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Use the evidence library to check the research behind our ingredient guides. Each review identifies the studied outcome, reported result and limitations, with sources you can inspect. Authorised EU claims are quoted separately where they exist.
This is separate from our buying guides, which help you choose a product. The evidence library exists to answer a narrower question: what does the research actually support, and how confident should you be in it?
How we describe the evidence
Each page in this library describes what was actually studied for a given outcome — the type of research (systematic reviews, meta-analyses, position stands, or individual controlled trials), the number and size of the trials behind it, and any open questions such as dose, population or duration. We describe this at the level of the outcome, not the ingredient as a whole — an ingredient can be well studied for one effect and barely studied for another.
What we look for
Multiple systematic reviews or meta-analyses, or a formal position stand from a recognised sports-nutrition body (e.g. the International Society of Sports Nutrition), covering a large body of human trials with consistent findings.
A narrower picture
A well-designed systematic review or meta-analysis exists, or several smaller controlled trials point the same direction, but the evidence base is narrower than the above or leaves some open questions (dose, population, duration).
A thinner picture
Only a handful of small human trials, mixed or inconsistent results, or evidence that mostly comes from short-term or indirect (e.g. blood-marker) outcomes rather than the effect people actually care about.
No human evidence yet
No controlled human trials support the specific claim, or the evidence is animal/mechanistic only. We state that directly rather than borrowing confidence from a related but different finding.
Where our sources come from
We draw on a small number of source types, ranked by how directly they answer the question:
- The EU Register of authorised nutrition and health claims (Regulation (EU) 432/2012 and related EFSA opinions) — for the exact wording and conditions of use of any authorised claim we quote.
- ISSN position stands — peer-reviewed consensus documents from the International Society of Sports Nutrition, published in the Journal of the International Society of Sports Nutrition and indexed on PubMed/PMC.
- Systematic reviews and meta-analyses on PubMed/PMC and in major sports-medicine journals.
- NHS and equivalent public-health guidance for general dietary context.
Every PMID, PMCID and DOI we cite is checked against the NCBI database before publication, so the link goes to the paper we actually mean — not a plausible-looking mismatch.
Review date policy
Each research page in this library is written by Daniel and shows the date it was last updated beside the author line. It is not an expert or medical review. An old date is a signal to treat the page with a little more caution, not a reason to distrust it outright.
A note on EU health claims
Where an authorised health claim exists for an ingredient, we quote it verbatim and state its condition of use. We never combine, intensify, or paraphrase an authorised claim, and we never make a claim — disease, medicinal, or body-composition — that isn’t on the authorised list. Where no claim is authorised (BCAAs are the clearest example), we say so plainly instead of implying one.
What’s in the library so far
- Creatine monohydrate: what the research actually says — dosing, forms, safety, and the authorised performance claim.
- Whey protein: what the research actually says — muscle mass, dose-response, timing, and the authorised protein claims.
- Vitamin D for athletes: what the evidence shows — the authorised vitamin D claims, how common low vitamin D status is in athletes, what the muscle-strength trials examined, and official intake figures.
- Omega-3 for athletes: what the evidence actually says — the authorised EPA and DHA claims with their daily intakes, supplement forms, and EFSA and NHS amounts.
- Electrolytes and hydration for athletes — the authorised magnesium, potassium and carbohydrate-electrolyte claims, sweat-loss research, and official intake figures.
We’re adding to this library on an ongoing basis, working through the ingredients covered in our guides. If you’re ready to compare live prices once you’ve read the evidence, our creatine and whey protein price trackers cover Malta, and creatine and whey protein cover Cyprus. Our live price pages track protein, creatine, pre-workout and EAA/BCAA products, so vitamin D, omega-3 and electrolytes are not price-tracked categories.
Frequently asked questions
How does CapyFuel describe the strength of the evidence on these pages?
Instead of a single grade, each page describes what was actually studied for a specific outcome: the type of research (systematic reviews, meta-analyses, position stands or individual trials), how many trials and participants were involved, and any open questions. We describe the outcome, not the whole ingredient — the same ingredient can be well studied for one effect and barely studied for another.
Who writes the evidence library?
Pages are written by Daniel, who has around 30 years of hands-on strength-training and bodybuilding experience. Each page shows the date it was last updated; it is not an expert or medical review. This is presented honestly as practical, hands-on experience — not a medical, dietetic or nutrition credential. The scientific authority on these pages comes from the cited, NCBI-verified studies and the EU's authorised claim wording, not from the author's title.
Are these pages medical advice?
No. They summarise published research and authorised EU health claims for general information. If you have a health condition, take medication, or are pregnant or breastfeeding, speak to a healthcare professional before starting any supplement.
How do you choose which sources to cite?
We prioritise the EU Register of authorised health claims for claim wording, ISSN position stands, and systematic reviews/meta-analyses on PubMed/PMC, with NHS or equivalent public-health guidance for general context. Every PMID, PMCID and DOI is checked against the NCBI database before publication so the citation matches the paper we mean.