Interesterified Palm Olein (IEPalm) and Interesterified Stearic Acid-Rich Fat Blend (IEStear) Have No Adverse Effects on Insulin Resistance: A Randomized Control Trial

Abstract

Chemically-interesterified (CIE) fats are trans-fat free and are increasingly being used as an alternative to hydrogenated oils for food manufacturing industries to optimize their products’ characteristics and nutrient compositions. The metabolic effects of CIE fats on insulin activity, lipids, and adiposity in humans are not well established. We investigated the effects of CIE fats rich in palmitic (C16:0, IEPalm) and stearic (C18:0, IEStear) acids on insulin resistance, serum lipids, apolipoprotein concentrations, and adiposity, using C16:0-rich natural palm olein (NatPO) as the control. We designed a parallel, double-blind clinical trial. Three test fats were used to prepare daily snacks for consumption with a standard background diet over a period of 8 weeks by three groups of a total of 85 healthy, overweight adult volunteers. We measured the outcome variables at weeks 0, 6, and at the endpoint of 8. After 8 weeks, there was no significant difference in surrogate biomarkers of insulin resistance in any of the IE fat diets (IEPalm and IEStear) compared to the NatPO diet. The change in serum triacylglycerol concentrations was significantly lower with the IEStear diet, and the changes in serum leptin and body fat percentages were significantly lower in the NatPO-diet compared to the IEPalm diet. We conclude that diets containing C16:0 and C18:0-rich CIE fats do not affect markers of insulin resistance compared to a natural C16:0-rich fat (NatPO) diet. Higher amounts of saturated fatty acids (SFAs) and longer chain SFAs situated at the sn-1,3 position of the triacylglycerol (TAG) backbones resulted in less weight gain and lower changes in body fat percentage and leptin concentration to those observed in NatPO and IEStear.

Palmitic Acid Versus Stearic Acid: Effects of Interesterification and Intakes on Cardiometabolic Risk Markers—A Systematic Review

“…The proportion of palmitic acids at sn-2 did not affect the concentrations of glucose [11][12][13], insulin [11,12], C-peptide [11,12], and C-reactive protein (CRP) [13]. Stearic acid sn-2 content also did not affect glucose and insulin concentrations [14].…”

“…The interesterification of palmitic acid-rich fats did not affect concentrations of TAG, total cholesterol (TC), LDL-C, or high-density lipoprotein (HDL)-C [8][9][10][11][12][13]. However, one study reported that men-but not women-showed a small, but statistically significant, increase in TC and LDL-C concentrations in response to the diet with a higher sn-2 content of palmitic acid [9].…”

“…In seven studies, the content of palmitic or stearic acid at sn-2 was increased by the interesterification of experimental fats, while in one study interesterification decreased the sn-2 content of palmitic acid [8]. Studies examining palmitic acid-rich fats used palm oil [9,10], palm olein [11,12], butter [8], or a blend consisting mainly of coconut and palm oil [13]. Two studies have reported the solid fat content at 37 • C; in one study, both the native and interesterified palm oils were liquid [9], while interesterification increased the solid fat content of palm olein from 0 to 6% in the other study [11].…”

“…The melting points of native and interesterified cocoa butter were not measured, but the authors indicated that native cocoa butter was liquid at 37 • C and assumed that the solid fat content of the interesterified fat at 40.5 • C was 19% [15]. Most of the studies had used a randomized cross-over design, except for two studies that used a parallel design [8,12]. The experimental periods varied from 21 to 56 days for studies examining palmitic acid-rich fats and diets provided 1 to 11 energy percent (en%) of palmitic acid.…”

“…However, one study reported that men-but not women-showed a small, but statistically significant, increase in TC and LDL-C concentrations in response to the diet with a higher sn-2 content of palmitic acid [9]. No differences were found for non-esterified fatty acid (NEFA) [13], apolipoprotein (apo)B [8,12], apoA1 [8,11,12], and lipoprotein[a] concentrations [11][12][13]. The sn-2 content of stearic acid also had no effects on the concentrations of TAG [14,15], TC [14,15], LDL-C, or HDL-C [14].…”