The Overlaps: Low Histamine vs Low FODMAP
If a healthcare professional has suggested you follow both a low histamine and a low FODMAP diet, your first reaction might be a mix of confusion and panic. The food lists can seem contradictory, and the thought of restricting your diet so heavily is understandably daunting.
This guide is not here to give you another restrictive food list, or offer any conflicting advice. Instead, we will explain the science behind each diet, show you where they overlap, and provide a framework for approaching this challenge. Most importantly, we will explain why navigating this journey with a qualified professional is not just recommended, it is essential for your long-term health and wellbeing.
What is a Low Histamine Diet? A Quick Recap
Before we can compare the two diets, let’s quickly revisit the purpose of a low histamine diet. As we explore in our Beginner's Guide to Histamine Intolerance, this approach is for people whose bodies struggle to break down histamine from food and drink.
Think of it using the Histamine Bucket analogy. Your body has a certain capacity for histamine. When your bucket overflows, you might experience reactions. A low histamine diet is a short-term diagnostic tool designed to lower the amount of histamine you are consuming (external histamine), giving your body a break and helping you and your dietitian identify your personal triggers.
The core issue is a problem with degradation: there is too much histamine and not enough of the enzyme, diamine oxidase (DAO), to process it.
What is a Low FODMAP Diet?
The low FODMAP diet is a tool used primarily for managing Irritable Bowel Syndrome (IBS). FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. In simple terms, these are types of short-chain carbohydrates that are not well absorbed in the small intestine.
When these undigested carbohydrates reach the large intestine, two things happen:
- They draw extra water into the bowel
- The bacteria that live in your gut rapidly ferment them, producing gas
In people with a sensitive gut, this combination of extra water and gas can lead to symptoms like bloating, pain, wind, and changes in bowel habits. A low FODMAP diet is a temporary elimination diet, followed by a structured reintroduction phase, to identify which specific FODMAPs are causing a problem. It must always be done under the supervision of a registered dietitian.
The core issue here is a problem with malabsorption and fermentation, not with the food itself.
The Key Difference: A Faulty Drain vs. A Rowdy Party
The easiest way to understand the difference is with an analogy.
- Histamine Intolerance is like an overflowing bucket. The histamine (the water) comes in, but the drain (your DAO enzyme) cannot clear it away fast enough. The bucket overflows which causes the problem. The issue was caused by the high histamine food that you've eaten
- FODMAP sensitivity is like a rowdy party. The FODMAPs (the uninvited guests) arrive in your gut undigested. The gut bacteria (the residents) throw a huge, noisy party with them, creating gas and chaos that upsets the whole house (your digestive system). The problem is the disruptive party, not the guests themselves
One is about failing to break down a specific chemical, while the other is about the downstream effects of poor carbohydrate absorption. This is why a food can be perfectly fine for one condition and problematic for the other.
Where the Diets Overlap: The Venn Diagram
Because the two diets work on completely different mechanisms, the food lists can be confusing. Some foods are fine on one diet but not the other, some are fine on both, and some are best avoided on both during an elimination phase.
- Low Histamine, High FODMAP Foods: These foods are low in histamine but contain carbohydrates that are easily fermented. Examples include onions, garlic, cauliflower, apples, pears, and honey
- High Histamine, Low FODMAP Foods: These foods are low in fermentable carbs but high in histamine. Examples include aged cheeses, cured meats (like salami), spinach, tomatoes, and fermented products like sauerkraut
- Low in Both Histamine and FODMAPs: This is the 'safest' column when you are starting out under supervision. Examples include fresh chicken, white fish, carrots, cucumber, potatoes, rice, and blueberries (in small portions)
- High in Both Histamine and FODMAPs: Some foods, like avocado and aubergine, can be high in both, making them likely candidates for temporary removal
This is not an exhaustive list, but a way to understand the categories your dietitian will be working with.
Why Might Someone Be Advised to Follow Both?
It is becoming more recognised that there is a significant link between gut health and histamine intolerance. Conditions like Small Intestinal Bacterial Overgrowth (SIBO) can be a root cause of both issues. In SIBO, an overgrowth of bacteria in the small intestine can lead to:
- Increased fermentation of FODMAPs, causing IBS-like symptoms
- Damage to the gut lining, which is where the DAO enzyme is produced
- Certain types of bacteria can even produce histamine themselves, adding to your overall bucket
In this scenario, the two conditions are not separate problems but are interconnected through an underlying issue in the gut. A practitioner might recommend a combined approach to calm the entire system down before working to address the root cause.
A Practical Approach: Why You Must Not Do This Alone
Attempting to follow a combined low histamine and low FODMAP diet without professional guidance is not only incredibly difficult but can also be harmful.
The Dangers of Over-Restriction: Combining these diets without a clear plan can lead to significant nutritional deficiencies and foster a negative, fearful relationship with food. This is the opposite of the intended goal.
The Role of a Dietitian is Non-Negotiable: A registered dietitian specialising in gut health and food intolerances is your most important ally. They can:
- Ensure your baseline diet is nutritionally complete
- Help you structure the process, often by tackling one diet at a time to avoid getting overwhelming
- Guide you through the reintroduction phase systematically to pinpoint your unique triggers
- Work with you to create the broadest, most varied, and most enjoyable diet possible for the long term
Remember, these diets are temporary diagnostic tools, not lifelong sentences. The goal is always to eat as freely as possible. You can find a list of dietitians who specialise in histamine intolerance on our About page.
Navigating this path is a challenge, but you do not have to do it alone. With the right professional support, you can move from a place of confusion and restriction to one of clarity and empowerment.
This article is for informational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional for advice specific to your situation.