Aged black garlic (ABG) was found to contain a series of allyl-sulfur compounds with the ability to modulate nitric oxide synthetase, angiotensin-converting enzyme system, and endothelial activation, top of dietary guidance lowers diastolic blood pressure (DBP) in men with moderately elevated cholesterol.
The researchers randomly assigned 67 individuals with moderate hypercholesterolemia (defined as LDL levels of at least 115 mg/dL) to receive one ABG tablet (250 mg ABG extract/1.25 mg SAC) or placebo daily for 6 weeks. Following a 3-week washout, the groups were reversed and the new intervention continued for another 6 weeks. Participants received dietary recommendations regarding Cardiovascular disease risk factors and had their dietary habits assessed through a 3-day food record at baseline and after 6 weeks during both treatments.
Participants receiving lipid-lowering treatment or antihypertensives were excluded, as were those with a body mass index of 35 kg/m2 or higher, a fasting blood glucose of at least 126 mg/dL, or were active smokers. There were no differences in baseline characteristics between the two groups. The mean systolic and diastolic pressures at baseline were 124/75 mm Hg in the ABG group and 121/74 mm Hg in the placebo group. Their mean age was 53 years.
Adherence with the protocol was “high” at 96.5% in both groups, and no adverse effects were reported. Although no significant differences between ABG and placebo were observed at 3 weeks, the decline in DBP after consumption of the ABG extract became significant at 6 weeks (mean change, -3.7 mm Hg vs -0.10 mm Hg; P = .007). When stratified by sex and categories of DBP, the mean change in DBP after 6 weeks of ABG consumption was particularly prominent in men and in those with a baseline DBP of at least 75 mm Hg.
The 6-week change in systolic blood pressure with ABG and placebo was 1.32 mm Hg and 2.84 mm Hg, respectively. The total cholesterol levels decreases at 6 weeks, after ABG treatment, but no other significant differences between groups were observed for lipid profile, apolipoproteins, or other outcomes of interest, including serum insulin, waist circumference, and body mass index.
The authors note that although systolic BP elevation “has a greater effect on outcomes, both systolic and diastolic hypertension independently influence the risk of adverse cardiovascular events, regardless of the definition of hypertension” and that the risk of death from ischemic heart disease and stroke doubles with every 10 mm Hg increase in DBP in people between the ages of 40 and 89 years.
“Thus, reducing DBP by 5 mm Hg results in a 40% lower risk of death from stroke and a 30% lower risk of death from ischemic heart disease or other vascular death,” they state.
After 6 weeks, consumption of ABG with a high concentration of s-allyl-L-cystine (SAC) was associated with a nearly 6-mm Hg reduction in DBP in men. Another cardiovascular disease (CVD) risk factor was not significantly affected. The observed reduction in DBP by ABG extract was similar to the effects of dietary approaches, including the effects of the Dietary Approaches to Stop Hypertension (DASH) diet on Blood pressure. The potential beneficial effects of ABG may contribute to obtaining an optimal DBP” but were “better observed in men and non-optimal DBP populations.
Pure SAC and aged garlic have shown healthy effects on multiple targets in vitro and in vivo tests. However, previous studies in humans have not focused on ABG but rather on other types of aged garlic in patients with some type of CVD risk factor and suffered from methodologic or design weaknesses.
However, these results are limited to a small study, and potentially other issues, such as sodium, potassium, or other nutrients known to be associated with blood pressure, were not reported, thereby raising questions about the exclusivity of the ABG over other accompanying dietary factors.