If a supplement is herbal, it is safe and can be taken without limits

Herbal sounds gentle, familiar and harmless, especially next to the chemical-sounding names of medicines. But the fact that a substance comes from a plant says nothing about its strength. Some of the most powerful substances in pharmacy come from plants: foxglove is the source of digitalis medicines, which strengthen and regulate the contractions of the heart muscle, and willow bark is the grandmother of aspirin.

A herb is a biologically active substance with a real effect on the body. And if it has an effect, it also has a dose, interactions and contraindications. Safe because it is natural is logic that does not pass at the pharmacy counter.

The most telling example is St John's wort, widely sold here for mood and sleep. It is a strong inducer of the liver enzyme CYP3A4, meaning it speeds up the breakdown of dozens of medicines and reduces their effect. Among those affected are contraceptive pills: the UK regulator MHRA received 19 reports of interaction between 2000 and 2014, of which 15 ended in unplanned pregnancy. The clinical study by Hall and colleagues (Clinical Pharmacology & Therapeutics, 2003) confirms the mechanism: in women on contraceptives taking St John's wort, breakthrough bleeding occurred in 7 out of 12 women, compared to 2 out of 12 without it.

And that is not all. Combined with antidepressants or with triptans for migraine, St John's wort can trigger serotonin syndrome, a potentially life-threatening condition. It also reduces the effect of warfarin, antiepileptic medicines and post-transplant drugs. One herb, sold without prescription, with drug interactions straight out of a pharmacology textbook.

St John's wort is not an exception, just the best-studied example. Ginkgo biloba amplifies the effect of blood-thinning medicines and raises bleeding risk. Echinacea can provoke allergic reactions in people sensitive to the daisy family. Liquorice (sweet root) with prolonged use raises blood pressure. Each of these plants has its place, but also its list of precautions.

That is why in Bulgaria food supplements are registered with the Food Safety Agency, and herbal medicinal products with the Bulgarian Drug Agency. Registration does not make a herb harmless, but it guarantees you know exactly what you are buying, unlike random products from the internet and markets.

Three rules for peace of mind. First: buy from a pharmacy, with a Bulgarian label and registration. Second: if you take any regular medicines, ask the pharmacist about interactions before adding a herb. Third: pregnancy, breastfeeding and childhood are periods when the natural requires more attention, not less.

Our verdict: the claim is a MYTH. Herbal supplements are a useful tool when used consciously, but herbal is not a synonym for safe. The right question is not whether the product comes from nature, but whether it is suitable for you and for the medicines you take. That is exactly the question a pharmacist answers best.

This article was written by Donka Arabadzhova, Master of Pharmacy, and confirmed by the following sources: the review of clinically relevant St John's wort drug interactions (British Journal of Pharmacology, 2020), the study by Hall and colleagues on interaction with oral contraceptives (Clinical Pharmacology & Therapeutics, 2003), the safety reports of the UK regulator MHRA (2000-2014) and the EMA/HMPC monographs on Hyperici herba.