugar spike. 

How Flavored Kefir May Be Spiking Your Blood Sugar

It Often Contains Added Sugar

Many types of flavored kefir are sweetened with added sugar. This can raise blood sugar, especially in people with diabetes or prediabetes, says Vandana Sheth, RDN, CDCES, FAND.  

The exact amount of sugar in kefir can vary from brand to brand, but here’s an example: One cup of plain kefir from Whole Foods has 12 grams of sugar, but the same amount of their strawberry kefir clocks in at 18 grams of sugar, including 7 grams of added sugars.,

Why the difference? “Sweetened kefir has added sugars—glucose and fructose,” says Amy Huelle, M.P.H., RDN ,BC-ADM, CDCES. “These sugars are rapidly absorbed and can cause more of a blood sugar spike than plain kefir.”

You may be wondering how much added sugar it takes to actually impact your blood sugar. But dietitians say it’s not that simple, as everyone’s body processes sugar differently. Generally speaking, “the effect of added sugar on blood glucose depends on the amount consumed,” Huelle says. “Larger amounts lead to higher blood sugar spikes.” 

There are also a few other factors to consider, like how much kefir you’re drinking and if you’re eating anything else with it, adds Sheth.

Its Sugars May Be Quickly Absorbed

“Liquids are absorbed much faster than solid foods,” says Huelle. This is because liquids don’t need to be broken down during digestion into tiny particles, the way food does. So they empty from the stomach more rapidly than solids. And if your drink is already high in sugar, those sugars can flood your bloodstream really quickly. 

The good news is that there are a few factors working in kefir’s favor that may contribute to a more gradual rise in blood sugar compared to other sweetened drinks, like soda, sweet tea or fruit juice. “[Kefir] contains protein and sometimes fat, which can help slow digestion and soften the glucose rise compared to a drink with sugar alone,” Sheth says. Some research shows that kefir may even improve blood sugar and decrease insulin resistance., However, adding sugars to this otherwise-healthy drink is likely to undo some of those benefits.

If plain kefir isn’t your thing, Lauren Harris-Pincus, M.S., RDN, suggests blending sweetened kefir into a smoothie with a healthy fat like peanut butter or avocado to slow down the release of its sugars. 

It’s Easy to Drink a Lot Without Realizing It

“Controlling glucose is always influenced by the portion size of a food and the company it keeps,” Harris-Pincus says. So, even though kefir offers many nutritional benefits, it’s important to keep an eye on portion size, especially if you’re choosing one with added sugars. 

Most brands list a standard portion as 8 ounces. However, Huelle points out that most glasses in the typical kitchen are larger than this, making it all too easy to drink more than a serving without even realizing it.

It Has a Bit of a Health Halo

Yes, kefir is great for you. But even healthy foods and drinks can go sideways when they’re laced with added sugars. “Some patients of mine often make kefir smoothies for the nutritional benefit and protein, which can be a great meal replacement,” Huelle says. “However, they are surprised to learn that smoothies made with otherwise-healthy ingredients can cause blood sugar spikes when ingredients include sweetened beverages [like sweetened kefir], multiple servings of fruit, honey or other added sugars.”

Blood Sugar–Friendly Tips to Enjoy Kefir

These expert-backed tips can help you enjoy kefir without all the added sugars.

• Check for added sugars: “Many people do best choosing kefir with zero added sugar,” Sheth says. To find out for sure, check the Nutrition Facts label to see exactly how much added sugar (if any) your favorite kefir contains. Unsweetened is ideal. However, if that’s a deal breaker, Huelle suggests choosing kefir with less than 5 grams of added sugar per serving.
• Choose plain, unsweetened kefir: Like most dairy products, plain, unsweetened kefir contains the milk sugar lactose (about 12 grams per 8-ounce serving). No need to worry about that. It’s the added sugars from sweetened varieties that cause trouble.  
• Watch the portion size: Those grams of added sugar can really add up! “A small portion a few times per week is very different from drinking a large bottle daily, especially on an empty stomach,” Sheth says. 
• Pair kefir with protein, fiber or healthy fats: If you do drink sweetened kefir, these nutrients can help blunt the rise in glucose afterward., “A simple handful of nuts, like almonds, walnuts or pistachios, with a cup of kefir should minimize the potential glucose response,” Harris-Pincus says. Alternatively, drink your kefir alongside a meal. 
• Add your own fruit to plain kefir: “Choose plain, unsweetened kefir and [blend in] fresh berries or a small amount of whole fruit for natural sweetness and fiber,” Huelle says.
• Consider a high-protein or higher-fat kefir. “Higher-protein and full-fat kefir tends to be more blood sugar–friendly than low-fat, sweetened versions, especially when consumed with food,” Sheth says. 

Our Expert Take

Plain, unsweetened kefir can be a nutritious part of your day. But if you opt for flavored sweetened kefir, keep an eye on the nutrition label for added sugars, which can spike your blood sugar. And the more sweetened kefir you drink, the more likely it is to raise your blood sugar. Because kefir is a liquid, any added sugars may be absorbed more quickly by the body. The best choice is plain, unsweetened kefir, which has zero added sugars. However, if only sweetened kefir works for you, look for a brand with no more than 5 grams of added sugars per serving and keep serving sizes small. Or, better yet, blend some plain, unsweetened kefir with fresh or frozen fruit and make your own lightly sweetened version. You’ll skip the added sugars and gain vitamins, minerals, fiber and antioxidants in the process.