On the 5th December 2013 I gave a talk at the Cardiovascular Research Trust Symposium on Diet, Active Lifestyle and Cardiovascular Health entitled: The Lifestyle Heart Trial: 23 years on, how far have we progressed?
The Lifestyle Heart Trial was carried out by Dean Ornish (author of The Spectrum) et. al from the University of California San Francisco (UCSF) School of Medicine. It was first published in The Lancet in 1990, with five-year results published in JAMA in 1998. It was a prospective, single-blind, randomised controlled trial designed to study the effects of a comprehensive lifestyle intervention on coronary heart disease progression. The intervention included a very low-fat (<10% of calories), whole-food, plant-based diet, smoking cessation, stress management, psychosocial support and exercise. It consisted of a week-long residential retreat in a hotel, followed by 2×4 hour group support meetings per week led by a clinical psychologist.
The primary outcome measure was the change in the amount of narrowing of the coronary arteries seen on angiogram at one and five years compared with baseline. Secondary outcome measures included adherence, lipids, blood pressure, weight, angina symptoms and cardiac events.
53 patients were assigned to the experimental group, and 28 (52.8%, 105 lesions) agreed to take part. 43 patients were assigned to the usual care control group, and 20 (46.5%, 90 lesions) agreed to take part. Differences in baseline characteristics were tested for using tests of statistical significance (t-tests). No significant differences in demographics, diet/lifestyle, functional status or cardiac history/disease severity were noted, although the control group had significantly higher HDL cholesterol and apolipoprotein A1.
Of the 48 patients enrolled, follow-up angiographic data was available for 41 at one year (reasons stated – 1 died) and 35 at five years (reasons stated – 2 died). At one year the average diameter stenosis reduced from 40.0% to 37.8% in the experimental group and increased from 42.7% to 46.1% in the control group (p=0.001, 2-tailed). The percentage change in angina symptoms at one year is shown below:
One of the criteria for attributing causality for an observed effect is whether or not the effect demonstrates a dose-response relationship with the putative causal agent. In this case, does greater adherence to the program produce a greater response? To answer this, participants were assessed for their degree of adherence and this was plotted against the change in percentage diameter stenosis, below:
An even more marked relationship was seen when all participants were assessed similarly, including the controls:
One of the features that struck me about this study was that it did achieve adherence (admittedly in those who initially agreed to participate) to a diet that is generally dismissed as untenable by conventional authorities on the subject. Furthermore, the reduction in fat content of the diet was really very marked, and was maintained in the experimental group for the full five years (8.51% in the experimental group and 25.03% in the controls):
|Mean Experiment Baseline||Mean Control Baseline||Mean Experiment 1 year||Mean Control 1 year||P-value (2-sided)|
Most studies of low-fat diets to date classify low-fat, and even very-low-fat, as diets taking 20-25% of their total calories as fat. They have often failed even to achieve their stated targets in terms of adherence, or to produce positive results, and concluded, misleadingly, that low-fat diets do not result in benefit for heart disease patients. Meanwhile the Department for Health continues to issue guidance stating that we should be taking 35% of our calories from fat, thus arguably leading yet another generation into the jaws of death.
At five years, among the 28 experimental group patients in the Lifestyle Heart Trial there had been 25 cardiac events, as compared to 45 in the 20 control group patients (risk ratio 2.47, 95% CI 1.48-4.20). This means that the control group patients were 2.47 times more likely to suffer an event than the experimental group patients. Also the results at five years indicated that the longer the programme was adhered to, the greater the benefit in terms of reduction in narrowing of the coronary arteries:
Dean Ornish MD continues to evaluate his intervention and it is currently being provided, with insurance cover, in the United States. It is a very intensive intervention that may be difficult to replicate or deliver on a large scale within the NHS. However with increasing evidence, less support may be required to motivate patients to make changes. It would be very useful to know the relative contributions of the various lifestyle modifications to the overall effect, particularly diet, which is in my view a strong contender for a large slice of the pie. Dean Ornish recommends one hour of meditation daily as part of his program, and it would certainly be helpful to know whether or not that is really necessary.
I wanted to know whether anyone has picked up on these results and taken them further, in the years since the Lifestyle Heart Trial was published. In particular I wanted to know if there have been any further dietary intervention studies utilising a very-low-fat plant-based diet as the main therapeutic intervention for established atherosclerotic cardiovascular disease. To find out, I searched the health database Medline for potentially relevant journal articles. My initial search produced 1244 articles, from which I identified 27 dietary intervention studies for further analysis. I was able to retrieve the full-text articles for 17 of these studies, and am still working on finding copies of the rest.
As I suspected, none of the 27 met the primary inclusion criteria of being randomised controlled trials carried out since 1990, assessing the effects of very low fat plant-based diets on cardiovascular outcomes, where the intervention was only dietary and did not include modification of other lifestyle factors.
A randomised controlled trial to assess the effect of this diet in isolation from other lifestyle factors would seem to me the logical next step, given the results of the Lifestyle Heart Trial, but in 23 years this has not been attempted anywhere in the world. Such a trial is feasible and has the potential to produce results of very great importance to many millions of people, given that atherosclerotic cardiovascular disease is the UK’s biggest killer, resulting in 180,000 deaths in 2010 alone. It would be costly, but not prohibitively so, given the amount being spent on research in the field already, not to mention the cost to the NHS of treating it (£8.7 billion in 2009), or the overall cost of the condition to the economy (£19 billion in 2009) (1). Something to think about. Watch this space…
1. British Heart Foundation Heart Statistics: http://www.bhf.org.uk/research/heart-statistics.aspx Accessed on 21st October 2013.