Can FODMAPs actually cause harm?

FODMAP is an acronym for:
Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols.

We know that FODMAPs can cause gas and other symptoms for those of us with IBS. But does continued intake of FODMAPs actually cause damage for susceptible people?

When bacteria degrade fermentable vegetables, this creates short chain fatty acids (SCFAs) and these are considered to be a good thing, in general. These SCFAs provide nourishment for the good bacteria, help to regulate the immune system  – in particular the regulatory T cells, so SCFAs are natural anti-inflammatories –  and generally help the health of the colon. SCFAs also keep the colon acidic, which keeps pathogens that prefer a more alkaline environment at bay. The process of SCFA production generally occurs in the colon, the large intestine.

But if you have IBS, and for some reason you can’t absorb FODMAPs or other vegetables all that well, there can be an over-abundance of SCFAs, and these might be in the small intestine as well. Can this cause inflammation and actually make you worse off?

Sue Shepherd, the founder of the FODMAP theory, asked this question in one of her studies, mainly relating to FODMAPs in relation to Crohn’s Disease, where she found the SCFAs exacerbated the inflammation causing Crohn’s. She found that the SCFAs from FODMAPs can cause Leaky Gut (intestinal permeability). SCFAs aren’t meant to be in the small intestine to a large degree as there are only supposed to be a few bacteria in the small intestine. (If you do have a lot of bacteria in the small intestine, this is SIBO – Small Intestinal Bacterial Overgrowth.) Most bacteria live in the colon, the large intestine. SCFAs from FODMAPs then, can cause cause apoptosis (cell death) of the epithelial cells lining the small intestine, especially in they are in large enough quantities.

This might be one of those instances where you should follow your gut instinct. Gas which is chronic, constant and non-stop just doesn’t feel healthy. It actually feels like something is wrong. Let alone the fact that it is a horrible way to live.

So SCFAs from well-digested carbohydrates are a good thing – in the colon; an over-abundance of SCFAs in the small intestine from poorly absorbed carbohydrates isn’t.

In his “Fast Tract” site,

Norm Robillard says “It’s important to remember that it only takes 30 grams (just over one ounce) of undigested carbohydrates for your gut bacteria to produce 10 liters of gas.”

That means that you can very easily sabotage your good diet with just one bad food, and undo all that effort and willpower. That one thing might be a small serve of baked beans but it’s enough to give you symptoms for a number of days.

The low FODMAP diet is supposed to be temporary, as high FODMAP vegetables are highly nutritious, for most people who can absorb them. The idea is to “heal the gut” first, although no-one ever says exactly wheat this means. Presumably it means to reduce the bacterial overgrowth so that carbohydrates can be digested normally in the small intestine. Once the bacteria populations have normalised (or you no longer have SIBO) then you can gradually re-introduce FODMAPs.


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