#504: Vegetable Oil vs. Saturated Fat – Analysis of the LA Veterans Study
Dec 5, 2023
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This episode discusses the LA Veterans Study, a landmark clinical trial from 1959 that investigated the effects of replacing saturated fats with polyunsaturated fats on heart disease risk. The study showed the benefits of polyunsaturated fats, but also reported an unexpected increase in non-cardiac mortality. The podcast analyzes the study design, dietary interventions, and the impact of long-term randomized controlled trials. It explores the relationship between dietary factors, such as polyunsaturated and saturated fats, and fatal carcinomas and cardiovascular endpoints. The hosts also discuss future episodes and the importance of subscriber support.
Replacing saturated fat with polyunsaturated fat from vegetable oils can reduce heart disease risk.
The LA Veterans Study showed the importance of sustained dietary change over time for significant risk reduction in cardiovascular disease.
Deep dives
Overview of the LA Veterans Study
The LA Veterans study was conducted in the 1960s and focused on the effects of a diet high in unsaturated fat, particularly polyunsaturated fat from vegetable oils, on atherosclerosis and cardiovascular disease risk. The study involved middle-aged and elderly men living in a veteran's home in Los Angeles who were randomly assigned to either an experimental diet or a controlled diet. The experimental diet aimed to replace saturated fat with polyunsaturated fat from various vegetable oils. The study found that the experimental group had lower blood cholesterol levels and a lower risk of primary and secondary cardiovascular events compared to the control group. The reduction in risk was more pronounced in men with pre-existing cardiovascular complications and in younger men. Adherence to the experimental diet was confirmed through biomarkers in adipose tissue.
Cumulative Exposure and Long-Term Impact
The LA Veterans study highlighted the importance of cumulative exposure to cholesterol and the sustained reduction in cholesterol levels over time in reducing cardiovascular risk. The study demonstrated the long-term impact of dietary intervention and the effects of replacing saturated fat with polyunsaturated fat. The reduction in risk was particularly evident after eight years of follow-up, reflecting the cumulative nature of cholesterol exposure. The study also showed that the intervention had a greater impact on individuals with higher baseline cholesterol levels and those with pre-existing cardiovascular complications. Adherence to the diet, although not perfect, still resulted in significant risk reduction.
Benefit of Early Intervention and Age-Related Findings
The LA Veterans study confirmed the benefit of early intervention in reducing cardiovascular risk. Stratification by age revealed that the intervention had a greater impact on men aged 54 to 65 compared to men aged 66 to 88. The cumulative incidence of cardiovascular events was substantially lower in the intervention group compared to the control group for younger men, highlighting the importance of intervening earlier in life. The study showed how the sustained dietary change over time can lead to significant risk reduction, especially in individuals with atherosclerosis and higher baseline cholesterol levels.
Misinterpretation of Cancer Deaths and Adherence Considerations
The study's findings regarding increased cancer deaths in the experimental group require careful interpretation. Further analysis revealed that the majority of fatal carcinoma cases occurred in participants with low adherence to the experimental diet, suggesting that the excess cancer deaths were unrelated to the diet itself. Additionally, the age and duration of the study must be considered when examining non-atherosclerotic deaths. The age-related incidence of cancer, coupled with the elderly participants' long follow-up period, suggests that the increased cancer deaths were likely due to age-related factors rather than the diet. The overall significant reduction in atherosclerotic events in the experimental group supports the positive impact of the intervention.
In 1959 a landmark clinical trial, often referred to as the LA Veterans Study, began with the aim to investigate the effects of replacing dietary saturated fats with polyunsaturated fats, on the progression of atherosclerosis and cardiovascular outcomes.
This was an eight-year clinical trial in 846 domiciled male veterans in the US. The diets between the control and experimental groups differed by saturated fat and polyunsaturated fat (particularly linoleic acid) content, but were similar in calories and total dietary fat.
The findings of the study suggested that replacing saturated fat with polyunsaturated fat was beneficial for reducing heart disease risk. However, the study also reported an unexpected increase in non-cardiac mortality in the intervention group, which raised concerns.
In this episode, we discuss why the LA Veterans Study was such a seminal trial and what we can learn from it.
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