What’s the timing of lactose intolerance?

November 23, 2024 10:55 AM

If you are lactose intolerant, and eat lactose, how long afterwards do your symptoms appear and how long do they last?

I suspect I might be lactose intolerant so I’m testing that by giving up dairy. I am new to this dietary restriction, so probably some dairy is sneaking through. But I don’t know how to interpret my symptoms relative to the food. Can dairy at noon on Monday still be giving me symptoms 24 hours later? 48 hours later?
Yes I’m seeing a GI doc but not for another month, so I have time for experimentation before the appointment.

posted by Vatnesine to Health & Fitness (12 answers total)

I would say that I have a limited tolerance rather than complete intolerance. Very subjectively, it seems like with larger doses, the worst of it comes and goes more quickly, perhaps within a few hours. With lower doses, I might have minor symptoms lingering for 12-24 hours.
posted by aincandenza at 11:15 AM on November 23

Usually for me it is within an hour or two, and lasts for a couple hours. It will be roughly the same as a 'food coma' and a little longer. So perhaps 1-3 or 1-4 hours is when I would be feeling gross.

The test of lactose intolerance is, if you eat a few Lactaid pills while you eat your dairy, and the extra gross feelings go away, it's the lactose. (Lactaid will not prevent you from feeling, say, full of sugar and fat when you eat an entire pint of ice cream. But it will prevent the extra lactose grossness.)
posted by panhopticon at 11:28 AM on November 23 [3 favorites]

For me, It took me way too many years of my life to make the connection.

But if I have a full glass of a real milk milkshake (made in a blender, with regular milk, regular ice-cream, etc.), I start getting a tightness of my throat that makes me feel like I'm getting asthma, within about 30 minutes (and I've been tested repeatedly, I don't have asthma nor the associated conditions).

And then symptoms of lethargy, an upset stomach, etc. typically last 3 - 5 days following.

Apart from the throat tightening, I have some similar post reactions to most eggs, and some meat / flesh products, for the 3-5 days of lethargy and an upset digestive system. But your experience of course is likely to vary.
posted by many-things at 11:34 AM on November 23

Pretty much the same for me as panhopticon. Symptom onset starts within an hour and symptoms (cramps, bloating, gas) last for up to four hours until everything, uh, passes. I can have cream or half & half in my coffee without taking any lactase pills, but if I want ice cream or a milkshake I need the pills.
posted by fedward at 11:59 AM on November 23 [1 favorite]

I can do things like eat a bit of ice cream, splash of skim milk in coffee, butter my toast literally every morning for 30 years no problem. Half a slice of pizza or someone sneaks cream cheese into chicken salad or something and I'm donzo. Bloaty pain and nauseated within 2 hours. Severe cramping (I've twice passed out from pain right off the toilet) for a few hours followed by a full 24-48 hours of constant toilet visits of varying urgency and.... Consistency.

If I take lactaid I don't get the nausea, the gas isn't too bad, no cramps, and only 6-10 hours of far less urgent far less issue laden but still... More than normal level visits to the toilet.

Which is why when people say "don't you miss cheese??" I say "no, that stuff has been like poison to me for 35 years..." You kinda lose the desire ya know?

So I'd wholeheartedly agree with the lactaid test. Take 2 extra strength and eat a normal amount of whatever cheese thing or milk thing you normally would. You'll know very quickly without having to spend months doing an elimination diet.

Couple bonus facts.
Active culture yogurt (I like activia) helps calm the nausea, and poopies. It does not trigger me for dairy. It actually tickles the ice cream thing for me so it's a nice treat.

Again, some small amounts of dairy (restaurants that cook food with butter etc) don't bother me enough to note. So I usually order or cook around cream and cheese things (so highly suspicious of anything creamy even if it had no cream - looking at you rissott which SHOULD NOT HAVE FRIGGING CREAM IN IT!!!!)

Fairlife milk is great. Tastes same, cooks the same says my pro chef wife. Makes ice cream at home the same. Custards the same etc etc.

A LOT of people are lactose intolerant and don't know it. That's actually normal. We're built to ween and not go back to the milk.

I will also say I know a lot of people who get farty and make a big deal about dairy. They should be wary but it's not the same level. If I get sandbagged it's assuredly coming out both ends sometimes and truly a lousy 36 hours.


Good luck!!
posted by chasles at 12:27 PM on November 23 [3 favorites]

I've had it last up to 24 hours but it goes away almost instantly if I take pepto bismol.
posted by stinker at 12:27 PM on November 23 [1 favorite]

it goes away almost instantly if I take pepto bismol

Interesting. I've never had any real luck with stomach remedies.... Amazing how differently bodies work.
posted by chasles at 12:31 PM on November 23

Response by poster: Lactaid! that would be an easier test, wouldn't it. I'm off to Walgreens, guys. Thanks!
posted by Vatnesine at 12:52 PM on November 23 [4 favorites]

If I eat any dairy, including hard cheeses and yogurt, I generally have gas within 30 minutes. When I am completely off dairy, making my own food, my gut settles down and I tolerate occasional small amounts of dairy reasonably well. There is a lot of hidden dairy in prepared foods.

In addition to gas, I seem to get generalized inflammation form dairy. This is anecdata, but it's mostly easier to not eat dairy at all and feel generally better. Lactaid seems useless.
posted by theora55 at 7:26 PM on November 23

FYI, there are multiple things in dairy that people can be 'reacting' too, not just lactose.

Lactose is a complex sugar found in most mammalian milk, including human breastmilk. Lactose is broken up into simpler, digestable sugars, by the enzyme lactase. If you don't produce your own, then you can take pills, like lactaid above. Many humans stop producing lactase at some point past infancy, but milk drinking cultures have developed genes to *keep* being able to digest it past childhood. Unfortunately sometimes those genes just make it easier to persist in digesting, but it's not a failsafe, and all it takes is going lactose free for awhile, or to get a stomach bug, for the body to decide that 'you should be weaned now'.

https://www.dairy.com.au/dairy-matters/you-ask-we-answer/what-is-the-lactose-content-of-different-dairy-products
Fresh milk contains the most lactose, about 15g per cup, while hard, mature yellow cheeses contain much less lactose.

If you react more to fresh milk, than to yellow cheeses, you probably just have standard lactose intolerance.


If however, you react more to yellow cheese than to fresh milk, then congratulations, you probably have something else going on, such as an allergy probably to a protein in dairy (casein, whey, etc etc etc).
For example, if a baby is fine with breastmilk but not cows milk, it's not a problem with lactose, but with at least one protein in cows milk, which just comes under the group heading "cows milk protein allergy" or CMPA. We're not talking about babies here, but it's a common misconception, and people will try lactose free milk etc, when that's not the problem, it's a different part of the milk that's causing issues.

My baby with CMPA has notable symptoms for about 3 days, and is a bit irregular for a few weeks after having dairy.
posted by Elysum at 12:32 AM on November 24 [2 favorites]

My understanding is, if you are going to try the Lactaid pills the timing is important. My relative with lactose intolerance takes the Lactaid with some non-dairy food at least 30 minutes before eating any dairy. He says the Lactaid helps but is not foolproof. From Wikipedia: “It functions well only in high-acid environments, such as that found in the human gut due to the addition of gastric juices from the stomach. Unfortunately, too much acid can denature it, so it should not be taken on an empty stomach. Also, the enzyme is ineffective if it does not reach the small intestine by the time the problematic food does.”
posted by LiverOdor at 9:42 PM on November 24

Dr Advicepig and I are both lactose intolerant, with painful bloating and gas coming on within half an hour, then urgent diarrhea. It usually doesn't linger after that.

One thing she often tells people is that you can't over do Lactaid, so if you need 6 pills for a Neapolitan pizza, sure, do that. So I guess I'm telling you the best Lactaid test is to take 6 and drink a couple ounces of milk.
posted by advicepig at 8:40 AM on November 26