Researchers from Baker IDI Heart and Diabetes Institute and Deakin University in Melbourne, have performed a study to assess the effect of dairy fat and soy oil on circulating postprandial lipids in men (Meikle et al., 2015). The study was funded by the Dairy Health and Nutrition Consortium. The study has shown that dairy foods promote a unique plasma phospholipid profile, which may be important to good health.
This randomised controlled crossover design trial, involved a total of sixteen men who consumed two breakfast meals on separate occasions containing either dairy fats or soy oil. The dairy meal consisted of cheddar cheese (60 g), butter (20 g), and extra creamy whole milk (300 mL), with toast (50 g) (3120 kJ, 54 g fat, 29 g protein, and 37 g carbohydrate). The meal high in vegetable oil-based foods (soy meal) contained cheddar flavoured soy cheese (100 g), soy beverage (300 mL), a non-dairy spread (20g), and toast (50g) (3290 kJ, 54 g fat, 29 g protein, and 47 g carbohydrate). The changes in the plasma lipidome during a 4 hour post-meal period were analysed using an electrospray ionisation tandem mass spectrometry and generated 316 lipid species in 23 classes and subclasses, representing sphingolipids, phospholipids, glycerolipids, and sterols.
The results revealed significant changes in multiple plasma lipid classes, subclasses and species in the post-meal period after both the dairy and soy meals. The major lipid changes included: ether linked phospholipids, plasmalogens, sphingomyelin (not present in soy), dihexosylceramide and GM3 ganglioside. Additionally, phosphatidylcholine and phosphatidylinositol were significantly elevated after the dairy meal, but were not significantly affected by the soy meal.
The authors conclude that, “The changes in postprandial plasma phospholipids in men relate to the diet composition and the relative size of the endogenous phospholipid pools. Despite similar lipemic responses as measured by changes in triglyceride concentrations, the differential responses between dairy and soy meals derived through lipidomic analysis of phospholipids, suggest differences in the metabolism of soybean oil and dairy fat. The increased concentrations of plasmalogens, with potential antioxidant capacity, in the postprandial period after dairy, but not soy meals, may represent a further important difference in the response to these sources of fat”.
The current study unravels some of the complexities of lipid metabolism following the consumption of two sets of complex foods containing lipids. The study also highlights that the underlying biochemical patterns following each group of foods is markedly different, even though basic measurements of triglycerides were similar. The researchers also add that “despite absence of substantial differences in neutral lipids between dairy and soy rich diets, the present study focuses attention on other important differences in lipid responses which are likely to have biological and possibly clinically relevant effects”, suggesting that some of these differences may be important to health.
The ether lipids and plasmalogens that were higher during the dairy meal compared to the soy meal have independently been shown to have a negative association with type 2 diabetes and with cardiovascular disease and are thought to relate to the degree of oxidative stress associated with these diseases.
Meikle et al., (2015) Postprandial Plasma Phospholipids in Men Are Influenced by the Source of Dietary Fat. The Journal of Nutrition, published online ahead of print, (doi: 10.3945/jn.115.210104).
Dr. Ramon Hall is Manager of the Dairy Health and Nutrition Consortium at Dairy Innovation Australia and is an Honorary Research Fellow at the School of Exercise & Nutrition Sciences, Deakin University.
