The Effects of the Onion-Pumpkin Extract on Blood Pressure

Hypertension has become one of the most common diseases in the world and considered a public health challenge due to its association with morbidity and mortality and increased cost to society. Hypertension is the most important risk factor for cardiovascular diseases such as coronary heart disease, stroke, congestive heart failure, and peripheral vascular disease. One fourth of adults in the United States have high blood pressure and among these, the blacks and the elderly have higher incidence of hypertension. This condition is characterized by abnormally high blood pressure with the systolic greater than 140 mmHg and diastolic greater than 90 mmHg (1).

Lowering blood pressure has been linked to 35% to 40% reductions in the incidence of stroke, 20%-25% in myocardial infarction, and 50% in heart failure. Management of hypertension includes lifestyle modifications and pharmacological therapy and antihypertensive drugs. Lifestyle modifications such as weight reduction in overweight and obese individuals, 8-week diet of fruits, vegetables, low-fat dairy products, whole grain, poultry fish and nuts with limited fats, red meat and sweets, reduction in dietary sodium, physical activity, and moderation of alcohol consumption have been shown to lower blood pressure. There are several classes of antihypertensive drugs, including angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) β-blockers (BBs), calcium channel blockers (CCBs) and the thiazide-class diuretics. Among these, the diuretic based therapy was more effective than other treatments in preventing cardiovascular diseases as demonstrated by the Antihypertensive and Lipid-lowering Treatment to prevent Heart Attack (ALLHAT) trial (1, 2).

Blood pressure can be lowered without using prescription drugs. Nutraceuticals have found their application in the treatment of hypertension. Omega-3 polyunsaturated fatty acids, omega-9 fatty acids, garlic, seaweed, and various vitamins and minerals have been shown to reduce blood pressure significantly (3).

Animal studies have demonstrated the potential benefits of onion in hypertensive rats. In one study involving rats fed with a control diet or a high-fat high-sucrose diet with or without Welsh onion for 4 weeks, lower blood pressure was observed in rats with onion diet, especially the green-leafy type. In addition, these rats have higher levels of nitric oxide (NO) metabolites in the urine and plasma, lower activity of NADH/NADPH oxidase in the aorta, and suppressed angiotensin II production (4). The mechanism of the antihypertensive effect of onion probably involves increased saving of NO (4, 5). A randomized, placebo-controlled, double-blind trial also demonstrated significant decrease in arterial blood pressure and reduction in plasma viscosity five hours after administration of a formulation containing onion and olive oil (6).

Pumpkin has been used as a traditional medicine and it is known for its antidiabetic, antitumor, antibacterial, anti-inflammatory, and antihypertensive properties (7). Animal studies confirmed that pumpkin seed oil supplementation resulted in lower systolic and diastolic blood pressure as well as improvements in lipid profile in both non-ovariectomized and ovariectomized rats (8). Using enzyme assays, it was demonstrated that pumpkin have moderate to high alpha-glucosidase and ACE inhibitory activities (9). A recent clinical trial involved postmenopausal women and the effects of supplemented pumpkin seed oil in cholesterol levels. The results of this trial showed that 12-week administration of 2g/day pumpkin seed oil led to a significant increase in HDL cholesterol and significant decrease in diastolic blood pressure. Pumpkin seed oil also improved menopausal symptom scores by decreasing hot flushes, headaches, and joint pains (10).

This open-label, adaptive-design, pilot study was designed to evaluate the effect of Onion-Pumpkin Extract in supporting healthy blood pressure as assessed by the change in systolic and diastolic blood pressures. The effect of the product on glucose metabolism, lipid levels, and antioxidant levels would also be determined. Tolerability and safety of the study product would also be investigated.