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Search Health Information    St. John’s Wort for Weight Control

St. John’s Wort for Weight Control

Why Use

St. John’s Wort

Why Do Dieters Use It?*

Some dieters say that St. John’s wort helps improve energy and alertness and relieves 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.

*Dieters and weight-management advocates may claim benefits for this supplement 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.

Dosage & Side Effects

St. John’s Wort

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.

Side Effects

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

Interactions with Supplements, Foods, & Other Compounds

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 Therefore, it could potentially cause a number of drug interactions that have not yet been reported. People taking any medication should consult with a doctor or pharmacist before taking St. John's wort.

Interactions with Medicines

Certain medicines interact with this supplement.

Types of interactions: Beneficial Adverse Check

Replenish Depleted Nutrients

  • none

Reduce Side Effects

  • none

Support Medicine

  • none

Reduces Effectiveness

  • Atazanavir

    Taking St. John’s wort (Hypericum perforatum) when taking atazanavir might result in reduced blood levels of the drug, which could lead to reduced effectiveness and eventual resistance. Individuals taking atazanavir should avoid taking St. John’s wort at the same time.

  • Atorvastatin
    St. John's wort increases the activity of an enzyme in the body that metabolizes atorvastatin 21. Consequently, supplementation with St. John's wort may increase the metabolism of, and therefore reduce the activity of, atorvastatin.
    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Cyclosporine

    Pharmacological research from Europe suggests that St. John’s wort (Hypericum perforatum) may reduce plasma levels of cyclosporine.25 Two case reports also describe heart transplant patients taking cyclosporine who showed signs of acute transplant rejection after taking St. John’s wort extract.26 In both cases, reduced plasma concentrations of cyclosporine were found. One report cites similar findings in three patients taking cyclosporine and St. John’s wort together.27 Finally, similar drops in cyclosporine blood levels were reported in 45 kidney or liver transplant patients who began taking St. John’s wort.28 Until more is known, people taking cyclosporine should avoid the use of St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Digoxin

    One preliminary trial has suggested that St. John’s  wort(Hypericum perforatum) may reduce blood levels of digoxin.34 In this study, healthy volunteers took digoxin for five days, after which they added 900 mg per day of St. John’s wort while continuing the daily digoxin. A normal blood level of digoxin was reached after five days of taking the drug, but this level dropped significantly when St. John’s wort was added. This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.35 , 36 Until more is known, people taking digoxin should avoid St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Fosamprenavir

    Taking St. John’s wort (Hypericum perforatum) when taking fosamprenavir might result in reduced blood levels of the drug, which could lead to reduced effectiveness and eventual resistance. Individuals taking fosamprenavir should avoid taking St. John’s wort at the same time.

  • Indinavir

    Studies have shown that taking indinavir together with St. John’s wort results in increased breakdown and dramatically reduced blood levels of indinavir.57 , 58 Therefore, people taking indinavir should not take St. John’s wort.

    Indinavir is a protease inhibitor used to treat people with HIV infection . A pharmacological study gave indinavir to healthy volunteers for two days.59 On day 3, volunteers added 900 mg of St. John’s wort extract per day. At the end of the study, it was found that St. John’s wort led to a significant reduction in serum levels of indinavir. Until more is known, people taking indinavir or other antiretroviral drugs for HIV infection should avoid using St. John’s wort.

  • Ketamine
    Ketamine is given primarily by injection as an anesthetic and to relieve pain. It can also be used orally to treat chronic pain. In a study of healthy volunteers, administration of St. John's wort along with ketamine, decreased blood levels of the drug, which suggests that St. John's wort would decrease the effectiveness of orally administered ketamine.60
  • Lovastatin
    St. John's wort increases the activity of an enzyme in the body that metabolizes lovastatin 65. Consequently, supplementation with St. John's wort may increase the metabolism of, and therefore reduce the activity of, lovastatin.
  • Omeprazole

    In a study of healthy human volunteers, supplementing with St. John's wort greatly decreased omeprazole blood levels by accelerating the metabolism of the drug.73 Use of St. John's wort may, therefore, interfere with the actions of omeprazole.

  • Simvastatin
    In patients taking simvastatin, treatment with St. John's wort increased serum cholesterol levels, apparently because St. John's wort interfered with the effect of the medication.82
  • Theophylline

    One case study of a 42-year old asthmatic woman reported that taking 300 mg per day of St. John’s wort extract led to a significant decrease in blood levels of theophylline.83 Following discontinuation of St. John’s wort, the patient’s blood levels of theophylline returned to an acceptable therapeutic level. This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.84 , 85 Until more is known, people taking theophylline should avoid St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Warfarin

    According to a preliminary report, volunteers taking 900 mg per day of St. John’s wort were given a single dose of an anticoagulant similar in action to warfarin.90 There was a significant drop in the amount of the drug measured in the blood. Seven case studies reported to the Medical Products Agency in Sweden also found a decrease in the anticoagulant activity of warfarin when St. John’s wort was taken at the same time.91 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.92 , 93 People taking warfarin should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Zolpidem
    In healthy volunteers, supplementation with St. John's wort (Hypericum perforatum) along with zolpidem decreased blood levels of zolpidem, apparently by accelerating the metabolism of the drug.94

Potential Negative Interaction

  • Alprazolam
    St. John's wort increases the activity of an enzyme in the body that metabolizes alprazolam14. Consequently, supplementation with St. John's wort may increase the metabolism of, and therefore reduce the activity of, alprazolam.
  • Amitriptyline

    Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.15 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.16 , 17 Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

  • Amoxapine

    Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.18 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.19 , 20 Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

  • Chlordiazepoxide

    In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Clomipramine

    Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.22 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.23 , 24 Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

  • Clonazepam

    In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Desipramine

    Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.29 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.30 , 31 Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

  • Desogestrel-Ethinyl Estradiol

    Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.32 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.33 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Diazepam

    In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Doxepin

    Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.37 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.38 , 39 Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

  • Estazolam

    In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Ethinyl Estradiol and Levonorgestrel

    Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.40 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.41 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Ethinyl Estradiol and Norethindrone

    Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.42 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.43 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Ethinyl Estradiol and Norgestimate

    Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.44 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.45 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Ethinyl Estradiol and Norgestrel

    Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.46 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.47 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Fluoxetine

    There have been no published reports about negative consequences of combining St. John’s wort (Hypericum perforatum)  (Hypericum perforatum)  (Hypericum perforatum) and fluoxetine. One case has been reported of an interaction between St. John’s wort and a weak serotonin reuptake inhibitor drug known as trazodone that is vaguely similar to fluoxetine.48 In another case, a patient experienced grogginess, lethargy, nausea, weakness, and fatigue after taking one dose of paroxetine (Paxil®, another SSRI drug) after ten days of St. John’s wort use.49 Nevertheless, some doctors are concerned about the possibility of an interaction between St. John’s wort and fluoxetine causing side effects (e.g., mental confusion, muscle twitching, sweating, flushing) known collectively as serotonin syndrome.50 , 51 Until more is known about interactions and adverse actions, people taking any SSRI drugs, including fluoxetine, should avoid St. John’s wort, unless they are being closely monitored by a doctor.

  • Fluvoxamine

    One report describes a case of serotonin syndrome in a patient who took St. John’s wort and trazodone , a weak SSRI drug.52 The patient experienced mental confusion, muscle twitching, sweating, flushing, and ataxia. In another case, a patient experienced grogginess, lethargy, nausea, weakness, and fatigue after taking one dose of paroxetine (Paxil®, an SSRI drug related to fluvoxamine) after ten days of St. John’s wort.53 Until more is known about interactions and adverse actions, people taking any SSRI drugs, including fluvoxamine, should avoid St. John’s wort, unless they are being closely monitored by a doctor.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Imipramine

    Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.54 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.55 , 56 Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

  • Levonorgestrel

    Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.61 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.62 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Levonorgestrel-Ethinyl Estrad

    Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.63 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.64 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Lorazepam

    In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Mestranol and Norethindrone

    Cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.66 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.67 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Nefazodone

    Although there have been no interactions reported in the medical literature, it is best to avoid using nefazodone with St. John’s wort unless you are under the supervision of a qualified healthcare professional.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Norgestimate-Ethinyl Estradiol

    Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.68 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.69 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Nortriptyline

    Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.70 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.71 , 72 Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

  • Paroxetine

    One report described a case of serotonin syndrome in a patient who took St. John’s wort and trazodone , a weak SSRI drug.74 The patient reportedly experienced mental confusion, muscle twitching, sweating, flushing, and ataxia. In another case, a patient experienced grogginess, lethargy, nausea, weakness, and fatigue after taking one dose of paroxetine after ten days of St. John’s wort use.75

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Phenelzine

    Although St. John’s wort contains chemicals that bind MAO in test tubes, it is believed that the action of St. John’s wort is not due to MAOI activity.76 However, because St. John’s wort may have serotonin reuptake inhibiting action (similar to the action of drugs such as Prozac®, it is best to avoid concomitant use of St. John’s wort with MAOI drugs.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Protriptyline

    Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.77 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.78 , 79 Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

  • Sertraline

    One report described a case of serotonin syndrome in a patient who took St. John’s wort and trazodone , a weak SSRI drug.80 The patient reportedly experienced mental confusion, muscle twitching, sweating, flushing, and ataxia. In another case, a patient experienced grogginess, lethargy, nausea, weakness, and fatigue after taking one dose of paroxetine (Paxil®, another SSRI drug) after ten days of St. John’s wort use.81

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Temazepam

    In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Trazodone

    One report described a case of serotonin syndrome in a patient who took St. John’s wort and trazodone.86 The patient reportedly experienced mental confusion, muscle twitching, sweating, flushing, and ataxia. Until more is known, St. John’s wort should not be combined with trazodone except under expert clinical supervision.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Trimipramine

    Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.87 This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.88 , 89 Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

  • Venlafaxine

    Although there have been no interactions reported in the medical literature, it is best to avoid using venlafaxine with St. John’s wort unless you are under the supervision of a qualified healthcare professional.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Explanation Required

  • Fexofenadine

    In a study of healthy volunteers, administration of 900 mg of St. John's wort one hour prior to fexofenadine resulted in a significant increase in blood levels of fexofenadine, compared with the blood levels after taking fexofenadine alone.95 On the other hand, long-term administration of St. John's wort (300 mg three times per day for two weeks) did not alter blood levels of fexofenadine. Until more is known, St. John's wort should not be combined with fexofenadine, except under the supervision of a doctor.

More Resources

St. John’s Wort

Resources

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