Researchers tested 162 adults to see if having too many bacteria in the small intestine (a condition called SIBO) actually changes blood test results. While people with SIBO did show some differences in initial tests, these differences disappeared when scientists accounted for factors like age, weight, and sex. This suggests that SIBO might not be as directly connected to blood health markers as previously thought, and that a person’s age and weight may matter more for these blood measurements.
The Quick Take
- What they studied: Whether having too many bacteria in the small intestine (SIBO) causes measurable changes in blood tests, including vitamin D levels, white blood cell counts, and inflammation markers.
- Who participated: 162 adults who came to a clinic for breath testing to check for bacterial overgrowth. The group included people of different ages and body weights.
- Key finding: At first glance, people with SIBO had lower vitamin D and more white blood cells. However, when researchers controlled for age, sex, and weight, SIBO was no longer connected to these blood test changes. This means other factors were probably responsible for the differences.
- What it means for you: If you have SIBO, abnormal blood test results may not be directly caused by the bacterial overgrowth itself. Your age, weight, and other personal factors likely play a bigger role. Talk to your doctor about what your specific test results mean for your health.
The Research Details
This was a cross-sectional study, which is like taking a snapshot in time. Researchers looked at 162 adults who came in for breath testing (a test that detects bacterial overgrowth by measuring hydrogen in your breath). They collected blood samples from everyone and measured four things: vitamin D levels, white blood cell counts, red blood cell variation, and inflammation markers.
The researchers compared people who tested positive for SIBO with those who tested negative. First, they looked at simple comparisons between the two groups. Then they used more advanced statistical methods to account for factors that might affect blood tests, like how old people were, whether they were male or female, and their body weight.
They also looked at how much hydrogen each person’s breath contained (a measure of how severe the bacterial overgrowth might be) and checked if this correlated with any blood test changes.
Understanding whether SIBO directly causes blood test abnormalities is important because it helps doctors figure out what’s really causing a patient’s health problems. If SIBO doesn’t independently affect these blood markers, then doctors need to look at other explanations for abnormal results. This approach—adjusting for age, weight, and sex—is crucial because these factors are known to affect blood tests, and we need to separate their effects from SIBO’s effects.
This study has moderate strength. The sample size of 162 is reasonable for this type of research. The study used objective measurements (blood tests and breath testing), which is good. However, because it’s a cross-sectional study (a snapshot in time), it can’t prove that SIBO causes changes in blood tests—it can only show whether they’re connected. The researchers properly adjusted their analysis for important factors like age, weight, and sex, which strengthens the conclusions.
What the Results Show
When researchers first compared the two groups without adjusting for anything, people with SIBO did have lower vitamin D levels and higher white blood cell counts compared to those without SIBO. This might have suggested that SIBO was causing these blood changes.
However, when the researchers adjusted their analysis to account for age, sex, and body weight, the connection between SIBO and these blood markers disappeared. This is a crucial finding because it suggests that the initial differences weren’t actually caused by SIBO itself, but rather by differences in age, weight, or sex between the groups.
The study also looked at red blood cell variation (a measure of how different red blood cells are in size) and found no connection to SIBO, even in the initial comparison. Additionally, when researchers looked at the amount of hydrogen in people’s breath (which indicates how severe the bacterial overgrowth might be), it didn’t correlate with any of the blood test measurements.
The analysis revealed that body weight (BMI) was independently connected to white blood cell counts, meaning heavier individuals tended to have higher counts regardless of SIBO status. Age was independently connected to red blood cell variation, with older adults showing different patterns. These findings highlight that personal characteristics matter more than SIBO status for these particular blood markers.
Previous research had suggested links between SIBO and vitamin D deficiency, as well as increased inflammation. This study challenges those findings by showing that when you account for other factors, SIBO doesn’t independently predict these blood changes. This doesn’t mean SIBO is harmless—it may affect other aspects of health—but it suggests the connection to these specific blood markers may be weaker or more indirect than previously thought.
This study is a snapshot in time, so it can’t prove that SIBO causes blood test changes—only that they’re connected or not connected. The study only included people who came for breath testing, which might not represent the general population. The researchers only adjusted for age, sex, and weight; other factors (like diet, medications, or other health conditions) weren’t accounted for and could have influenced results. Finally, the study doesn’t tell us about long-term effects or whether treating SIBO changes these blood markers.
The Bottom Line
Based on this research (moderate confidence level): If you have SIBO, don’t assume that abnormal blood test results are caused by the bacterial overgrowth. Work with your doctor to investigate other possible causes, particularly considering your age and weight. If you’re considering SIBO treatment, know that it may not directly improve these specific blood markers, though it might help with other symptoms. This research suggests a single-cause explanation for blood test abnormalities is unlikely.
This matters most for people with diagnosed SIBO who have abnormal blood tests and wonder if the SIBO is responsible. It’s also relevant for doctors trying to understand what’s causing their patients’ blood test abnormalities. People considering SIBO treatment should understand that improving these particular blood markers may not be a realistic goal. This research is less relevant for people without SIBO or those with normal blood tests.
If you treat SIBO, don’t expect immediate changes in vitamin D levels or white blood cell counts. These markers are influenced more by age and weight than by SIBO status, so changes would likely take months and would depend more on addressing weight or other factors than on treating the bacterial overgrowth.
Want to Apply This Research?
- Track your weight weekly and note any SIBO symptoms (bloating, gas, digestive discomfort) separately from blood test results. This helps you see whether symptom improvement correlates with weight changes rather than assuming blood markers will improve.
- If you have SIBO, focus on tracking digestive symptoms and weight management rather than expecting blood test improvements. Use the app to monitor how your symptoms change with treatment while maintaining realistic expectations about blood test results.
- Set reminders for blood tests every 3-6 months if you have SIBO, but track them alongside weight and age-related changes. Create a log showing SIBO treatment, weight changes, and blood test results over time to help your doctor see the full picture of what’s affecting your health.
This research suggests SIBO may not directly cause the blood test abnormalities previously thought to be associated with it. However, this does not mean SIBO is harmless or doesn’t affect your health in other ways. If you have been diagnosed with SIBO or have abnormal blood tests, consult with your healthcare provider about what these results mean for your individual situation. Do not use this information to self-diagnose or self-treat SIBO. Blood test abnormalities can have many causes, and your doctor needs to evaluate your complete health picture. This study represents one point in time and should not be the sole basis for medical decisions.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.