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St John's wort

Supplement botanical general nutrition
Aka: Hypericum perforatum
Brands seen in Singapore: California Gold Nutrition, Swanson Vitamins, Nature's Way, Nature's Answer, Nutricost
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Sold for mood · may help mild or moderate depression
Pros & cons
Pros
  • NCCIH: beats placebo for mild or moderate depression
  • Matches standard antidepressants in those trials
  • Up to 12 weeks looks safe if on no other medicine
Cons
  • Weakens many medicines, sometimes dangerously
  • HSA annex b: warfarin, digoxin, the pill, SSRIS
  • Large doses: severe skin reactions after sun
Sources
  1. NIH NCCIH — St. John's Wort, how much do we know · read 2026-08-27
    what it says
    “results indicate that it may be helpful for mild or moderate depression … It has been clearly shown that St. John's wort can interact in dangerous, sometimes life-threatening ways with a variety of medicines.”
  2. NIH NCCIH — St. John's Wort, what have we learned · read 2026-08-27
    what it says
    “appears to be more effective than a placebo … and as effective as standard antidepressant medications for mild or moderate depression. It's uncertain whether this is true for severe depression or for time periods longer than 12 weeks.”
  3. NIH NCCIH — St. John's Wort, what do we know about safety · read 2026-08-27
    what it says
    “For most adults who are not taking any kind of medicine, St. John's wort appears to be safe when used for up to 12 weeks … might cause severe skin reactions after sun exposure.”
  4. NIH NCCIH — St. John's Wort, list of medicines whose effects it weakens · read 2026-08-27
    what it says
    “St. John's wort can weaken the effects of many medicines … Birth control pills … Cyclosporine … Some drugs used to prevent seizures, including phenytoin and carbamazepine … Some heart medications, including digoxin and ivabradine … Warfarin”
  5. NIH NCCIH — St. John's Wort, serotonin-related side effects · read 2026-08-27
    what it says
    “taking St. John's wort with certain antidepressants or other drugs that affect serotonin … may lead to increased serotonin-related side effects, which can be serious.”
  6. NIH NCCIH — St. John's Wort, pregnancy and breastfeeding · read 2026-08-27
    what it says
    “It may be unsafe to use St. John's wort during pregnancy because it may increase the risk of birth defects. Breastfeeding infants of mothers who take St. John's wort can experience colic, drowsiness, and lethargy.”
  7. HSA — Guidelines on Prohibited and Restricted Ingredients in HS and TM (Oct 2025), Annex B (substances with potential safety issues), row 3: Hypericum perforatum (St John's wort) · read 2026-08-27
    what it says
    “Hypericum perforatum affects the metabolism of some medicines thus reducing the medicines' therapeutic effects, e.g. warfarin, digoxin, oral contraceptives, anticonvulsants, SSRIs, etc. … Caution consumers to consult doctor prior to use of product if they are on medication.”
  8. HSA Singapore — Health Supplements Guidelines (January 2026), clause 7.1, medical advertisement and sales promotion permit control · read 2026-08-27
    what it says
    “Some types of HS are subject to medical advertisements and sales promotion permit control. These include Quasi-Medicinal (QM) vitamins and/or mineral HS, as well as some other HS (e.g. St John's wort, melatonin products).”
  9. HSA Singapore — Health Supplements Guidelines (January 2026), clause 4.8 and Tables 4–5 (vitamins and minerals only) · read 2026-08-27
    what it says
    “HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5.”
  10. iHerb Singapore — Supplements > Herbs > St. John's Wort category page, default order (1 - 43 of 43 results); first 5 distinct brands: California Gold Nutrition, Swanson Vitamins, Nature's Way, Nature's Answer, Nutricost · read 2026-08-27
    what it says
    “California Gold Nutrition, EuroHerbs™, St. John's Wort Extract … Swanson Vitamins, Full Spectrum® St. John's Wort, 375 mg … Nature's Way, St. John's Wort … Nature's Answer, St. John's Wort Extract … Nutricost, St. John's Wort, 500 mg”
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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.