Epidemiological studies have shown a strong direct (positive) association between the intake of trans fatty acids (TFA) and the risk of coronary heart disease (CHD), primarily accounted for by industrially produced TFA (IP-TFA). However, comparisons between ruminant TFA (R-TFA) and IP-TFA and risk of CHD have been based on quintiles of intake, which implies that the associations between the two sources of TFA and the risk of CHD were described across different ranges of intake. Controlled metabolic studies of the effect of intake of total and specific R-TFA on CHD risk factors are warranted. Moreover, further epidemiological studies of intake of R-TFA and risk of CHD in populations with a high intake of R-TFA are warranted.