Bad Breath

We have a lot of choices to make about our diet. Add to that – doing the right thing when it comes to treating a chronic illness, fighting a virus, or losing weight, and suddenly, our nutrition choices can seem almost overwhelming.  

Well, I’m here to help. Welcome to the Nutrition Facts podcast. I’m your host – Dr. Michael Greger.

Today, we discuss a condition that we might not even know we have – until someone is brave enough to tell us:  bad breath.  

The word halitosis is derived from the Latin and Greek terms for abnormal or diseased breath––though it may be less of a medical term and more of a marketing term, as it was supposedly coined by the Listerine Company. Halitosis is commonly referred to as bad breath, though medical and dental professionals often use, instead of bad breath, the less judgy term, breath odor.

As described in the Journal of Breath Research, halitosis has been classified into four types. There is genuine halitosis, either transient or chronic, which is contrasted with pseudo-halitosis, when someone thinks they have bad breath, but it’s evidently all in their head, and halitophobia, where they start out with genuine halitosis, but then they treat it, and get rid of it, but still think they have it. These are rare, though. The vast majority of cases are IOH, which stands for intra-oral halitosis––bad breath arising from inside the mouth, as opposed to lungs or stomach, and not just anywhere in the mouth, but specifically, in most cases, apparently coming off the coating on the tongue.

Most people have a tongue coating, a grayish-white deposit on the tongue, which is the main cause of bad breath. Now, there are pathological conditions like black hairy tongue, whose symptoms may include an unattractive appearance of the tongue, which can be caused by certain drugs, but the normal tongue coating is just a thin, slightly moist, whitish substance across the upper surface of the tongue composed of sloughed tongue cells, bacteria, seepage from our blood supply, and secretions from our gums and postnasal area, like mucus discharge from our sinuses dripping onto the back of our tongue.

Those with gum disease tend to have four times as much coating, in terms of the wet weight scraped off the tongue due to the migration of white blood cells from periodontal pus pockets onto the tongue surface, but even in people with perfect dental hygiene, food particles can get trapped between all the little bumps and cracks on the tongue and form a thick bacterial biofilm coating. If we eat the right foods, though, our mouth may be self-cleaning. Just the act of chewing and swallowing foods that actually need chewing can cleanse off the tongue, leaving you with just the normal, thin layer of coating, but fast food is engineered to be eaten fast. It’s soft, you can just gulp it down and consequently, the thickness of the tongue coating might increase, and that could contribute to bad breath, but you don’t know until you put it to the test.

 “The effect of a chewing-intensive, high-fiber diet on oral halitosis,” a randomized clinical cross-over study, in which subjects were examined over a period of 2.5 hours after consumption of a high-fiber vs. low-fiber meal using an organoleptic assessment of halitosis. Although a few electronic bad-breath detectors have appeared on the market, organoleptic scoring is still the ‘gold standard,’ which is just a fancy name for when dentists or doctors just give your breath a sniff. Here’s the ratings they use: no halitosis detected even up close and personal, or yeah, bad breath, but only up to about four inches away, or out to a foot, or all the way out to more than a yard.

We know halitosis is reduced by eating, due to the “self-cleaning” of the mouth while chewing food, and it seems obvious that foods that need to be chewed more intensively have a stronger self-cleaning effect than foods that require less chewing. But whether this is actually the case had never been examined, until now. The participants were randomized to a high-fiber, high-chew meal with a whole grain roll with jam and a raw apple, versus a low-fiber, low-chew white bread roll with jelly and a cooked apple and, the result: a significantly lower bad breath score immediately after the high-fiber meal, and then two-and-a-half hours later, compared to the low-fiber meal. The researchers conclude that a chewing-intensive, high-fiber meal led to a greater reduction of halitosis.

Most bad breath is due to the decay of sulfur-containing proteins. Here’s the story.

It has been estimated that 90 million Americans, or approximately 30 percent of the U.S. population, currently suffer from bad breath on a regular basis. And for those of you thinking “Phew, I’m glad I’m not one of those,” it is believed that people with bad breath can’t actually smell the odor coming out of their own mouth. Maybe this is because they’re just used to it. Or it’s because when you sniff, you’re breathing air from below, rather than in front where you’re exhaling. Either way, the mouth air of chronic malodor sufferers is tainted with compounds such as hydrogen sulfide, which produce a stream of foul air that can be gravely offensive to the people in their vicinity.

The characteristic smells in halitosis include compounds that smell like feces, like scatole, the rotten egg gas hydrogen sulfide, a corpse-like aroma from cadaverine, a sweaty feet compound, putrescine for the smell of decaying meat, rotten cabbage, rotten fish, pee; apples don’t sound so bad, and I don’t even know what squashed bedbugs smell like. But, the major compounds that contribute to oral malodor are the VSCs, the volatile sulfur compounds such as hydrogen sulfide. Bacteria in our mouth, predominantly on our tongue, have the capacity to produce these odorous sulfur compounds through putrefaction of sulfur-containing proteins.

Okay, so what can we do about it? Many have concentrated on trying to reduce the bacterial load in the mouth with antiseptic mouthwashes, or finding ways to trap the VSCs. Mechanically, you can disrupt the biofilm of bacteria on the tongue, like with various tongue-scraping techniques, though tongue cleaning seems to work more through reducing the substrates for putrefaction, rather than the bacteria themselves. Okay, but if the substrates for VSC production are the sulfur-containing amino-acids, and the sulfur-containing amino acids are derived mainly from animal protein, meat and dairy, what about using a dietary approach? The VSCs from animal protein may actually explain why carnivore poop smells so much different than herbivore poop.

And indeed, limiting the amount of consumed proteins may significantly reduce fetor ex ore, from the Latin meaning stench mouth. The reason they add fats and alcohol is that they can both cause relaxation of lower esophageal sphincter. Normally, the only time you exhale odors from your stomach is when you burp, because the sphincter at the top of the stomach prevents stuff from backing up, but alcohol or a fat-rich diet increases the relaxation of that sphincter, which further increases the risk and severity of bad breath.

But most cases of halitosis occur due to the decay of food residues in the mouth by the bacteria that decompose proteins and amino acids, and produce the volatile sulfur compounds. So, the treatment of oral halitosis should involve not just professional advice on oral hygiene, but also diet. Dairy proteins, for example, are known to break down in the mouth, leading to the release of amino acids that are rich in sulfur. Dairy products are rich sources of the milk protein casein, and casein is rich in the sulfur-containing amino acid cysteine, which is a precursor to the formation of the rotten egg gas hydrogen sulfide in the oral cavity. In fact, that’s how you can test people for bad breath. Cysteine challenge testing: just have people swish their mouth with it.

When cysteine is degraded, not only do you get the hydrogen sulfide, which comprises a large part of the bad breath bouquet, but you get sulfhydryl anions that favor the growth of the very bacteria within the mouth responsible for the protein putrefaction that’s central to the production of oral malodor in the first place, and to the development of gum disease. So, it’s not just a one-two punch, but a triple threat. Bad breath isn’t just some aesthetic issue; these volatile sulfur compounds can be toxic to the gums, even at extremely low concentrations.

Hydrogen sulfide reacts with collagen and can alter the protein structure, thereby rendering your gums and jaw more susceptible to destruction. Then, you can develop these pockets of putrid pus that can lead to more halitosis. The periodontal pockets are the second main source of the volatile sulfur compounds. Even people with mild periodontitis may have twice the risk of reporting bad breath.

Finally, let me touch on the role diet has in so-called extra-oral halitosis, bad breath that doesn’t originate in the mouth. There are lots of drugs that can do it, including dietary supplements like fish oil, but there’s another way people can smell fishy: trimethylamine.

Trimethylaminuria is one the largest causes for undiagnosed body odor. It’s when you can’t sufficiently metabolize a malodorous compound called trimethylamine, which is formed in your gut when you eat lots of choline. The textbook presentation is urine, breath, sweat, and reproductive fluids smelling like rotten or decaying fish, but what many doctors don’t realize is that the fish odor presentation may only occur in like 10 percent of individuals who have this predisposition. Yes, at high concentrations, trimethylamine has a foul, rotten fish odor. But at low concentrations, it can just give you kind of unpleasant garbage-like breath. And because there are many foods that are rich in choline, like the fact that there are eggs found in so many foods, you may not make the connection between your diet and your body odor. But you can always try cutting out foods like egg yolks for a few weeks, and see if you smell any better.

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