NCCIH Clinical Digest

for health professionals

Complementary Health Approaches for Hypertension: What the Science Says

May 2021

Clinical Guidelines, Scientific Literature, Info for Patients: 
Complementary Health Approaches for Hypertension

Man checking his blood pressure

Relaxation Techniques

Relaxation techniques have shown modest, short-term reductions in blood pressure; however, many of these studies were of poor quality.

What Does the Research Show?

  • A 2010 systematic review of 36 randomized controlled trials found no convincing evidence that consistently demonstrates the effectiveness of any biofeedback intervention in the control of hypertension when compared with pharmacotherapy, placebo, or no treatment.
  • A 2009 Cochrane systematic review of 25 randomized controlled trials involving 1,198 participants found that overall, relaxation techniques resulted in small reductions in blood pressure, but many trials were not well designed and had inconsistent results. The reviewers concluded that the evidence of causal association between relaxation and the reduction of blood pressure is weak.

Safety

  • Relaxation techniques are generally safe for healthy people if properly performed by a qualified practitioner or taught by a well-trained instructor.

Yoga

There is some evidence that yoga may be a useful adjunct intervention for the management of hypertension.

What Does the Research Show?

  • A 2019 systematic review and meta-analysis of 49 controlled trials involving 3,517 participants found that when yoga was practiced 3 sessions per week among participants with hypertension, yoga interventions that included breathing techniques and meditation/mental relaxation elicited blood pressure reductions of 11/6 mm Hg compared with those that did not.
  • A 2013 systematic review of 6 studies involving a total of 386 patients found some encouraging evidence of yoga for lowering systolic and diastolic blood pressure; however, the trials included in the review were of low methodological quality, so definitive conclusions about the efficacy and safety of yoga for essential hypertension could not be drawn.

Safety

Yoga is generally safe for healthy people if properly performed by a qualified practitioner or taught by a well-trained instructor. However, yoga may not be appropriate for people with certain health conditions. For example, people with high blood pressure may need to modify or avoid some yoga poses.

Garlic Supplements

There is evidence that garlic preparations may lower blood pressure in people with hypertension, but most of the research consists of small, preliminary, or low-quality studies.

What Does the Research Show?

  • A 2015 systematic review and meta-analysis of 9double-blind trials involving 482 participants found some evidence suggesting that garlic preparations may lower blood pressure in hypertensive individuals, but the evidence is not strong.
  • A 2012 Cochrane review of two randomized controlled trials found insufficient evidence to determine if garlic provides a therapeutic advantage compared to placebo in terms of reducing the risk of mortality and cardiovascular morbidity in patients diagnosed with hypertension. Although garlic appeared to reduce mean supine systolic and diastolic blood pressure compared with placebo, the reviewers noted that the difference in blood pressure reduction falls within the known variability in blood pressure measurements, making it difficult to determine the impact, if any, of garlic on lowering blood pressure.

Safety

  • Taking garlic supplements may increase the risk of bleeding in people taking anticoagulants.
  • Garlic has been found to interfere with the effectiveness of some drugs, including saquinavir.

Green Tea Supplements

Results of research suggest that green tea extract supplementation may reduce blood pressure over the short-term.

What Does the Research Show?

  • A 2020 systematic review and meta-analysis of 24 trials involving 1,697 participants found green tea significantly reduced systolic blood pressure and diastolic blood pressure over the duration of the short-term trials. The authors noted that before green tea supplementation can be recommended as part of an antihypertensive therapy, additional high-quality trials, with larger sample sizes, longer duration, and various catechin dosages are needed.
  • A 2015 systematic review and meta-analysis of 14 randomized controlled trials involving 971 participants found that among overweight and obese adults, green tea or green tea extract supplementation produced a small but significant reduction in blood pressure.

Safety

  • Although uncommon, liver problems have been reported in a number of people who took green tea products, primarily green tea extracts in pill form.
  • Green tea is an ingredient in many over-the-counter weight loss products, some of which have been identified as the likely cause of rare cases of liver injury.
  • Green tea at high doses has been shown to reduce blood levels and therefore the effectiveness of the beta-blocker nadolol. It may also interact with other medicines.

Omega-3 Fatty Acid Supplements

Results from randomized controlled trials are mixed, but overall, data suggest some benefit of omega-3 fatty acids from fish oils in lowering blood pressure.

What Does the Research Show?

  • A 2020 randomized controlled trial involving 2,157 adults ages 70 years or older evaluated whether vitamin D, omega-3s, and a strength-training exercise program, alone or in combination, improved health outcomes, including hypertension, among older adults. The study found that treatment with vitamin D3, omega-3s, or a strength-training exercise program did not result in statistically significant differences in improvement in systolic or diastolic blood pressure, nonvertebral fractures, physical performance, infection rates, or cognitive function.
  • A 2014 meta-analysis of 70 randomized controlled trials concluded that overall, available evidence suggests that eicosapentaenoic and docosahexaenoic acids (EPA+DPA) provision reduces systolic and diastolic blood pressure compared with placebo. The strongest effects were seen among untreated hypertensive participants indicating that ≥2g/d EPA+DHA may reduce both systolic and diastolic blood pressure. Data suggested a lower dose (1–2g/d) may reduce systolic but not diastolic blood pressure.

Safety

  • Side effects of omega-3 supplements are usually mild. They include unpleasant taste, bad breath, bad-smelling sweat, headache, and gastrointestinal symptoms.
  • Several large studies have linked higher blood levels of long-chain omega-3s with higher risks of prostate cancer. However, other research has shown that men who frequently eat seafood have lower prostate cancer death rates and that dietary intakes of long-chain omega-3s aren’t associated with prostate cancer risk. The reason for these apparently conflicting findings is unclear.
  • Omega-3 supplements may interact with anticoagulant drugs.
  • It’s uncertain whether people with seafood allergies can safely take fish oil supplements.

References

NCCIH Clinical Digest is a service of the National Center for Complementary and Integrative Health, NIH, DHHS. NCCIH Clinical Digest, a monthly e-newsletter, offers evidence-based information on complementary health approaches, including scientific literature searches, summaries of NCCIH-funded research, fact sheets for patients, and more.

The National Center for Complementary and Integrative Health is dedicated to exploring complementary health products and practices in the context of rigorous science, training complementary health researchers, and disseminating authoritative information to the public and professionals. For additional information, call NCCIH’s Clearinghouse toll-free at 1-888-644-6226, or visit the NCCIH website at nccih.nih.gov. NCCIH is 1 of 27 institutes and centers at the National Institutes of Health, the Federal focal point for medical research in the United States.

Copyright

Content is in the public domain and may be reprinted, except if marked as copyrighted (©). Please credit the National Center for Complementary and Integrative Health as the source. All copyrighted material is the property of its respective owners and may not be reprinted without their permission.