Histamine and IBS

You might be more familiar with histamine as a cause of allergic symptoms like a runny nose, itchy eyes and itchy skin, but histamine can also be associated with IBS symptoms.

What is histamine?

Histamine is a natural chemical made by your body that plays many important roles; it’s definitely not a ‘bad’ thing to have. In fact, we need it as part of the immune system histamine to protect us against infections, supports digestion. It helps by releasing stomach acid, and acts as a messenger in the brain and immune system.

Histamine is also released by immune cells during allergic reactions, which is why it can cause itching, swelling, or redness. In addition to being produced in the body, histamine is present in some foods, especially those that are aged, fermented, or not very fresh (e.g. your last night dinner leftovers).

When histamine gets out of balance it can cause issues all around the body, because it’s essential in so many processes.

Can histamine cause digestive issues?

Histamine has three main actions in the digestive system

• affecting how fast the gut moves (gastric motility)
• production of stomach acid
• changing the amount of mucus in the intestines.

If you have high histamine levels possible digestive symptoms could include abdominal cramps, diarrhoea, excessive gas and heartburn.

• Overproduction of histamine by mast cells in the gut may be responsible for diarrhoea.
• Stomach pains may be linked to histamine release in the colon

Other non-digestive signs of possible high histamine levels are congestion, itchy, watery eyes, headaches, anxiety, brain fog, and urticaria or eczema. It’s also been linked to symptoms of long Covid

Something I frequently see with histamine sensitive clients is insomnia, because histamine has an excitatory effect, meaning it’s hard to switch off your brain, leaving you feeling wired at night.

Does SIBO increase histamine intolerance?

If you have an overgrowth of bacteria in the small intestine (SIBO) you may have higher levels of histamine for two reasons:

1. Increased histamine absorption due to lack of the enzymes to break down histamine. If you have SIBO you might make less of these enzymes, called DAO or HNMT. In healthy people, histamine from food intake is cleared in two ways.

Firstly, through the enzyme diamine oxidase (DAO). DAO is found mostly in the small intestine and acts between the cells to keep histamine from moving to other parts of the body through blood flow. Secondly, the enzyme histamine-N-methyltransferase (HMNT) works within cells to regulate histamine through the body.

Excessive microbes or other damage the lining of the small intestine might affect DAO production. The other reason for increased histamine absorption is that some bacteria actually create more histamine from food that we eat. Particular bacteria associated with higher histamine production are

• Hafnia alvia
• Klebsiella pneumonia
• Morganella morganii
• Citrobacter freundii
• E-coli

These microbes may be found in people who have SIBO.

2. Increased histamine release – People with IBS may have an increased number of mast cells in the digestive tract. And they could be more active which would cause more digestive issues.

Mast cells contain histamine, and they can also activate and sensitize nerves in the gut. Mast cells may also modulate the integrity of the epithelial barrier (sometimes called leaky gut).

What is a low histamine diet for IBS?

It’s very hard to find an accurate source of histamine levels in our food, so it’s difficult to know how it will impact your IBS. However we do know that the things affecting histamine levels in your food include:

• the age of food, especially proteins (leftovers tend to have more histamine)
• length of fermentation process (the longer it’s fermented the more histamine)
• cooking method (frying and grilling increases histamine levels whereas boiling can reduce it in some cases. In this study the boiling of most meats (e.g. in a stew) decreased the histamine level.)

Some foods contain histamine, whereas some foods cause us to be less effective in getting rid of it.

• Some food contains histamine such as aged cheese, tinned meat & fish, deli meats.
• Histamines are higher in fermented foods such as yoghurt , wine or sauerkraut.
• Small amounts of naturally occurring histamine is found in tomatoes, spinach, aubergine and avocado. However, data on histamine levels is patchy and there is a real lack of evidence that shows vegetables are high in histamine. 
• Caffeine, chocolate, and alcohol metabolites can inhibit the activity of DAO, the enzyme which breaks down histamine, leaving you with higher levels.

Histamine liberators in an IBS diet

Some foods don’t contain histamine but it’s thought they may cause our bodies to release histamine. These include:

• Kiwi (often recommended for IBS- constipation)
• citrus (oranges, lemons, grapefruit),
• raspberries,
• alcohol

Can you eat eggs on a low histamine diet for IBS?

There is no evidence that eggs have high histamine levels or that cooking them changes the histamine levels. Some people may get a reaction to eggs, it could be due to the proteins in the egg white, or yolk, but it’s unlikely to be the histamine.

Does a low histamine diet help in IBS?

If you haven’t yet already tried the low FODMAP diet, you might want to start there. The low FODMAP diet has been shown to lower histamine levels by up to 8 times. (I’ve got lots of blog articles about the FODMAP diet, the Beginners Guide to the low FODMAP diet is a good place to start.)

There is no harm in trying a low histamine diet for a few weeks to notice if your symptoms improve. Some people find their symptoms are worse when eating a higher histamine diet. You could also try taking an antihistamine to see if symptoms improve (with advice from your doctor).

This is quite a restrictive diet, and it’s important to get to the reason why histamine levels are high in the first place. For example, do you have bacteria which are reducing your clearance enzymes (DAO) or are you creating more histamine from the food?

If you want to test a low histamine diet a try my suggested process for reducing histamines in your diet is

1. Remove high histamine foods for 2-3 weeks, as well as histamine liberating foods
2. If symptoms have improved move to phase 2 which is to bring back the histamine liberating foods slowly.
3. If this goes well you can trial higher histamine foods. You aren’t judging each food individually, but more looking at the overall intake of histamine. If you get a reaction stop the trial, wait for the symptoms to clear before trying another set of foods.

If you don’t feel any better after the low histamine diet, it’s time to get back to your doctor again and ask for more investigations.

If your symptoms improved during the four-week restriction, then you can now start to bring histamine foods back in your diet. Histamine reintroduction is based on testing your ‘bucket’ and how much you can tolerate over time (unlike the low FODMAP reintroduction where you’re testing individual fermentable foods per meal).

You can start off with a single higher histamine food if that helps you gain confidence, but it’s the cumulative effect of a higher histamine load you need to test.

Slowly increasing your consumption of caffeine, meats, fish, and any histamine containing vegetables you’ve avoided.  

What else causes high histamine?

Other than histamine in food, what else could cause histamine to be in excess? Common medication can be a cause of high histamine. Examples include:

• anti sickness (metoclopramide)
• some antiarrhythmic and blood pressure medication
• pain medication (aspirin, NSAIDs)
• antidepressants (amitriptyline, venlafaxine)

Ask your doctor if you suspect your medication is causing histamine symptoms. Don’t stop taking the medication unless a doctor has agreed this for you. 

Other factors which contribute to histamine intolerance:

• Alcohol – Competes with histamine for an enzyme which clears them both, so when you’ve been drinking alcohol there can be too much work for this enzyme to do. Stopping drinking any alcohol might help you to see this connection.
• Caffeine – Coffee might activate cells involved in histamine production.
• Probiotics – Some probiotic strains can produce histamine in the gut from histidine (a common amino acid in protein foods). The strains that could be linked to histamine production include Lactobacillus casei (TISTR 389) and Lactobacillus delbrueckii subsp. bulgaricus (TISTR 895). If you’re taking these probiotics, you could be adding to the histamine load in your digestion.

Talk to your doctor about whether you can test your histamine reaction by taking an antihistamine medication. Antihistamines prevent the histamine from entering the cells. Taking them in the short term may help you see if histamine really is causing the digestive issues.

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