Many people lump yogurt and kefir together. Though they can both be sources of beneficial probiotics for the gut, there are some unique disadvantages of kefir. The main difference between kefir and yogurt is that the latter contains fewer probiotic cultures.
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Like all fermented foods, not everyone can tolerate kefir. Although kefir is typically consumed for digestive benefits, its effect on the gut is not as positive for all people. Though one person may credit kefir as the answer to all of their digestive woes, kefir may cause side effects in other people. Since everyone has different levels of tolerance to certain foods, it's best to introduce kefir into your diet slowly if you have a sensitive stomach.
Many of the kefir side effects are mild. In fact, the overwhelming majority of the research on kefir is in support of the fermented milk drink. Many people tolerate kefir well due to the rich probiotic content. However, if you experience kefir side effects, discontinue use immediately.
What Is Kefir?
Kefir refers to a drink that has been made with cultured kefir grains in liquid. Typically, that liquid is milk, though it can also be juice or water with sugar. Since kefir is usually milk-based, people with dairy allergies should avoid kefir made from cow or goat milk. People with lactose intolerance may be able to tolerate kefir since the fermentation process reduces the lactose content. Nondairy kefir is less common, though it is an option for people with dietary restrictions.
Kefir milk is often consumed as an alternative to yogurt. It has a thin consistency much like regular milk. The taste is often described as tart and sweet, though some kefir milks are flavored. If you consume kefir, be cautious of added sugar.
People on a calorie deficit will appreciate that most kefirs are not a significant source of calories. A serving size of kefir can range from 2 ounces to 1 cup. According to the USDA, a 1-cup serving of plain nonfat kefir milk contains 130 calories. A 2-ounce serving would be contain roughly 33 calories. A 1-cup serving also contains 35 percent of your daily calcium needs and 4 percent of your vitamin A needs.
Benefits of Kefir
Though there are reported disadvantages of kefir, much of the research is positive. Being a milk-based drink, kefir shares many of the same advantages as dairy products such as whole milk and yogurt. However, the fermented nature of kefir milk adds an extra layer of benefits.
Fermented foods like kefir are rich in probiotics. According to Mayo Clinic, probiotics contain live microorganisms that encourage "good" bacteria in the gut microbiome. If you take a lot of antibiotics, which kill off both "good" and "bad" bacteria, probiotics may help restore the balance of overall gut flora.
Additionally, side effects of probiotics, whether supplemental or dietary, are rare. Probiotics can be taken in supplement form or in foods like kefir, kimchi, sauerkraut, miso and tempeh.
The benefits of probiotic-rich food aren't seen just on the microscopic level. When consumed regularly, you may be able to experience noticeable benefits of probiotics in fermented foods like kefir.
An October 2015 study published in Frontiers in Microbiology recognizes kefir as a source of dietary probiotics. The research suggests that kefir is a source of antioxidants and has antimicrobial and antitumor properties. Further studies are being conducted to determine kefir's other roles and benefits.
Disadvantages of Kefir
One area of concern is kefir's insulinemic index. In an August 2012 study published in the Journal of the American College of Nutrition, researchers found that kefir has a low to moderate glycemic index (GI) score but a high insulinemic score. This means that kefir may increase blood insulin levels more so than other foods. The study also compared kefir to white bread in terms of satiety, so consuming kefir milk as a snack will not keep you satisfied for long.
Another disadvantage of kefir is that it tends to be high in sugar. Some of the sugar content in kefir milk is natural sugar from the fruit juice or milk, though manufacturers often add sugar and other flavorings to make the drink taste sweeter. You can make your own kefir at home to control how much sugar and added ingredients go into the recipe, though making fermented foods can be time-consuming and complicated.
Kefir Side Effects
Kefir has very few known side effects. However, it may share some of the same side effects as other milk-based products. According to Cleveland Clinic, intolerance to lactose in foods containing dairy may result in the following symptoms:
Other possible side effects include upset stomach, constipation and abdominal pain. It is unclear if other types of kefir, such as those made with water or fruit juice, yield fewer symptoms.
Though kefir is widely studied and the general consensus is that it is safe to drink, much of the research is based on animal studies. A June 2017 study published in Nutrition Research Reviews found kefir to be a beneficial product for digestive health, though researchers found a lack of human-based studies from which to draw their conclusions.
Should You Drink Kefir?
Despite the mild kefir side effects, the fermented drink remains highly regarded as a source of probiotics among experts and studies. However, some people experience digestive symptoms, which can likely be attributed to the milk in kefir. Some people are also sensitive to fermented foods in general.
If you are intolerant to dairy products or experience discomfort after consuming fermented foods, you may not want to choose kefir as your primary source of beneficial probiotics. However, kefir contains less lactose than other dairy products. Depending on the severity of your lactose intolerance, you may be able to tolerate kefir better than other dairy products that contain higher amounts of lactose.
Fortunately, there are many other dietary and supplemental sources of probiotics that do not contain milk. Alternatively, you can opt for a nondairy or fruit juice kefir rather than kefir milk. There are both advantages and disadvantages of kefir. For some, the pros outweigh the cons, and vice versa.
- Mayo Clinic: “What Are Probiotics and Prebiotics?”
- Frontiers in Microbiology: “Milk Kefir: Composition, Microbial Cultures, Biological Activities and Related Products”
- Nutrition Research Reviews: “Milk Kefir: Nutritional, Microbiological and Health Benefits.”
- Cleveland Clinic: “Lactose Intolerance”
- Journal of the American College of Nutrition: “Glycemic Index, Insulinemic Index, and Satiety Index of Kefir”
- USDA FoodData Central: "Kefir"