St. John’s Wort for Weight Control

Common name: Klamath weed

Botanical name: Hypericum perforatum

Why do dieters use it?*

Some dieters say that St. John’s wort

helps improve energy and alertness.
helps relieve stress and anxiety.

What do the advocates say?*

St. John’s wort is well established as a remedy for mild to moderate depression. Since depression can lead to weight gain, and since medications with actions similar to that of St. John’s wort have been used for weight loss, some people have proposed that St. John’s wort can be useful for weight loss. However, no research at all has investigated whether St. John’s wort has any value for this purpose.

How much is usually taken by dieters?

The standard recommendation for mild to moderate depression is 500 to 1,050 mg of St. John’s wort extract per day.¹ ² ³ Length of use should be discussed with a healthcare professional.

Are there any side effects or interactions?

St. John’s wort has a low incidence of side effects compared to prescription antidepressants. An adverse events profile of St. John’s wort found that, of 14 controlled clinical trials, seven reported no adverse reactions, two had no information, and five reported a total of seven mild reactions.⁴ Adverse effects reported included stomach upset, fatigue, itching, sleep disturbance, and skin rash. The rate of adverse reactions was always similar to that of the placebo. Additionally, in seven trials comparing St. John’s wort with other antidepressants, the adverse reaction rate for St. John’s wort was consistently lower than that of the antidepressant drugs with which it was compared.

St. John’s wort can make the skin more sensitive to sunlight.⁵ Therefore, fair-skinned people should be alert for any rashes or burns following exposure to the sun. Three cases of severe blistering and burns were reported in people taking St. John’s wort internally or applying it topically and then being exposed to sunlight.⁶ There is a case report of a woman experiencing neuropathy (nerve injury and pain) in sun-exposed skin areas after taking 500 mg of whole St. John’s wort for four weeks.⁷ Although St. John’s wort has photosensitizing properties, the severity of this reaction is not typical for people taking the herb.

People with a history of manic-depressive illness (bipolar disorder) or a less severe condition known as hypomania, should avoid use of St. John’s wort as it may trigger a manic episode.⁸ ⁹ ¹⁰ ¹¹

There is a single case report in which ingestion of St. John's wort appeared to cause high blood pressure in a 56-year-old man. The blood pressure returned to normal when the herb was discontinued.¹²

Are there any drug interactions?
Certain medicines may interact with St. John’s wort. Refer to drug interactions for a list of those medicines.

Caution: It is likely that there are many drug interactions with St. John's wort that have not yet been identified. St. John's wort stimulates a drug-metabolizing enzyme (cytochrome P450 3A4) that metabolizes at least 50% of the drugs on the market.¹³ Consequently, St. John's wort could potentially interfere with a large number of medications. Individuals taking any medication should, therefore, consult with a physician before taking St. John's wort.

Parts used and where grown

St. John’s wort is found in Europe and the United States. It is especially abundant in northern California and southern Oregon. The above-ground (aerial) parts of the plant are gathered during the flowering season.

Resources

See a list of books, periodicals, and other resources for this and related topics.

*Dieters and weight-management advocates may claim benefits for St. John’s wort based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles on St. John’s wort. For more complete and detailed information, including references and safety information, see St. John's Wort as an herbal remedy .

References

1. Brown DJ. Herbal Prescriptions for Better Health. Rocklin, CA: Prima Publishing, 1996, 159–65.

2. Woelk H. Comparison of St. John’s wort and imipramine for treating depression: Randomized controlled trial. BMJ 2000;321:536–9.

3. Philipp M, Kohnen R, Hiller KO. Hypericum extract versus imipramine or placebo in patients with moderate depression: randomized multicenter study of treatment for eight weeks. BMJ 1999;319:1534–9.

4. Ernst E, Rand JI, Barnes J, et al. Adverse effects profile of the herbal antidepressant St. John’s wort (Hypericum perforatum L.) Eur J Clin Pharmacol 1998;54:589–94.

5. Brockmöller J, Reum T, Bauer S, et al. Hypericin and pseudohypericin: Pharmacokinetics and effects on photosensitivity in humans. Pharmacopsychiatry 1997;30(suppl):94–101.

6. Lane-Brown MM. Photosensitivity associated with herbal preparations of St. John’s wort (Hypericum perforatum). MJA 2000;172:302[Letter].

7. Bove GM. Acute neuropathy after exposure to sun in a patient treated with St John’s Wort. Lancet 1998;352:1121–2 [letter].

8. Nierenberg AA, Burt T, Matthews J, Weiss AP. Mania associated with St. John’s wort. Biol Psychiatry 1999;46:1707–8.

9. Moses EL, Mallinger AG. St. John’s wort: Three cases of possible mania induction. J Clin Psychopharmacol 2000;20:115–7.

10. O’Breasail AM, Argouarch S. Hypomania and St John’s wort. Can J Psychiatry 1998;43:746–7 [letter].

11. Schneck C. St. John’s wort and hypomania. J Clin Psychiatry 1998;59:689 [letter].

12. Zullino D, Borgeat F. Hypertension induced by St. John's Wort: a case report. Pharmacopsychiatry. 2003;36:32.

13. Markowitz JS, Donovan JL, DeVane CL, et al. Effect of St John's wort on drug metabolism by induction of cytochrome P450 3A4 enzyme. JAMA 2003;290:1500–4.

The information presented in this website is for informational purposes only and was created by a team of U.S. registered dietitians and food experts. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements, making dietary changes, or before making any changes in prescribed medications.