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More people are becoming full- or part-time vegetarians. In fact, 42 per cent of Australians are trying to eat less meat or are choosing to go without completely.

Reducing or eliminating our consumption of meat and animal products can be an ethical choice, and plant-based diets benefit the health of the planet the most. A new study by Oxford University researchers found that people who follow a vegetarian diet have one quarter of the environmental impact as those who eat meat every day.

Vegetarian diets can have a protective effect on our hearts, but not all forms are equal.Credit: iStock

Along with the environment benefits, a plant-based diet can also be better for our bodies and, as a new study conducted by the University of Sydney has found, it may play a protective role in developing heart disease.

“As vegetarian diets continue to gain popularity worldwide… it becomes crucial to understand the impact of different dietary compositions on human health,” says co-author Professor Luigi Fontana, the director of the Healthy Longevity Research and Clinical Program at the Charles Perkins Centre

Cardiovascular diseases remain the leading cause of disease burden worldwide and could be largely mitigated through lifestyle prevention strategies.

“Poor diet is the leading contributor to the burden of coronary heart disease,” says Heart Foundation dietitian Jemma O’Hanlon.

Researchers already know that Western-style diets rich in animal products and processed foods markedly increase the risk of developing diabetes, high blood pressure and cardiovascular disease. They also know that plant-based diets rich in non-starchy vegetables, whole grains, beans, nuts and fish may help to prevent cardiovascular disease and cancer in the general population.

Previously, research on the effectiveness of plant-based diets in people at high risk of cardiovascular disease was lacking. So, Fontana and his team conducted a meta-analysis of 20 randomised controlled trials, comparing participants with or at high risk of cardiovascular disease on a vegetarian diet to those on comparison diets.

Some vegetarian diets were vegan, while others included dairy and/or eggs. Some studies emphasised wholefoods, while others did not.

Overall, researchers found that, after six months, those on vegetarian diets experienced significant positive changes in cardiometabolic risk factors. These included better cholesterol levels, blood sugar management and body weight.

“Individuals with type 2 diabetes and those at a high risk of cardiovascular disease showed the most significant improvements in hemoglobin A1c and LDL-cholesterol levels when following vegetarian diets,” says Fontana. “These findings emphasise the potential protective and complementary benefits of plant-based diets in preventing cardiovascular disease as a primary measure.”

Plant-based is the key word here, adds O’Hanlon.

“You don’t have to be a strict vegetarian to have a healthy heart,” she says.

For instance, including fish two to three times a week can enhance the health benefits of a plant-based diet, further reducing the risk of heart disease and blood pressure, while boosting our good cholesterol.

And most diet studies don’t make a distinction between processed meats and eating a quality cut of red meat, so the true effects of meat on cardiovascular health are unclear. It is likely that some quality red or white meat in the context of a diet made up primarily of plant-based whole foods, is fine. “It really is that overall dietary pattern that is most important,” says O’Hanlon.

Interestingly, the participants on a vegetarian diet that included eggs had the greatest reduction in cholesterol.

O’Hanlon says the recommendations for eggs have changed as science has evolved, and today the Heart Foundation puts no limits on eggs for healthy Australians.

Eggs and full-fat yoghurt, milk and cheese have a “neutral effect” on the heart, she adds. “So they don’t significantly increase our risk of heart disease, nor do they significantly reduce our risk of heart disease. So, it means that they can be included in a heart health eating pattern.”

If plant-based is the first key term, wholefoods is the second. And that is because many food companies leverage the health halo effect of “plant-based” to market their ultraprocessed foods, and it is, of course, possible to be vegetarian and eat a diet full of French fries, refined grains and junk foods.

“Not all plant-based foods are equally healthy,” Fontana says. “Unhealthy vegetarian diets that lack specific nutrients (vitamin B12, iron, zinc, calcium) and contain refined flours, hydrogenated oils, high-fructose corn syrup (HFCS), sucrose, artificial sweeteners, salt and preservatives can increase morbidity and mortality.”

An unhealthy vegetarian diet is associated with a 32 per cent higher risk of coronary heart disease.

There are several reasons why a plant-based, wholefoods approach is so good for our bodies and our hearts.

The fibre in vegetables, legumes, and whole grains keeps us full for longer and steadies our blood sugar levels.

The production of short-chain fatty acids by the microbial metabolism of resistant starch and oligosaccharides – a type of carbohydrate – makes us feel of full, Fontana adds, while metabolic hormones called incretins also significantly reduce blood glucose levels and body weight.

“Furthermore, wholefood vegan and vegetarian diets may result in fewer bioavailable calories,” he says. “It is well established that calorie restriction with adequate nutrition has a powerful impact on improving glucose tolerance, insulin sensitivity, and various cardiometabolic, inflammatory and hormonal factors that play a role in the development of cardiovascular disease and cancer.“

Whether we are full or part-time vegetarians, the message for good heart health, may be to approach our plates differently, says O’Hanlon.

“It’s flipping that model of the meat being the number one hero on the plate and making plants the hero of the plate. This research really demonstrates the impacts of making that switch.”

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