Mediterranean and low-fat diet programs reduce the likelihood of death and heart attack in people at heightened risk of cardiovascular disease, finds the first comparative review based on randomized trials of seven popular dietary programs.
Dietary programs are diets with or without exercise and other health behaviours, such as smoking cessation support.
Mediterranean dietary programs are also likely to reduce stroke risk, but other dietary programs have shown little or no benefit compared to minimal intervention (e.g., usual diet or brief dietary advice from a health professional).
Several analyses of randomised controlled trials have suggested that some diets and dietary programs can reduce major cardiovascular events, such as heart attacks (myocardial infarction) and strokes, but any beneficial impact on death is still uncertain.
About the research
To address this, researchers examined databases for randomized trials looking at the impact of dietary programs for preventing death and major cardiovascular events in people at increased risk of cardiovascular disease.
Forty eligible trials were identified involving 35,548 participants who were followed for an average of three years across seven dietary programs (low-fat; Mediterranean; very-low-fat; modified-fat; combined low-fat and low-sodium; Ornish; and Pritikin.
Based on moderate certainty evidence, Mediterranean dietary programs were better than minimal intervention at preventing all-cause mortality, non-fatal heart attack and stroke for participants at intermediate risk of cardiovascular disease.
Low-fat diet programs were also superior to minimal intervention with moderate certainty for prevention of all-cause mortality and non-fatal heart attack.
When compared with one another, there were no convincing differences between Mediterranean and low-fat diet programs for mortality or non-fatal heart attack.
The beneficial effects for both diets were more pronounced for participants at high risk of cardiovascular disease.
The five other diet programs had little or no benefit compared with minimal intervention typically based on low to moderate certainty evidence.
Study limitations
The researchers acknowledged several limitations, such as being unable to measure adherence to dietary programs and the possibility that some of the benefits may have been due to other elements within the programmes like drug treatment and support to stop smoking.
Nevertheless, this was a comprehensive review based on a thorough literature search, rigorous assessment of study bias, and adherence to recognized methods to assess the certainty of evidence.
As such, the researchers concluded that Mediterranean and low fat diet programs “probably reduce the risk of death and non-fatal heart attack in people at increased cardiovascular risk.”
Source: The BMJ, March 29, 2023.
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