Has the Diet-Heart Hypothesis led us down a path of deception and ill health? A new editorial in BMJ EBM suggests that it has.
Briefly, the Diet-Heart Hypothesis dates back to the 1950s, when Ancel Keys argued that dietary fat, specifically saturated fat, caused heart disease. The idea infiltrated our government's nutrition guidelines and became the standard of care for preventative health as well as treating and preventing heart disease. The problem is that the scientific evidence does not support it, and after four decades, it is not serving us well.
As the authors, Drs. DuBroff and de Longeril, point out in their evidence-based editorial, the majority (not all, but definitely the majority) of published studies and meta-analyses show there is NO association between saturated fat intake and cardiovascular events or mortality. In addition, the unfortunate unintended consequence of promoting low-fat foods as "healthy," fueled generations of sugar and carbohydrate-craving individuals. In the end, this likely led to increased rates of obesity, metabolic syndrome and other negative health consequences.
The confusing part is that this isn't a secret. Studies and meta-analyses that contradict the Diet-Heart Hypothesis are published for all to see. In addition, observational data clearly shows a sky-rocketing of obesity and diabetes rates coinciding with the institution of low-fat guidelines.
So, why do most established health and medical institutions continue to promote the Diet-Heart Hypothesis as if it were fact?
The authors offer a couple of suggestions:
- Confirmation bias - paying attention only to the studies that confirm consensus beliefs while ignoring the rest.
- Focusing on the wrong outcomes - LDL cholesterol is the most common benchmark for cardiovascular risk. But LDL does not exist in a vacuum, and its contribution to cardiovascular disease is dependent on HDL, triglycerides and underlying metabolic health. Thus, monitoring changes in LDL as a solitary variable does not reflect the complexity of predicting cardiovascular disease or mortality.
Regardless of the exact reason for the confusion surrounding fat and saturated fat, we will continue to evaluate all the evidence, all the unintended consequences, and promote metabolic health as the cornerstone of overall health. The totality of evidence does not support saturated fat as a nutrient of concern, especially when combined with a healthy low-carb lifestyle. For more information, see our complete guide on saturated fat, and of course, explore our recipes for delicious low-carb meals that help promote metabolic health.
Thanks for reading,
Bret Scher, MD FACC
