Complementary medicine and hypertension: garlic and its implications for patient centred care and clinical practice
Angus S Lane
Tuesday, September 1st, 2015
This review aims to explore the impact that patient attitudes, values and beliefs have on healing and the relevant implications these have for clinical practice and patient centred care. Using a Cochrane review as a platform, garlic as a complementary medicine was evaluated based on current societal trends and pertinent clinical practice points. The study found that when engaging with a patient using complementary medicine it is important to consider not only the efficacy of the proposed treatment, but also variation in preparations, any possible interactions and side effects, and the effect of patient beliefs and the placebo effect on clinical outcomes. The use of garlic in the treatment of hypertension could serve to enhance the therapeutic alliance between clinician and patient and potentially improve clinical outcomes.
Hypertension is the most common cardiovascular disease in Australia. Approximately eleven percent of the population (2.1 million people) are affected by the condition.  The prevalence is twice as high in the indigenous population, affecting 22 percent of those aged 35 or older. Hypertension is a significant risk factor for transient ischaemic attack, stroke, coronary heart disease and congestive heart failure, increasing the risk of these by two to three fold.  Cardiovascular disease accounts for 47,637 or 36 percent of deaths in Australia each year and costs the economy a total of $14.2 billion AUD per annum – 1.7 percent of GDP. [3,4] Hypertension also accounts for six percent of all general practice consultations, making it the most commonly managed condition.  Given the significant effect hypertension has on society, it is imperative to evaluate potential therapies to combat hypertension.
Hippocrates is quoted as saying “let food be thy medicine and medicine be thy food”.  A considerable number of complementary therapies are thought to be effective in the treatment of hypertension by the general public. Such medicines include cocoa, acupuncture, coenzyme Q10 and garlic.  Medical texts from the ancient civilisations of India, China, Egypt, Rome and Greece all reference the consumption of garlic as having numerous healing properties.  Garlic (Allium sativum) was selected as the medicine of choice for this review as it is one of the most widely used and better studied complementary therapies in the management of hypertension. 
In addition to the effect of garlic on blood pressure, it is interesting to consider the implications of using this complementary medicine in light of patient centred care and clinical practice. It is highly recommended to medical students and clinicians that a patient’s cultural attitudes, values and beliefs are recognised and incorporated into clinical decision-making. The incorporation of patient perspectives into clinical practice may be done by negotiating the use of garlic as a complementary medicine alongside the use of a recognised antihypertensive drug. This study therefore aims to explore the findings and implications of controlled studies on the use of garlic to prevent cardiovascular morbidity and mortality in hypertensive patients in relation to good clinical practice and patient centred care. The aim of this investigation is to use a Cochrane review as a platform to explore garlic as an antihypertensive, and to discuss this treatment in the context of patient centred care and clinical practice.
The review focused on recent literature surrounding the use of garlic as an antihypertensive. A Cochrane review was used as an exemplar to discuss the broader implications of using garlic as a therapy for hypertension. Use of garlic was explored through the framework of current societal trends, clinical practice and patient centred care. Selected publications present both qualitative and quantitative data.
While the literature search retrieved a number of randomised controlled studies suggesting a beneficial effect of garlic on blood pressure, [5,10] the most recent Cochrane review by Stabler et al. retrieved only two controlled studies that assessed the benefit of garlic for the prevention of cardiovascular morbidity and mortality in hypertensive patients. [5,11,12] Of the two studies, Kandziora did not report the number of people randomised to each treatment group, meaning their data could not be meta-analysed.  They did report however, that 200mg of garlic powder in addition to hydrochlorothiazide-triamterene baseline therapy produced a mean reduction of 10-11 mmHg and 6-8mmHg in systolic and diastolic pressure respectively, compared to placebo therapy.  Auer’s 1990 study randomised 47 patients to receive either 200 mg garlic powder three times daily or placebo determining that garlic reduces mean arterial systolic blood pressure by 12mmHg and diastolic blood pressure by approximately 6-9mmHg in comparison to a placebo.  Ried’s meta-analysis revealed a mean systolic decrease of 8.4mmHg ± 2.6mmHg (P≤0.001) and a mean diastolic reduction of 7.3mmHg ± 1.5mmHg (P≤0.001) in hypertensive patients. 
Given these findings fall within the normal parameters for blood pressure measurement variability, the efficacy of garlic as an antihypertensive is inconclusive. It is also difficult to ascertain the implications of the Cochrane review for morbidity and mortality as neither of the trials reported on clinical outcomes for patients using garlic as a hypertension treatment and insufficient data was provided on adverse events. As such, garlic cannot be recommended as a monotherapy for the reduction of hypertension.  Despite this, there are other potential uses for garlic in the treatment of hypertension which encompass both patient centred care (PCC) and evidence based practice.
Different garlic preparations
Several garlic preparations are available for the treatment of hypertension including: garlic powder (as per the Cochrane studies), garlic oil, raw garlic, cooked garlic and aged garlic extract. [5,14] Ried and colleagues suggests that aged garlic extract is the best preparation for treatment of hypertension, and may reduce mean systolic blood pressure by 11.8mmHg ± 5.4mmHg over 12 weeks compared to placebo (P=0.006). Ried also noted that aged garlic extract did not interact with any other medications, particularly warfarin. 
A number of drug interactions may occur when using garlic. Edwards et al. noted an increased risk of bleeding in patients who take garlic and blood thinning agents such as aspirin and warfarin. The same study also noted that the efficacy of HIV medications such as saquinavir may be reduced by garlic interactions, and some patients suffer allergies to garlic. 
Patient beliefs and the placebo effect
Patient beliefs must be incorporated into clinical practice not only for adherence to PCC but also as a therapy itself. Numerous studies have suggested that placebo treated control groups frequently experience a relevant decrease of blood pressure in pharmacological investigations into hypertension. 
The findings of the Cochrane review are useful in making evidence based decisions regarding patient care, yet it is important to reflect on the issue of hypertension holistically and to consider what the review may have overlooked. Given that the Cochrane review provided insufficient data on the potential adverse effects, including drug interactions, of garlic consumption, prescribing garlic as a therapy for hypertension at this stage would be a failure to uphold best evidence based practice and would breach ethical principles such as non-maleficence.
Different types of garlic preparation are available. If a patient wishes to use this complementary therapy they should be guided to the most appropriate type. On a biochemical level, aged garlic extract has two main benefits for clinical practice. It contains the active and stable component (S)-allyl-cysteine which is measurable, and may allow for standardisation of dosage.  Aged garlic extract is also reportedly safer than other preparations and does not cause the bleeding issues associated with blood thinning medications such as warfarin. 
Patient centred care is particularly important as patient centred approaches have numerous influences over clinical outcomes. Bauman et al. proposes that PCC reduces patient anxiety and morbidity, improves quality of life, patient engagement and both patient and doctor satisfaction.  Evidence also suggests PCC increases treatment adherence and results in fewer diagnostic tests and unnecessary referrals, which is important to consider given the burden of hypertension on the health care system. [17,18] Particularly significant for all stakeholders (patients, clinicians and financiers) is the use of PCC as a dimension of preventative care. For the primary prevention of disease, clinicians should discuss risk and lifestyle factors with patients and the detrimental effects they can have on a patient’s health. [2,5] Given the effect of PCC on treatment adherence it is important to consider open communication and discussion with patients not only as a part of treatment, but also as a part of preventative medicine. Further, if a patient is willing to take garlic for hypertension it may be a tool for further discussion between clinician and patient, especially if the treatment sees some success. This success may open windows for a clinician to discuss further the effects of lifestyle modification on health. 
Being a multifaceted dimension of health, PCC recognises each patient is a unique individual, with different life experience, cultural attitudes, values and beliefs. Capraz et al. found that a percentage of patients use garlic in preference to antihypertensive drugs whilst others use it as a complementary medicine in combination with another antihypertensive drug.  This affirms the potential for disparity in patient ideals. A patient may prefer garlic because of concern over the
addictive potential of drugs (including antihypertensive).  Such concerns should be explored with the patient to ensure patients can make informed decisions about their healthcare. Other viewpoints may be complex, for example mistrust in pharmaceutical companies, or simply having a preference for natural therapies.  Again, these somewhat concerning perceptions are worthy of discussion with a willing patient.
Amongst all the information provided it is worth taking the time to appreciate the role of demographic and religious factors. The social context of a patient’s health may influence how a patient considers the findings of the review.  It may also provide an indicator for the likelihood of complementary medicine use.  Xue et al. suggests that females aged 18-34 who have higher-than-average income, are well educated and had private health cover were more likely to use a complementary or alternative medicine, such as garlic for hypertension.  Religion is also a significant determinant in patient centred care. Adherents to Jainism are unlikely to be concerned with the findings of the review, as they do not consume garlic, believing it to be an unnecessary sexual stimulant.  Similarly, some Hindus have also been noted to avoid garlic during holy times for the same reason.  A clinical decision regarding garlic as a complementary medicine would have to consider these factors in consultation with the patient.
When making decisions about the course of clinical practice in consultation with a patient, it is important to remember patients have a right to making a well informed decision.  It would be appropriate to disclose the findings of this review to patients considering the use of garlic so that a patient can make an informed decision regarding treatment options. It is essential that patients seeking treatment for hypertension understand the true extent of the efficacy of garlic: that it only has minimal (if any) blood pressure lowering effects. Patients should also be advised against garlic as a monotherapy for the reduction of hypertension until there is sufficient evidence to support its use. It is also important to inform patients of their right to use garlic as a complementary medicine if the patient so wishes to do so. [13,19] Given the potential detrimental effects of some garlic preparations, the implications of these effects should also be discussed with patients. If there is discrepancy between the views of the patient and the clinician, then the clinician must remain professional, upholding the codes of ethics which necessitates clinicians respecting the needs, values and culture of their patients.  The clinician must also provide the best clinical advice, and negotiate an outcome that is agreeable to both parties’ agendas. 
Hypertension is the most commonly managed condition in general practice. A Cochrane review assessing the benefit of garlic for the prevention of cardiovascular morbidity and mortality in hypertensive patients found a negligible effect on morbidity and mortality.  The study did not reflect on clinical outcomes for patients and neglected to discuss different garlic preparations used in the studies, potential differences this may have had on patient outcomes or any pertinent side effects. It is recommended that more studies be performed on the clinical effectiveness and side effects of different types of garlic preparations, particularly aged garlic extract. Patient centred care is important for the best clinical outcomes and for disease prevention. [17,18] Regardless of the efficacy of garlic, it is highly recommended to clinicians that a patient’s cultural attitudes, values and beliefs are recognised and incorporated into clinical practice. This may be done by negotiating the use of garlic as a complementary medicine, along with the use of a prescribed recognised antihypertensive drug if the patient desires a complementary medicine. The significant effect that patient values have on healing should be realised and utilised by clinicians and students alike. Ultimately, the use of garlic in the treatment of hypertension could serve to enhance the therapeutic alliance between clinician and patient and potentially improve clinical outcomes.
Jacob Bonanno for his assistance in proof-reading this article.
Conflict of interest None declared.
A S Lane: email@example.com
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