Let's discuss some considerations around how long to stay on the elimination phase of a FODMAP elimination diet. The short answer is, don't stay on it any longer than you have to!
- An elimination diet is a learning diet, not meant to be a permanent restricted diet.
- The time period should be long enough for it to be apparent whether or not the low FODMAP approach will help the individual person.
- A low FODMAP diet, no matter what the duration, is not going to cure IBS, only successfully manage symptoms. So there is no particular benefit of staying on the restricted phase of the diet for any longer than necessary.
- As it is, even during the challenge process the underlying diet is selected from the foods that are suitable for the elimination phase, so it does last longer than it might seem at first.
- In order to get a balanced diet with a variety of nutrients from food, it is important to liberalize the diet as tolerated, using either food challenges as described in IBS--Free at Last! or a more cautious approach.
- Let's face it, lots of people have a limited attention span for dietary change. If we stretch the process out too long, we may lose focus, and could leave valuable information about how food affects us on the table.
- It is true that several of the clinical studies on low FODMAP diets happen to have been conducted with longish elimination phases of 6-8 weeks--that's where those numbers you read about come from, but I am not aware it has been shown that shorter elimination periods aren't effective.
- In fact, the osmotic effects of FODMAPs (pulling fluid into the gut) literally cannot take place after they have passed out of your body. "They must be present to win." So, for example, if a lactose intolerant person eats ice cream on Sunday night, has a bout or two of watery diarrhea on Monday and passes all the lactose remnants by Monday night, that lactose is gone. It cannot still be causing osmotic effects on Thursday, or 6 to 8 weeks later, for that matter.
- On the other hand, it is possible that people who tend toward constipation and have very slow transit times might still have some lactose on board for days. These may be people for whom the fermentability of FODMAPs is a bigger problem than the osmotic activity. At first it would seem that once the excess gas produced by fermentation has been passed, this effect of FODMAPs would also cease, and I have worked with many constipated patients who did feel much better withing a day or two.
- But, because FODMAPs basically feed the biomass (collection of microbes) in the gut, there could certainly be improvements that could build up over time for some people, as the biomass evolves.
- If you've been on the diet for weeks and weeks and you just aren't feeling better, staying on it longer, sadly, is not going to help. Time to try something else.
- If you are feeling better, its time to move on, using either food challenges or the more cautious approach described in IBS--Free at Last!
- If you are working with a dietitian, he or she may be using FODMAPs in a slightly different way, with different timelines tailored to your personal medical situation. That's a good thing!
Bottom line, two to three weeks, is plenty of time in most cases to know if the FODMAP approach has worked. Re-read IBS--Free at Last! for help planning the challenge phase, and please consult a registered dietitian if you need individualized advice.