Trans fats — not saturated fat — linked to heart disease, death

Evidence is mounting in favour of saturated and animal fats over ‘industrial’ fats, with the latest study finding trans fats are associated with greater risk of death and coronary heart disease, while no association was seen between saturated fats and an increased risk of death, heart disease, stroke or Type 2 diabetes.

The study, published in the British Medical Journal (BMJ), analysed the results of 50 observational studies assessing the association between saturated and/or trans fats and health outcomes in adults.

The research team found no clear association between higher intake of saturated fats and death for any reason, coronary heart disease (CHD), cardiovascular disease (CVD), ischemic stroke or type 2 diabetes.

However, consumption of industrial trans fats was associated with a 34% increase in death for any reason, a 28% increased risk of CHD mortality and a 21% increase in the risk of CHD.

Saturated fats come mainly from animal products, such as butter, cow’s milk, meat, salmon and egg yolks, and some plant products such as chocolate and palm oils. Trans unsaturated fats (trans fats) are mainly produced industrially from plant oils (a process known as hydrogenation) for use in margarine, snack foods and packaged baked goods.

“For years everyone has been advised to cut out fats. Trans fats have no health benefits and pose a significant risk for heart disease, but the case for saturated fat is less clear,” said lead author Russell de Souza, an assistant professor in the Department of Clinical Epidemiology and Biostatistics with the Michael G. DeGroote School of Medicine.

“That said, we aren’t advocating an increase of the allowance for saturated fats in dietary guidelines, as we don’t see evidence that higher limits would be specifically beneficial to health.”

Current guidelines recommend that saturated fats are limited to less than 10%, and trans fats to less than 1% of energy, to reduce risk of heart disease and stroke.

The researchers could not confirm an association between trans fats and type 2 diabetes, and they found no clear association between trans fats and ischemic stroke.

As the results are based on observational studies, the researchers stress that no definitive conclusions can be drawn about cause and effect. However, the authors write that their analysis “confirms the findings of five previous systematic reviews of saturated and trans fats and CHD”.