Reducing animal product intake and following a primarily plant-based diet can decrease the risk of heart disease, say researchers, adding that it's because plant-based food minimises the negative effects of a gut-microbiome associated with an increased risk of coronary heart disease.

The body's gut microbiota is comprised of a series of microbes that play an important role in our metabolism, nutrient absorption, energy levels and immune response.

A gut-microbiota related metabolite known as trimethylamine N-oxide (TMAO) is produced when gut bacteria digest nutrients commonly found in animal products such as red meat. It has been connected to increased heart attack and coronary heart disease (CHD) risk.

According to the researchers, maintaining a vegan or vegetarian diet has been found to reduce the amount of TMAO produced in the body.

"The findings of the study provide further evidence for the role of TMAO as a predictive biomarker for heart disease and strengthens the case for TMAO as a potential intervention target in heart disease prevention," said Paul A Heidenreich, Professor at Stanford University in the US.

In the study, women were asked to report data on dietary patterns, smoking habit and physical activity, plus other demographic data and provide two blood samples taken at Cleveland Clinic, 10 years apart.

The researchers measured plasma concentrations of TMAO from the first collection to the second blood collection.

After adjusting for participants with available plasma TMAO levels at both collections, there were 380 cases of CHD and 380 demographically matched-control participants without CHD chosen by the researchers included in the analysis.

The risk of CHD was calculated by changes in TMAO levels in the body throughout the follow-up period.

According to the researchers, women who developed CHD had higher concentrations of TMAO levels, higher BMI, family history of heart attack and did not follow a healthy diet including higher intake of vegetables and lower intake of animal products.

Women with the largest increases in TMAO levels across the study had a 67 per cent higher risk of CHD, the study said.

The researchers found no differences in TMAO levels between the CHD and control participants at the first blood sample collection.

TMAO levels examined in the second blood sample collection taken 10 years later were significantly higher the participants with CHD. Every increase in TMAO was associated with a 23 per cent increase in CHD risk, the researchers said.

"Our findings show that decreasing TMAO levels may contribute to reducing the risk of CHD, and suggest that gut-microbiomes may be new areas to explore in heart disease prevention," said the study's senior author Lu Qi, Director of Obesity Research Centre, Tulane University, US.