The evidence is mounting and is becoming indisputable: Gut bacteria play a role in strokes and heart attacks. The link may seem a little far-fetched, but cardiovascular disease may have less to do with what we eat and more to do with what chemicals gut bacteria make from the food we eat.
New research published in Circulation, a journal of the American Heart Association focused on the role of the compound choline — a building block of protein and essential to our diet — gut bacteria, and heart health. But, past research has been building up to this point, and it's important to understand the evidence that has led us here.
An analysis of 21 studies that included 347,747 people showed that an increase in saturated fats and cholesterol in the diet doesn't correlate with an increased risk of heart attacks. Supporting that controversial finding was another study, published in March, which concluded that heart disease is not caused by saturated fat in the diet.
If saturated fats don't cause heart disease, what does?
A study from 2013, which analyzed 4007 people with and without cardiovascular disease over three years, found that higher trimethylamine N-oxide levels (a compound produced by gut bacteria) at the start of the study were more likely to die, and have heart attacks and strokes.
Now, a new research study from the Cleveland Clinic has provided the missing link between diet, trimethylamine N-oxide, and heart disease.
The Cleveland Clinic researchers found a dietary supplement increased trimethylamine N-oxide and clot formation, a process involved in heart disease.
Western diets — rich in meat, eggs, and milk — are also rich in choline that it could represent a risk factor for excess trimethylamine N-oxide production, so the researchers studied people who ate a Western diet and compared it to vegetarians. But, they also tested whether it was the choline itself that increased trimethylamine N-oxide.
Both vegan or vegetarians and omnivores — people who ate a varied diet that included meat, dairy, and vegetables took part in the study. The study participants were given 5oo mg choline bitartrate supplements to take twice a day for two months. This supplementation was more than three times the average daily intake of about 302 mg a day.
In both groups, blood levels of trimethylamine N-oxide increased more than ten times after one or two months of taking the supplement, compared to starting levels.
The participants' blood platelets — small blood cell fragments that clump together to form clots — were more apt to aggregate into a clot when trimethylamine N-oxide levels were higher in the blood.
A daily 81 mg dose of aspirin for at least a month decreased the clotting potential of the participants' blood.
The new study by senior author Stanley L. Hazen, of the Cleveland Clinic in Ohio, and colleagues showed an association between increased choline, increased trimethylamine N-oxide, and increased clotting. The research presents an intriguing new possibility for one of the causes of heart disease.
We already know that gut bacteria produce trimethylamine N-oxide from the food we eat, including foods rich in choline. Could it be that it's not the fat in the food we eat, but the choline in it that causes heart disease?
"A Mediterranean diet or vegetarian diet is reported to help reduce trimethylamine N-oxide," Hazen said in a press release from the American Heart Association.
He stressed that more research is needed to flesh out the implications of these findings.
"These studies suggest patients without known cardiovascular disease but with elevated trimethylamine N-oxide levels may benefit from aspirin and diet modification in preventing blood clotting, which can lead to heart attack and stroke. They also suggest that a high trimethylamine N-oxide level in a patient with known cardiovascular disease should be considered for more aggressive anti-platelet therapy," said Hazen in the press release.
Once again, our gut bacteria have proven to play a critical role in a disease process. Our heart health may not depend on what we eat, but on what we feed our gut bacteria. Scientists seem to be closing in on a heart-healthy gut bacteria diet.
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