N-of-One Supplement Test
Change one variable, measure the response, and retest before drawing conclusions
- Difficulty
- Moderate
- Time to result
- ~months to results
- Steps
- 5
- Confidence
- 91%
The N-of-One Supplement Test is a personal experiment designed to separate a product's effect from everything else changing in life. Byers describes seeing testosterone rise after beginning Tongkat Ali, but refuses to credit the supplement because training, stress, and other behaviors changed at the same time. His remedy is to stabilize the surrounding conditions, remove the supplement, measure again, and then potentially add it back. The mechanism is controlled comparison within one person: define a marker, establish a baseline, alter one variable, allow a suitable interval, and retest. Removal and reintroduction strengthen the signal if the response reverses and returns. Because this involves health decisions and laboratory interpretation, appropriate clinical oversight and safety constraints remain essential.
Origin
Byers describes removing Tongkat Ali from his own routine and planning another blood test because too many variables changed during the original improvement.
Core principles
- 01Bodies respond differently
- 02Multiple simultaneous changes prevent clean attribution
- 03Objective testing is stronger than impressions alone
- 04Removing and re-adding an intervention can test whether the effect repeats
How to run it
- 1
Define the outcome
Choose one measurable marker and specify what improvement would mean. Establish why the intervention is relevant to that marker.
Pro tip Prefer an objective measure that can be repeated under similar conditions.
Watch out Do not self-experiment on a condition requiring medical treatment.
- 2
Capture the baseline
Measure before changing the intervention and record relevant context such as training, stress, diet, and sleep.
Watch out A result without a baseline is difficult to attribute.
- 3
Change one variable
Add or remove only the intervention being tested while keeping other relevant behaviors as stable as practical.
Pro tip Delay optional routine changes until the test window closes.
Watch out Changing several things at once destroys the comparison.
- 4
Retest after the right interval
Wait long enough for the intervention and marker to respond, then repeat the measurement under comparable conditions.
Pro tip Set the retest date before beginning.
- 5
Test repeatability
When safe and professionally appropriate, remove or reintroduce the intervention and measure whether the direction repeats. Use the pattern, not a single reading, to update your conclusion.
Watch out Do not withdraw prescribed treatment without the responsible clinician.
In the wild
Byers saw his testosterone numbers increase after beginning Tongkat Ali, but training and stress also changed. He removed the supplement while keeping other factors more similar and planned another blood test, with the option to add it back afterward.
→ The next measurements can provide a cleaner signal about whether the supplement contributed.
Common mistakes
Changing everything at once
A better result cannot be assigned to one intervention when stress, training, diet, and supplements all changed together.
Trusting one reading
A single before-and-after result may reflect noise or an uncontrolled factor rather than the intervention.
Is it for you?
Best for
People working with appropriate professionals who can safely measure a defined response over time.
Not ideal for
Urgent medical issues, unsafe self-experimentation, or interventions that cannot ethically be withdrawn.
From the transcript
“I was on it I saw my numbers go up but I changed a lot so what I'm testing is I'm keeping a lot of…”
“let's pull it out and see what happens. And see what happens and then let's add it back in because not also a lot of…”
From the episode
Episode 457: Jeff Byers: The Former NFL Player Exposing the $200 Billion Supplement Scam
Jeff Byers