Content area
Full Text
Introduction
Hypertension, defined as a systolic blood pressure (BP) >140 mmHg and/or a diastolic BP >90 mmHg, is one of the major risk factors for various cardiovascular morbidities, including stroke, coronary heart disease and kidney dysfunction, as well as for mortality (1). Although hypertension affects up to 30% of the adult population in the majority of countries (2), >50% of hypertensive individuals are unaware of their condition (3). Prehypertension, formerly termed borderline hypertension or high-normal BP, is usually defined as a systolic BP of 130–139 mmHg and a diastolic BP of ≤89 mmHg, or as a systolic BP of ≤139 mmHg and a diastolic BP of 85–89 mmHg (2,4). This condition is known to be a precursor of hypertension (4,5) and is associated with excess morbidity and mortality from cardiovascular causes (4,6). Thus, lowering BP may be beneficial not only for the hypertensive population but also for the prehypertensive population. For the initial management of high BP, relevant lifestyle modifications, including ensuring optimal nutrition, weight reduction and regular physical activity, were established by The Japanese Society of Hypertension (JSH) in 2004 (7). In recent years, food supplementation, mainly using natural foods or their components, has been considered to provide another, less strenuous non-pharmacological option for lowering BP, particularly for individuals with borderline to mildly high BP that does not warrant the prescription of antihypertensive drugs.
Garlic (Allium sativum) has a long history of use as a foodstuff and as a pungent spice in numerous countries. Garlic has also been used in a number of cultures for various medicinal purposes. Previous pharmacological studies concerning garlic have revealed that it has various prophylactic and remedial properties beneficial to good health, among which its hypotensive activities are the most notable (8–11). Over the last 30 years, numerous clinical studies have been carried out to examine the effects on health of using various garlic-based products containing dried garlic powder, garlic oil or garlic extract as the basal component. Such varied types of garlic preparation may contain widely varying types of sulfur-containing phytochemicals due to the different methods of producing the preparations. This may precipitate varying biological responses in humans. Although several clinical trials have suggested that garlic lowers systolic and/or diastolic BP, negative results have been obtained...