Plant-based diets for prevention and treatment ischaemic heart disease
Some of the strongest evidence supporting a plant-based diet relates to prevention and treatment of ischaemic heart disease. Large prospective cohort studies and meta-analyses have consistently shown a reduced risk of ischaemic heart disease in those following a vegetarian or vegan diet, including the EPIC-Oxford and Adventist Health Studies, with an average risk reduction of around 25%. When data from non-vegetarian study cohorts, such as the Nurses’ Health Study and the Health Professionals Follow-up study, have been analysed using the plant-based diet index to assess intake of plant foods and examine associations with health outcome, they have also found a similar reduction in the risk of ischaemic heart disease in those eating the most whole plant foods. High adherence to a plant-based diet in general was associated with an 8% reduced risk of developing coronary heart disease but eating a healthy plant-based diet was associated with a 25% reduced risk. An unhealthy plant-based diet increased the risk of coronary heart disease by 32%. The study showed a dose response, with those eating the most animal derived foods and unhealthy plant foods having the worst outcome and those eating the most plant foods having the best outcome. These data not only emphasise the protective effect of whole plant foods, but also that unhealthy plant foods and animal-derived foods can have a similar detrimental effect on heart health.
Within the Nurses’ Health Study and the Health Professionals Follow-up Study, the impact of saturated fats, unsaturated fats and sources of carbohydrate on cardiovascular health has been analysed. This study included >120, 000 participants who were followed for 24–30 years. Higher consumption of both polyunsaturated fats and carbohydrates from whole grains was associated with a significant reduction in the risk of coronary heart disease — 20% and 10% reduction in risk respectively. Carbohydrates from refined starches and free sugar increased the risk of coronary heart disease by 10%. Replacing 5% of energy intake from saturated fats with equivalent energy intake from polyunsaturated fatty acids, monounsaturated fatty acids, or carbohydrates from whole grains was associated with a 25%, 15%, and 9% lower risk of CHD, respectively. Previous analyses of the Nurses’ Health Study and the Health Professionals Follow-up Study have demonstrated the benefits of fruits, vegetables and legumes consumption for heart health. Each serving per day of fruits and vegetables was shown to reduce the risk of coronary heart disease by 4%.
Plant-based diets for treatment of heart disease
Some of the seminal work on the use of plant-based diets as treatment for chronic disease has been performed in those with ischaemic heart disease. Dr Dean Ornish published The Lifestyle Heart Study in 1990. In this study, patients with coronary artery disease were randomised to the lifestyle intervention or to standard treatment at the time. The lifestyle intervention consisted of a low fat, predominately whole food plant-based diet (low fat dairy and egg white was allowed in the original protocol but has subsequently been removed), stress management activities and regular exercise. After one year and then five years follow up, 82% of patients in the intervention group showed regression of coronary artery disease (demonstrating by quantitative angiography) with significant improvement in symptoms, blood cholesterol levels (similar to cholesterol-lowering medication) and weight. The benefits continued out to five years with further regression of atherosclerosis and benefits proportional to the degree of adherence to the study protocol. Listen to Dr Dean Ornish in this TED talk.
A very similar study to that conducted by Dr Dean Ornish, called the The Mount Abu Open Heart Trial, was performed in India and showed almost identical results. Dr Caldwell B. Esselstyn has also been treating patients with coronary artery disease with a whole food plant-based diet since 1985. His original protocol also included cholesterol-lowering medication but no mandated physical activity. He published the results for 198 patients treated with the dietary intervention in 2014. He reported that in those adherent to the dietary protocol at a median follow-up of 3.7 years, the recurrence rate of cardiovascular disease was 0.6% (1 of 177 patients had a stroke). He was also able to demonstrate reversal of atherosclerosis using PET imaging and angiography.
So there is now convincing evidence that not only can a plant-based diet prevent ischaemic heart disease, but it can be used to treat established coronary artery disease both preventing progression and in many leading to regression of already established disease. In recognition of the strength of these data, The American College of Cardiology and the American Heart Association have published updated guidelines on the primary prevention of cardiovascular disease in March 2019. The recommendation for diet is to follow either a plant-based or Mediterranean dietary pattern.
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