Kefir
Dairy · Other Dairy
Fermented does not mean lactose-free, and kefir is the drink that proves it. A third of a cup, 90 ml, rates green with 0.6 g of lactose, while a full 250 ml cup reaches 1.7 g and is rated red. The cultures have taken most of the milk sugar out, and what stays is enough to put the glass people actually pour over the line.
Last updated 4 September 2026Serving sizes for kefir
A third of a cup (90 ml) is rated green. A full cup (250 ml) is rated red.
Tested serving sizes
| Serving | Amount | Main FODMAP | Rating |
|---|---|---|---|
| 1/3 cup | 90 ml | Lactose 0.6 g | |
| 1 cup | 250 ml | Lactose 1.7 g |
Breakdown for 0.33 cups
Is kefir low FODMAP?
Kefir begins as milk and is fermented with grains that carry yeasts as well as bacteria, a broader and hungrier culture than the pair of bacteria that set yoghurt. Those organisms live on lactose, so a good deal of it has gone by the time the bottle is capped: a 250 ml cup of regular milk records 7.5 g, and the same measure of kefir records 1.7 g. That is most of the way, not all of it, and the figure still clears the 1 g mark at which lactose counts as high.
Kefir and IBS: what to know
Most people drink kefir for its live cultures rather than its flavour, and that is where this guide stops. A rating describes what is in the glass, not what those organisms may or may not do for your symptoms, and probiotics in IBS remain an unsettled question better weighed with a dietitian than with a serving figure. The practical tension is worth naming: the reason people drink kefir pushes the volume up, and the lactose pushes it down, while the green measure here is a small tumbler.
Gut-friendly ways to eat kefir
A third of a cup is a splash rather than a drink, which suits kefir better than it sounds. Pour it over oats instead of milk, blend it with strawberries into a modest smoothie, or whisk it with lemon and herbs into a dressing that would otherwise want garlic. If what you want is dairy by the glassful, lactose-free milk rates green at a full cup. Water and coconut kefirs sidestep dairy entirely, though neither is rated in our guide, so treat them as untested rather than proven.
Frequently asked questions
Is kefir lactose free?
No. Fermentation converts a large share of the milk sugar into acids, which is what makes kefir tart, but a share survives into the bottle and the full-cup serve is rated red on it. Lactose-free dairy is treated with lactase so the sugar is already split before you drink it. Kefir simply holds less of it than the milk it was made from.
How much kefir can I drink a day?
The data gives you one green point at a third of a cup and one red point at a full cup, so a small tumbler is what you can lean on. Half a cup falls in a gap nobody has measured, which makes it a guess. If kefir is a daily routine, the smaller pour taken alongside food is the version that stays inside the evidence.
Is kefir better than yoghurt for IBS?
On lactose alone it has an edge, because kefir has a green serve where regular yoghurt has none, its smallest tested amount being amber. Kefir is drunk rather than spooned, though, and volume climbs faster in a glass than in a bowl. Which one suits you comes down to the format you will actually keep to.
Does kefir help IBS symptoms?
Our rating answers a narrower question than that. It measures the lactose in a given serve; it says nothing about whether live cultures ease bloating, pain or urgency. The research on probiotics in IBS is mixed, and strains differ enough from one another that a result for one product does not carry across to the next. A dietitian who knows your history is the person to weigh it with.
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