A recent Presidential Advisory from the American Heart Association on Dietary Fats and Cardiovascular Disease makes sweeping statements that have been further oversimplified by the media, at the risk of grossly oversimplifying a complex topic.
The article’s stated aims are admirable: to review and discuss “the scientific evidence, including the most recent studies, on the effects of dietary saturated fat intake and its replacement by other types of fats and carbohydrates on CVD [cardiovascular disease].” According to the authors, the review was prompted by confusion resulting from recent reviews and meta-analyses questioning the link between dietary fat consumption and heart disease.
Given the need to put hundreds of studies into context, one would expect an extensive review. However, the authors only identified four “Core Trials” – performed in 1968, 1969, 1970, and 1979 – as suitable for consideration in reaching their conclusion. When the results of just these four studies are combined, the authors can demonstrate a statistical correlation between replacing saturated fats with polyunsaturated fats and reducing the “primary endpoint” related to cardiovascular disease defined by each trial.
Their summary conclusion is as follows:
In summary, randomized controlled trials that lowered intake of dietary saturated fat and replaced it with polyunsaturated vegetable oil reduced CVD by ≈30%, similar to the reduction achieved by statin treatment.
In other words, after selecting four trials out of hundreds performed over the past fifty years, we’re encouraged to replace saturated fat, as a homogeneous group, with “vegetable oil”.
The message amplified by the mainstream media is even more simplistic. “Coconut oil isn’t healthy. It’s never been healthy.” declares the USA Today's clickbait headline. Why? Because increased coconut oil consumption studied in isolation raises LDL cholesterol (along with butter and other saturated fats). Again, not new insight.
Simply adding coconut oil, butter, or other sources of saturated fat to a Standard American Diet rich in sugar, refined carbohydrates, and oxidized fatty acids but poor in fiber and omega-3 fatty acids is not a recipe for good health or longevity.
However, this news must come as a surprise to the indigenous people who obtain significant calories from coconut-derived saturated fats, and experience little heart disease, diabetes, or obesity:
The Pukapuka and Tokelau Island study by Prior et al found a low incidence of CVD in the populations of these two islands, despite a large portion of energy intake (34% among Pukapukans and 63% among Tokelauans) and dietary fat intake being from coconut flesh. It has been reported that the diets of these two populations were low in sugar and high in fiber-rich foods, resulting in low cholesterol levels (4.5mmol/L and 4.6 mmol/L in Pukapukans and Tokelauans, respectively).
Might the fact that their traditional diet consists of whole or minimally-processed foods devoid of added sugar and refined carbohydrates play a role? Might also it be noteworthy that these same people who can safely eat a high-fat native diet see precipitous health declines if they adopt a modern diet of convenient processed foods either in their own country, or after migration?
Diet, metabolism, and disease are incredibly complex topics. A broader view of current research paints a more nuanced picture – high saturated fat consumption in the presence of refined carbohydrates, added sugars, and insufficient omega-3 unsaturated fatty acids leads to chronic systemic inflammation associated with various disease states from obesity to diabetes, heart disease and even neurological degeneration.
However, when we are eating whole or minimally-processed food without added sugars and with adequate fiber and omega-3 fatty acids, saturated fats play an important role stabilizing proteins in cell membranes, facilitating intracellular communication, and reducing inflammation.
Despite what the media will proclaim, replacing coconut oil or other saturated fats with vegetable oil is unlikely to be the cure for our epidemic of diabetes, obesity, heart disease, and autoimmune/inflammatory conditions. Want to improve your lipid profile? Cut out the sugar, and eat real food.