Graphic: E. J. Stanley, 1901



The New York Times, by Nicholas Bakalar  —  DENTAL cavities are not good news, but when it comes to preventive oral health, they may be among the smaller problems.

The advice is familiar: brush and floss regularly, use fluoride mouthwash, limit snacks and sweet drinks, visit the dentist twice a year. Good suggestions, even if not everyone follows them: by age 12, 50 percent of children have cavities. But there are two much more serious problems, common dental diseases that can lead not only to loss of teeth but also to loss of life: periodontal disease and oral cancer.

Periodontal disease — a chronic bacterial infection of the gums that destroys the bone and tissues that hold the teeth — is the leading cause of tooth loss in adults. Some people are genetically susceptible, and the problem can be aggravated by smoking, taking certain medications, stress and other factors.

Several studies have found that gum disease is associated with an increased risk for heart attack. “It isn’t nailed down yet,” said Dr. Martin J. Davis, professor of clinical dentistry at the College of Dental Medicine at Columbia, “but there seems to be a link between the inflammation of gums and the inflammatory markers of heart disease.”

It may be that oral bacteria enter the bloodstream, attach to fatty plaques in the coronary arteries and cause clots to form. Or maybe inflammation itself increases plaque buildup. A 2007 study showed that periodontal disease increased the risk of heart disease in men by one third and doubled it in women, even after controlling for smoking.

Studies also suggest that gum disease is associated with the risk for stroke, altered glycemic control in people with diabetes and adverse pregnancy conditions like pre-eclampsia (pregnancy-induced high blood pressure), low birth weight and preterm birth. When periodontal disease is treated by reducing inflammation and lowering the quantities of harmful bacteria in the mouth, it can have a major impact on inflammation in the rest of the body.

Oral cancer is the second serious dental problem. It afflicts about 34,000 people a year and kills 8,000. Dr. Michael Kahn, a professor of oral pathology at Tufts University, compares oral cancer with the 11,000 cases of cervical cancer that are detected by the 60 million pap smears administered every year. “A person dies every hour around the clock from oral cancer,” he said, “yet it’s a struggle to get insurance to cover any of the new screening tests. It causes at least twice as many deaths as cervical cancer, but we’ve paid for pap smears — which have reduced cervical cancer by 90 percent.”

Smoking and alcohol abuse are the major causes, but 25 percent of oral cancers appear in people who have never smoked or drunk to excess. The suspected cause of at least some of these cancers is human papillomavirus, or H.P.V., the same sexually transmitted virus that causes most cervical cancers, which can invade the mouth during oral sex. “Some are already hypothesizing that if kids are inoculated against H.P.V.,” Dr. Kahn said, “there will be a turnaround in the oral cancers caused by H.P.V., too.”

For now, prevention, screening and early treatment are crucial to lowering the death rate.

The first sign of oral cancer is often a tiny white or red spot in the mouth, but the disease can be detected before a sore appears. In the last two or three years, manufacturers have produced noninvasive devices for detecting abnormal tissue that may be invisible to the naked eye, and some dentists are beginning to use them, even though their effectiveness remains controversial.

“The literature says they work,” Dr. Kahn said. “Some would like more or stronger evidence, but for others, they’re convinced. In dentistry, you don’t have much time to look. The theory is that if you use one of these devices, it gives you some additional help.” If a dentist finds a suspicious lesion, Dr. Kahn recommends referral to an oral pathologist as the next step.

There is more to good oral health than conscientious brushing and flossing, even though they remain important. “You have to take care of your mouth like any other part of the body,” Dr. Davis said, “because it’s linked to the rest of the body.”

Dr. George Chapman
, September 6, 2011, by Alice Park  —   A new study shows that what we eat can affect our gut, both inside and out. The community of bacteria that colonize our intestines may shift depending on the makeup of our overall diet.

Why is that important? Increasingly, research in the field of gut flora shows that these bugs have a big impact on some crucial bodily functions: they aid digestion and metabolism, affect immunity and determine how many calories we extract from food, possibly contributing to obesity and diabetes, among other health effects.

Now researchers in the U.S. and Brazil report online in the journal Science that the dominant species of bacteria in the gut microbiome, as it’s known, may change in accordance with your diet — at least if you stick with a particular diet for a long enough period of time.

Gary Wu, a professor medicine in the division of gastroenterology at the University of Pennsylvania, and his colleagues studied the eating habits and gut flora (the latter is most easily examined by looking at stool samples) of 98 participants over two time periods. In the long-term comparison, the researchers looked at how frequently people ate certain kinds of foods over the course of a year; in the short-term analysis, they looked at what people ate over three consecutive 24-hour periods.

Analyzing the longer term data, the researchers found that two types of diets were linked with certain dominant species of guts bugs. The gut microbiomes of people who ate higher-fat and low-fiber diets rich in animal proteins predominately contained bugs of the Bacteroides genus, while those who ate more fiber and less animal fat and protein showed higher concentrations of Prevotella microbes.

In the shorter-term analyses, the researchers did not find the same patterns emerging between diet and gut flora, suggesting that gut bugs are relatively consistent in terms of their composition over the long term, says Wu.

The research team also looked at whether they could alter the makeup of the microbiome by changing people’s diets — whether, for example, a low-fat diet could lead to a drop in Bacteroides microbes and boost the population of Prevotella. The scientists sequestered 10 people in a hospital setting and controlled every bit of food they ate for 10 days to see what would happen.

“Almost all of the participants started out in the Bacteroides group — high animal protein, high fat — which is not surprising since the study took place in the U.S. where the western diet is more prevalent,” says Wu. “None of them switched permanently into the other when they changed their diet.”

Wu notes that the participants were sequestered for only 10 days, which is a relatively short time period of time. And while there wasn’t a switch from one dominant microbe to the other, the scientists did see an overall change in the composition of the gut flora within 24 hours of the participants’ change in diet. It wasn’t enough to boost populations of the fiber-loving Prevotella, but the shift does hint that diet may, over the long term, help change the gut environment to one that may be linked to healthier eating.

It’s not clear yet whether the relationship also works the other way around — whether different types of gut flora influence your eating habits. For example, could having more Prevotella make it easier or even more appealing to eat high-fiber, low-fat foods? It’s also not clear whether one gut bug profile is better for your health than another — that’s the subject of ongoing research. But the current study certainly gives new meaning to the idea that you are what you eat., September 6, 2011  —  We all know that what we eat can affect our risk of heart disease – for years health professional have been giving the message that cutting the amount of fat in your diet can help to cut your risk. But it’s not clear exactly how a high-fat diet contributes to heart disease risk, as it’s not a straight relationship between the fat you eat and the fatty compounds that get laid down in your arteries and cause problems.

Now a new paper from researchers in the US, published in the journal Nature this week, provides an interesting new angle – they think that it might be the bacteria in your gut that turn fat in your diet into the glop that clogs your arteries.

The scientists, led by Zeneng Wang, started off by taking a relatively new approach, known as metabolomics, to search for molecules in the body that might be involved in heart disease. They took blood samples from people who had suffered a heart attack or a stroke, and compared the levels of a range of small molecules in their blood with levels in the blood of healthy people.

Intriguingly, they found that people who had suffered heart disease had much higher levels of three molecules that are all produced in the body by the breakdown of phosphatidylcholine, or lecithin – a  nutrient that’s found in a wide range of foods, but particularly in fatty foods.

When you eat something containing lecithin, enzymes in your gut break it down to produce a molecule called choline. A lack of choline in the diet can cause liver disease and muscle damage, so it’s pretty important. But then it gets interesting. Choline is then broken down by bacteria in the gut to produce trimethylamine – a chemical that stinks of rotten fish. This trimethylamine gets taken into your bloodstream and goes to the liver, where it’s turned into trimethylamine oxide – and it’s this chemical that seems to contribute to the formation of the fatty plaques that can clog arteries and cause disease.

To prove the link between a fatty diet and the levels of the bad chemical trimethylamine oxide (TMAO), the scientists gave a lecithin-rich diet to mice prone to developing heart disease. They found that the fatty diet increased the levels of TMAO in the animals’ blood, and the mice had more artery-clogging plaques. And to show that the gut bacteria were involved, the researchers treated mice with some strong antibiotics that nuked all the bacteria in their gut. They found that trimethylamine oxide – the bad chemical – was no longer produced.

We need the bugs in our guts to help us digest our food and keep the gut healthy, so it’s not practical (or even really possible) to just get rid of them all. But if scientists can identify exactly which species of bacteria are producing the trimethylamine, then it might be possible to specifically get rid of them. Alternatively, maybe researchers could hunt for some “good” bacteria that might help to control the bad bacteria producing trimethylamine.

And it might also be possible to develop drugs that specifically block the liver enzyme that converts trimethylamine into the plaque-causing TMAO.  The research also helps to explain why a fatty diet, with lots of lecithin, might contribute to heart disease – interestingly, choline, produced from lecithin, is sometimes taken by people as a health supplement, so this work suggests that might not be such a great idea if you want to reduce your risk of heart disease.

References: Zeneng Wang, Elizabeth Klipfell, Brian J. Bennett, Robert Koeth, Bruce S. Levison, Brandon DuGar, Ariel E. Feldstein, Earl B. Britt, Xiaoming Fu, Yoon-Mi Chung, Yuping Wu, Phil Schauer, Jonathan D. Smith, Hooman Allayee, W. H. Wilson Tang, Joseph A. DiDonato, Aldons J. Lusis & Stanley L. Hazen. Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease. Nature, Volume: 472, Pages: 57–63 Date published: (07 April 2011), September 6, 2011  —  Exposure to probiotic bacteria can alter brain chemistry and calm anxiety responses, new research has revealed.

Mice fed a diet enriched with Lactobacillus rhamnosus, a common probiotic constituent, showed significant reductions in stress and depression-related behaviors, and lower levels of the stress hormone cortisol, compared with control, broth-fed animals.

The numbers of chemical receptors for GABA, one of the brain’s inhibitory neurotransmitters, also changed significantly during the experiments, particularly in a number of brain regions known to play a role in mood and stress responses.

Critically, these effects could be abolished by cutting the Vagus nerve, the main connection between the brain and the intestines. In mice that underwent this procedure, administration of the probiotic bacteria subsequently had no effect compared with broth-fed animals.

The work, published in the journal PNAS by University College Cork scientist Javier Bravo and his colleagues, is the first to show a direct effect on the brain and behavior of animals administered probiotics similar to those used by humans.

As yet, say the researchers, it’s not known how the effect is being achieved other than by some local host-microbe intestinal interaction that is signaled centrally to the brain via the Vagus nerve. It’s also likely that, alongside GABA, other nerve-transmitter chemicals are likely to be impacted too, although this wasn’t directly studied in the present series of experiments and remains as food for thought for future experiments.

What the new findings unequivocally confirm, however, is that you clearly are what you eat…


References: PNAS doi: 10.1073/pnas.1102999108