What the AI found
“Your daily blueberry intake significantly correlated with a 15% reduction in gut transit time and a 20% increase in short-chain fatty acid markers within three weeks.”
Before
Vague gut discomfort, no clear triggers
After
Quantified impact of specific foods
The same system, three states — real screens, not a screenshot
- Gut discomfort, bloating, random.
- Foods? Coffee? Stress? Hard to tell.
- Tried probiotics, not much changed.
- Need to figure out what actually helps.
Prompt
I've been tracking my gut transit time and symptoms, along with daily blueberry intake, for the last three weeks. My transit times (in hours) are in column B, and blueberry consumption (0 for none, 1 for yes) is in column D. Here's the raw data: Date,Transit Time (hrs),Symptoms,Blueberries? Oct 1,48,Bloating,0 Oct 2,46,Mild discomfort,0 Oct 3,42,Normal,0 Oct 4,38,Normal,1 Oct 5,36,Normal,1 Oct 6,34,Very good,1 Oct 7,32,Excellent,1 Oct 8,40,Mild discomfort,0 Oct 9,38,Normal,0 Oct 10,36,Normal,0 Oct 11,32,Normal,1 Oct 12,30,Good,1 Oct 13,28,Excellent,1 Oct 14,26,Excellent,1 Oct 15,36,Mild discomfort,0 Oct 16,34,Normal,0 Oct 17,32,Normal,0 Oct 18,28,Good,1 Oct 19,26,Excellent,1 Oct 20,24,Excellent,1 Oct 21,22,Superb,1 Analyse this data. Is there a discernible correlation between blueberry intake and gut transit time? Quantify the average transit time on days with and without blueberries.
I've been tracking my gut transit time and symptoms, along with daily blueberry intake, for the last three weeks. My transit times (in hours) are in column B, and blueberry consumption (0 for none, 1 for yes) is in column D. Here's the raw data: Date,Transit Time (hrs),Symptoms,Blueberries? Oct 1,48,Bloating,0 Oct 2,46,Mild discomfort,0 Oct 3,42,Normal,0 Oct 4,38,Normal,1 Oct 5,36,Normal,1 Oct 6,34,Very good,1 Oct 7,32,Excellent,1 Oct 8,40,Mild discomfort,0 Oct 9,38,Normal,0 Oct 10,36,Normal,0 Oct 11,32,Normal,1 Oct 12,30,Good,1 Oct 13,28,Excellent,1 Oct 14,26,Excellent,1 Oct 15,36,Mild discomfort,0 Oct 16,34,Normal,0 Oct 17,32,Normal,0 Oct 18,28,Good,1 Oct 19,26,Excellent,1 Oct 20,24,Excellent,1 Oct 21,22,Superb,1 Analyse this data. Is there a discernible correlation between blueberry intake and gut transit time? Quantify the average transit time on days with and without blueberries.
AI
Based on your provided data, there appears to be a clear inverse correlation between blueberry intake and gut transit time. Days with blueberry consumption show a faster transit time. * **Average transit time without blueberries:** 40.8 hours * **Average transit time with blueberries:** 29.3 hours This indicates an average reduction of approximately 11.5 hours (about 28%) in gut transit time on days when blueberries were consumed.| Blueberry Impact | Confirmed |
| Gut Transit Time (avg w/ blueberries) | 29.3 hrs |
| Gut Transit Time (avg w/o blueberries) | 40.8 hrs |
One Variable at a Time: Tracking Gut Impact of Polyphenols
A structured approach transformed vague dietary concerns into precise, actionable insights about gut health.
A 38-year-old software engineer, Northern Europe
Tools used
The real tools used here — swap any for your own equivalent. Each links to how we’d set it up.
Starting state
Before anything was set up
For years, the engineer experienced intermittent gut discomfort, bloating, and unpredictable bowel movements. She suspected certain foods were the culprits but lacked the data or method to pinpoint them. Her food diary was sporadic, tracking only symptoms, not specific dietary components or their measured impact. The sheer volume of information on gut health online felt overwhelming, making any attempt at self-experimentation feel aimless and inconclusive.
- Gut discomfort, bloating, random.
- Foods? Coffee? Stress? Hard to tell.
- Tried probiotics, not much changed.
- Need to figure out what actually helps.
Working state
Core Course, doing its job
Following the Core Course, she decided to test the impact of polyphenols. She adopted a strict elimination diet, then systematically reintroduced blueberries, tracking her gut transit time and collecting stool samples for microbiome analysis. Each morning, she logged her food intake, symptoms, and the previous day's transit time into a simple Google Sheet. On Sundays, she used a custom GPT, prompted with her weekly data, to identify emerging patterns and quantify the effect of the blueberry reintroduction.
Prompt
I've been tracking my gut transit time and symptoms, along with daily blueberry intake, for the last three weeks. My transit times (in hours) are in column B, and blueberry consumption (0 for none, 1 for yes) is in column D. Here's the raw data: Date,Transit Time (hrs),Symptoms,Blueberries? Oct 1,48,Bloating,0 Oct 2,46,Mild discomfort,0 Oct 3,42,Normal,0 Oct 4,38,Normal,1 Oct 5,36,Normal,1 Oct 6,34,Very good,1 Oct 7,32,Excellent,1 Oct 8,40,Mild discomfort,0 Oct 9,38,Normal,0 Oct 10,36,Normal,0 Oct 11,32,Normal,1 Oct 12,30,Good,1 Oct 13,28,Excellent,1 Oct 14,26,Excellent,1 Oct 15,36,Mild discomfort,0 Oct 16,34,Normal,0 Oct 17,32,Normal,0 Oct 18,28,Good,1 Oct 19,26,Excellent,1 Oct 20,24,Excellent,1 Oct 21,22,Superb,1 Analyse this data. Is there a discernible correlation between blueberry intake and gut transit time? Quantify the average transit time on days with and without blueberries.
I've been tracking my gut transit time and symptoms, along with daily blueberry intake, for the last three weeks. My transit times (in hours) are in column B, and blueberry consumption (0 for none, 1 for yes) is in column D. Here's the raw data: Date,Transit Time (hrs),Symptoms,Blueberries? Oct 1,48,Bloating,0 Oct 2,46,Mild discomfort,0 Oct 3,42,Normal,0 Oct 4,38,Normal,1 Oct 5,36,Normal,1 Oct 6,34,Very good,1 Oct 7,32,Excellent,1 Oct 8,40,Mild discomfort,0 Oct 9,38,Normal,0 Oct 10,36,Normal,0 Oct 11,32,Normal,1 Oct 12,30,Good,1 Oct 13,28,Excellent,1 Oct 14,26,Excellent,1 Oct 15,36,Mild discomfort,0 Oct 16,34,Normal,0 Oct 17,32,Normal,0 Oct 18,28,Good,1 Oct 19,26,Excellent,1 Oct 20,24,Excellent,1 Oct 21,22,Superb,1 Analyse this data. Is there a discernible correlation between blueberry intake and gut transit time? Quantify the average transit time on days with and without blueberries.
AI
Based on your provided data, there appears to be a clear inverse correlation between blueberry intake and gut transit time. Days with blueberry consumption show a faster transit time. * **Average transit time without blueberries:** 40.8 hours * **Average transit time with blueberries:** 29.3 hours This indicates an average reduction of approximately 11.5 hours (about 28%) in gut transit time on days when blueberries were consumed.Use case implemented
The finished system, running on its own
Now, the engineer has a clear, actionable protocol. She consistently incorporates blueberries into her diet, having empirically validated their positive impact on her gut markers. Her weekly review is a swift, data-driven process. The system allows her to systematically test other dietary variables, building a personalised understanding of her gut health, moving from anecdotal guesses to quantified, reproducible insights. She now approaches new dietary ideas with a test-and-measure mindset.
| Blueberry Impact | Confirmed |
| Gut Transit Time (avg w/ blueberries) | 29.3 hrs |
| Gut Transit Time (avg w/o blueberries) | 40.8 hrs |
| SCFA Markers (post-blueberry) | +20% |
| Next Variable to Test | Fermented Foods |
What an outside observer would notice
6 minutes
Weekly Data Review Time
Down 70%
Gut Discomfort Episodes
High
Dietary Insight Clarity
The stack — build it yourself
Flexible and simple for logging specific daily variables without app bloat.
Enables nuanced, quantitative analysis of personal data without manual calculation.
Used for its simple logging of specific symptoms and basic biometrics.
Provided the structured framework for systematic self-experimentation.
These are the tools used in this story. Any can be swapped for an equivalent you already trust.
Go deeper
Do this yourself
See Core Course
This story runs on Core Course. The tools and prompts above are the real build — swap any tool for your own equivalent and follow the same steps.