Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. Histamine is a naturally occurring chemical compound, known as a biogenic amine, that plays a broad role in the body, including regulating the immune response, acting as a neurotransmitter, and stimulating stomach acid secretion. The relationship between probiotic supplements and the body’s histamine levels is complex because certain bacteria can either produce or help degrade this compound. For individuals with sensitivity, the composition of a probiotic blend directly influences the overall amount of histamine in the digestive system, making the metabolic activity of specific bacterial strains the key factor.
Understanding Histamine Intolerance
Histamine intolerance is a condition that arises from a disequilibrium between the accumulation of histamine in the body and the capacity to break it down. It is not a true allergy but a functional disorder where the body’s clearance system is overwhelmed.
The primary enzyme responsible for breaking down extracellular histamine is Diamine Oxidase (DAO), mainly produced in the small intestine. A second enzyme, Histamine N-methyltransferase (HNMT), breaks down histamine inside cells. When DAO activity is compromised due to factors like genetic issues or intestinal damage, histamine accumulates in the bloodstream. This excess can trigger a wide range of symptoms, including headaches, flushing, digestive upset, and skin reactions.
The Bacterial Role: Production Versus Degradation
Bacteria in the gut and in probiotic supplements interact with histamine through two opposing biochemical processes. The first is histamine production, which occurs when certain bacteria possess the histidine decarboxylase (HDC) enzyme. This enzyme converts the amino acid L-histidine, abundant in protein-rich foods, directly into histamine, potentially increasing the histamine load in the digestive tract.
Conversely, other bacteria contribute to histamine management either directly or indirectly. Some strains possess enzymes capable of degrading histamine and other biogenic amines. Other beneficial bacteria indirectly support the host’s histamine-clearing mechanisms by strengthening the gut barrier or modulating the immune system. The overall effect of a probiotic depends on which of these two enzymatic processes—production or degradation—dominates within the specific blend.
Identifying Specific Probiotic Strains
The effect of a probiotic is highly strain-specific, meaning that not all bacteria within the same species will have the same impact on histamine levels. Strains are generally categorized based on their metabolic activity regarding histamine.
High-Histamine Producers
Certain strains are recognized as high-histamine producers because they express the histidine decarboxylase gene. These strains include Lactobacillus casei, Lactobacillus bulgaricus, Streptococcus thermophilus, and Lactobacillus delbrueckii. Some strains of Lactobacillus reuteri have also been observed to raise histamine levels.
Neutral or Low-Histamine Strains
In contrast, other strains are considered generally neutral or low-histamine producers, such as many species within the genus Bifidobacterium. This neutral group includes strains like Bifidobacterium infantis, Bifidobacterium bifidum, and Bifidobacterium breve.
Histamine-Regulating Strains
A third category of strains demonstrates potential histamine-degrading or regulating properties. These strains include Bifidobacterium longum, which assists in histamine degradation. Other beneficial strains include Lactobacillus rhamnosus (especially the GG strain), which may help stabilize mast cells and support gut barrier function, and Lactobacillus plantarum, known to break down biogenic amines. The yeast Saccharomyces boulardii is also often well-tolerated, as it has been shown to increase the activity of the host’s DAO enzyme. Navigating these distinctions requires careful attention to the full scientific name of the strain, which includes the species and the alphanumeric designation.
Navigating Probiotic Selection
For individuals concerned about histamine-related symptoms, the most practical step is to scrutinize the product label for the full strain designation, such as Lactobacillus rhamnosus GG. A product that simply lists “Lactobacillus” is insufficient and carries a risk of including a histamine-producing strain.
Consumers should also be mindful of other ingredients, particularly prebiotics like fructooligosaccharides (FOS) or inulin. While prebiotics are beneficial for many, they can feed existing histamine-producing bacteria already present in the gut, potentially exacerbating symptoms. Starting with a very low dose of a new probiotic and gradually increasing it allows the body to adjust and helps determine tolerance. Consulting with a healthcare professional knowledgeable about histamine intolerance is recommended to select a targeted strain and minimize the risk of adverse reactions.