Did Ornish's trials show that a plant-based diet reverses heart disease?

Dean Michael OrnishMD · internal medicine and cardiovascular disease; founder and president, Preventive Medicine Research Institute

The programme reversed coronary disease in a randomised trial, and the diet is the largest part of it.

What it rests onLifestyle Heart Trial, Lancet 1990: 48 patients randomised, 195 lesions read by quantitative coronary angiography, one year. Average percentage diameter stenosis regressed from 40.0% to 37.8% in the 28 experimental patients and progressed from 42.7% to 46.1% in the 20 controls, with 82% of experimental patients showing average change toward regression and no lipid-lowering drugs. The 5-year follow-up (JAMA 1998) reports 25 cardiac events among 28 experimental patients against 45 among 20 controls, risk ratio 2.47 (95% CI 1.48 to 4.20). On the confounding charge specifically, his printed reply is that only one patient smoked at baseline and that 'I'm not aware of any studies showing that walking and stress management techniques alone can reverse heart disease.' Interest: the trials are run by a nonprofit he leads and support a programme he holds equity in.

Nina TeicholzPhD · investigative science journalist and author

The trial cannot show that the diet did it, because the diet was never the only thing that changed.

What it rests onIn a peer-reviewed paper she writes: 'Although vegan diets are often considered to be the best for disease reversal, there are surprisingly few clinical trials on this approach, and existing trials tend to be flawed. For instance, the renowned Ornish et al. study, which reported that a vegan diet reversed heart disease, was confounded by interventions other than diet, including exercise, stress management training, smoking cessation, and vitamin supplements, while the controls were provided with none of these.' Her longer critique adds that he ran one well-controlled trial with heart-disease endpoints rather than several, that the comparator is the standard American low-fat diet, and that the findings have never been successfully replicated. Interest: the Nutrients paper's competing-interests note lists six co-authors and then 'all other authors report no conflicts of interest', which includes her, while she declared book royalties and speaking fees in three earlier papers.