How constipation could double the risk of having a heart attack

It affects more than 20 per cent of the population, but few of us would think that constipation increases the risk of having a heart attack or stroke. However, a large new study published in the American Journal of Physiology-Heart and Circulatory Physiology found that it may be a significant risk factor for serious cardiac events.

For the last eight years, Professor Francine Marques from the School of Biological Sciences at Monash University has been studying the links between our gut microbiome and cardiovascular disease.

Through that research, her team found that changes in the bacteria and substances produced in the gut, which influence cholesterol, inflammation and metabolic pathways, can either increase or reduce the risk of cardiac events.

Constipation may be an unlikely, but significant risk factor for a heart attack.Credit: Getty Images

They were also interested in the gut as an organ itself, beyond the microbiome it contains.

For instance, a thin wall of cells acts as a barrier keeping bacteria and other substances inside the gut. When the connection between these cells breaks down, and those bacteria and substances “leak” into the body, it can cause inflammation, which puts us at a higher risk of cardiovascular disease.

Gut leaks and dysbiosis (an imbalance of harmful bacteria that can promote disease states) can also affect how quickly food passes through the gastrointestinal tract, and cause constipation.

While some research looking at elderly, hospitalised patients had suggested a link between constipation and cardiac events, Marques and her team were interested in whether it predicted heart issues in healthy people.

So for the new study, they analysed the data of more than 400,000 healthy, adult participants over nearly two decades.

Men or women with constipation, defined as passing fewer than three stools a week, were twice as likely to have a cardiac event.

“This was independent of having other risk factors such as high blood pressure or high cholesterol, diabetes or smoking,” Marques says. “It is also independent of medication that can cause constipation.”

Participants with high blood pressure as well as constipation had a 34 per cent higher chance of developing cardiovascular disease.

There appears to be some genetic component to the risks, Marques says, explaining that about 20 to 27 per cent of genetic variants are common with both constipation and developing cardiovascular disease. However, further research is needed to identify exactly what those variants are.

The other risk factors that are common for both constipation and cardiovascular disease are not having enough fibre and not doing enough exercise.

When asked whether the constipation is somehow contributing directly to cardiovascular disease risk – or whether they are just happening simultaneously – Professor Garry Jennings, the chief medical adviser at the Heart Foundation, wonders: “[Is] there a link because many people with constipation are not following a heart-healthy eating pattern involving lots of vegetables, fruit, whole grains, nuts, seeds and other important sources of dietary fibre?”

Marques is more tentative. “They are not necessarily just happening at the same time but a long-term risk as well,” she says.

Her current research is looking at whether dietary fibre might help by restoring the barrier of a leaky gut and relieving constipation.

Dietary fibre comes in various forms which are all beneficial, Marques says. Soluble fibre foods include oats, peas, beans, apples, citrus fruits, carrots, barley and psyllium; fermented fibre foods include kefir, yoghurt (with live cultures), kimchi, miso and sauerkraut; while resistant starches include cereal foods, such as breads and pasta, and legumes such as lentils, chickpeas and red kidney beans.

When our gut microbes digest fibre they release certain substances that can help to lower blood pressure and improve heart health, Marques explains.

“The same substances help to feed the cells in our gut, helping to keep that barrier intact,” she adds. “We think strategies to increase fibre intake might be beneficial in decreasing the risk of constipation as well as cardiovascular disease.”

Jennings says more research is needed to fully understand the causal links between constipation and poor heart health.

“We also know that the toilet can be a dangerous place for some people as there is a syndrome called micturition syncope (fainting while or immediately after urinating), and there is some strain on the heart related to the isometric exercise associated with straining ‘at stool’,” he adds.

“In these situations, any cardiac consequences would be triggered – but not caused – by straining.”

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