The Impact of Natural and Industrial Trans Fats on Cardiovascular Risk
Director, Nutraceuticals and Functional Foods Institute
Université Laval
The impact of dietary saturated fatty acids (SFA) on the risk of cardiovascular disease (CVD) has been well established over the last 50 years. Recently, trans fatty acids (TFA) in foods have attracted worldwide attention owing to their potentially undesirable effects on human health. Most epidemiological studies have shown that, over time, increased intake of TFA is associated with even greater CVD risk than is SFA. An increase in TFA intake equivalent to 2% of daily energy has been shown to be associated with a significant 25% greater risk of CVD over time. On a gram for gram basis, TFA may have a greater impact on the risk of CVD than SFA.
It has been estimated that approximately 3.5% of the fatty acids in milk fat are TFA, mostly in the form of 11-trans 18:1 vaccenic acid. Based on this estimate, it has been calculated that a significant proportion of dairy products (>50%) will surpass the threshold of 0.2 g TFA/portion—defined by Health Canada as the cut-off point for “trans-fat free” labelling. Clearly, this is an important issue for the dairy industry. Only a few studies have investigated the impact of ruminant TFA on blood cholesterol and CVD risk. During their investigations of TFA on CVD risk, a few groups have observed that, unlike TFA from industrial sources, TFA from dairy products were not associated with an increased risk of CVD. Specifically, the large-scale Nurses’ Health Study demonstrated a protective effect of ruminant TFA on CVD risk. In another study, levels of elaidic acid and trans,10-18:1 (hydrogenated fat) in platelets were positively associated with the degree of coronary artery disease diagnosed angiographically in 191 non-diabetic patients (134 men and 57 women), while vaccenic acid and other TFA showed no such association. As well, a nutritionally controlled study in healthy subjects has shown that compared with a diet rich in dairy fat, consumption of TFA from industrial sources led to a 19% significantly higher LDL:HDL cholesterol ratio. However, the lack of association between ruminant TFA and CVD risk has not been a consistent observation. In a relatively small case-control study, vaccenic acid levels measured in adipose tissue (a marker of long-term consumption) were higher in first MI cases than in matched controls. The dairy fat trans 16:1 levels in adipose tissue were also higher in cases.
In conclusion, while the negative impact on health—particularly on CVD risk—of consuming industrial TFA is relatively well established, it remains to be proven whether the impact of ruminant TFA on CVD risk is different from that of industrial TFA. Well-controlled, randomized trials are required to address this important public health issue.
