Review finds Omega-3s Benefits to be Well Established
In 1995, the American Heart Association introduced their Heart-Check program to help consumers identify low-fat foods at point-of-purchase. To institutionalize health and nutrient content claims in the United States, Congress created the FDA Modernization Act in 1997 (FDAMA). Significant scientific agreement on the role of dietary fat, especially saturated fat, with cancer and cardiovascular disease led to several fat-related health claims.
The food industry responded and removed saturated fat from many food products. But people did not change their dietary patterns and total energy intake and percent calories from fat (32-33%) has not changed. Recommendations to avoid fat in the late 1990’s may have inadvertently increased added sugar consumption, a trend that is reversing in recent years (100g/d in 1999-2000 to 77 g/d in 2007-2008).
Today, many question the role of different types of fat in health. High cholesterol and triglyceride concentrations in the blood (dyslipidemia) are still an accepted risk factor for cardiovascular disease.
Ooi and colleagues published a comprehensive review of the effects of dietary fatty acids on human lipoprotein metabolism. Here are some takehome messages:
Most of our advances in knowledge on the role of fatty acids on health have related to omega-3 fatty acids. Elevated blood triglycerides are a risk factor for cardiovascular disease. Omega-3 long-chain polyunsaturated fatty acids (LCPUFA) reduce triglyceride synthesis. 1.23 g daily of EPA and DHA have been reported to decrease non-fasting plasma triglycerides.
Omega-6 LCPUFAs are the predominant dietary LCPUFA in the US. Imbalances between omega-3 and omega-6 LCPUFAs affect cardiovascular disease risk. For the secondary prevention of cardiovascular disease, a n-3:n-6 ratio of 1:4 is associated with a 70% reduction in total mortality.
Most of the fat consumed in our diet is as saturated and monounsaturated fatty acids, not LCPUFA. We consume many fatty acids with differing lengths and degree of saturation every day. Dependign upon the substitutions made, even in clinical trials, the effect on blood lipid concentrations can vary. Replacing dietary fat with carbohydrates (and was the substitution with sugar or complex carbohydrates?) or exchanging one type of fat (saturated) for another (monounsaturated or trans fatty acid) can affect metabolism and health.
Scientists don’t have all the answers. Modifying fat type or amount within a diet affects the balance of other macronutrients in the diet and metabolism.
More lipid research is needed to give definitive advice on fat intake but be confident that almost everyone isn’t consuming enough omega-3 fatty acids.
Ooi EMM, Watts GF, Ng TWK, Barrett PH. Effect of dietary fatty acids on human lipoprotein metabolism: A comprehensive review. 2015 Nutrients doi: 10.3390/nu7064416
Welsh JA, Sharma AJ, Grellinger L, Vos MB. Consumption of added sugars is decreasing in the United States. 2011 Am J Clin Nutr doi: 10.3945/ajcn.111.018366
Ooi EMM, Lichtenstein AH, Millar JS, Diffenderfer MR, Lamon-Fava S, Rasmussen H, Welty FK, Barrett PH, Schaefer EJ. Effects of Therapeutic Lifestyle Change diets high and low in dietary fish-derived FAs on lipoprotein metabolism in middle-aged and elderly subjects. 2012 J Lipid Res doi: 10.1194/jlr.P024315
Blasbalg TL, Hibbeln JR, Ramsden CE, Majchrzak SF, Rawlings RR. Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century. 2011 Am J Clin Nutr doi:10.3945/ajcn.110.006643
Candela CG, Lopez LMB, Kohen VL. Importance of a balanced omega6/omega3 ratio for the maintenance of health. Nutritional recommendations. 2011 Nutr Hosp doi: 10.3305/nh.2011.26.2.5117