The AI shelf for magnesium, September 2026
ShelfSignal asked twenty magnesium buying questions on ChatGPT, Claude, Gemini, Perplexity and Grok, five times each. Across those 500 answers the assistants named 228 distinct brands. Ten of them took most of the shelf.
Measured 1 September 2026. Re-run monthly. Brands are shown as measured from public AI answers; none are ShelfSignal customers or partners.
This public index was measured and published by ShelfSignal.pro, an AI shelf analytics system that helps brands understand how AI assistants read, cite, and recommend products in a category.
Share of the AI shelf
Share of voice is the share of the 500 answers in which a brand is named. Assistants name several brands per answer, so shares overlap and do not sum to 100%.
| # | Brand | Share of voice |
|---|---|---|
| 1 | Thorne | 44% |
| 2 | Pure Encapsulations | 35% |
| 3 | Nature Made | 19% |
| 4 | NOW Foods | 18% |
| 5 | Doctor's Best | 13% |
| 6 | Transparent Labs | 9% |
| 7 | Nutricost | 8% |
| 8 | Optimum Nutrition | 7% |
| 9 | Life Extension | 7% |
| 10 | Ritual | 7% |
The same question, a different shelf on each assistant
No two assistants agree. Thorne takes 66% of Grok's answers and 25% of Claude's, on the same questions on the same day. A single blended visibility score hides that, which is why ShelfSignal reports every category per model.
| Brand | ChatGPT | Perplexity | Gemini | Claude | Grok |
|---|---|---|---|---|---|
| Thorne | 53% | 25% | 52% | 25% | 66% |
| Pure Encapsulations | 37% | 15% | 40% | 24% | 60% |
| Nature Made | 38% | 17% | 14% | 0% | 25% |
| NOW Foods | 18% | 12% | 19% | 14% | 29% |
| Doctor's Best | 10% | 7% | 11% | 7% | 32% |
| Transparent Labs | 19% | 0% | 11% | 3 of 100 | 10% |
| Nutricost | 18% | 5% | 3 of 100 | 9% | 3 of 100 |
| Optimum Nutrition | 11% | 0% | 13% | 1 of 100 | 12% |
| Life Extension | 3 of 100 | 10% | 6% | 0% | 16% |
0% means the assistant answered these questions and never named the brand. A count such as "3 of 100" means too few mentions to state a rate, so the raw number is printed instead.
What the assistants read before they answer
Answering these twenty questions, the assistants opened 4,957 links, and they took them from a narrow set of domains. A brand absent from these pages is usually absent from the answer.
| Domain | Share of citations |
|---|---|
| healthline.com | 5% |
| amazon.com | 3% |
| pmc.ncbi.nlm.nih.gov | 3% |
| mitohealth.com | 2% |
| consumerlab.com | 2% |
| mcpress.mayoclinic.org | 2% |
| verywellhealth.com | 2% |
| nebraskamed.com | 1% |
| drugs.com | 1% |
| cymbiotika.com | 1% |
The twenty questions
Non-branded, written the way shoppers ask them. No brand name appears in any prompt.
| best magnesium supplement | best magnesium brands 2026 |
| best magnesium for sleep | best magnesium for anxiety |
| best magnesium for muscle cramps | best magnesium for constipation |
| best magnesium for heart health | best magnesium for restless legs |
| best magnesium for athletes and recovery | best magnesium for women over 40 |
| best magnesium for sensitive stomach | best magnesium powder |
| best vegan magnesium capsules | best magnesium and calcium supplement |
| magnesium glycinate vs citrate | magnesium for migraines which form |
| third party tested magnesium supplement | practitioner grade magnesium brands |
| hypoallergenic magnesium supplement | magnesium without magnesium stearate |
How this was measured
AI answers are not deterministic: the same question asked twice can name different brands. ShelfSignal asks every question five times on every assistant, so the figures describe a pattern rather than one lucky answer. All answers are collected through official APIs with web grounding enabled, never by scraping chat interfaces. Every run is stored with its model version, prompt, run index and timestamp, so any number on this page can be traced back to the answers behind it.
Where does your brand sit?
This page shows the top ten of 228. Your own report adds the questions you lose, the pages of yours the assistants read, and six moves ranked by effort.
Read a full report Get yours