Stabler Sarah N, Tejani Aaron M, Huynh Fong, Fowkes Claire
Cardiac Clinics, Royal Columbian Hospital, Lower Mainland Pharmacy Services, Vancouver, Canada.
Cochrane Database Syst Rev. 2012 Aug 15;2012(8):CD007653. doi: 10.1002/14651858.CD007653.pub2.
Garlic is widely used by patients for its blood pressure lowering effects. A meta-analysis published in 2008 concluded that garlic consumption lowers blood pressure in hypertensive and normotensive patients. Therefore, it is important to review the currently available evidence to determine whether garlic may also have a beneficial role in the reduction of cardiovascular events and mortality rates in patients with hypertension.
To determine whether the use of garlic as monotherapy, in hypertensive patients, lowers the risk of cardiovascular morbidity and mortality compared to placebo.
A systematic search for trials was conducted in the Cochrane Hypertension Group Specialised Register, CENTRAL, MEDLINE, EMBASE, AGRICOLA, AMED, and CINAHL up to November 2011. A hand search of reference lists of identified reviews was conducted. Experts in the area were also contacted to identify trials not found in the electronic search. Clinicaltrials.gov was searched for ongoing trials.
Randomized, placebo-controlled trials of any garlic preparation versus placebo for the treatment of hypertension were included.
Two reviewers independently extracted data and assessed trial quality using the risk of bias tool. Data synthesis and analysis was performed using RevMan 5.
The search identified two randomized controlled trials for inclusion. One trial included 47 hypertensive patients and showed that garlic significantly reduces mean supine systolic blood pressure by 12 mmHg (95% CI 0.56 to 23.44 mmHg, p=0.04) and mean supine diastolic blood pressure by 9 mmHg (95% CI 2.49 to 15.51 mmHg, p=0.007) versus placebo. The authors state that garlic was "free from side effects" and that no serious side effects were reported. There were 3 cases "where a slight smell of garlic was noted."The second trial could not be meta-analysed as they did not report the number of people randomized to each treatment group. They did report that 200 mg of garlic powder given three times daily, in addition to hydrochlorothiazide-triamterene baseline therapy, produced a mean reduction of systolic blood pressure by 10-11 mmHg and of diastolic blood pressure by 6-8 mmHg versus placebo.Neither trial reported clinical outcomes and insufficient data was provided on adverse events.
AUTHORS' CONCLUSIONS: There is insufficient evidence to determine if garlic provides a therapeutic advantage versus placebo in terms of reducing the risk of mortality and cardiovascular morbidity in patients diagnosed with hypertension. There is also insufficient evidence to determine the difference in withdrawals due to adverse events between patients treated with garlic or placebo.Based on 2 trials in 87 hypertensive patients, it appears that garlic reduces mean supine systolic and diastolic blood pressure by approximately 10-12 mmHg and 6-9 mmHg, respectively, over and above the effect of placebo but the confidence intervals for these effect estimates are not precise and this difference in blood pressure reduction falls within the known variability in blood pressure measurements. This makes it difficult to determine the true impact of garlic on lowering blood pressure.
大蒜因其降血压作用而被患者广泛使用。2008年发表的一项荟萃分析得出结论，食用大蒜可降低高血压和血压正常患者的血压。因此，重要的是回顾现有证据，以确定大蒜在降低高血压患者心血管事件和死亡率方面是否也具有有益作用。
确定高血压患者使用大蒜单一疗法与使用安慰剂相比，是否能降低心血管疾病发病率和死亡率。
截至2011年11月，在Cochrane高血压组专业注册库、Cochrane系统评价数据库、医学期刊数据库、荷兰医学文摘数据库、农业与生命科学数据库、护理学与健康领域数据库中对试验进行了系统检索。对已识别综述的参考文献列表进行了手工检索。还联系了该领域的专家，以识别电子检索中未找到的试验。在临床研究数据库中搜索正在进行的试验。
纳入任何大蒜制剂与安慰剂治疗高血压的随机、安慰剂对照试验。
两名评价员独立提取数据，并使用偏倚风险工具评估试验质量。使用RevMan 5进行数据合成和分析。
检索确定了两项随机对照试验纳入分析。一项试验纳入了47例高血压患者，结果显示与安慰剂相比，大蒜可使平均仰卧位收缩压显著降低12 mmHg（95%可信区间为0.56至23.44 mmHg，p=0.04），平均仰卧位舒张压显著降低9 mmHg（95%可信区间为2.49至15.51 mmHg，p=0.007）。作者称大蒜“无副作用”，且未报告严重副作用。有3例“闻到轻微大蒜味”。第二项试验无法进行荟萃分析，因为他们未报告随机分配到各治疗组的人数。他们确实报告称，在氢氯噻嗪-氨苯蝶啶基线治疗基础上，每日三次给予200 mg大蒜粉，与安慰剂相比，收缩压平均降低10-11 mmHg，舒张压平均降低6-8 mmHg。两项试验均未报告临床结局，且关于不良事件的数据不足。
没有足够证据确定大蒜在降低已诊断高血压患者死亡率和心血管疾病发病率方面是否比安慰剂具有治疗优势。也没有足够证据确定大蒜治疗组与安慰剂治疗组因不良事件退出的差异。基于87例高血压患者的两项试验，似乎大蒜除了安慰剂效应外，还可使平均仰卧位收缩压和舒张压分别降低约10-12 mmHg和6-9 mmHg，但这些效应估计值的可信区间不精确，且血压降低的差异在已知的血压测量变异性范围内。这使得难以确定大蒜对降低血压的真正影响。
