前几天，科学网援引中国新闻网的一则报道：研究称常用漱口水有风险！其出处是《自由基生物学与医学》（Free Radical Biology and Medicine）杂志上发表的一篇最新论文“口腔硝酸盐还原细菌在血压控制中的生理作用“（Physiological role for nitrate-reducing oral bacteria in blood pressure control）。这篇文章是open access，点击上述论文的英文标题，即可阅读全文并下载保存。

这篇文章的核心内容是强调”漱口水升高血压“，以前科学网也曾引用过另一篇报道称：漱口水可能增加口腔癌风险！看来漱口水”十恶不赦“，堪称日常生活中危及人类健康的”毒品“。可是，为什么漱口水仍在生产，产品仍在销售（如高露洁的”贝齿“）？当你看到这些报道后，你还会购买和使用漱口水吗？对此，我觉得有必要科普一下，澄清一些模糊认识，也避免一些误会。

为什么漱口水可以让人的血压升高呢？其实原理很简单，一氧化氮（NO）可以通血管，而使用漱口水能减少NO的产生。口腔内含有丰富的硝酸盐（NO₃^-），它既可直接来自食物，也能由唾液腺分泌，后者来自血液中NO的氧化。细菌含有硝酸还原酶，可以将硝酸盐还原成亚硝酸盐（NO₂^-），后者可被人体的酶类（黄素氧化酶、呼吸链酶类、去氧血红蛋白或肌红蛋白等）继续还原成NO。

不难理解，漱口水就是”杀菌水“，其中含有的杀菌成分（如西吡氯铵、氟化钠等）可以使口腔细菌全部被杀死，于是硝酸盐就无法经亚硝酸盐产生NO了。推而广之，按此结果，今后凡是含有杀菌成分的牙膏（如含氟牙膏）都不能购买和使用了，因为要保护口腔细菌，避免血压升高。

有人会问：使用含氟的漱口水或含氟牙膏的后果真的有那么严重吗？根据论文的实验结果，在7天内使用含氯己定（另一种杀菌成分）漱口水的自愿者，其血压仅仅升高了2-3.5毫米汞柱，可能还不及一次面试可能导致的血压升高，何况人体内产生NO的主要途径是由精氨酸在一氧化氮合酶（NOS）催化下合成，而细菌转化的NO含量微乎其微！大家看完下面这张示意图就会完全明白。

这篇文章只是说明一个事实，而并不表明其生理意义有多么重要。必须指出的是，这个实验是用健康志愿者做的，假如你患有口腔疾病（如蛀齿、牙周炎、牙龈炎），除了积极治疗以外，常用漱口水至少可以缓解牙疼，并防止病情恶化。因此，口腔细菌中有害菌对人体的坏处远远大于有益菌对健康的好处。

另外，至于漱口水致癌是基于其含有不纯的酒精成分，其中的乙醛可以致癌。人体对乙醛的耐受性存在个体差异（遗传差异），也就是有人能分解乙醛，有人不能分解。喝一次白酒接触的乙醛比用一次漱口水接触的乙醛要多得多。不过，现在出品的漱口水都不含酒精，所以其致癌风险也就不存在了。

以下是该论文的英文摘要：

Physiological role for nitrate-reducing oral bacteria in blood pressure control

Circulating nitrate (NO₃⁻), derived from dietary sources or endogenous nitric oxide production, is extracted from blood by the salivary glands, accumulates in saliva, and is then reduced to nitrite (NO₂⁻) by the oral microflora. This process has historically been viewed as harmful, because nitrite can promote formation of potentially carcinogenic N-nitrosamines. More recent research, however, suggests that nitrite can also serve as a precursor for systemic generation of vasodilatory nitric oxide, and exogenous administration of nitrate reduces blood pressure in humans. However, whether oral nitrate-reducing bacteria participate in “setting” blood pressure is unknown. We investigated whether suppression of the oral microflora affects systemic nitrite levels and hence blood pressure in healthy individuals. We measured blood pressure (clinic, home, and 24-h ambulatory) in 19 healthy volunteers during an initial 7-day control period followed by a 7-day treatment period with a chlorhexidine-based antiseptic mouthwash. Oral nitrate-reducing capacity and nitrite levels were measured after each study period. Antiseptic mouthwash treatment reduced oral nitrite production by 90% (p < 0.001) and plasma nitrite levels by 25% (p = 0.001) compared to the control period. Systolic and diastolic blood pressure increased by 2–3 .5 mm Hg, increases correlated to a decrease in circulating nitrite concentrations (r² = 0.56, p = 0.002). The blood pressure effect appeared within 1 day of disruption of the oral microflora and was sustained during the 7-day mouthwash intervention. These results suggest that the recycling of endogenous nitrate by oral bacteria plays an important role in determination of plasma nitrite levels and thereby in the physiological control of blood pressure.