Osteoarthritis: In Depth
Osteoarthritis (OA) is the most common type of arthritis. It occurs most often in the hands, knees, hips, and spine.
OA affects cartilage—the slippery tissue that covers the ends of bones in a joint. Cartilage allows bones to glide over each other and absorbs the shock of movement. In OA, the top layer of cartilage breaks down and wears away, allowing the bones under it to rub against each other. This can cause pain, swelling, and difficulty in moving the joint.
OA is most common in older people, but younger people can have it too, especially in joints that have been injured.
More About Osteoarthritis
You may have OA if you have these symptoms. Check with your health care provider.
- Stiffness in a joint after getting out of bed or sitting for a long time.
- Swelling or tenderness in one or more joints.
- A crunching feeling or the sound of bones rubbing together.
If you feel hot or your skin turns red, or if your joint pain is accompanied by other symptoms such as a rash or fever, you probably have a different problem.
OA is usually managed with a combination of treatments, which may include exercise, weight loss to reduce strain on the hips and knees, rest and relief from stress on joints, and medications to control pain.
What the Science Says About Complementary Health Approaches for Osteoarthritis
Complementary approaches can be classified by their primary therapeutic input (how the therapy is taken in or delivered), which may be:
- Nutritional (e.g., special diets, dietary supplements, herbs, probiotics, and microbial-based therapies).
- Psychological (e.g., meditation, hypnosis, music therapies, relaxation therapies).
- Physical (e.g., acupuncture, massage, spinal manipulation).
- Combinations such as psychological and physical (e.g., yoga, tai chi, dance therapies, some forms of art therapy) or psychological and nutritional (e.g., mindful eating).
Nutritional approaches include what the National Center for Complementary and Integrative Health (NCCIH) previously categorized as natural products, whereas psychological and/or physical approaches include what was referred to as mind and body practices.
A variety of complementary approaches have been studied for osteoarthritis. The following sections summarize the evidence on the effectiveness and safety of specific approaches.
Glucosamine and Chondroitin Sulfate
Glucosamine and chondroitin are substances found in cartilage. Both are produced naturally in the body. They are also available as dietary supplements. Researchers have studied their effects, individually or in combination, in people with OA.
Studies of glucosamine for pain in knee OA have had conflicting results. Some, including a major National Institutes of Health (NIH)-sponsored study, found little or no evidence that glucosamine can relieve pain, but several other studies indicated that it can. Studies of chondroitin for pain from OA of the knee have had inconsistent results, but in general, the largest, highest quality studies have not shown an effect. There isn’t enough evidence to show whether glucosamine or chondroitin lessens pain from OA in other joints.
A few studies have looked at whether glucosamine or chondroitin or the combination can have beneficial effects on joint structure in people with OA. Some but not all of these studies found evidence that chondroitin or a glucosamine/chondroitin combination might help, but the improvements seen in most studies may be too small to make a difference to patients. There’s little evidence that glucosamine alone has beneficial effects on joint structure.
Glucosamine and chondroitin supplements may interact with the anticoagulant (blood-thinning) drug warfarin (Coumadin). Overall, studies have not shown any other serious side effects.
DMSO and MSM
Dimethyl sulfoxide (DMSO) and methylsulfonylmethane (MSM) are two chemically related substances that have been studied for OA. DMSO is applied to the skin. MSM is used as a dietary supplement.
Very little research has been done on DMSO and MSM, so it’s uncertain whether they’re helpful for OA symptoms.
Both DMSO and MSM can have side effects. DMSO can cause digestive upset, skin irritation, and a garlic-like taste, breath, and body odor. MSM can cause allergic reactions, digestive upsets, and skin rashes.
S-Adenosyl-L-methionine (SAMe) is a molecule that is naturally produced in the body. It’s also sold in the United States as a dietary supplement.
Studies of SAMe for OA have had inconsistent results. In some studies, SAMe appeared to be as effective as nonsteroidal anti-inflammatory drugs (NSAIDs) in relieving symptoms associated with OA, but in others it was no more helpful than a placebo (an inactive substance).
Side effects of SAMe are uncommon and usually mild. However, little is known about the long-term safety of SAMe because most studies have been brief. SAMe may have special risks for people with bipolar disorder and those who are HIV positive. It also may interact with drugs, including some antidepressants and levodopa, a drug used for Parkinson’s disease.
Oral Herbal Remedies
A variety of herbal products that are taken orally (by mouth) have been studied for OA. A 2014 evaluation of oral herbal remedies for OA found enough evidence to conclude that avocado-soybean unsaponifiables (ASUs) and Boswellia serrata, an herb used in Ayurvedic medicine, may produce slight improvements in pain and function; however, the improvements were so small that patients might not consider them meaningful. For all other herbal products, the amount of research is too small to allow any conclusions to be reached.
Little information is available on the safety of most herbal products used for OA, including ASUs and Boswellia serrata. Herbs and other dietary supplements may cause health problems if not used correctly, and some may interact with prescription or nonprescription medications or other dietary supplements. To learn more, visit the National Center for Complementary and Integrative Health’s (NCCIH) webpage on dietary supplements and interactive module on drug-supplement interactions.
Topical Herbal Remedies
Some herbal products have been used topically (applied to the skin) for OA. A 2013 evaluation of the evidence on topical herbal products concluded that arnica gel and comfrey extract gel might be helpful, and capsicum extract gel probably is not. The evidence on other products was insufficient to allow conclusions to be reached.
There’s not much information on the safety of topical herbal therapies for OA, but it’s been reported that some products, such as capsicum extract gel, can cause skin irritation or other side effects.
Psychological and Physical Approaches
A 2012 combined analysis of data from several studies indicated that acupuncture can be helpful and a reasonable option to consider for OA pain. A 2013 analysis using different statistical methods also concluded that acupuncture may help relieve knee OA pain. After these analyses were completed, a 2014 Australian study showed that both needle and laser acupuncture were modestly better at relieving knee pain from OA than no treatment but not better than simulated (sham) laser acupuncture. These results are generally consistent with previous studies, which showed that acupuncture is consistently better than no treatment but not necessarily better than simulated acupuncture at relieving OA pain. A 2016 review of U.S. studies found evidence that acupuncture, as practiced in the United States, may help some patients with knee OA manage their pain.
How acupuncture works to relieve pain is unclear. Current evidence suggests that many factors—like expectation and belief—that are unrelated to acupuncture needling may play important roles in the beneficial effects of acupuncture on pain.
Acupuncture is generally considered safe when performed by an experienced practitioner using sterile needles. Improperly performed acupuncture can cause potentially serious side effects.
Cupping and Moxibustion
In addition to acupuncture, other traditional Asian practices that have been used for OA include cupping (applying a cup to the skin and creating suction either mechanically or by using heat) and moxibustion (burning an herb above the skin to apply heat to acupuncture points). Only a small amount of research has been done on the use of these practices for OA. A single study evaluated cupping for OA; its results were promising, but it’s a very preliminary study. Several studies evaluated moxibustion for OA symptoms and found that it might be helpful; however, because the amount of research was small and the studies may have been biased, definite conclusions cannot be reached.
Both cupping and moxibustion can leave marks on the skin, which are usually temporary. Because cupping may draw blood, it could expose people to disease-causing microorganisms if the same device is used on more than one person without being sterilized after each use. Moxibustion has been linked to allergic reactions, burns, and infections.
Very few studies have evaluated massage therapy for OA. The small amount of available evidence suggests that massage may help to reduce symptoms in people with knee OA.
Massage therapy appears to have few risks when performed by a trained practitioner. However, arthritis-stressed joints are sensitive, so massage therapists who treat people with OA need to be familiar with the special needs of people with this condition.
Tai Chi and Qi Gong
Tai chi and qi gong combine certain postures and gentle, dance-like body movements with mental focus, breathing, and relaxation.
Several studies have evaluated the effects of tai chi on knee OA. In general, they showed short-term improvements in pain, stiffness, and physical function. Some studies also showed other desirable changes, such as improved balance or reduced depression. In a 2016 study in which tai chi was compared with physical therapy for knee osteoarthritis and patients were encouraged to continue their exercises after the 12-week study period ended, patients in both the tai chi and physical therapy groups showed improvement in pain for a full year. Much less research has been done on qi gong, but the few studies that have been completed showed improvements in some OA symptoms.
Tai chi and qi gong are generally considered to be safe practices. However, side effects, such as temporarily increased knee pain, have been reported in some people with OA.
Yoga incorporates several elements of exercise that may be beneficial for arthritis, including activities that may help improve strength and flexibility. However, very little research has been done on yoga for OA, so it’s uncertain whether it’s helpful.
Before starting to do yoga, people with OA should discuss their special needs with their health care provider and the yoga instructor. Props and modifications may be necessary to make yoga safe and comfortable for people with OA.
Other Complementary Health Approaches for Osteoarthritis
Balneotherapy is the technique of bathing in mineral water for health purposes; it also includes related practices such as mud packs. Although some studies have reported that balneotherapy can reduce pain in OA, the amount of high-quality research is too small for definite conclusions to be reached.
Balneotherapy has a good safety record.
There’s little evidence to support homeopathy as an effective approach for OA symptoms, particularly pain. There’s been no recent research on the effects of homeopathy on OA.
Although most homeopathic products are highly dilute and therefore considered to be safe, some contain ingredients in amounts large enough that they could cause harmful effects. There have also been instances when potentially harmful contaminants have been found in homeopathic products.
The available scientific evidence does not support using static magnets for pain relief. Static magnets are magnets often sold in shoe insoles, wrist wraps, headbands, and similar products. A small amount of evidence suggests that electromagnetic field therapy, which involves the use of small machines or mats to deliver an electromagnetic field to a joint or to the whole body, may provide some pain relief in OA, but it’s unclear whether it has a meaningful effect on physical function or quality of life for OA patients.
Static magnets are generally considered safe. Information about the safety of electromagnetic field therapy is limited, but few adverse effects have been reported in studies of this technique. Magnetic devices of any kind may be hazardous for people with certain types of implanted medical devices, such as pacemakers.
NCCIH is funding a variety of studies on OA. Topics include:
- A comparison of the effectiveness and cost-effectiveness of tai chi and standard physical therapy in patients with OA of the knee.
- The effects of a chair yoga program on elderly people with OA.
- An investigation of brain activity patterns associated with pain relief in people with knee OA who are receiving acupuncture or simulated acupuncture treatments.
More To Consider
- Don’t use complementary health approaches to postpone seeing your health care provider about joint symptoms or any other health problem.
- Keep in mind that dietary supplements may interact with medications or other supplements and may contain ingredients not listed on the label. Your health care provider can advise you. To learn more about using dietary supplements, see the NCCIH fact sheet Using Dietary Supplements Wisely.
- Tell all your health care providers about any complementary or integrative health approaches you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.
For More Information
- Bartlett SJ, Moonaz SH, Mill C, et al. Yoga in rheumatic diseases. Current Rheumatology Reports. 2013;15(12):387.
- Brien S, Prescott P, Lewith G. Meta-analysis of the related nutritional supplements dimethyl sulfoxide and methylsulfonylmethane in the treatment of osteoarthritis of the knee. Evidence-Based Complementary and Alternative Medicine. 2011;2011;528403.
- Cameron M, Chrubasik S. Oral herbal therapies for treating osteoarthritis. Cochrane Database of Systematic Reviews. 2014;(5):CD002947. Accessed at http://www.thecochranelibrary.com on October 31, 2014.
- Cameron M, Chrubasik S. Topical herbal therapies for treating osteoarthritis. Cochrane Database of Systematic Reviews. 2013;(5):CD010538. Accessed at http://www.thecochranelibrary.com on October 31, 2014.
- Choi T-Y, Choi J, Kim KH, et al. Moxibustion for the treatment of osteoarthritis: a systematic review and meta-analysis. Rheumatology International. 2012;32(10):2969-2978.
- Clegg DO, Reda DJ, Harris CL, et al. Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis. New England Journal of Medicine. 2006;354(8):795–808.
- Hinman RS, McCrory P, Pirotta M, et al. Acupuncture for chronic knee pain: a randomized clinical trial. JAMA. 2014;312(13):1313-1322.
- Miller KL, Clegg DO. Glucosamine and chondroitin sulfate. Rheumatic Diseases Clinics of North America. 2011;37(1):103-118.
- Rutjes AW, Nüesch E, Reichenbach S, et al. S-Adenosylmethionine for osteoarthritis of the knee or hip. Cochrane Database of Systematic Reviews. 2009;(4):CD007321. Accessed at www.thecochranelibrary.com on November 3, 2014.
- Singh JA, Noorbaloochi S, MacDonald R, et al. Chondroitin for osteoarthritis. Cochrane Database of Systematic Reviews. 2015;(1):CD005614. Accessed at www.thecochranelibrary.com on February 3, 2015.
- Verhagen AP, Bierma-Zeinstra SM, Boers M, et al. Balneotherapy for osteoarthritis. Cochrane Database of Systematic Reviews. 2007;(4):CD006864 [edited 2008]. Accessed at www.thecochranelibrary.com on November 3, 2014.
- Vickers AJ, Cronin AM, Maschino AC, et al. Acupuncture for chronic pain: individual patient data meta-analysis. Archives of Internal Medicine. 2012;172(19):1444-1453.
- Yan J-H, Gu W-J, Sun J, et al. Efficacy of tai chi on pain, stiffness and function in patients with osteoarthritis: a meta-analysis. PLoS One. 2013;8(4):e61672.
All Other References
- Birdee GS, Wayne PM, Davis RB, et al. Tai chi and qigong for health: patterns of use in the United States. Journal of Alternative and Complementary Medicine. 2009;15(9):969-973.
- Brien S, Prescott P, Bashir N, et al. Systematic review of the nutritional supplements dimethyl sulfoxide (DMSO) and methylsulfonylmethane (MSM) in the treatment of osteoarthritis. Osteoarthritis and Cartilage. 2008;16(11):1277-1288.
- Cahlin BJ, Dahlström L. No effect of glucosamine sulfate on osteoarthritis in the temporomandibular joints—a randomized, controlled, short-term study. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics. 2011;112(6):760-766.
- Chavez M. SAMe: S-Adenosylmethionine. American Journal of Health-System Pharmacy. 2000;57(2):119-123.
- Chyu M-C, von Bergen V, Brismée J-M, et al. Complementary and alternative exercises for management of osteoarthritis. Arthritis. 2011;2011:364319.
- Corbett MS, Rice SJ, Madurasinghe V, et al. Acupuncture and other physical treatments for the relief of pain due to osteoarthritis of the knee: network meta-analysis. Osteoarthritis and Cartilage. 2013;21(9):1290-1298.
- Cramer H, Lauche R, Langhorst J, et al. Yoga for rheumatic diseases: a systematic review. Rheumatology. 2013;52(11):2025-2030.
- Dahmer S, Schiller RM. Glucosamine. American Family Physician. 2008;78(4):471-476.
- Debbi EM, Agar G, Fichman G, et al. Efficacy of methylsulfonylmethane supplementation on osteoarthritis of the knee: a randomized controlled study. BMC Complementary and Alternative Medicine. 2011;11:50.
- De Silva V, El-Metwally A, Ernst E, et al. Evidence for the efficacy of complementary and alternative medicines in the management of osteoarthritis: a systematic review. Rheumatology. 2011;50(5):911-920.
- Ernst E. Complementary or alternative therapies for osteoarthritis. Nature Clinical Practice. Rheumatology. 2006;2(2):74-80.
- Falagas ME, Zarkadoulia E, Rafailidis PI. The therapeutic effect of balneotherapy: evaluation of the evidence from randomised controlled trials. International Journal of Clinical Practice. 2009;63(7):1068-1084.
- Fransen M, Agaliotis M, Nairn L, et al. Glucosamine and chondroitin for knee osteoarthritis: a double-blind randomised placebo-controlled clinical trial evaluating single and combination regimens. Annals of the Rheumatic Diseases. 2015;74(5):851-858.
- Gabay C, Medinger-Sadowski C, Gascon D, et al. Symptomatic effects of chondroitin 4 and chondroitin 6 sulfate on hand osteoarthritis: a randomized, double-blind, placebo-controlled clinical trial at a single center. Arthritis & Rheumatism. 2011;63(11):3383-3391.
- Haaz S, Bartlett SJ. Yoga for arthritis: a scoping review. Rheumatic Diseases Clinics of North America. 2011;37(1):33-46.
- Herrero-Beaumont G, Ivorra JA, Del Carmen Trabado M, et al. Glucosamine sulfate in the treatment of knee osteoarthritis symptoms: a randomized, double-blind, placebo-controlled study using acetaminophen as a side comparator. Arthritis & Rheumatism. 2007;56(2):555-567.
- Hochberg MC. Structure-modifying effects of chondroitin sulfate in knee osteoarthritis: an updated meta-analysis of randomized placebo-controlled trials of 2-year duration. Osteoarthritis and Cartilage. 2010;18(Suppl 1):S28-S31.
- Hochberg MC, Altman RD, April KT, et al. American College of Rheumatology 2012 recommendations for the use of nonpharmacologic and pharmacologic therapies in osteoarthritis of the hand, hip, and knee. Arthritis Care & Research. 2012;64(4):465-474.
- Hochberg MC, Martel-Pelletier J, Monfort J, et al. Combined chondroitin sulfate and glucosamine for painful knee osteoarthritis: a multicenter, randomised, double-blind, non-inferiority trial versus celecoxib. Annals of the Rheumatic Diseases. 2016;75:37-44.
- Jahnke R, Larkey L, Rogers C, et al. A comprehensive review of health benefits of qigong and tai chi. American Journal of Health Promotion. 2010;24(6):e1-e25.
- Jevsevar DS, Brown GA, Jones DL, et al. The American Academy of Orthopaedic Surgeons evidence-based guideline on: treatment of osteoarthritis of the knee, 2nd edition. Journal of Bone and Joint Surgery. American Volume. 2013;95(20):1885-1886.
- Kahan A, Uebelhart D, De Vathaire F, et al. Long-term effects of chondroitins 4 and 6 sulfate on knee osteoarthritis: the study on osteoarthritis progression prevention, a two-year, randomized, double-blind, placebo-controlled trial. Arthritis & Rheumatism. 2009;60(2):524-533.
- Knudsen JF, Sokol GH. Potential glucosamine-warfarin interaction resulting in increased international normalized ratio: case report and review of the literature and MedWatch database. Pharmacotherapy. 2008;28(4):540-548.
- Lao L. Safety issues in acupuncture. Journal of Alternative and Complementary Medicine. 1996;2(1):27-31.
- Lauche R, Langhorst J, Dobos G, et al. A systematic review and meta-analysis of tai chi for osteoarthritis of the knee. Complementary Therapies in Medicine. 2013;21(4):396-406.
- Liu H, Zeng C, Gao SC, et al. The effect of mud therapy on pain relief in patients with knee osteoarthritis: a meta-analysis of randomized controlled trials. Journal of International Medical Research. 2013;41(5):1418-1425.
- Lu SC, Mato JM. S-Adenosylmethionine in liver health, injury, and cancer. Physiological Reviews. 2012;92(4):1515-1542.
- Mato JM, Lu SC. S-Adenosylmethionine. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements, 2nd ed. New York, NY: Informa Healthcare; 2010:1-5.
- Müller T, Fowler B, Kuhn W. Levodopa intake increases plasma levels of S-adenosylmethionine in treated patients with Parkinson disease. Clinical Neuropharmacology. 2005;28(6):274-276.
- Nahin RL, Boineau R, Khalsa PS, Stussman BJ, Weber WJ. Evidence-based evaluation of complementary health approaches for pain management in the United States. Mayo Clinic Proceedings. 2016;91(9):1292-1306.
- National Institute of Arthritis and Musculoskeletal and Skin Diseases. Handout on Health: Osteoarthritis. National Institute of Arthritis and Musculoskeletal and Skin Diseases Web site. Accessed on November 11, 2014.
- National Institute of Arthritis and Musculoskeletal and Skin Diseases. What Is Osteoarthritis? National Institute of Arthritis and Musculoskeletal and Skin Diseases Web site. Accessed on November 11, 2014.
- Nielsen A, Kligler B, Koll BS. Safety protocols for gua sha (press-stroking) and baguan (cupping). Complementary Therapies in Medicine. 2012;20(5):340-344.
- Park J-E, Lee S-S, Lee MS, et al. Adverse effects of moxibustion: a systematic review. Complementary Therapies in Medicine. 2010;18(5):215-223.
- Pavelká K, Gatterová J, Olejarová M, et al. Glucosamine sulfate use and delay of progression of knee osteoarthritis: a 3-year, randomized, placebo-controlled, double-blind study. Archives of Internal Medicine. 2002;162(18):2113-2123.
- Perlman AI, Ali A, Njike VY, et al. Massage therapy for osteoarthritis of the knee: a randomized dose-finding trial. PLoS One. 2012;7(2):e30248.
- Pittler MH, Brown EM, Ernst E. Static magnets for reducing pain: systematic review and meta-analysis of randomized trials. CMAJ. 2007;177(7):736-742.
- Reginster JY, Deroisy R, Rovati LC, et al. Long-term effects of glucosamine sulphate on osteoarthritis progression: a randomised, placebo-controlled clinical trial. Lancet. 2001;357(9252):251-256.
- Reichenbach S, Sterchi R, Scherer M, et al. Meta-analysis: chondroitin for osteoarthritis of the knee or hip. Annals of Internal Medicine. 2007;146(8):580-590.
- Sawitzke AD, Shi H, Finco MF, et al. Clinical efficacy and safety of glucosamine, chondroitin sulphate, their combination, celecoxib or placebo taken to treat osteoarthritis of the knee: 2-year results from GAIT. Annals of the Rheumatic Diseases. 2010;69(8):1459-1464.
- Sawitzke AD, Shi H, Finco MF, et al. The effect of glucosamine and/or chondroitin sulfate on the progression of knee osteoarthritis: a report from the Glucosamine/Chondroitin Arthritis Intervention Trial. Arthritis & Rheumatism. 2008;58(10):3183-3191.
- Shengelia R, Parker SJ, Ballin M, et al. Complementary therapies for osteoarthritis: are they effective? Pain Management Nursing. 2013;14(4):e274-e288.
- Sherman KJ, Cherkin DC, Kahn J, et al. A survey of training and practice patterns of massage therapists in two U.S. states. BMC Complementary and Alternative Medicine. 2005;5:13.
- Tai chi versus physical therapy for knee osteoarthritis [summary for patients of full article: Wang C, Schmid CH, Iversen MD, et al. Comparative effectiveness of tai chi versus physical therapy for knee osteoarthritis]. Annals of Internal Medicine. 2016;165(2).
- Teut M, Kaiser S, Ortiz M, et al. Pulsatile dry cupping in patients with osteoarthritis of the knee—a randomized controlled exploratory trial. BMC Complementary and Alternative Medicine. 2012;12:184.
- Thie NM, Prasad NG, Major PW. Evaluation of glucosamine sulfate compared to ibuprofen for the treatment of temporomandibular joint osteoarthritis: a randomized double blind controlled 3 month clinical trial. Journal of Rheumatology. 2001;28(6):1347-1355.
- Wandel S, Jüni P, Tendal B, et al. Effects of glucosamine, chondroitin, or placebo in patients with osteoarthritis of hip or knee: network meta-analysis. BMJ. 2010;341:c4675.
- Wang C. Role of tai chi in the treatment of rheumatologic diseases. Current Rheumatology Reports. 2012;14(6):598-603.
- Wang C, Schmid CH, Iversen MD, et al. Comparative effectiveness of tai chi versus physical therapy for knee osteoarthritis: a randomized trial. Annals of Internal Medicine. 2016;165(2):77-86.
- Wilkens P, Scheel IB, Grundnes O, et al. Effect of glucosamine on pain-related disability in patients with chronic low back pain and degenerative lumbar osteoarthritis: a randomized controlled trial. JAMA. 2010;304(1):45-52.
- Wong HC, Wong JK, Wong NY. Signs of physical abuse or evidence of moxibustion, cupping or coining? CMAJ. 1999;160(6):785-786.
- Xu S, Wang L, Cooper E, et al. Adverse events of acupuncture: a systematic review of case reports. Evidence-Based Complementary and Alternative Medicine. 2013;2013:581203.
NCCIH thanks Partap Khalsa, D.C., Ph.D., NCCIH, for his contributions to the 2016 update of this publication.
This publication is not copyrighted and is in the public domain. Duplication is encouraged.
NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your health care provider(s). We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.