ChatGPT, Gemini, Copilot: how good is their advice on food supplements?

Journal · AI & health

ChatGPT, Gemini, Copilot: how good is their advice on food supplements?

Asking an AI which supplement to take has become a reflex. Three scientific studies published in 2025 and 2026 checked how good these answers really are. The verdict: AI explains things well, but often gets efficacy wrong, cites weak sources and sometimes misses the warning signs.

By Alexis Brousse, founder of Biologyst · Published on 2 October 2026 · Studies checked on PubMed

At Biologyst, we receive more and more questions that start with “ChatGPT told me that…”. That is not bad news: people are looking for information. But an AI answer is not a source. Here is what research has measured, and a simple method to get the best out of these tools without getting the dose or the product wrong.

How good are ChatGPT’s answers on food supplements?

Researchers at the University of Tokyo asked GPT-4 and GPT-4o about the effect of 30 food supplements on six common diseases, then compared each answer with an evidence-based grid drawn up by doctors.

In other words, ChatGPT is rather cautious, which is a good thing, but its caution often takes the form of vagueness that does not help you decide. And when it does take a position, it is still wrong almost one time in two.

Do AI tools cite reliable sources?

An AI that shows links inspires trust. So the same team tested Copilot, Microsoft’s web-connected assistant, with 180 questions asked in its three response modes, giving 540 answers to analyse.

The authors also note the AI’s tendency to avoid taking a position and to go along with what the user seems to expect. If your question already assumes that a product works, the answer is likely to reassure you.

Where do AI tools go wrong most often?

A third scientific study, published in 2026, put 58 questions on vegetarian and vegan nutrition to five assistants: ChatGPT, Gemini, Copilot, DeepSeek and Doubao. Five assessors trained in clinical nutrition rated the 290 answers.

An AI summarises what it has read. It cannot see the label in your hands.

Illustrative exchange: the answer stays vague, the label gives the dose.

What AI tools do well

• Explaining: describing what a vitamin, a mineral or an ingredient is, in simple words.
• Recalling the basics: a varied diet, sleep and physical activity, before any supplement.
• Preparing an appointment: listing the questions to ask your doctor or pharmacist.
• Comparing concepts: for example vitamin D3 and vitamin D2, or the different forms of magnesium.

What should you ask an AI about a supplement?

The quality of an answer depends a great deal on the question. These five questions push the AI out of vagueness, and give you something to check.

• “What dose was studied in humans, and for how long?” A result obtained with 500 mg a day says nothing about a product that contains 50.
• “In what form?” Vitamin D3 or D2, three forms of vitamin B12, magnesium bisglycinate or oxide: the form changes everything.
• “Give me the PubMed reference for the study.” Then open the link: check that the study exists and really says what the AI claims.
• “What contraindications and what interactions with my medication?” And describe your situation: pregnancy, chronic disease, current treatment.
• “Which health claim is authorised in Europe for this nutrient?” This is the official list of what a manufacturer is allowed to promise.

How do you check an AI’s answer against a label?

An honest label answers three questions in ten seconds: how much of the ingredient per serving (in mg or µg, with the percentage of the nutrient reference values), in what form, and how many servings a day. Compare this dose with the one in the study cited. If the dose is lower, the study result does not apply.

The three questions to ask a label, using B12 Cell Boost as an example.

Example: Cynatine® HNS keratin was studied at 500 mg a day, which is the dose provided by the 3 daily capsules of Hair & Nail Regenesis. We explain this in our article on hair loss in autumn. The same logic applies to vitamin D, detailed in Vitamin D: from October to March, the sun is no longer enough.

Why does vitamin B12 come up so often?

Because it is a textbook case. Vitamin B12 is found almost only in foods of animal origin. A vegan therefore needs a reliable source: fortified foods or a food supplement. This is precisely the point on which the 2026 study found potentially harmful AI answers.

The form matters too. B12 Cell Boost combines three forms of vitamin B12: methylcobalamin, hydroxocobalamin and cyanocobalamin. Vitamin B12 contributes to the reduction of tiredness and fatigue, to normal energy-yielding metabolism and to normal functioning of the nervous system.

B12 Cell Boost: three forms of vitamin B12, 4 sprays a day.

Where to start, without AI or guesswork?

On each of our product pages, you will find the dose per serving, the form of the ingredient, the dosage on the label and, where one exists, the study with its link. To help you choose, our Where to start selection brings together five simple formulas, including B12 Cell Boost. For busy periods, the Garder le cap ritual combines B12 Cell Boost, Magnesium Active+ and Adaptive Boost, at €93.90.

And if you want an AI’s opinion, keep our five questions to hand: they turn a vague answer into one you can check.

Frequently asked questions

Can you trust ChatGPT to choose a food supplement?

To understand the basics, yes. To decide, no: in a 2026 scientific study, GPT-4 and GPT-4o gave an accurate answer on the efficacy of 30 supplements in only about 57% of cases. Check the dose, the form and the source, and ask a healthcare professional.

Why do AI tools get food supplements wrong?

Because they rely on texts of uneven quality: in a 2025 study on Copilot, 72.7% of the sources cited came from blogs, retail sites or social media. They also tend to stay vague or to go along with the question asked.

What should you ask an AI about a supplement?

Ask for the dose studied in humans and the duration, the form of the ingredient, the PubMed reference for the study, the contraindications and interactions, and the health claim authorised in Europe. Then check these points on the label.

Should vegans take vitamin B12?

Vitamin B12 is found almost only in foods of animal origin: a vegan needs a reliable source, fortified foods or a food supplement. Talk to a healthcare professional about it, especially if you are pregnant or breastfeeding.

How do you take B12 Cell Boost?

4 sprays a day. The 20 ml bottle contains about 133 sprays, or 33 days. Do not exceed the recommended daily dose.

Further reading

• B12 Cell Boost: the product page
• Where to start: our selection
• The Garder le cap ritual, under pressure
• Vitamin B12: essential for everyone
• Vitamin D: from October to March, the sun is no longer enough
• Hair loss in autumn: why it happens