Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host, primarily by supporting the balance of the gut microbiome. Nausea is a common, unpleasant sensation in the stomach that often precedes vomiting and can be a symptom of various underlying conditions, ranging from pregnancy to chronic illness. The gut and the brain communicate constantly, suggesting that an imbalance in gut bacteria might contribute to this digestive distress. Current research is investigating whether the introduction of beneficial bacteria through probiotics can modulate this communication pathway to alleviate the feeling of nausea.
How Probiotics Influence Nausea Signals
The connection between the gut and the brain is often referred to as the gut-brain axis, a bidirectional signaling network that uses neural, hormonal, and immunological pathways. The vagus nerve serves as the primary physical link, allowing the gut microbiome to send direct signals to the brain’s central nervous system, including the vomiting center. Probiotics can influence this axis by producing metabolites and modulating the gut environment, thereby impacting how signals are transmitted.
The gut is responsible for producing the majority of the body’s serotonin, a neurotransmitter that plays a role in mood, sleep, and appetite, but also strongly regulates gut motility and sensation. An imbalance in gut flora can affect the production and signaling of serotonin, potentially leading to dysmotility and the sensation of nausea. Certain probiotic strains can help regulate serotonin levels or alter the activity of receptors in the gut, which may normalize the signals sent to the brain.
Inflammation in the gastrointestinal tract can also trigger nausea, as inflammatory compounds activate local nerves that signal distress to the brain. Probiotics may reduce this inflammation by strengthening the gut barrier and promoting anti-inflammatory compounds. By calming the gut environment, these beneficial bacteria reduce inflammatory signals traveling to the brain via the vagus nerve, mitigating the feeling of sickness.
Clinical Evidence for Specific Nausea Conditions
Clinical studies have explored the effect of probiotics across several conditions known to cause nausea, with promising results for specific patient populations. Nausea and vomiting during pregnancy (morning sickness) affects up to 85% of pregnant individuals. A study found that taking a blend of Lactobacillus and Bifidobacterium strains reduced the hours spent feeling nauseous by 16% and reduced vomiting episodes by 33% over a 16-day period. The probiotic intervention appeared to work by rebalancing the gut microbiome, which is often altered by the hormonal changes of pregnancy.
For individuals undergoing cancer treatment, chemotherapy-induced nausea and vomiting (CINV) is a common and debilitating side effect. Probiotics containing strains like Lactobacillus rhamnosus and Bifidobacterium species have shown potential in reducing the severity of these symptoms. One meta-analysis found that probiotics reduced the odds of chemotherapy-induced nausea by 49% in patients, primarily children with leukemia, though the overall certainty of evidence was noted to be variable. These findings suggest that probiotics may protect the gut lining from the cytotoxic effects of chemotherapy, thereby mitigating gastrointestinal distress.
Nausea Related to GI Disorders
Nausea is a frequent symptom for those with gastrointestinal disorders, such as Irritable Bowel Syndrome (IBS). Certain strains, including Bacillus coagulans and combinations of Lactobacillus acidophilus and Bifidobacterium longum, have been shown to alleviate IBS symptoms like abdominal pain and bloating, which can indirectly reduce associated nausea.
Nausea from Medication Use
Nausea stemming from antibiotic use disrupts the natural gut flora and can be mitigated by probiotics. Strains like Lactobacillus rhamnosus and Saccharomyces boulardii show promise in restoring gut balance and reducing related side effects. The use of Lactobacilli has also been shown to reduce nausea and diarrhea in the context of H. pylori eradication therapy, which often causes gastrointestinal side effects.
Selecting and Dosing Probiotic Supplements
Selecting a probiotic for nausea relief requires focusing on specific strains that have demonstrated efficacy in clinical trials, rather than simply choosing a product with a high number of different bacteria. For stress-related or general nausea, a combination of Lactobacillus acidophilus Rosell-52 and Bifidobacterium longum Rosell-175, taken at 3 billion Colony-Forming Units (CFU) twice daily for a minimum of three weeks, is supported by some evidence. Individuals experiencing chemotherapy-related nausea may find benefit from Lactobacillus rhamnosus at a higher dose, such as 5 billion CFU taken twice daily.
The dosage, measured in CFUs, is highly strain-specific, but effective doses often fall in the range of 3 to 10 billion CFU per dose, administered once or twice daily. Consistency is important, and for maximum effect, it is recommended to continue the supplement for several weeks to allow the beneficial bacteria to colonize the gut. When taking probiotics alongside antibiotics, it is advisable to separate the doses by a few hours to prevent the antibiotic from killing the beneficial bacteria.
Probiotics are generally considered safe, especially well-studied Lactobacillus and Bifidobacterium strains. However, individuals with compromised immune systems, such as those undergoing chemotherapy, should use probiotics only under the guidance of a healthcare provider due to a small risk of infection. Pregnant individuals should also consult their doctor before starting any new supplement regimen. The most effective probiotic is one that is strain-specific to the underlying cause of the nausea, taken at a clinically relevant dosage.