Nutrition and heart disease: time to raise our standards

Fuelled up by the results of recent investigations highlighting the null relationship between saturated fat consumption (dietary fats from animal sources) and heart disease risk, an increasing amount of observers have called into question current recommendations of many health organizations around the world that currently suggest that the intake of saturated fats should be reduced under a certain threshold for optimal cardiovascular health. Although the results of these large-scale studies are valid and credible, they did not test the hypothesis that the consumption of other macronutrients could be more beneficial or detrimental to cardiovascular health and failed to take into account the sources or the dietary quality of macronutrient intake.

A study published by the group of Frank B. Hu from the Harvard T.H. Chan School of Public Health in Boston shed light on the association between saturated fats compared with unsaturated fats and sources of carbohydrates in relation to heart disease risk in a study that included more than 84,000 women and 42,000 men who were followed between 24 and 30 years. This study confirmed the absence of a relationship between saturated fat consumption and heart disease and the positive association between trans fat consumption and heart disease risk. Interestingly, a higher consumption of polyunsaturated fatty acid was associated with a lower heart disease risk. The association between carbohydrate intake and heart disease risk was neutral. However, upon further investigation of dietary carbohydrate quality, the authors found that the consumption of poor-quality carbohydrates such as refined starches/added sugars were associated with a greater heart disease risk while the consumption of high-quality carbohydrates such as whole grains was rather associated with a lower cardiovascular risk. The authors also performed statistical modelling analyses that showed that replacing 5% of energy intake from saturated fats with equivalent energy from poly- or monounsaturated fats or whole grains would lead to a reduction in cardiovascular risk that ranged between 9% and 25%.

Despite the fact that this study is characterized by the limitations of a typical nutritional epidemiologic studies (self-reported dietary intake, residual confounding, etc.), that it did not consider the sources of saturated fats (dairy products vs. red meat, etc.) and that it should not be considered as a substitute of a randomized clinical trial of cardiovascular outcomes, the results of this investigation should have important implications for public health policies. First, considering the increasing amount of patients coping with heart disease in almost every country of the world, simply accepting saturated fats as healthy because they apparently do no harm and keeping the status quo means that this trend will slowly continue to progress. It is time to raise our standards and put the emphasis on foods and dietary pattern that prevent heart disease and not simply on those who do not apparently cause them. Second, by highlighting that the current recommendation of reducing saturated fat intake will improve cardiovascular health of targeted populations IF this reduction is paralleled by increases in unsaturated fats (fish, olive oil, nuts, etc.) or high-quality carbohydrates such as whole grains, this study underscores the futility of the low-fat vs. low-carb debate. It is a call for a shift of focus towards improving nutritional quality if we want to have any chance of reducing the burden of cardiovascular disease around the globe.