A large review of existing research published in The BMJ suggests that for healthy people, a reasonable amount of saturated fat in the diet may pose no health risk.
However, trans fats may be associated with an increased risk of death from any cause, death from cardiovascular disease, and a diagnosis of coronary heart disease.
For the new review, researchers included data from 41 studies of the association between saturated fat intake and health outcomes, covering more than 300,000 people, and 20 studies of trans fat intake and health outcomes that covered more than 200,000 individuals.
The researchers found that saturated fat intake was not tied to coronary heart disease, cardiovascular disease, stroke, or type 2 diabetes, but its link to risk of death from coronary heart disease was unclear. In addition, they found that consuming industrial trans fats was associated with a 34% increase in all-cause mortality, a 28% increased risk of heart disease mortality, and a 21% increase in the risk of heart disease.
They noted that because the evidence was uncertain for saturated fats, more studies are needed. It should also be noted that none of the studies included were randomized controlled trials; they were all based on observation over time. This means that other factors in participants' lives could have played a role in their health outcomes.