Herbs & supplements

Follow the claim back to the study

An ingredient name on a label is only the start of an evidence check. NCCIH explains that supplements can have biological effects and that research quality varies. Look for studies in people, the actual preparation tested, the outcome measured and how long participants used it. A change in a laboratory marker is a different result from feeling better or avoiding illness.

Compare preparations rather than front labels

Write down the amount in a stated serving and how many capsules or scoops make that serving. For a plant extract, also record the plant part and any stated extract standardisation. Two products with the same large ingredient name can be difficult to compare when those details differ. A blend that hides individual amounts leaves a specific question unanswered: how much of each ingredient would you actually take?

• Identify the ingredient and the amount per stated serving.
• Separate human trial results from laboratory ideas and testimonials.
• Check whether the study preparation matches the product being considered.

Natural products can still interact

The NHS advises checking with a pharmacist before taking herbal medicines alongside other medicines, including those bought without a prescription. Some herbs can change how medicines work. Pregnancy, breastfeeding, childhood and kidney or liver problems need particular care. Give a clinician the actual product names rather than describing everything as vitamins; that makes an interaction check more useful.

Understand cycling and duration

A regular nutrient need, a loading phase, a prescribed treatment course and an on/off supplement cycle answer different questions. The duration of a study does not establish a repeating schedule, and a research washout is not a consumer instruction to stop and restart.

Each supplement profile now separates its on/off guidance, duration evidence and review point. Where no validated cycling pattern has been identified, the profile says so. Review the actual preparation, amount and reason for use rather than assuming a scheduled break makes an unsuitable product safe.

Read the guide to supplement cycling & duration

Decide what information is still missing

UK guidance separates food supplements from products authorised as medicines and warns against claims to prevent, treat or cure disease. A marketplace listing is therefore not proof of a treatment benefit. Before buying, note the unanswered question: evidence for this use, suitability with a medicine, seller identity or the full ingredient list. Persistent or unexplained symptoms deserve assessment rather than repeated trials of different bottles. Do not stop prescribed treatment to try a supplement.