{"url":"https://whatshealthyandwhy.com/kefir/gut-bone-and-immune-health","path":"/kefir/gut-bone-and-immune-health","alternates":{"json":"https://whatshealthyandwhy.com/api/articles/kefir/gut-bone-and-immune-health.json","markdown":"https://whatshealthyandwhy.com/kefir/gut-bone-and-immune-health.md"},"topic":{"slug":"kefir","name":"Kefir","url":"https://whatshealthyandwhy.com/kefir"},"slug":"gut-bone-and-immune-health","order":1,"title":"Gut, Blood Sugar, Bone, and Immune Health","question":"Does kefir improve gut, bone and immune health?","answer":"Kefir may improve gut, immune and bone markers in small trials, but a 2023 review rated most kefir trials high risk of bias.","description":"What clinical trials show about kefir and gut health, insulin resistance, bone turnover, immune markers, and lactose digestion","confidence":2,"confidenceNote":"Five small RCTs (15 to 45 people) and one uncontrolled study; a review of 16 RCTs called the evidence insufficient for recommendations.","evidenceSummary":{"rctCount":6,"observationalCount":0,"metaAnalysisCount":2,"totalParticipants":"160+","replicated":true,"newestStudyYear":2023},"category":{"categoryTitle":"What's Good For You","categorySlug":"good-for-you","subcategoryName":"Foods & Drinks","subcategorySlug":"foods","url":"https://whatshealthyandwhy.com/explore/good-for-you/foods"},"actions":["If milk upsets you, try kefir instead: adults with lactose maldigestion had 61% less breath hydrogen and less flatulence [5].","Drink 200–400 mL of plain, traditionally fermented kefir daily, the range used in trials; commercial kefir did not match it [6].","Make it at home: add grains to whole milk, cover with cloth, leave 24–48 hours at room temperature, then strain and refrigerate."],"cautions":["With severe lactose intolerance or a milk protein allergy, start with small amounts or consider water kefir.","A 2023 review of 16 RCTs found most had a high risk of bias and judged the evidence insufficient for clinical recommendations [7].","Commercial kefir made from starter cultures may not deliver the same benefits, and it increased TNF-α in one trial [6]."],"simpleText":"Kefir is a fermented milk drink made by culturing dairy with kefir grains — a symbiotic community of bacteria and yeasts unlike any other fermented food. It contains a broader and more diverse range of live microorganisms than yogurt, and those microbes do measurable things: they shift the gut microbiome [1], reduce markers of inflammation [2], and help people who cannot normally digest milk tolerate it comfortably [5]. Pooled trial data also point to lower insulin resistance [9]. It is one of the most well-researched fermented foods, with clinical trials on gut health, blood sugar, bone metabolism, and immune markers — though most of them are small.","mediumText":"What Makes Kefir Different from Yogurt\n\nYogurt typically contains two to four bacterial strains added during manufacturing. Kefir grains — the irregular, cauliflower-like clusters used to ferment kefir — harbor dozens of bacterial species plus several yeasts, all living together in a stable, self-perpetuating community. When those grains ferment milk, they produce the same microorganisms along with organic acids, bacteriocins (natural antimicrobials), and bioactive peptides derived from the partial digestion of milk proteins.\n\nThis complexity matters because different microbial species colonize different niches in the gut, produce different metabolites, and interact with the immune system in different ways. A 2023 crossover trial found that traditionally fermented kefir — made with natural grain cultures — significantly reduced LDL cholesterol, CRP, and the adhesion molecules ICAM-1 and VCAM-1, while commercially produced kefir (often made from starter cultures rather than full grains) did not show the same benefits and actually increased TNF-α in some participants [6]. The microbial community, not just the presence of probiotics, appears to drive the outcome.\n\nGut Health and the Microbiome\n\nIn people with metabolic syndrome, 12 weeks of daily kefir was followed by lower fasting insulin, insulin resistance (HOMA-IR), and pro-inflammatory cytokines including TNF-α and IFN-γ within the kefir group (the difference from the unfermented-milk comparison group was not statistically significant). It also increased the relative abundance of Actinobacteria — a phylum associated with gut lining integrity and metabolic health [1].\n\nIn a trial with inflammatory bowel disease patients, 400 mL of kefir per day for four weeks significantly increased Lactobacillus counts in stool, reduced CRP and erythrocyte sedimentation rate in Crohn's disease patients, and improved quality-of-life scores [2]. Bloating scores improved during the final two weeks of the trial.\n\nA 2023 systematic review of 16 randomized controlled trials found the most consistent evidence for kefir's benefit in three areas: reducing oral Streptococcus mutans (a cavity-causing bacterium), supporting eradication of Helicobacter pylori, and improving lipid profiles and blood pressure in adults with dyslipidemia or hypertension [7]. The reviewers noted that 12 of 18 included studies had methodological limitations, so these findings are promising rather than definitive.\n\nBlood Sugar and Insulin Resistance\n\nIn a double-blind trial of 60 adults with type 2 diabetes, drinking 600 mL of kefir a day for eight weeks was followed by significantly lower fasting glucose and HbA1c than the same amount of ordinary fermented milk; blood fats did not differ between the groups [8]. A 2023 meta-analysis of six randomized trials (314 participants) found that kefir lowered fasting insulin and insulin resistance (HOMA-IR) but had no significant effect on fasting glucose, HbA1c, cholesterol, triglycerides, or body weight [9]. Taken together, the better-supported benefit is improved insulin sensitivity rather than a reliable drop in blood sugar, and the trials are small.\n\nLactose Intolerance\n\nPeople who cannot digest lactose — estimated at 68% of the global adult population — often tolerate kefir significantly better than regular milk. In a crossover trial, adults with confirmed lactose maldigestion exhaled 61% less hydrogen gas after drinking kefir versus plain milk (87 vs. 224 ppm×h on breath hydrogen testing). Perceived flatulence was reduced by 54–71% [5].\n\nThe mechanism is straightforward: the microorganisms in kefir produce lactase (beta-galactosidase), which pre-digests much of the lactose before the drink is consumed. Additionally, the slow gastric emptying caused by the slightly viscous consistency of kefir gives remaining lactase more time to act in the small intestine. This makes kefir accessible to many people who avoid dairy entirely due to digestive discomfort.\n\nBone Health\n\nIn a six-month double-blind trial in osteoporotic patients, kefir shifted the balance between bone resorption and bone formation more favorably than calcium supplementation alone. The bone resorption marker beta-CTX decreased in patients with higher baseline bone density, and the bone formation marker osteocalcin showed a positive trend at six months in the kefir group [3]. Hip bone mineral density increases were greater in the kefir group than in the calcium-only control group, though the study was small (40 participants) and short enough that larger structural changes are unlikely to be fully captured.\n\nThe proposed mechanisms include the role of kefir-derived peptides in modulating osteoclast and osteoblast activity, improved calcium and phosphorus absorption in a more acidic gut environment, and vitamin K2 produced by some strains of bacteria in the fermentation process. See our vitamin K2 page for more on how K2 directs calcium into bone rather than arterial walls.\n\nImmune Modulation\n\nA six-week trial in healthy adults found that 200 mL of kefir per day significantly reduced IL-8 (a pro-inflammatory cytokine) at both three and six weeks, with suppression persisting three weeks after consumption stopped [4]. IL-5 (associated with allergic response) initially rose then declined, and the authors interpreted the pattern as a shift toward a Th1-dominant immune response — a pattern generally associated with reduced allergic and inflammatory reactivity. The study was small (18 participants), so these findings should be treated as preliminary.\n\nPractical Guidance\n\nPlain, traditionally fermented kefir made from whole grains offers the most diverse microbial community. Commercially produced kefir varies considerably — some products are made from defined starter cultures and may not deliver the same benefits. If purchasing commercial kefir, look for products listing multiple bacterial species and genuine Lactobacillus kefiranofaciens or Lactobacillus kefiri on the label.\n\nHomemade kefir from purchased grains is straightforward: add grains to whole milk, cover with cloth, leave at room temperature for 24–48 hours, strain, and refrigerate. The grains reuse indefinitely.\n\nTypical amounts used in clinical trials range from 200 to 400 mL per day. Most people tolerate kefir well; those with severe lactose intolerance or milk protein allergy should start with small amounts or consider water kefir, which ferments sugar water or coconut water with a related but distinct set of grains.\n\nSee our fermented foods page for broader context on how fermentation transforms food, and our probiotics page for guidance on probiotic strains and clinical evidence.","deepText":"Evidence Review\n\nGut Microbiome and Metabolic Health\n\nBellikci-Koyu et al. (2019, PMID 31487797) conducted a 12-week parallel-group RCT in 22 adults with metabolic syndrome. The kefir group consumed 180 mL/day. Within-group analysis showed significant reductions in fasting insulin (p ≤ 0.05), HOMA-IR (p ≤ 0.05), TNF-α (p ≤ 0.05), and IFN-γ (p ≤ 0.05), along with decreased systolic and diastolic blood pressure. Relative abundance of Actinobacteria increased significantly (p = 0.023). Between-group differences did not reach statistical significance, which the authors attributed to the small sample size and the parallel (rather than crossover) design, which reduces power. The study is limited by short duration and reliance on within-group changes.\n\nYilmaz et al. (2019, PMID 30662004) enrolled 45 IBD patients (25 kefir, 20 control) in a 4-week trial using 400 mL/day. In Crohn's disease patients, ESR (erythrocyte sedimentation rate) and CRP decreased significantly (p < 0.05) and hemoglobin increased. Lactobacillus counts in stool increased significantly (p = 0.001 in ulcerative colitis; p = 0.005 in Crohn's). Bloating scores improved over the final two weeks (p = 0.012), and quality-of-life scores (IBDQ) improved (p = 0.032). The control group received no placebo, introducing potential bias.\n\nBlood Sugar and Insulin Resistance\n\nOstadrahimi et al. (2015, PMID 25905057) randomized 60 adults aged 35–65 with type 2 diabetes (30 per group) to 600 mL/day of kefir (containing Lactobacillus casei, L. acidophilus, and bifidobacteria) or of conventional fermented milk for 8 weeks. After the intervention fasting glucose differed significantly between the groups (p = 0.01); HbA1c fell from baseline in the kefir group (p = 0.001) and was lower than in the control group after adjustment for baseline glucose, baseline HbA1c, and energy intake (p = 0.02). Triglycerides and total, LDL, and HDL cholesterol did not differ significantly within or between the groups [8]. The 600 mL daily dose is well above the 180–400 mL used in the other trials reviewed here.\n\nYahyapoor et al. (2023, PMID 37102491) pooled six randomized trials (314 participants). Kefir lowered fasting insulin (weighted mean difference −3.69 µIU/mL, 95% CI −6.30 to −1.07; I² = 0%) and HOMA-IR (−2.56, 95% CI −3.82 to −1.30; I² = 19%). It had no significant effect on total, LDL, or HDL cholesterol, triglycerides, fasting glucose, HbA1c, or body weight [9]. The pooled glucose and HbA1c result does not agree with the positive single trial above [8], so a glucose-lowering effect is not established; the insulin-resistance finding is the more consistent one.\n\nSystematic Evidence Base\n\nKairey et al. (2023, PMID 35913411) systematically reviewed 18 publications from 16 RCTs of kefir. The highest-quality evidence supported: reduction of oral Streptococcus mutans and dental caries risk; improved H. pylori eradication rates when kefir was added to standard antibiotic therapy; and improvements in dyslipidemia and hypertension in adults. However, 12 of the 18 studies had high risk of bias by Cochrane criteria, and only 5 assessed safety outcomes. The reviewers concluded that current evidence is insufficient to make clinical recommendations, and called for larger, well-designed trials.\n\nLipid and Inflammation Profiles\n\nBourrie et al. (2023, PMID 37224566) conducted a randomized crossover trial in 21 healthy males using two 4-week treatment periods (traditional kefir vs. commercial kefir) separated by a 4-week washout. Traditional kefir significantly reduced LDL cholesterol, ICAM-1, and VCAM-1 versus baseline (p < 0.05). Compared to commercial kefir, traditional kefir produced significantly greater reductions in IL-8, CRP, VCAM-1, and TNF-α (all p < 0.05). Commercial kefir unexpectedly increased TNF-α. The study demonstrates that microbial community composition — not merely the label \"kefir\" — determines health outcomes. Limitations: small sample, male-only, pilot design.\n\nBone Metabolism\n\nTu et al. (2015, PMID 26655888) conducted a 6-month double-blind RCT in 40 osteoporotic patients randomized to kefir-fermented milk or calcium-supplemented control milk. In patients with T-scores above −1 (less severe bone loss), beta-CTX (C-terminal telopeptide, a bone resorption marker) decreased significantly at 3 months in the kefir group. Osteocalcin (a bone formation marker) showed net positive change at 6 months in the kefir group versus negative change in controls. Hip BMD increases were numerically greater in the kefir group, though statistical significance for group differences was not consistently reached. Parathyroid hormone rose significantly with kefir but fell in the control group; the authors suggest this may promote bone remodeling. Study limitations: small sample, single center, short duration relative to meaningful BMD change timelines.\n\nLactose Digestion\n\nHertzler and Clancy (2003, PMID 12728216) tested 15 adults with confirmed lactose maldigestion in a randomized block design. Breath hydrogen AUC after 500 mL of plain milk was 224 ± 39 ppm·h. After plain kefir it was 87 ± 37 ppm·h (p < 0.001), a 61% reduction. Flavored kefir reduced it to 156 ± 26 ppm·h. Perceived flatulence severity decreased by 54–71% across kefir and yogurt conditions. Abdominal pain and diarrhea were negligible. This is the most rigorously designed human trial on kefir and lactose tolerance, though it predates modern microbiome analysis, which may have provided mechanistic detail.\n\nImmune Function …","deepTruncated":true,"references":[{"id":"1","title":"Effects of Regular Kefir Consumption on Gut Microbiota in Patients with Metabolic Syndrome: A Parallel-Group, Randomized, Controlled Study","authors":"Bellikci-Koyu E, Sarer-Yurekli BP, Akyon Y, Aydin-Kose F, Karagozlu C, Ozgen AG, Brinkmann A, Nitsche A, Ergunay K, Yilmaz E, Buyuktuncer Z","year":2019,"journal":"Nutrients","pmid":"31487797","url":"https://pubmed.ncbi.nlm.nih.gov/31487797/"},{"id":"2","title":"Effect of administering kefir on the changes in fecal microbiota and symptoms of inflammatory bowel disease: A randomized controlled trial","authors":"Yılmaz İ, Dolar ME, Özpınar H","year":2019,"journal":"Turkish Journal of Gastroenterology","pmid":"30662004","url":"https://pubmed.ncbi.nlm.nih.gov/30662004/"},{"id":"3","title":"Short-Term Effects of Kefir-Fermented Milk Consumption on Bone Mineral Density and Bone Metabolism in a Randomized Clinical Trial of Osteoporotic Patients","authors":"Tu MY, Chen HL, Tung YT, Kao CC, Hu FC, Chen CM","year":2015,"journal":"PLoS One","pmid":"26655888","url":"https://pubmed.ncbi.nlm.nih.gov/26655888/"},{"id":"4","title":"The effect of kefir consumption on human immune system: a cytokine study","authors":"Adiloglu AK, Gonulates N, Isler M, Senol A","year":2013,"journal":"Mikrobiyoloji Bulteni","pmid":"23621727","url":"https://pubmed.ncbi.nlm.nih.gov/23621727/"},{"id":"5","title":"Kefir improves lactose digestion and tolerance in adults with lactose maldigestion","authors":"Hertzler SR, Clancy SM","year":2003,"journal":"Journal of the American Dietetic Association","pmid":"12728216","url":"https://pubmed.ncbi.nlm.nih.gov/12728216/"},{"id":"6","title":"Consumption of kefir made with traditional microorganisms resulted in greater improvements in LDL cholesterol and plasma markers of inflammation in males when compared to a commercial kefir: a randomized pilot study","authors":"Bourrie BCT, Forgie AJ, Makarowski A, Cotter PD, Richard C, Willing BP","year":2023,"journal":"Applied Physiology, Nutrition, and Metabolism","pmid":"37224566","url":"https://pubmed.ncbi.nlm.nih.gov/37224566/"},{"id":"7","title":"The effects of kefir consumption on human health: a systematic review of randomized controlled trials","authors":"Kairey L, Leech B, El-Assaad F, Bugarcic A, Dawson D, Lauche R","year":2023,"journal":"Nutrition Reviews","pmid":"35913411","url":"https://pubmed.ncbi.nlm.nih.gov/35913411/"},{"id":"8","title":"Effect of probiotic fermented milk (kefir) on glycemic control and lipid profile in type 2 diabetic patients: a randomized double-blind placebo-controlled clinical trial","authors":"Ostadrahimi A, Taghizadeh A, Mobasseri M, Farrin N, Payahoo L, Beyramalipoor Gheshlaghi Z, Vahedjabbari M","year":2015,"journal":"Iranian Journal of Public Health","pmid":"25905057","url":"https://pubmed.ncbi.nlm.nih.gov/25905057/"},{"id":"9","title":"Effects of Kefir Consumption on Cardiometabolic Risk Factors: A Systematic Review and Meta-analysis of Randomized Controlled Trials","authors":"Yahyapoor F, Haghighat N, Sohrabi Z, Asbaghi O, Bagherniya M, Jamialahmadi T, Sahebkar A","year":2023,"journal":"Current Drug Targets","pmid":"37102491","url":"https://pubmed.ncbi.nlm.nih.gov/37102491/"}],"wordCount":2079,"source":{"path":"src/content/topics/kefir/gut-bone-and-immune-health.md"},"citeAs":"“Does kefir improve gut, bone and immune health?.” What's Healthy and Why. https://whatshealthyandwhy.com/kefir/gut-bone-and-immune-health","notice":"General information backed by peer-reviewed research, not medical advice."}