The 3 phases of the low FODMAP diet

Who is it for?

Monash describes the FODMAP diet as a 3 step diet to help manage symptoms of medically diagnosed IBS. It has two aims:

1. find out which foods and FODMAPs you tolerate and which trigger symptoms
2. find out whether your IBS is sensitive to FODMAPs at all

Monash says around three in four people with IBS improve on the diet, and about one in four don’t. If you’re in the second group, that’s useful to know too.

If you haven’t been diagnosed, start with a GP. Symptoms like weight loss or bleeding need checking first (see the red flags box below).

Step 1: swap (2 to 6 weeks)

In Step 1, you swap high FODMAP foods for low FODMAP alternatives. Monash’s own example: if you normally have wheat-based toast with honey, you could swap to sourdough spelt toast with jam.

A few more swaps from Monash’s sample list:

Instead of	Try
Cow’s milk, yoghurt	Lactose-free milk, almond milk
Apples, pears, mango	Kiwifruit, orange, pineapple, blueberries
Garlic, onion, mushrooms	Carrot, cucumber, green beans, bok choy
Cashews, pistachios	Macadamias, peanuts
Honey	Maple syrup, table sugar

Monash says to stay on Step 1 for 2 to 6 weeks. If things improve, move on. If they don’t, your symptoms may not be FODMAP-sensitive, and other options like stress reduction, gut-directed hypnotherapy or medicines are worth discussing.

Our FODMAP foods guide has more on where each FODMAP group shows up.

Step 2: test (the challenges)

You stay on your Step 1 diet, but test FODMAP groups one by one. Monash describes a challenge as eating a food rich in only one FODMAP group daily for 3 days and watching how you feel. Milk is a classic lactose challenge, because it’s high in lactose and has no other FODMAPs.

After each 3-day challenge, you record how well you tolerated it. Monash mentions a paper diary or the diary in its own app. Our FODMAP reintroduction log shows a simple way to lay it out.

Step 3: personalize

Step 3 is about relaxing restrictions as much as you can. Foods you tolerated come back. Poorly tolerated foods are limited, but only to the level that gives you relief. Monash also suggests re-testing poorly tolerated foods over time, because tolerance can change.

Why a dietitian matters

Monash says a FODMAP diet should be followed with a dietitian who has specialty skills in IBS. Cutting lots of foods without support can leave gaps. The NHS also says to see a GP if you need to avoid lots of different foods to control IBS symptoms; they may refer you to a dietitian.

Where PoopAI fits

PoopAI doesn’t have a FODMAP database, and it isn’t a replacement for the Monash app or your dietitian. What it does well is the logging around them: snap or type each meal, add trigger tags like FODMAPs, dairy or gluten, and log each poop’s Bristol type. The weekly report shows how your poops looked during each step.

Step 2, lactose challenge
Mon 08:00  Breakfast (text): 1 cup milk, rice cereal  tags: dairy, FODMAPs
Tue 07:45  Poop: type 4
Tue 08:00  Breakfast (text): 1 cup milk, rice cereal  tags: dairy, FODMAPs
Wed 07:30  Poop: type 6

Wrap-up

Swap, test, personalize. The low FODMAP diet is a short experiment, not a life sentence, and the goal is the widest diet that keeps you comfortable. Bring a dietitian along if you can.