Perspective: interesterified triglycerides, the recent increase in deaths from heart disease, and elevated blood viscosity

Abstract

The authors hypothesize that consumption of interesterified fats may be the cause of the continuous increase in cardiovascular deaths in the United States which began in 2011. Interesterification is a method of producing solid fats from vegetable oil and began to supplant partial hydrogenation for this purpose upon recognition of the danger of trans fats to cardiovascular health. Long, straight carbon chains, as are present in saturated and trans fatty acids, decrease the fluidity of the erythrocyte cell membrane, which decreases erythrocyte deformability and increases blood viscosity. This decrease in cell membrane fluidity is caused by increased van der Waals interactions, which also solidify dietary fats. Elevated blood viscosity is favored as the pathogenic mechanism by which trans fats increase cardiovascular mortality because changes in lipoprotein levels do not account for all the mortality attributable to their consumption. The rapid changes in cardiovascular mortality noted with the introduction and withdrawal of trans fats from the food supply are reviewed. The evidence implicating elevated blood viscosity in cardiovascular disease is also reviewed. Data regarding the production and consumption of interesterified fats in the US should be released in order to determine if there is an association with the observed increase in cardiovascular deaths.

Keywords: blood; deformability; erythrocyte; interesterification; lipids; trans; triglycerides; viscosity.

Figure 1.

Interesterification. In this example, enzymatic catalysis results in the transfer of fatty acids involving the sn-1,3 positions of the glycerol backbone. Chemical interesterification can result in the random transfer of fatty acids and involve the sn-2 position. Figure courtesy of Teledork at English Wikipedia.

Figure 2.

Structural formulae of 18-carbon fatty acids. The straight configuration of trans and saturated fatty acids allows them to be tightly packed in the erythrocyte plasma membrane, which maximizes van der Waals interactions and raises their melting point. Cis double bonds cause bends in the carbon chain, preventing close packing, decreasing van der Waals interactions and lowering the melting point of linoleic acid.

Figure 3.

The effect of bends in the carbon chains of fatty acids on lipid bilayer fluidity. The top lipid bilayer is composed entirely of triglycerides with saturated and trans fatty acids. The linear configuration of these carbon chains allows tight-packing. This maximizes van der Waals interactions and stiffens the plasma membrane. The lower lipid bilayer contains triglycerides with cis double bonds, which cause bends in carbon chains. This prevents close packing of triglycerides, increasing membrane fluidity. Figure courtesy of Wikimedia Commons.