You probably already know that trans fat is bad for you. But what about saturated fat, monounsaturated fat and polyunsaturated fat? A long-term study sheds some light on just what are healthy fats.
The study followed 80,082 women over 14 years. Questionnaires were sent to the women periodically, asking for detailed information on their diets (among other questions). Each woman was scored on how much they ate trans fats, saturated fats, monounsaturated fats and polyunsaturated fats. The researchers then compared the different diets to incidence of coronary heart disease after controlling for a number of potential confounders like exercise, smoking, and alcohol use. The researchers found that overall fat intake was not associated with heart disease risk. Looking deeper though, trans fat and saturated fat were significant associated with heart disease. Monounsaturated and polyunsaturated fats, however, were associated with a significant reduced risk. Replacing just 2% of energy from carbohydrates with trans fats was associated with a 91% increase in heart disease risk. Replacing 5% of energy from carbohydrates with saturated fat was associated with a 17% increase in heart disease risk. Replacing 5% of energy from carbohydrates with monounsaturated fat and polyunsaturated fat was associated with a 19% and 38% reduction respectively (see chart).
A separate meta analysis found no association between saturated fats and monounsaturated fats and heart disease, but reinforced the benefits of polyunsaturated fats. For that reason, you’re best off focusing on reducing trans fats and increasing polyunsaturated fats. Foods high in polyunsaturated fats include: walnuts, canola oil, sunflower seeds, sesame seeds, chia seeds, unsalted peanuts, salmon, mackerel, sardines, salmon, peanut butter, soybeans, seaweed, avocado oil, and olive oil.
Hu, Frank B., et al. “Dietary fat intake and the risk of coronary heart disease in women.” New England Journal of Medicine 337.21 (1997): 1491-1499.
Jakobsen, Marianne U., et al. “Major types of dietary fat and risk of coronary heart disease: a pooled analysis of 11 cohort studies.” The American journal of clinical nutrition 89.5 (2009): 1425-1432.