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Complementary Health Approaches for Travelers

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Photo by Chris Brignola on Unsplash

What’s the Bottom Line?

How much do we know about complementary health approaches for travelers?

We know a fair amount about complementary health approaches for a few common travel-related health problems, including jet lag and altitude illness.

What do we know about the effectiveness of complementary health approaches for travelers?

Some complementary health approaches may be helpful for travel-related health problems, such as melatonin for jet lag, but most either haven’t been studied for travel-related problems or haven’t been shown to work.

What do we know about the safety of complementary health approaches for travelers?

The safety records are mixed for complementary health approaches for travel-related health concerns.

During your travels, you may develop a travel-related health problem, which could vary from something serious, like malaria, to just annoying, like mild diarrhea. Some travelers seek out complementary health approaches to ward off or treat health issues. The information about these approaches on consumer websites or in advertisements is often unsupported by research and misleading or false.

This fact sheet explains what studies tell us about herbal products, dietary supplements, and other complementary health approaches for travel-related ailments. A version of this fact sheet for health professionals is available online as part of the Centers for Disease Control and Prevention (CDC) Yellow Book. You can also find travel-related health information at the CDC’s Travelers’ Health webpage.


One of the most serious health concerns facing travelers to many countries is malaria, which you can get when bitten by Anopheles mosquitoes. Many consumer websites promote “natural” ways to prevent or treat malaria, which often involve making dietary changes or taking herbal products.

People who travel to countries where malaria is present should follow official recommendations and not rely on unproven natural approaches in an attempt to prevent or treat such a serious disease. Malaria prevention may involve mosquito avoidance and taking medicine to reduce the risk of the disease.

Vitamin and Mineral Supplements

  • Taking vitamin A and zinc supplements may help improve malaria symptoms, but only in malnourished children, studies suggest. There’s no evidence that travelers should be taking vitamin A or zinc to prevent or treat malaria.
  • Safety:
    • Large or frequent doses of vitamin A may build up in your body, causing severe side effects.
    • Taking beta-carotene, a form of vitamin A, has been linked to increased risks of lung cancer and heart disease in some smokers.
    • There can be short- and long-term side effects of taking excess zinc, from nausea to lower immune function. Zinc supplements can also interact with several types of medications.


The Zika virus, spread primarily by infected mosquitoes, isn’t dangerous to most people. In fact, many people infected with the Zika virus do not become sick, and those who do often have a mild illness. However, the virus can be passed from a pregnant woman to her fetus, and infection during pregnancy can cause certain serious birth defects. Pregnant women should not travel to areas where there is a Zika outbreak. Having unprotected sex with an infected partner may also pose a risk. For more information, see the CDC’s webpage on Zika and pregnancy.

There’s no vaccine or medicine for Zika. Some consumer websites and YouTube videos claim that herbs or other products, such as activated charcoal and diatomaceous earth, will protect against or treat the Zika virus. There’s no evidence that any complementary health products or practices can protect against the virus or treat an infection. Moreover, most dietary supplements haven’t been tested in pregnant women.

Travelers’ Diarrhea

One of the more common illnesses facing travelers is diarrhea; 30 to 70 percent of travelers, depending on where and when they travel, get it. You can’t escape travelers’ diarrhea by just avoiding certain foods or untreated water—you may need over-the-counter or prescription medications. No complementary health approaches have clearly been shown to be helpful in preventing or treating travelers’ diarrhea. 


  • The results of studies of probiotics for travelers’ diarrhea have been difficult to interpret because of short follow-up periods, different causes of diarrhea, and differences in the types and doses of probiotics, the timing of their use, and the use of other treatments in addition to probiotics. In its 2017 guidelines for the prevention and treatment of travelers’ diarrhea, the International Society of Travel Medicine concluded that the evidence is insufficient to make recommendations about the use of probiotics for either prevention or treatment of travelers’ diarrhea.
  • The U.S. Food and Drug Administration (FDA) hasn’t approved any health claims for probiotics.
  • Safety: Probiotics generally have only minor side effects, if any. However, people with underlying health problems (for example, a weakened immune system) may have serious complications, including infections.
  • For more information, see the National Center for Complementary and Integrative Health (NCCIH) webpage on probiotics.


  • You may see goldenseal, an herb, being promoted on the internet as a dietary supplement for a variety of ailments, including travelers’ diarrhea. However, there isn’t research to back up those claims.
  • Safety: Studies show that goldenseal may increase the toxicity or alter the effects of many commonly used prescription medicines.
  • For more information, see the NCCIH webpage on goldenseal.

Activated Charcoal

  • There’s no scientific evidence that activated charcoal, which is made from regular charcoal, helps with travelers’ diarrhea, bloating, stomach cramps, or gas.
  • Safety: The side effects of activated charcoal haven’t been well documented but were mild when it was tested by healthy people. Warning: Children should not be given activated charcoal for diarrhea and dehydration. It may absorb nutrients, enzymes, and antibiotics and also hide signs that they are dehydrated.

Grapefruit Seed Extract

  • Despite claims that grapefruit seed extract will keep you from getting sick, there’s no research on its effectiveness or safety for travelers’ diarrhea.

Altitude Illness

Altitude illness can occur when you travel to heights that you aren’t accustomed to, usually above 8,000 feet. Your body needs time to get used to the change in oxygen levels. Symptoms of altitude illness can be mild, such as dizziness, loss of appetite, or nausea, but can also become much more severe. There’s little, if any, evidence that dietary or herbal supplements can help prevent or treat altitude illness (also referred to as mountain sickness).


  • Coca tea is often used for altitude illness, but there’s no strong evidence on whether it works or has adverse effects.
  • Safety: Coca tea, made from the leaves of the coca plant, will result in a positive drug test for cocaine.


  • There’s no evidence supporting claims that garlic helps with altitude illness.
  • Safety: Possible side effects of taking garlic include breath and body odor, heartburn, and upset stomach. Short-term use of most commercially available garlic supplements poses only a limited risk of interacting with medications.
  • For more information, see the NCCIH webpage on garlic.

Ginkgo biloba

  • The several small studies looking at whether the herb ginkgo can help prevent altitude illness had conflicting results but were mostly negative. It’s unclear whether the conflicting results occurred because the ginkgo products differed.
  • Safety: For many healthy adults, ginkgo appears to be safe when taken in moderate amounts. However, ginkgo may interact with anticoagulants (blood thinners) and other medications. Fresh (raw) or roasted ginkgo seeds can be poisonous.
  • For more information, see the NCCIH webpage on ginkgo.

Vitamin E

  • Vitamin E, in combination with other antioxidants, has been studied for altitude illness and is recommended for it on some consumer websites. But the limited research done suggests that it’s not effective.
  • Safety: Vitamin E supplements may increase your risk of having a stroke and interact with medications, including a blood thinner, statins, and niacin.

Motion Sickness

Children older than age 2 are the most likely to get motion sickness, but anyone can feel nauseous from the motion of traveling by boat, plane, train, or car. Medications may help prevent the nausea but may also have side effects.

Ways To Avoid Motion Sickness

  • Sit in the front seat of the car or bus and, if you can, be the driver instead of the passenger.
  • In a plane, choose a seat that is over the wing.
  • Lie down, shut your eyes, or look at the horizon.
  • Stay hydrated, eat small meals, and limit alcohol and caffeinated beverages.
  • Distract yourself with music or a pleasant scent.

Complementary health approaches have been studied or advertised for motion sickness but haven’t been shown to work well.

Acupressure and/or Magnets

  • Acupressure is sometimes recommended to prevent or treat motion sickness. It involves pressing firmly down on the inside of your wrist or wearing a special wristband that presses that area.
  • Studies are mixed on whether acupressure helps with motion sickness.
  • Magnets are also sold for motion sickness, but there’s no research that supports their use.
  • Safety: Some magnets may interfere with medical devices, such as pacemakers and insulin pumps. Children may swallow or accidentally inhale small magnets, which can be deadly.


  • Despite ginger’s reputation for helping with nausea, we don’t have any strong evidence that it helps with motion sickness.
  • Safety: The effect of combining ginger supplements and over-the-counter drugs for motion sickness is unknown. In some people, ginger can have mild side effects such as stomach upset, heartburn, diarrhea, and gas.
  • For more information, see the NCCIH webpage on ginger.

Other Dietary Supplements or Products for Motion Sickness

  • There’s no evidence supporting claims that vitamin B6 or homeopathic products prevent or alleviate motion sickness.
  • Safety:
    • Like any drug or dietary supplement that contains chemical ingredients, some products labeled as homeopathic may cause side effects or drug interactions. For more information, see the NCCIH webpage on homeopathy.
    • Taking large doses of vitamin B6 for a year or longer can have side effects, ranging from skin problems, extreme sensitivity to sunlight, or nausea to severe nerve damage.

Nausea and Vomiting (“Morning Sickness”) in Pregnant Travelers

Feeling nauseous or even vomiting when pregnant isn’t unusual. For guidance on whether and when to seek medical care for this problem, visit this MedlinePlus webpage.

Following are complementary health approaches studied for morning sickness.


  • Ginger may help ease pregnancy-related nausea and vomiting. Studies suggest ginger is generally safe during pregnancy, but whether it’s always safe for pregnant women isn’t certain. Talk with your health care provider about using ginger (or any dietary supplements) during pregnancy.
  • Ginger can have mild side effects such as stomach pain, heartburn, diarrhea, and gas. People with gallstone disease should avoid ginger. Concerns have been raised that ginger might interact with blood thinners.

Vitamin B6

  • The American Congress of Obstetrics and Gynecology announced in 2015 that treatment of nausea and vomiting of pregnancy with vitamin B6 or vitamin B6 plus doxylamine (an antihistamine) is safe and effective and should be considered first-line drug treatment. But before taking a vitamin B6 supplement or doxylamine, consult your doctor.

Jet Lag/Sleep

Jet lag occurs when you travel across time zones and your body’s biological clock hasn’t caught up yet. Jet lag can have different symptoms, such as feeling tired and irritable, having an upset stomach, and having difficulty falling asleep or waking up on time.


  • Melatonin, a hormone our body produces and also available in dietary supplements, may help with jet lag, studies show. Study participants who were given melatonin before air travel across time zones reported having less jet lag than participants who received a placebo.
  • Safety:
    • People with epilepsy or who take a blood thinner should not use melatonin without medical supervision.
    • Taking melatonin appears to be safe for most people when used short-term; less is known about its long-term safety.
    • Melatonin should not be taken early in the day, when it may cause sleepiness and delay your adjustment to local time.
    • The amount of melatonin in products and the dosages recommended on labels can vary significantly.
    • Side effects from melatonin are uncommon but can include drowsiness, headache, dizziness, or nausea.
    • For more information, see the NCCIH webpage on melatonin.

Relaxation Techniques

Other Dietary Supplements and Aromatherapy

  • There’s very little evidence that aromatherapy, or taking the herbs chamomile or valerian, helps with insomnia. Kava is also advertised for sleep but we don’t have good research on kava for insomnia.
  • Safety:
    • Aromatherapy and valerian don’t have significant side effects. Chamomile can cause allergic reactions in some people.
    • Kava supplements may cause severe liver damage.

Colds and Flu

Your best protection against getting the flu is getting vaccinated. Everyone age 6 months and older should be vaccinated against the flu each year.

Here are some complementary health approaches that have been studied for avoiding colds and decreasing symptoms:


  • Taking zinc products by mouth may reduce the length and severity of a cold, studies show.
  • Safety: Zinc, particularly in large doses, can have side effects, including nausea and diarrhea. Don’t use any zinc products in your nose; you may lose your sense of smell.

Salt Water Rinses

  • Rinsing your nose and sinuses with salt water may help relieve a stuffed-up nose, though the research isn’t definitive.
  • Safety: If you do rinse your nose and sinuses, use only sterile or distilled water to avoid getting an infection. For more information, see the FDA’s webpage Is Rinsing Your Sinuses With Neti Pots Safe?

Vitamin C

  • Taking vitamin C supplements regularly may slightly reduce the length and severity of your colds but not the number of colds you get.
  • Safety: Even at high doses, vitamin C supplements appear safe.

Other Approaches for Colds and Flu

  • There’s no strong evidence that echinacea, garlic, Chinese herbs, oil of oregano, or eucalyptus essential oil prevent or treat colds or that the homeopathic product Oscillococcinum prevents or treats influenza or influenza-like illness.
  • Safety: Some traditional Chinese medicine products may have serious side effects—they’ve been found to be contaminated with undeclared plant or animal material, drugs, heavy metals, or pesticides. For more information, see the NCCIH webpage on traditional Chinese medicine.
  • See NCCIH’s tips on natural products for flu and colds.

Hepatitis C

  • The risk of being infected with the virus that causes hepatitis C, a liver disease, when traveling is generally low. However, you can get it from unsterile needles used for acupuncture, a tattoo, or injection drug use; through a medical procedure; or even from sharing personal items contaminated with infected blood, such as razors or a toothbrush.
  • No dietary supplement is an effective treatment for hepatitis C. Silymarin, an extract of milk thistle, has been studied for hepatitis C. It has not been found to decrease the levels of the virus in patients’ bodies or improve their liver function.
  • Safety: Side effects from silymarin in people with hepatitis C are infrequent and usually include only mild digestive problems.
  • For more information, see the NCCIH webpage on hepatitis C.

Vaginal Infections/Urinary Tract Infections

  • In studies, probiotics haven’t been shown to help with vaginal or urinary tract infections.
  • Safety: Probiotics generally have only minor side effects, if any.
  • For more information, see the NCCIH webpage on probiotics.

Insect Bites

Avoiding bites isn’t just for your comfort; bugs can spread a number of diseases.

Mosquitoes and Ticks

You can reduce your risk of getting sick by taking these steps to prevent bites:

  • Wear protective clothing, sleep in a screened room or an air-conditioned room with the windows closed, and use a bed net if outdoors to avoid getting bitten.
  • The CDC recommends using an insect repellent that is at least 20 percent DEET. It helps to ward off mosquitoes, ticks, and other bugs.
    • Other repellents such as oil of lemon eucalyptus (OLE) or para-menthane-diol (PMD) protect against mosquitoes but may not be effective against ticks or other bugs.
    • “Pure” OLE (an essential oil not formulated as a repellent) hasn’t been well tested and isn’t recommended.
    • Insect repellents made from plants, including citronella products, work for less time than products containing DEET.
    • Neem oil is used in agricultural insecticides and promoted on some websites for people, but there’s no evidence that it works or is safe for people.

Bed Bugs

  • The risk of picking up bed bugs when you travel is low, but bed bugs have become a problem that travelers need to consider.
  • Many products are marketed to repel bed bugs “naturally,” such as essential oils, but we don’t have evidence that they work.
  • Follow steps for detecting and avoiding bed bugs, such as inspecting your mattress and keeping your luggage off the floor or bed. It won’t help to spray bug repellent on your clothing or luggage, and it may pose health hazards.
  • For more information, see Simple Ways To Avoid Bed Bugs When You Travel and How To Find Bed Bugs.

Sun Exposure

Too much sun can cause skin cancer, the most common type of cancer in the United States. Being near the equator or at high elevation increases your exposure to the sun’s dangerous ultraviolet radiation. A few common medications, including some antibiotics, may make you more sensitive to the sun. You also need to watch for sun reflecting off of snow, sand, and water.

To Guard Against Sunburns and Possibly Lower Your Risk of Skin Cancer

  • Use a broad-spectrum sunscreen.
  • Limit how much time you are in the sun.
  • Avoid peak sun hours (10 a.m. to 2 p.m.).
  • Wear protective clothing.

“Natural Sunscreens”

Many so-called natural sunscreen products are available on the internet, along with recipes for making your own and advice on consuming dietary supplements or drinking tea to protect against sun damage. Products containing aloe vera and green tea, among other natural ingredients, are promoted as sunscreens. But studies have not proven that any herbal product or dietary supplement, including aloe, beta carotene, selenium, or epigallocatechin gallate (EGCG), an extract from green tea, reduces the risk of skin cancer or sun damage.


  • Homeopathic products called “nosodes” or “homeopathic immunizations” are promoted as substitutes for conventional immunizations. There’s no evidence that they work nor any scientific reason they should work.
  • It’s important that you are properly vaccinated against serious diseases before you travel. To find out what vaccines you may need, go to the CDC webpage on vaccines for people traveling outside of the United States.

More To Consider

  • Dietary supplements may interact with your medications or pose risks if you have certain medical problems or are going to have surgery.
  • Many dietary supplements haven’t been tested in pregnant women, nursing mothers, or children.
  • Dietary supplements may contain ingredients not listed on the label, prescription drugs not allowed in dietary supplements, and other dangerous chemicals.
  • For more recommendations, see Using Dietary Supplements Wisely on the NCCIH website.
  • NCCIH has safety tips on supplements and mind and body practices for children and teens.
  • Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

For More Information

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 1-888-644-6226

Telecommunications relay service (TRS): 7-1-1


Email: (link sends email)

Know the Science

NCCIH and the National Institutes of Health (NIH) provide tools to help you understand the basics and terminology of scientific research so you can make well-informed decisions about your health. Know the Science features a variety of materials, including interactive modules, quizzes, and videos, as well as links to informative content from Federal resources designed to help consumers make sense of health information.

Explaining How Research Works (NIH)

Know the Science: How To Make Sense of a Scientific Journal Article

Understanding Clinical Studies (NIH)


A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed.



To provide resources that help answer health questions, MedlinePlus (a service of the National Library of Medicine) brings together authoritative information from the National Institutes of Health as well as other Government agencies and health-related organizations.


U.S. Food and Drug Administration (FDA)

The FDA oversees the safety of many products, such as foods, medicines, dietary supplements, medical devices, and cosmetics. See its webpage on Dietary Supplements.

Toll-free in the U.S.: 1-888-463-6332


Federal Trade Commission (FTC)

The FTC is the Federal agency charged with protecting the public against unfair and deceptive business practices. A key area of its work is the regulation of advertising (except for prescription drugs and medical devices).

Toll-free in the U.S.: 1-877-382-4357


Key References

Altitude Sickness

Colds and Flu

Hepatitis C

Jet Lag/Sleep

Motion Sickness



Travelers’ Diarrhea

Vaginal Infections/Urinary Tract Infections

Other References

Altitude Sickness

  • Bailey DM, Davies B. Acute mountain sickness; prophylactic benefits of antioxidant vitamin supplementation at high altitude. High Altitude Medicine & Biology. 2001;2(1):21-29.
  • Baillie JK, Thompson AA, Irving JB, et al. Oral antioxidant supplementation does not prevent acute mountain sickness: double blind, randomized placebo-controlled trial. QJM. 2009;102(5):341-348.
  • Brown BG, Zhao X-Q, Chait A, et al. Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease. New England Journal of Medicine. 2001;345(22):1583-1592.
  • Dumont L, Mardirosoff C, Tramèr MR. Efficacy and harm of pharmacological prevention of acute mountain sickness: quantitative systematic review. BMJ. 2000;321(7256):267-272.
  • Garlic. In: Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E Monographs. Newton, MA: Integrative Medicine Communications; 2000:139-148.
  • Gertsch JH, Seto TB, Mor J, et al. Ginkgo biloba for the prevention of severe acute mountain sickness (AMS) starting one day before rapid ascent. High Altitude Medicine & Biology. 2002;3(1):29-37.
  • Leadbetter G, Keyes LE, Maakestad KM, et al. Ginkgo biloba does—and does not—prevent acute mountain sickness. Wilderness & Environmental Medicine. 2009;20(1):66-71.
  • Mansoor JK, Morrissey BM, Walby WF, et al. L-arginine supplementation enhances exhaled NO, breath condensate VEGF, and headache at 4,342 m. High Altitude Medicine & Biology. 2005;6(4):289-300.
  • Mazor SS, Mycyk MB, Wills BK, et al. Coca tea consumption causes positive urine cocaine assay. European Journal of Emergency Medicine. 2006;13(6):340-341.
  • Moraga FA, Flores A, Serra J, et al. Ginkgo biloba decreases acute mountain sickness in people ascending to high altitude at Ollagüe (3696 m) in northern Chile. Wilderness & Environmental Medicine. 2007;18(4):251-257.
  • Subudhi AW, Jacobs KA, Hagobian TA, et al. Changes in ventilatory threshold at high altitude: effect of antioxidants. Medicine and Science in Sports and Exercise. 2006;38(8):1425-1431.
  • Wing SL, Askew EW, Luetkemeier MJ, et al. Lack of effect of rhodiola or oxygenated water supplementation on hypoxemia and oxidative stress. Wilderness & Environmental Medicine. 2003;14(1):9-16.

Colds and Flu

  • Sowerby LJ, Wright ED. Tap water or “sterile” water for sinus irrigations: what are our patients using? International Forum of Allergy & Rhinology. 2012;2(4):300-302.

Hepatitis C

  • Abenavoli L, Capasso R, Milic N, et al. Milk thistle in liver diseases: past, present, future. Phytotherapy Research. 2010;24(10):1423-1432.
  • Liu JP, Manheimer E, Tsutani K, et al. Medicinal herbs for hepatitis C virus infection. Cochrane Database of Systematic Reviews. 2001(4):CD003183 [edited 2009]. Accessed at on July 5, 2016.
  • Yang Z, Zhuang L, Lu Y, et al. Effects and tolerance of silymarin (milk thistle) in chronic hepatitis C virus infection patients: a meta-analysis of randomized controlled trials. BioMed Research International. 2014;2014;941085.

Insect Protection

  • Fradin MS, Day JF. Comparative efficacy of insect repellents against mosquito bites. New England Journal of Medicine. 2002;347(1):13-18.
  • Kongkaew C, Sakunrag I, Chaiyakunapruk N, et al. Effectiveness of citronella preparations in preventing mosquito bites: systematic review of controlled laboratory experimental studies. Tropical Medicine & International Health. 2011;16(7):802-810.
  • Trongtokit Y, Rongsriyam Y, Komalamisra N, et al. Comparative repellency of 38 essential oils against mosquito bites. Phytotherapy Research. 2005;19(4):303-309.
  • Wang C, Lü L, Zhang A, et al. Repellency of selected chemicals against the bed bug (Hemiptera: Cimicidae). Journal of Economic Entomology. 2013;106(6):2522-2529.
  • Wang C, Singh N, Cooper R. Efficacy of an essential oil-based pesticide for controlling bed bug (Cimex lectularius) infestations in apartment buildings. Insects. 2014;5(4):849-859.

Jet Lag/Sleep

  • Cummings C. Melatonin for the management of sleep disorders in children and adolescents. Paediatrics & Child Health. 2012;17(6):331-336.
  • de Niet G, Tiemens B, Lendemeijer B, et al. Music-assisted relaxation to improve sleep quality: meta-analysis. Journal of Advanced Nursing. 2009;65(7):1356-1364.
  • Ferguson SA, Rajaratnam SM, Dawson D. Melatonin agonists and insomnia. Expert Review of Neurotherapeutics. 2010;10(2):305-318.
  • Gross CR, Kreitzer MJ, Reilly-Spong M, et al. Mindfulness-based stress reduction versus pharmacotherapy for chronic primary insomnia: a randomized controlled clinical trial. Explore. 2011;7(2):76-87.
  • Jacobs GD. Clinical applications of the relaxation response and mind-body interventions. Journal of Alternative and Complementary Medicine. 2001;7 (suppl 1):S93-S101.
  • Kierlin L. Sleeping without a pill: nonpharmacologic treatments for insomnia. Journal of Psychiatric Practice. 2008;14(6):403-407.
  • Meoli AL, Rosen C, Kristo D, et al. Oral nonprescription treatment for insomnia: an evaluation of products with limited evidence. Journal of Clinical Sleep Medicine. 2005;1(2):173-187.
  • Morin CM, Bootzin RR, Buysse DJ, et al. Psychological and behavioral treatment of insomnia: update of the recent evidence (1998-2004). Sleep. 2006;29(11):1398-1414.
  • Srivastava JK, Shankar E, Gupta S. Chamomile: a herbal medicine of the past with bright future. Molecular Medicine Reports. 2010;3(6):895-901.
  • van Geijlswijk IM, Korzilius HP, Smits MG. The use of exogenous melatonin in delayed sleep phase disorder: a meta-analysis. Sleep. 2010;33(12):1605-1614.


  • Mayo-Wilson E, Junior JA, Imdad A, et al. Zinc supplementation for preventing mortality, morbidity, and growth failure in children aged 6 months to 12 years of age. Cochrane Database of Systematic Reviews. 2014;(5):CD009384. Accessed at on May 3, 2016.
  • Owusu-Agyei S, Newton S, Mahama E, et al. Impact of vitamin A with zinc supplementation on malaria morbidity in Ghana. Nutrition Journal. 2013;12:131.
  • Shankar AH, Genton B, Semba RD, et al. Effect of vitamin A supplementation on morbidity due to Plasmodium falciparum in young children in Papua New Guinea: a randomised trial. Lancet. 1999;354(9174):203-209.
  • Veenemans J, Milligan P, Prentice AM, et al. Effect of supplementation with zinc and other micronutrients on malaria in Tanzanian children: a randomised trial. PLoS Medicine. 2011;8(11):e1001125.
  • Zeba AN, Sorgho H, Rouamba N, et al. Major reduction of malaria morbidity with combined vitamin A and zinc supplementation in young children in Burkina Faso: a randomized double blind trial. Nutrition Journal. 2008;7:7.

Motion Sickness

  • Bendich A, Cohen M. Vitamin B6 safety issues. Annals of the New York Academy of Sciences. 1990;585:321-330.
  • Ding M, Leach M, Bradley H. The effectiveness and safety of ginger for pregnancy-induced nausea and vomiting: a systematic review. Women and Birth. 2013;26(1):e26-e30.
  • Eccles NK. A critical review of randomized controlled trials of static magnets for pain relief. Journal of Alternative and Complementary Medicine. 2005;11(3):495–509.
  • Gdynia HJ, Müller T, Sperfeld AD, et al. Severe sensorimotor neuropathy after intake of highest dosages of vitamin B6. Neuromuscular Disorders. 2008;18(2):156-158.
  • Pittler MH, Brown EM, Ernst E. Static magnets for reducing pain: a systematic review and meta-analysis of randomized trials. CMAJ. 2007;177(7):736-742.


  • Heitmann K, Nordeng H, Holst L. Safety of ginger use in pregnancy: results from a large population-based cohort study. European Journal of Clinical Pharmacology. 2013;69(2):269-277.


  • Abad MJ, Bedoya LM, Bermejo P. An update on drug interactions with the herbal medicine Ginkgo biloba. Current Drug Metabolism. 2010;11(2):171-181.
  • Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. New England Journal of Medicine. 1994;330(15):1029-1035.
  • Ashley JT, Ward JS, Anderson CS, et al. Children’s daily exposure to polychlorinated biphenyls from dietary supplements containing fish oils. Food Additives & Contaminants: Part A. 2013;30(3):506-514.
  • Bressler R. Herb-drug interactions: interactions between Ginkgo biloba and prescription medications. Geriatrics. 2005;60(4):30-33.
  • Centers for Disease Control and Prevention. Hepatic toxicity possibly associated with kava-containing products—United States, Germany, and Switzerland, 1999-2002. MMWR. 2002;51(47):1065-1067.
  • Davidson TM, Smith WM. The Bradford Hill criteria and zinc-induced anosmia: a causality analysis. Archives of Otolaryngology—Head & Neck Surgery. 2010;136(7):673-676.
  • Gardiner SJ, Begg EJ. Pharmacogenetics, drug-metabolizing enzymes, and clinical practice. Pharmacological Reviews. 2006;58(3):521-590.
  • Goodman GE, Thornquist MD, Balmes J, et al. The Beta-Carotene and Retinol Efficacy Trial: incidence of lung cancer and cardiovascular disease mortality during 6-year follow-up after stopping beta-carotene and retinol supplements. Journal of the National Cancer Institute. 2004;96(23):1743-1750.
  • Gurley BJ, Fifer EK, Gardner Z. Pharmacokinetic herb-drug interactions (part 2): drug interactions involving popular botanical dietary supplements and their clinical relevance. Planta Medica. 2012;78(13):1490-1514.
  • Gurley BJ, Swain A, Hubbard MA, et al. Clinical assessment of CYP2D6-mediated herb-drug interactions in humans: effects of milk thistle, black cohosh, goldenseal, kava kava, St. John’s wort, and echinacea. Molecular Nutrition & Food Research. 2008;52(7):755-763.
  • Johnson AR, Munoz A, Gottlieb JL, et al. High dose zinc increases hospital admissions due to genitourinary complications. Journal of Urology. 2007;177(2):639-643.
  • Ko RJ. A U.S. perspective on the adverse reactions from traditional Chinese medicines. Journal of the Chinese Medical Association. 2004;67(3):109-116.
  • National Toxicology Program. NTP Technical Report on the Toxicology and Carcinogenesis Studies of Ginkgo biloba Extract (CAS No. 90045–36–6) in F344/N Rats and B6C3F1/N Mice (Gavage Studies). Research Triangle Park, NC: National Toxicology Program; 2013. NIH publication no. 13-5920.
  • Pawar RS, Grundel E, Fardin-Kia AR, et al. Determination of selected biogenic amines in Acacia rigidula plant materials and dietary supplements using LC-MS/MS methods. Journal of Pharmaceutical and Biomedical Analysis. 2014;88:457-466.
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NCCIH thanks Dr. John Williamson, NCCIH, for his technical expertise and review of the 2017 update of this publication.

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Last Updated: November 2017