Why do dogs lick their wounds? They even lick our wounds. This leads to a question posed in the medical literature nearly a half century ago: Might there be some healing property of dog saliva? Well, it appears that there are a number of immune defense mechanisms in saliva, one of which involves nitric oxide. Licking of human skin results in production of nitric oxide from salivary nitrite, which kills skin pathogens and comes from the nitrates we eat in our diet.
How do we know we can get nitric oxide from licked human skin? Researchers had a bunch of volunteers lick their hands all over, front and back. Today, we have a better way to clean wounds: soap and water. (And we should never let our pets lick open wounds because cases of serious infections have been reported).
The reason I bring it up is that this transformation of nitrates from our diet into nitrites in our mouth has important implications for our health. Insufficient nitric oxide production is recognized as the earliest event in the onset and progression of a number of chronic diseases, including high blood pressure, peripheral artery disease, and a number of inflammatory conditions.
Nitrates come from vegetables in our diets, such as beets and green leafy vegetables. Good bacteria on our tongue convert nitrates into nitrites which can circulate throughout the body to create nitric oxide, and any nitrates our tongue bacteria missed the first time around get pumped by our body back into our saliva to give our tongue bacteria a second chance. One way we can become nitric-oxide-production-deficient is by not eating enough vegetables in the first place. So, eating vegetables should be the first step. But, if our tongue bacteria die off, the cycle is broken no matter how many vegetables we eat.
That’s why we should not use antiseptic mouthwash. Previously, I profiled an important study in my post Don’t Use Antiseptic Mouthwash. The most protective food for our heart may be green leafy vegetables because, like beets, they have lots of nitrates. So, if you drink some beet juice, you can get a remarkable drop in blood pressure within just hours, but only if you swallow.
The nitric oxide pathway can be interrupted if you use an antibacterial mouthwash or by spitting and not swallowing because of the critical action of our tongue bacteria on the nitrates in our saliva. So, we have to eat our vegetables and keep our tongue bacteria happy––so, no antibacterial mouthwash. But what about antibacterial toothpaste?
There’s a toothpaste on the market that contains an antibacterial chemical called triclosan. In my video below, I present a study that showed there was no difference in the levels of nitric oxide, nitrite, and nitrate after brushing with regular toothpaste and triclosan toothpaste. Our good tongue bacteria live in the cracks on the surface of our tongue, so if you just brush your teeth and not your tongue, the chemical doesn’t seem to get down there. Does that mean triclosan toothpaste is safe?
The use of triclosan toothpaste may not be associated with any increase in serious adverse cardiac events. And though studies on rats suggest the chemical can affect thyroid function, the use of triclosan toothpaste does not seem to affect human thyroid function. A study funded by Colgate concluded that triclosan was both safe and effective, producing “a significant reduction in gingivitis, plaque, and bleeding.” However, an independent review by the Cochrane Group suggested the reduction may be statistically significant but may not be beneficial enough to yield clinical significance.
Regarding safety, states are starting to ban the stuff because of data showing that despite the lack of efficacy, triclosan is so ubiquitous that most of the U.S. population is exposed to it. “Because the rapid rise in obesity in the U.S. parallels the introduction of triclosan, and because triclosan has two potential mechanisms by which it might alter human weight”—that is, by mucking with our gut flora or our hormones––researchers at Stanford decided to assess the association between triclosan levels flowing through people’s bodies and how heavy they are. And, indeed, they found an association between triclosan levels and increase in body mass index, and suggested further studies on how this chemical could be altering human growth and well-being.
Michael Greger, M.D.
PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations—2015: Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet, and my latest, 2016: How Not to Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers.