If you follow health and weight loss trends at all, you've probably heard of kefir. Like kombucha before it, kefir has been extolled by numerous nutritionists and health professionals for its nutritional content and positive effects on gut health and digestion. Some claim that kefir can do even more by helping aid in weight loss—but is this just another case of something being labeled a weight loss wonder food without actual scientific evidence?
Before you fill your fridge with this cultured dairy (or non-dairy!) drink, here's what you need to know about kefir and how it may be able to help you reach and maintain a healthy weight.
What is Kefir?
There's a good chance you've flipped through an article on kefir or walked past it sandwiched between the dairy products in the grocery store without really knowing what it is. Simply put, kefir is a cultured and fermented milk beverage that tastes like a slightly-more-tangy yogurt drink. Dairy milk (cow's milk or goat's milk) is the most common base ingredient for kefir, but non-dairy alternatives such as coconut milk, rice milk, soy milk, and even coconut water can be used if you prefer entirely non-milk kefir. During the fermentation process, lactic acid bacteria produce lactase, which then consumes lactose, meaning that all kefir—even those varieties that are dairy-based—can be enjoyed by those who suffer from lactose intolerance.
Even if you've enjoyed kefir before, you may not have known how it's made. The base ingredient (dairy or otherwise) is combined with "grains," which consist of a mixture of bacteria, yeasts and milk proteins known as casein. Think of these grains as a "starter" for kefir in the same way that you would use a starter to make sourdough bread. When added to the milk, the grains ferment it and transfer their beneficial bacterial strains and yeasts to the resulting cultured drink. The kefir grains are then strained away, leaving behind tart, creamy kefir drink.
Many of kefir's ingredients are beneficial and can provide a wide range of health benefits. The high amounts of calcium in combination with vitamin K2, for example, may be helpful in improving bone health and reducing the risk of osteoporosis; likewise, the potassium in kefir is key for supporting heart health. Ultimately, though, it's the distinctive side effects of kefir's special grains that give kefir its most potent health benefit.
The Powerful Properties of Kefir's Natural Probiotics
It's the good bacteria and yeasts that are left behind as a result of kefir's unique fermentation process that make it such a powerful health food. While kefir is often compared to yogurt—and in taste, they can be quite similar—the room temperature fermentation process that kefir goes through helps to provide it with a significantly larger range of healthy bacteria strains. Also known as probiotics, these beneficial types of bacteria can support a wide range of bodily processes, from digestion to immune system regulation. Multiple studies have found that kefir has an average of 30 different strains of bacteria and yeasts. In comparison, the average yogurt has just four to six types of probiotic strains.
The diversity in probiotics found in kefir helps to support whole body health. Different probiotic strains provide benefits to different areas of the body and help to boost different bodily processes, so the wide variety of strains in the average serving of kefir allow it to address several health concerns. For example, a strain that is unique to kefir—Lactobacillus kefiri—has been found to guard against several harmful bacterial infections such as salmonella, staphylococcus, and other pathogens. (2) Other strains of probiotics in kefir can help support digestive system function, helping with both occasional digestive issues and ongoing conditions such as irritable bowel syndrome. There's even some evidence that certain probiotics in kefir might be able to inhibit tumor growth. (3)
And what about weight loss? Besides the immune system support and digestive health benefits of kefir's natural probiotics, there's plenty of evidence that naturally-occurring probiotics like those found in kefir can indeed rev your metabolism and potentially help you reach your weight loss goals.
How Probiotics Can Help Support Weight Loss
All probiotic health benefits—and there are a lot of them!—come from their ability to bring balance to the gut microbiome, the population of trillions of bacteria that call your digestive tract home. By helping to improve the health of your gut microbiome, probiotics can deeply affect the way your system processes food and thereby change your metabolic rate. This is key for anyone struggling with weight gain/weight loss issues. Your metabolic rate determines how many calories you burn each day, and supporting your metabolic rate can mean the difference between heavily dieting without any change on the scale and eating a healthy balanced diet and seeing real results. If you are experiencing persistent, unusual, or recurrent body weight issues, seek medical advice.
So how can probiotics like those in kefir help improve your metabolic function? Research has uncovered a number of ways that probiotics affect metabolism. For example, researchers at Imperial College London found that probiotics help the body metabolize bile acids; because bile acids are key for breaking down fat, increasing the number of probiotics in your diet could set off a chain reaction that changes the amount of fat that your body stores. (4)
Other studies have demonstrated that probiotics play a role in regulating levels of various hormones, which in turn affects metabolism and lowers the risk of obesity. (5) Scientists have even directly tested the effects of increasing the intake of the probiotic Lactobacillus rhamnosus on weight loss, and it's been found that probiotics alone may be able to increase weight loss in general while lowering body fat, especially for women. (6) In short, there's a growing scientific consensus that probiotics—whether from foods like kefir or from a daily probiotic supplement—have an important role to play in maintaining a healthy weight. (7)
So should you try drinking kefir regularly if you're trying to lose weight? Well, kefir is a high protein food, important for feeling full and maintaining muscle mass; it's also nutrient-dense with plenty of calcium, potassium, and vitamin B, key for maintaining your health while supporting your metabolism. The incredible numbers and diversity of probiotics in each serving also help you take advantage of the wide range of metabolism supporting benefits that probiotics can provide. And, of course, kefir has one last selling point: it's delicious!
- Jianzhonga, Zhou, Liu Xiaolia, Jiang Hanhub, and Dong Mingshengb. "Analysis of the microflora in Tibetan kefir grains using denaturing gradient gel electrophoresis." Food Microbiology 26, (2009): 770-775. http://depa.fquim.unam.mx/amyd/archivero/Kefir_1_12695.pdf.
- Carasi, Paula, Mariángeles Díaz, Silvia M. Racedo, Graciela De Antoni, María C. Urdaci, and María de los Angeles Serradell. (2014). "Safety Characterization and Antimicrobial Properties of Kefir-Isolated Lactobacillus kefiri." BioMed Research International, (2014): 208974. doi: 10.1155/2014/208974.
- Khoury, N, S El-Hayek, O Tarras, M El-Sabban, M El-Sibai, S Rizk. "Kefir exhibits anti‑proliferative and pro‑apoptotic effects on colon adenocarcinoma cells with no significant effects on cell migration and invasion." Int J Oncol 45, no. 5 (2014): 2117-27. doi: 10.3892/ijo.2014.2635.
- Martin, FP, Y Wang, N Sprenger, IK Yap, T Lundstedt, P Lek, S Rezzi, et al. "Probiotic modulation of symbiotic gut microbial–host metabolic interactions in a humanized microbiome mouse model." Mol Syst Biol 4, (2008): 157. doi: 10.1038/msb4100190.
- Yadav, Hariom, Ji-Hyeon Lee, John Lloyd, Peter Walter, and Sushil G Rane. "Beneficial metabolic effects of a probiotic via butyrate induced GLP-1 secretion." The Journal of Biological Chemistry 288, (2013): 25088-25097. doi: 10.1074/jbc.M113.452516.
- Sanchez, Marina, Christian Darimont, Vicky Drapeau, Shahram Emady-Azar, Melissa Lepage, Enea Rezzonico, Catherine Ngom-Bru, et al. "Effect of Lactobacillus rhamnosus CGMCC1.3724 supplementation on weight loss and maintenance in obese men and women." British Journal of Nutrition 111, no. 8 (2014): 1507-1519. doi: 10.1017/S0007114513003875.
- Angelakis, Emmanouil, Vicky Merhej, and Didier Raoult. "Related actions of probiotics and antibiotics on gut microbiota and weight modification." The Lancet Infectious Diseases 13, no. 10 (2013): 889-899. doi: 10.1016/S1473-3099(13)70179-8.