FODMAP and Brain Fog

If you feel you can’t think, remember things, process information, or speak clearly after having a meal, you may be suffering from brain fog.

The brain exerts a great degree of control over the gut but it turns out the reverse might also be true. Your gut health can have a great impact on your cognitive abilities and many gut conditions — like celiac disease — have been linked with cognitive dysfunction.

So let’s take a look at how brain fog develops and what foods (or conditions) can contribute to it.

How does brain fog develop?

The mechanism behind FODMAP (or diet-related) brain fog isn’t exactly clear but we do have some explanations.

What’s clear is that FODMAP brain fog is a real phenomenon. This review of 13 clinical trials showed that eliminating FODMAPs and gluten from diet can lead to an improvement in not only brain fog, but also depression, anxiety, schizophrenia, and autism spectrum disorder.

Some sources suggest that blocking stomach acid and taking probiotics is a combination that can lead to brain fog.

Acid production in the stomach can be blocked using drugs like H2-receptor blockers and proton pump inhibitors. These drugs are often prescribed to patients suffering from acid reflux or stomach ulcers.

Apart from helping in food digestion, stomach acid also keeps the small intestine relatively empty of bacteria. When acid production is blocked in the stomach, the small intestine can become colonized by bacteria.

Bacterial colonization is worsened if patients are consuming probiotics like lactobacillus. There are a wide range of uses for lactobacillus. People take it to reduce stomach pain, eczema, constipation, diarrhea, and hay fever among other uses.

When the small bowel has been colonized by bugs like lactobacillus as a result of acid suppression, the food you consume can be fermented by these bacteria. This results in gas and D-lactic acid production, which can cause bloating and brain fog, respectively.

Lactic acid is produced naturally in the body during strenuous exercise. However, that form of lactic acid is called L-lactic acid and is not as harmful for the body as D-lactic acid.

D-lactic acid interferes with normal energy-producing mechanisms of cells such as glycolysis and oxidative phosphorylation. This reduces energy production and metabolically active cells like brain and heart cells suffer the most.

As energy production in the brain declines, normal functions like neurotransmitter turnover and neuron firing (also known as action potential development) are compromised, which leads to brain fog.

Toxic amounts of D-lactic acid can be produced when people taking a lactobacillus probiotic consume milk as bacteria ferment the milk sugar lactose.

The other explanation has to do with histamine, which is a compound normally present in our bodies. In patients with large amounts of bacteria in the small intestine, consumption of a FODMAP-rich diet can lead to the production of high amounts of histamine as a result of bacterial processing.

Just like D-lactic acid, high levels of histamine may lead to brain fog. This is supported by the fact that eliminating FODMAPs from diet has been shown to improve brain fog symptoms.

What are FODMAPs (and low-FODMAP diet)?

In case you’re not clear about FODMAPs, they are fermentable oligo-, di-, mono-saccharides and polyols.

FODMAPs are basically sugars resistant to digestion. Since they can’t be broken down, they’re fermented by bacteria if there is an overgrowth, leading to the production of excess gas and harmful compounds like lactic acid and histamine.

Some examples of FODMAPs include:

● Lactose — a sugar found in milk and other dairy products
● Fructose — a sugar found in honey and most fruits
● Fructans — found in wheat, barley, and rye
● Polyols — used as sweeteners but also found in some fruits and vegetables
● Galactans

Since eliminating FODMAPs from the diet has been shown to improve brain fog, you can try a low-FODMAP diet if you suspect your brain fog is being caused by FODMAPs. A low-FODMAP diet has demonstrated to be especially beneficial for patients with irritable bowel syndrome (IBS).

It’s unlikely that your brain fog is triggered by all FODMAP-rich foods in the diet. The goal of a low-FODMAP diet is to identify the foods that trigger your symptoms and eliminate only those.

You start by eliminating all FODMAP-containing foods from your diet and wait for your brain fog to get better. You then re-introduce each food one by one to catch the culprit behind your symptoms. This is the food you need to eliminate from your diet permanently.

It’s important that you start a low-FODMAP diet under a doctor’s supervision. In addition to ensuring that you don’t get malnourished, a doctor can evaluate you for other potential causes of brain fog.

What other foods cause the most brain fog?

Apart from FODMAPs, many other foods have been reported to cause brain fog. These include:

● Allergenic foods. These include items like dairy, eggs, peanuts, and wheat, which are common causes of food allergies. Patients with food allergies can experience brain fog.

● Histamine-rich foods. These include vinegar, fermented foods, and aged cheese. People intolerant to histamine-containing foods may experience brain fog.

● Gluten. Gluten is a major component of wheat and can lead to an autoimmune reaction in the gut (called celiac disease). Other patients are simply insensitive to gluten. Whatever the case may be, gluten is associated with a wide range of neurological issues including brain fog. The only cure for celiac disease is a lifelong gluten-free diet.

● Simple or refined carbohydrates. These include sugar and fructose corn syrup. They cause a sharp rise in blood sugar levels followed by a rapid decline. As blood sugar falls, you may experience brain fog.

● Food additives. These include monosodium glutamate and artificial sweeteners like aspartame and sucralose.

To find out which of these is causing your brain fog, maintaining a food diary may be helpful. This is where you write down what you eat and how you feel after it in a diary. After some time, you can review this diary with a doctor and identify foods that are consistently causing your brain fog.

Medically Reviewed by Onikepe Adegbola, MD PhD

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