It sounds like secondary lactose intolerance caused by the stomach virus.

Lactase, the enzyme that breaks down lactose, is produced in the fragile cells that form the brush border lining your small intestine. These cells are damaged by gut infections by viruses and bacteria and it takes a while for the gut wall to heal up again. Even then it can take longer before these cells start producing enough lactase enzyme again.

This is a personal story on the UK National Health Service advice website that sounds similar to yours:

Lactose intolerance - Gary's story.

From this paper:

Lactose Intolerance in Infants, Children, and Adolescents

Lactose intolerance is a clinical syndrome of 1 or more of the following: abdominal pain, diarrhea, nausea, flatulence, and/or bloating after the ingestion of lactose or lactose-containing food substances. The amount of lactose that will cause symptoms varies from individual to individual, depending on the amount of lactose consumed, the degree of lactase deficiency, and the form of food substance in which the lactose is ingested.

Secondary lactase deficiency is lactase deficiency that results from small bowel injury, such as acute gastroenteritis, persistent diarrhea, small bowel overgrowth, cancer chemotherapy, or other causes of injury to the small intestinal mucosa, and can present at any age but is more common in infancy.

The cells lining your small intestine will most likely remember how to make lactase again after a while.

Second lactose intolerance question today! Welcome to the wonderful world of lactose intolerance.

It is extremely common to have "sudden onset" of lactose intolerance, even if you've had dairy products your entire life. For me it happened just like you've described -- seemingly overnight. I was 26 when it started, personally.

You should find your happy-spot with dairy. Understand that it may be zero dairy. For me, I can use ghee and butter, but most everything else causes an intolerable reaction. A touch of Parmesan is fine, but if I have it two days in a row, I'm asking for trouble. Mozzarella is a death sentence ... or at least a painful night in. :-\ If you are really craving dairy, consider goat's milk and cheese, which will have a lower level of lactose, and a higher level of lactase.

Honestly, I find it pretty easy to just not eat milk and cheese. However, you may want to invest in a product like Lactaid if you ever introduce dairy into your system again.

Good luck!

Hi Stefanie, I live in Melbourne and I have found raw milk at my local farmers market. It's not cheap, about $7 a litre but raw dairy can be found in Australia if you search around. Also Thomas Dux stores sell cultured butter and some other 'better' dairy products. Personally I could not live without dairy, it might not be strictly paleo but I can't let it go.

Matthew explained above what caused it. To get the ability to have dairy again, don't do yogurt.

Do home-made lactose-free GOAT kefir (preferably from raw goat milk, if you can trust the farm, since raw milk has additional dairy-breaking enzymes). Kefir is 5x-10x more potent than yogurt in every respect. Your kefir has to be home-made (bottled kefir is essentially runny yogurt-type because of regulations), and you will have to ferment it for 36 hours, so most lactose gets eaten away by the bacteria & yeasts. And you need to go goat instead of cow, because goat's casein is more tolerable (human-compatible). In the beginning, only have 1/4 cup of kefir, and increase the dosage to 1 cup daily as the grains grow in a month's time. Kefir's yeasts will push your body to create the needed enzymes for digesting the rest of the dairy.

There are many guides on how to do kefir online. It's really easy and it requires no special equipment. You just need to buy the kefir grains (I bought mine on amazon), have a plastic spoon and a plastic strainer (don't let the grains touch metal, and never touch them yourself), and 1-2 glass containers. That's all.

I'm not 100% sure about it being intolerance to lactose necessarily, but in my case I've noticed a new sensitivity to dairy as well. No problems with heavy cream and butter of course, though I also seem to do okay with goat yogurt and several different hard cheeses I've tried.

However...I had some Sargento shredded mozzarella awhile back and it really did mess me up. Lots of bloating and abdominal pain and moderate diarrhea for hours. Same thing seems to happen with regular milk, though the few times I've had it were in small capacity so it wasn't as noticeable. I've tried goat's milk and seem to do okay with it, but it's pricier and I'm at the point now where I just drink a small amount of heavy cream straight or have it with blueberries or the occasional 1/2 cup of rice cereal.

Since I've been sticking with full-fat everything and the aged cheeses, my issues with it seem to be minimal. Only other thing I'll mention is that it seemed like a cheese or two that I tried at some point may have been what caused a few minor acne breakouts (weird big pimples on my arm out of nowhere!?), but I'm still experimenting. So far I've found a couple that I really like, especially the goat gouda.

So I look for raw milk cheeses and avoid cow's milk anything, and stick with butter and cream.

Same thing here. Not sure what causes it, but for me, once I looked back and really thought about it, I realised that there were minor symptoms showing up in the recent past that I guess I wasn't noticing (bloating and gas mostly). Plus I never liked plain milk or cream, just hot chocolate milk, chocolate ice cream, lots of cheese and occasional sugary yoghurt. So I think I've always displayed a meek instinctual aversion. Within a week of paleo, it was like my body 're-calibrated' and was able to respond with full force reactions to any dairy I consumed. So I may have already had an intolerance, my body just was unable to communicate this to me effectively cos it was not operating at its best. That's my theory anyway!

I am still testing the waters so to speak, I'm going to try goat's cheese soon, and I wish I could try raw dairy-anything but it's impossible to find here (in Australia). Luckily I am having some success with using coconut milk as a replacement. But sometimes I would just love some cheeeeeeeese.

Once I began drinking goat milk, I cannot tolerate cow milk anymore, let alone store bought. I am okay with butter though.

Same thing happened to me! I cut out dairy for 30 days when I began paleo then had some cheese one night and spent the next day running to the toilet! I was very surprised as well having eaten dairy my whole life. I am now keeping small amounts of dairy in my diet (as in I don't go out of my way to eat it but have some cheese, butter now and then). Basically because I am off to Paris later in the year and I want to EAT CHEESE on that holiday big time!!

If only we could get raw dairy in Australia!

It's not always a "you became intolerant", sometimes we are intolerant, but never noticed the symptoms. That is why cutting it out and putting back in tells you so much.

So I was searching for answers to my problem when I found this thread. Rather than create a new one -- since this one is already here! -- I'll contribute.

JUST today, in the morning I started having terrible smelling farts. No stomach upset or anything...Just, yeah. Last night I grazed lightly, I didn't have much in the way of food -- had some coconut shrimp & cocktail sauce and that doesn't bother me. I also had a few spoonfuls of the least yucky ingredient ice cream I could find. If I "cheat" on the diet I usually do it on the night before work, because this day of work sucks (18+ hours).

This morning I made myself a smoothie with ripe bananas, strawberries, blueberries, coconut milk, kombucha, and whey protein isolate. Later in the morning I had pastured eggs with homemade chili paste & chicken breast. Then I had for lunch, chicken broccoli & a salad. The farts started going away as the day went on, and then I had some food for dinner, and I'm having the farts, again. I had a sweet potato with lots of butter, some chicken breast, and broccoli.

I'm going to guess it is the dairy...But I can't figure out if it was the ice cream (I hadn't had any in months), the whey protein isolate, or the butter :( I guess I'll have to experiment! I've had the whey protein isolate before, just not the entire recommended "scoop" before in a smoothie.