Why do FODMAP lists contradict each other?

Updated May 29, 2024.

We all had the same frustrations in the early days of the diet.

Digging around and cross-check different fodmap lists, you soon start to realize that many of them contradict each other. It can be hard to know which list to trust.

What’s the reason for this?

Several reasons:

• Many aren’t precise enough, especially those that list just the ingredients without specifying any weight. Sure, there aren’t any restrictions on foods like potatoes or carrots. But for many foods, you have to consider quantities. It’s impossible to generalize by simply saying that pineapple is acceptable or beetroot is to be avoided. What’s more important is to avoid them over certain amounts: two slices are the limit on beets, but you can eat one cup of pineapple. Details matter.
• Some of them are downright mistaken. The FODMAP diet is a highly specialized subject that requires a certain expertise. I try to stay away from “listicles” written by the popular press or women’s magazines. These pieces tend not to explain the subtleties of the diet and instead just want to capitalize on what they perceive to be the latest food trend. 

But the most common reason is that recommendations have evolved!

Recommendations are evolving

It’s important to understand how the FODMAPs level of different foods is determined.

Monash University, which developed the FODMAP diet, refined its recommendations by conducting extensive tests of a wide range of foods to measure their FODMAP content. They made two important findings:

• Some foods did not have the same FODMAP levels depending on which part of the fruit or vegetable was tested. A broccoli head, for example, is very different from the branch. The green part of the leek is low in FODMAPs while the white part is high. The examples go on and on.
• The level of FODMAPs increases with ripening. The best known example is the banana, which has been retested and found to be much higher in FODMAPs when ripe than when it is greener.

Where to find reliable information?

Because the research is constantly evolving, I suggest you avoid any FODMAP list older than one year. Don’t consult books that have not been updated. Also exclude any list that does not specify weight or that only refers to some foods in their entirety, rather than breaking down into parts (for example with broccoli, the head and the stem.) 

Monash University in Australia has conducted the most extensive research on FODMAPs. Any person compiling a list is probably relying directly or indirectly on their work.

Recent books on the FODMAP diet are generally a good resource, too.

Online, try to find lists created by dietitians and experts in FODMAPs or my database of foods, Fodmapedia.