Digestion and lactose
Can kefir help with lactose intolerance?
Yes. Kefir can make lactose easier to digest for some people. One controlled human study found better lactose digestion and less flatulence after kefir than after milk.
Why fermented milk can feel different
Fermentation uses part of the lactose before you drink it. The study result is useful, but it came from 15 adults eating single test meals.
- 01Milk
The original lactose load.
- 02Fermentation
Microbes and their enzymes use part of the lactose.
- 03Your response
Tolerance still differs from person to person.
Why kefir can be easier to digest
Lactose is the natural sugar in milk. When the small intestine does not break down enough of it, more lactose reaches the colon. Gut bacteria ferment it there, which can produce gas and digestive discomfort.
Kefir is fermented milk. Fermentation changes the milk before you drink it, and the microbes in fermented dairy can also affect how lactose is handled during digestion. The human study measured the result directly through breath hydrogen, a marker of undigested lactose reaching the colon.
The finding is useful and direct, but it comes mainly from one small controlled study.
What the human study found
Hertzler and Clancy studied 15 healthy adults with lactose maldigestion. After an overnight fast, each participant consumed five test meals on separate occasions: milk, plain kefir, raspberry kefir, plain yogurt, and raspberry yogurt. Every meal contained 20 grams of lactose. Researchers measured breath hydrogen and digestive symptoms every hour for eight hours.
Plain kefir produced a significantly lower breath-hydrogen response than milk. Its result was similar to the yogurt results. All kefir and yogurt meals reduced perceived flatulence by 54% to 71% compared with milk. Abdominal pain and diarrhea were negligible across the five treatments.
What the study cannot tell us
The study was small and examined short-term responses to single meals. It did not test daily kefir use. The participants were healthy adults with lactose maldigestion, so the result may not apply to children, people with other digestive conditions, or people with severe symptoms. It also tested only two kefir preparations.
A practical way to try kefir
If milk causes gas or bloating, try a small amount of plain kefir with food. Plain kefir makes it easier to judge your response without a large serving or extra flavourings. Increase only if you feel comfortable.
Kefir is not lactose-free. If even a small amount of dairy causes clear symptoms, do not assume kefir will suit you.
Who should be careful?
Lactose intolerance is different from milk allergy. This evidence does not show that kefir is safe for someone with a milk allergy. Speak with a qualified health professional before changing your diet if you have a diagnosed digestive disease, a medically required dairy restriction, or severe, persistent, or unexplained symptoms.
Common questions
Is kefir lactose-free?
No. Fermentation can make lactose easier for some people to digest, but the amount left varies between kefirs.
Is kefir better than yogurt for lactose intolerance?
This study found similar breath-hydrogen responses and similar reductions in flatulence for plain kefir and plain yogurt. It did not prove that kefir is generally better.
Can kefir cure lactose intolerance?
No. It improved digestion and tolerance during the test meals. It did not permanently restore lactase production.
Sources
- Hertzler SR, Clancy SM. Kefir improves lactose digestion and tolerance in adults with lactose maldigestion. Journal of the American Dietetic Association. 2003;103(5):582-587. PMID: 12728216.
- Kairey L, et al. The effects of kefir consumption on human health: a systematic review of randomized controlled trials. Nutrition Reviews. 2023;81(3):267-286. PMID: 35913411.