研究发现西瓜降低血压

iavjssssmqee · 发表于 2010-10-19 21:21:55

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Watermelon Lowers Blood Pressure, Study Finds

http://www.sciencedaily.com/releases/2010/10/101013173847.htm

No matter how you slice it, watermelon has a lot going for it -- sweet, low calorie, high fiber, nutrient rich -- and now, there's more. Evidence from a pilot study led by food scientists at The Florida State University suggests that watermelon can be an effective natural weapon against prehypertension, a precursor to cardiovascular disease.

It is the first investigation of its kind in humans. FSU Assistant Professor Arturo Figueroa and Professor Bahram H. Arjmandi found that when six grams of the amino acid L-citrulline/L-arginine from watermelon extract was administered daily for six weeks, there was improved arterial function and consequently lowered aortic blood pressure in all nine of their prehypertensive subjects (four men and five postmenopausal women, ages 51-57).

"We are the first to document improved aortic hemodynamics in prehypertensive but otherwise healthy middle-aged men and women receiving therapeutic doses of watermelon," Figueroa said. "These findings suggest that this 'functional food' has a vasodilatory effect, and one that may prevent prehypertension from progressing to full-blown hypertension, a major risk factor for heart attacks and strokes.

"Given the encouraging evidence generated by this preliminary study, we hope to continue the research and include a much larger group of participants in the next round," he said.

Why watermelon?

"Watermelon is the richest edible natural source of L-citrulline, which is closely related to L-arginine, the amino acid required for the formation of nitric oxide essential to the regulation of vascular tone and healthy blood pressure," Figueroa said.

Once in the body, the L-citrulline is converted into L-arginine. Simply consuming L-arginine as a dietary supplement isn't an option for many hypertensive adults, said Figueroa, because it can cause nausea, gastrointestinal tract discomfort, and diarrhea.

In contrast, watermelon is well tolerated. Participants in the Florida State pilot study reported no adverse effects. And, in addition to the vascular benefits of citrulline, watermelon provides abundant vitamin A, B6, C, fiber, potassium and lycopene, a powerful antioxidant. Watermelon may even help to reduce serum glucose levels, according to Arjmandi.

"Cardiovascular disease (CVD) continues to be the leading cause of death in the United States," said. "Generally, Americans have been more concerned about their blood cholesterol levels and dietary cholesterol intakes rather than their overall cardiovascular health risk factors leading to CVD, such as obesity and vascular dysfunction characterized by arterial stiffening and thickness -- issues that functional foods such as watermelon can help to mitigate.

"By functional foods," said Arjmandi, "we mean those foods scientifically shown to have health-promoting or disease-preventing properties, above and beyond the other intrinsically healthy nutrients they also supply."

Figueroa said oral L-citrulline supplementation might allow a reduced dosage of antihypertensive drugs necessary to control blood pressure.

"Even better, it may prevent the progression from prehypertension to hypertension in the first place," he said.

While watermelon or watermelon extract is the best natural source for L-citrulline, it is also available in the synthetic form in pills, which Figueroa used in a previous study of younger, male subjects. That investigation showed that four weeks of L-citrulline slowed or weakened the increase in aortic blood pressure in response to cold exposure. It was an important finding, said Figueroa, since there is a greater occurrence of myocardial infarction associated with hypertension during the cold winter months.

"Individuals with increased blood pressure and arterial stiffness -- especially those who are older and those with chronic diseases such as type 2 diabetes -- would benefit from L-citrulline in either the synthetic or natural (watermelon) form," Figueroa said. "The optimal dose appears to be four to six grams a day."

Approximately 60 percent of U.S. adults are prehypertensive or hypertensive. Prehypertension is characterized by systolic blood pressure readings of 120-139 millimeters of mercury (mm Hg) over diastolic pressure of 80-89 mm Hg. "Systolic" refers to the blood pressure when the heart is contracting. "Diastolic" reflects the blood pressure when the heart is in a period of relaxation and expansion.

Findings from Figueroa's latest pilot study at Florida State are described in the American Journal of Hypertension. A copy of the paper ("Effects of Watermelon Supplementation on Aortic Blood Pressure and Wave Reflection in Individuals With Prehypertension: A Pilot Study") can be accessed online.

The paper's lead author, Figueroa holds a medical degree, a doctoral degree in physiological sciences, and a master's degree in sports medicine. He has been a faculty member in the Florida State University Department of Nutrition, Food and Exercise Sciences since 2004. Figueroa's coauthor and colleague Arjmandi serves as chairman of the department, which is a part of Florida State's interdisciplinary College of Human Sciences. Arjmandi also is the author or coauthor of an extensive body of published research on the health benefits of prunes and other functional foods.

Coauthors of the Figueroa-Arjmandi paper in the American Journal of Hypertension are Marcos A. Sanchez-Gonzalez, a Florida State doctoral student in exercise physiology, and Penelope Perkins-Veazie, a horticulture professor at North Carolina State University.

iavjssssmqee · 发表于 2010-10-19 21:25:05

研究发现西瓜降低血压

不管你怎么切，西瓜总是都还是那样——味甜、低卡路里、高纤维、营养丰富，现在，又有了其他的好处。佛罗里达大学的食物科学家们做的一个初步研究中有证据支持西瓜可成为一种对付高血压前期的有效的自然武器，高血压前期是心血管疾病的前兆。

这是在人类中的第一个此类研究。佛罗里达大学Arturo Figueroa副教授和Bahram H. Arjmandi教授发现给予9名高血压前期患者（4名男性，5名绝经后女性，年龄：51岁-57岁）服用从西瓜汁中提取的6克L-瓜氨酸/ L-精氨酸，每天一次，持续6周，所有患者动脉功能改善，大动脉血压降低。

Figueroa说：“我们是文献记载的第一批仅仅让健康的中年男性和女性接受治疗剂量的西瓜就改善大动脉血流动力学的人。这些发现提示这样的‘功能保健食品’有血管舒张作用，也许可以阻止高血压前期逐步发展为高血压，高血压是心脏病发作和卒中的一个主要危险因素。”

他说：“尽管这个初步研究提供了令人鼓舞的证据，但我希望继续在下一次的研究中纳入更多的参与者。”

为什么是西瓜？

Figueroa说：“西瓜是自然界中富含L-瓜氨酸最多的食物，L-瓜氨酸与L-精氨酸密切相关，而L-精氨酸可形成对血管调节和健康血压必不可少的一氧化氮。”

L-瓜氨酸是在体内转化为L-精氨酸的。所以单纯从膳食中补充L-精氨酸并非很多成人高血压患者的选择，Figueroa说，因为这会引起恶心、胃肠道不适和腹泻。

相反，西瓜却可以被很好的耐受。佛罗里达的初步研究中的参与者并没有发生不良反应。另外，除了瓜氨酸能使血管获益之外，西瓜还富含大量的维生素A、B6、C、纤维、钾和一种强抗氧化剂：番茄红素。西瓜甚至还能帮助降低血糖水平,Arjmandi介绍道。

Arjmandi说：“冠心病（CVD）仍然是美国人的头号死亡原因。通常美国人比较关注他们的血胆固醇水平和饮食胆固醇摄入，而不是导致CVD的总的心血管健康危险因素，例如以动脉硬化和增厚为特征的肥胖和血管功能失调，功能保健食品如西瓜可使病变减轻。”

Arjmandi说：“功能性保健食品，就是那些被证明有系统的健康促进和疾病防止作用的食物，它们同时还可或多或少的提供健康的营养物质。”

Figueroa说口服L-瓜氨酸也许能减少对控制血压非常必要的抗高血压药的用量。

他说：“更好的情况是，这也许可以在第一时间阻止高血压前期发展为高血压。”

西瓜或西瓜汁是L-瓜氨酸最好的自然来源，Figueroa在先前的一个研究中对年龄稍小的男性受试者使用人造药丸也有类似的效果。这个研究显示服用4周的L-瓜氨酸后，受到冷刺激时大动脉血压升高速度减慢、幅度减小。Figueroa说，这是一个重要的发现，因为在冬季与高血压相关的心肌梗死出现的概率更高。

“血压升高和动脉硬化的个体——尤其是那些高龄和那些合并慢性疾病如2型糖尿病的人——将会从人造的或者自然的（西瓜）成分中获益。最佳剂量可能是4-6克/天。”

将近有60%的美国成人为高血压前期或高血压患者。高血压前期的收缩压读数为120-139毫米汞柱（mmHg），舒张压为80-89 mmHg。“收缩压”是指心脏收缩时的的血压。“舒张压”是指心脏放松和扩张时的血压。

Figueroa在佛罗里达最近的初步研究的发现发表在《美国高血压杂志》上。可从网上得到该论文（“对高血压前期患者补充西瓜对大动脉血压的影响和波浪反射：一个初步研究”）的拷贝。

该文的主要作者Figueroa拥有一个医学学位、一个生理学博士学位和一个运动医学硕士学位。他从2004年就成为了佛罗里达大学营养、食物和运动科学部的一名教员。Figueroa 合著者兼同事Arjmandi是佛罗里达大学人类科学学科部的主席。Arjmandi还是大量关于通过西梅和其他功能保健食品使健康获益的已发表研究的作者或合著者。

Figueroa和Arjmandi在《美国高血压杂志》中合著的文章里的合著者为Marcos A。Sanchez-Gonzalez是一个佛罗里达运动生理学的博士生，Penelope Perkins-Veazie是一个北卡罗来纳州大学的园艺学教授。

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