This study was a prospective cohort of 198 self-selected, adult patients with documented coronary artery disease, cerebrovascular disease, carotid artery disease, or peripheral arterial disease who followed a strict, plant-based dietary intervention in addition to standard medical therapy. The study examined compliance with diet as well as adverse cardiovascular events in both adherent and nonadherent patients.
“A way to reverse CAD?” J Fam Pract 2014 Jul;63(7):356-364b.
This study was a prospective cohort of 198 self-selected, adult patients with documented coronary artery disease (CAD), cerebrovascular disease, carotid artery disease, or peripheral arterial disease (PAD) who followed a strict, plant-based dietary intervention in addition to standard medical therapy.1 The study examined compliance with diet as well as adverse cardiovascular events in both adherent and nonadherent patients.
The mean age of participants was 62.9 (SD +/- 10) and the mean study follow-up was 3.7 years. 195 (98%) of the participants had documented CAD (myocardial infarction, positive stress test, or angiography/CT angiography); the remaining patients reported cerebrovascular disease, carotid artery disease, or PAD, respectively. Of 198 who completed the study (2 had been lost to follow-up), 177 patients (89%) were determined to be compliant with the dietary intervention throughout the study course.
During the study, 13 of the 21 nonadherent patients (68%) experienced an adverse event (MI, stroke, CABG, PCI with stenting, endarterectomy, or sudden cardiac death). No nonadherent patients showed symptom improvement or disease regression.
Of the adherent patients, 18 (10%) suffered an adverse event, although 5 had were nonvascular-related deaths. Many of the other events were explained by the authors as attributed to other than advancement of vascular disease, reporting that there was only a single vascular-related adverse outcome (<0.6%) attributed to advancing disease in an adherent group (P<0.001, Fisher’s exact test). Of the 112 adherent patients who reported initial anginal symptoms, 104 showed improvement or resolution of anginal symptoms.
This non-randomized population of patients with known vascular disease included those who were willing to make their diet all plant based. The results showed a decrease in vascular disease related symptoms as well as vascular events compared to those who did not stay adherent to the diet.
This cohort study was an expansion on previous pilot studies examining the effects of plant-based nutritional interventions on vascular disease progression and regression. This study appears to be the next step on the road to a randomized trial and seems timely given the growing body of evidence suggesting that dietary interventions may be underestimated as a means of not only primary, but also secondary prevention of coronary disease.
The authors cite several previous studies that reported evidence of plant-based dietary cultures having lower incidence of coronary disease. This included a study published in 2013 that followed 44,561 men and women, 34% of whom reported being vegetarians, for 11.6 years.2
Reported vegetarians had a hazard ratio of 0.68 for CAD compared to non-vegetarians. Also discussed were studies showing that the gut flora of patients who consumed animal sources of protein created atherogenic compounds such as trimethylamine oxide. Such evidence became the basis of the arguments for the strict dietary intervention involved in this study.
The dietary intervention presented here is strict, including only specific plant-based foods and vitamin supplements while barring all animal-based proteins (meat, poultry, seafood, and dairy) as well as all oils, nuts, avocados, and excess salt. Given the radical change used in this intervention, the 89% adherence rate over a 3.7-year time frame is impressive and suggests larger numbers of patients can comply if appropriately motivated. The success may be attributed to the strength and quality of the initial 5-hour group counseling and follow-up support for patients who could ask questions by email or phone.
The nonadherent group in this study had a relative recurrent event rate of 62%, but that was most likely due to the small number of nonadherent patients and may not represent a statistically significant difference from the natural history rate reported by Stone, et al., of 20.4% over a 3-year cumulative period in patients (n=697) with acute coronary syndrome and PCI.3
The confusing interpretation of the adverse events in the adherent group suggests the events described were not a result of advancement of disease. These explanations seem fully justified in the five noncardiac deaths (cancer, PE, pneumonia) but appear less definitive in the others.
The authors provide a range of possibilities in the actual event rate being as low as 0.6% and up to 10%. Regardless, the number is well below the natural history rate reported by Stone, et al. and represents a statistical and clinically significant difference from the nonadherent event rate of 62%.
Patients with baseline anginal symptoms did show symptom improvement, although that improvement was not quantified in this study. As a result, it is difficult to say that the symptom improvement recorded was statistically significant. However, in 39 of those patients that reported symptom improvement, stress test or radiographic evidence was available to show disease regression, which was also not quantified in this study.
The limitations of this study are apparent and not hidden by the authors. Among the most noticeable were: patients were self-selected after hearing about plant-based dietary interventions in patients with CAD and thus were highly motivated from the start.
Arguably, those in the adherent group were more motivated than those who eventually became part of the nonadherent group and they may have been subject to reporting bias, particularly when reporting symptoms at follow-up. Interpreting the adverse events remains a factor in making broad generalizations about the benefits of this intervention.
Finally, the lead author of the study has a financial investment in the success of this sort of intervention as he is the author of a book and corresponding cookbook that tout such plant-based diets to treat disease. Despite these limitations, this study argues for a randomized trial of plant based diet to treat known vascular disease.
1) Esselstyn CB Jr, Gendy G, Doyle J, Golubic M, Roizen MF. A way to reverse CAD? J Fam Pract. 2014 Jul;63(7):356-364b.
2) Crowe FL, Appleby PN, Travis RC, et al. Risk of hospitalization or death from ischemic heart disease among British vegetarians and nonvegetarians: results from the EPIC-Oxford cohort study. Am J Clin Nutr. 2013;97:597-603.
3) Stone GW, Maehara A, Lansky AJ, de Bruyne B, Cristea E, Mintz GS, Mehran R, McPherson J, Farhat N, Marso SP, Parise H, Templin B, White R, Zhang Z, Serruys PW; PROSPECT Investigators. A prospective natural-history study of coronary atherosclerosis. N Engl J Med. 2011 Jan 20;364(3):226-35. doi: 10.1056/NEJMoa1002358.
About the Author
Scott P. Grogan, DO, MBA, FAAFP is a faculty family physician at the Dwight David Eisenhower Army Medical Center Family Medicine Residency at Fort Gordon, GA and an Assistant Professor of Family Medicine at the Uniformed Services University of Health Sciences.