"I've taken it for two years, but I'm not sure what it does" is a common way to describe a supplement routine. It is also a sign that it was never set up as a test. Here is a simple structure.
The five questions
- Problem: what specific thing are you trying to change?
- Hypothesis: which single substance has trial evidence for that problem?
- Window: how long did the trials run before an effect showed up?
- Marker: what will you measure, before and after?
- Stop rule: what result, or side effect, ends the test?
One substance at a time. Change two things at once and you cannot tell which one worked.
Windows, from the trials
The test window should come from trial design, not from a bottle's "30-day supply".
| Substance | Problem tested | Trial length | Source |
|---|---|---|---|
| Rhodiola | Fatigue under acute stress | 2 to 4 weeks | PubMed 11081987, 19016404 |
| Ashwagandha | Sleep | Effects larger at 8 weeks or more | PubMed 34559859 |
| Creatine | Muscle saturation at 3 to 5 g a day | About 4 weeks | PubMed 33557850 |
| Vitamin D | Testosterone in deficient men | 12 months | PubMed 21154195 |
Markers you can actually measure
Some problems have hard markers. A good example is taurine and blood pressure. A 2024 meta-analysis of 25 RCTs with 1,024 participants, using 0.5 to 6 g a day for 5 to 365 days, found taurine lowered:
- systolic blood pressure by about 4 mmHg;
- diastolic blood pressure by about 1.5 mmHg;
- fasting blood glucose by about 5.9 mg/dL;
- triglycerides by about 18 mg/dL.
HDL cholesterol did not change. Four mmHg is a small shift, not a treatment for high blood pressure. But it is the kind of effect a home blood pressure cuff, used at a consistent time, can track. If you are on blood pressure medication, effects may add up, so talk to your doctor first.
Other examples of hard markers: 25(OH)D for vitamin D, triglycerides for omega-3. Where there is no lab marker, as with fatigue or focus, a short daily rating on the same scale is the next best thing.
Know what the scale will do
Some markers move for reasons unrelated to the goal. Creatine can raise scale weight in the first days through water moving into muscle (details). Plan for that before you start, so you don't misread it.
The stop rule
Write it down before you start: no measurable change by the end of the window, or a side effect, means it comes out of the routine. Without that, supplements tend to stay forever.
Sources
- Tzang CC et al. 2024. Taurine reduces the risk for metabolic syndrome: a systematic review and meta-analysis of randomized controlled trials. Nutr Diabetes 14(1):29. PubMed 38755142
- Darbinyan V et al. 2000. Rhodiola rosea in stress induced fatigue. Phytomedicine. PubMed 11081987
- Olsson EM et al. 2009. A randomised, double-blind, placebo-controlled, parallel-group study of the standardised extract SHR-5 of the roots of Rhodiola rosea in the treatment of subjects with stress-related fatigue. PubMed 19016404
- Cheah KL et al. 2021. Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLoS One. PubMed 34559859
- Antonio J et al. 2021. Common questions and misconceptions about creatine supplementation. J Int Soc Sports Nutr. PubMed 33557850
- Pilz S et al. 2011. Effect of vitamin D supplementation on testosterone levels in men. Horm Metab Res. PubMed 21154195
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