Saturday July 30, 2016 (foodconsumer.org) -- Eating foods with trans fat, or otherwise known as partially hydrogenated vegetable oils can increase risk of strokes, according to a study released in 2014 in the American Journal of Clinical Nutrition.

Intake of trans fat has been linked to increased risk of death from heart disease and increased risk for ovarian cancer  , breast cancer, infertility, and diabetes among other risks.  It is estimated that more than one million Americans will die from heart disease and strokes in 2017.

The current study shows that men who had intake of merely 2 grams of trans fat per day were at 14% increased risk of stroke.  The association was not found in women though.  Please note that another early study has linked intake of trans fat with elevated risk for stroke in women.

There are two types of strokes, ischemic stroke and hemorrhagic stroke.  The former is caused by blockage of a blood vessel and the latter is caused by bleeding due to blood vessel rupture.  

It is unknown why intake of trans fat is associated with increased risk of stroke.   It is possible that trans fat may both help block the blood vessel, and promote the aging process leading to vessel rupture, particularly in people with high blood pressure. In other words, trans fat may increase risk for both types of stroke.

Partially hydrogenated vegetable oils have been used in various processed foods and restaurant-prepared foods.  A food without trans fat added, but with polyunsaturated fat added such as soybean oil and corn oil can contain trans fat if the food is thermally processed.   For instance, fries can contain trans fat if ordinary cooking oil is used to cook the food.   This is so because the thermal processing can induce the formation of trans fat.

Note that just because a food label says there is zero trans fat does not necessarily mean there is no trans fat in the food. It only says that the trans fat is less than 0.5 trans fat per serving.  Because the serving size is an arbitrary measure, any foods with even high levels of trans fat can be labeled as zero trans fat when the serving size is small enough. (David Liu)

James N Kiage, Peter D Merrill, Suzanne E Judd, Ka He, Loren Lipworth, Mary Cushman, Virginia J Howard, and Edmond K Kabagambe, Intake of trans fat and incidence of stroke in the REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort, Am J Clin Nutr May 2014 , vol. 99 no. 5 1071-1076