ESTONIA

In Estonia it blooms at midsummer, a golden herb gathered on the longest days and named for a saint.
It genuinely eases low mood, and it can quietly sabotage half the medicines in your cabinet.

St John's wort  ·  Hypericum perforatum  ·  Mechanism: hyperforin (mood, and interactions)

In Estonia, St John's wort flowers at midsummer, opening its small golden blooms around the solstice, when the northern night barely darkens at all. It is gathered on those longest, brightest days and named for St John, whose feast falls at that same bright turn of the year.

Crush one of its flowers and a blood-red oil stains your fingers, and hold a leaf up to the light and it looks pricked with tiny holes, from the oil glands that give it the Latin name perforatum. For centuries, across Europe, it was the herb reached for against melancholy, frayed nerves, and low spirits, a plant of pure sunlight set against the dark.

That old use for the mood is the one that modern science actually took seriously, and, unusually, largely upheld. St John's wort became the single herbal remedy with real, repeated evidence behind it as a true antidepressant, mainstream enough that German doctors prescribe it widely.

But it comes with a warning larger than almost any other herb in this whole series. The very thing that makes it work is also what makes it meddle, dangerously, with other medicines.

For mild to moderate depression, the evidence is genuinely good. A large review of around thirty trials found St John's wort clearly better than placebo and about as effective as standard antidepressants, with fewer side effects, and its compounds, chiefly hyperforin, lift mood by raising the brain's available serotonin and other signaling chemicals, much as those drugs do.

That is also exactly where the real danger lies. The same hyperforin powerfully switches on the liver's main drug-clearing enzyme and a transporter in the gut, so it speeds the breakdown of a startling range of medicines and quietly saps their strength, contraceptives, blood thinners, transplant, HIV, and cancer drugs, heart and seizure medicines, and combined with a prescription antidepressant it can push serotonin to genuinely dangerous levels.

The one herb that truly works like an antidepressant also interferes like one.

So the honest verdict is a real remedy that is not remotely a casual one. For mild low mood it is a legitimate option, but only ever as a doctor's decision, never alongside an antidepressant, the pill, a blood thinner, or most prescriptions without medical advice, and never a stand-in for professional care, because depression that is moderate, severe, lasting, or bringing any thought of harming yourself needs a doctor now, not a supplement.

The how-to

If low mood is mild, this is a real option, but only with a doctor who knows every medicine you take.

Before considering St John's wort, tell a doctor or pharmacist every medication and supplement you take, because its interactions are the whole story. This is not a herb to quietly start on your own.
Do not take it with a prescription antidepressant, which risks serotonin syndrome, and do not rely on it if you use hormonal contraception, which it can undermine into breakthrough bleeding or unplanned pregnancy, or blood thinners, transplant, HIV, seizure, heart, or cancer medicines, all of which it can weaken.
If your doctor agrees it fits mild low mood, use a standardized extract and give it several weeks, since the effect builds gradually, and a mild stomach upset or sun-sensitive skin can occur, so take care in strong sun.
St John's wort is for mild, not serious, depression. If your mood is deeply low or persistent, or you have any thoughts of harming yourself, please reach out to a doctor, a therapist, or a crisis line now, because that is not a job for a supplement.

Tomorrow: Scotland and oats
the humble breakfast grain whose soluble fibre genuinely, measurably lowers cholesterol.

See you then.