What is the Story on Omega-3s, DHA and EPA?
Here’s the deal, it is in our nature to want things. To weigh less and be fitter. To have lower blood triglycerides. To have lower blood pressure. To live free of cancer, advanced macular degeneration, memory loss, or heart disease. Deep inside, we know that our diet affects the structure and function of our bodies (what we are made of). If only the experts would tell us what to eat or avoid. Because people want this information, the media asks experts to share their knowledge and insights. We read (scan?) headlines hoping find definitive answers (or maybe to justify our actions and/or reinforce our beliefs).
A retrospective review by a senior Canadian cardiology expert questioned the quality of 40 year old data linking arctic diets, rich in fish oils, with cardiovascular mortality. Lots of things (cars, telephones, airplanes), industries (farming, manufacturing, medical), and jobs were different 40 years ago. Research tools and practices have also changed.
Supplementation with omega-3 fatty acids (α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) changes red blood cell membrane composition within weeks. However, it is fish oil, rich in EPA + DHA, but not flaxseed oil, primarily ALA, that increase RBC DHA levels. Using uniformly carbon-13-labeled docosahexaenoic acid (DHA), Plourde and colleagues showed that supplementing eicospaentaenoic acid (EPA) and DHA (3.2g/d) increases the oxidation rate of DHA and shortens its half-life in the plasma in older healthy adults. Overfeeding saturated fat for 7 weeks significantly increases hepatic and visceral fat deposition (compared to overfeeding polyunsaturated fat). The fatty acid composition of our body reflects our recent dietary fat intake. Regardless of the original methodology used to generate the ‘fish oil and heart disease’ hypothesis, science has subsequently confirmed that dietary fat intake affects our bodies.
So how does one interpret headlines like “Fish oil may not prevent heart disease after all”? Remember, newly published scientific studies are newsworthy. Journalists choose research articles using a variety of criteria – journal reputation, number of subjects, topic, etc. They read the manuscripts (or should) and interview experts. After the article is written, copy editors create headlines that will attract readers. Hopefully, people will read more than the headline to get the full story.
Nutrition is a life plan. Nutrients are not magic bullets but we are what we eat. What we eat changes us. Many nutrients – DHA, lutein, vitamin E – must be consumed to maintain healthy bodies, eyes and brains. And our health can be at risk because we are not consuming adequate amounts of these nutrients.
Rosqvist F, Iggman D, Kullberg J, Cedernaes J, Johansson H-E, Larsson A, Johannson L, Ahlstrom H, Arner P, Dahlman I, Riserus U. Overfeeding polyunsaturated and saturated fat causes distinct effects on liver and visceral accumulation in humans. 2014 Diabetes doi: 10.2337/db13-1622
Fodor GJ, Hellis E, Yazdekhasti N, Vohnout B. “Fishing”for the origins of the “Eskimos and heart disease” story. Facts of wishful thinking? A review. 2014 Can J Cardiol doi: 10.1016/j.cjca.2014.04.007
Cao J, Schwichtenberg KA, Hanson NQ, Tsai MY. Incorporation and clearance of omega-3 fatty acids in erythrocyte membranes and plasma phospholipids. 2006 Clin Chem doi: 10.1373/clinchem.2006.072322
Plourde M, Chouinard-Watkins R, Rioux-Perreault C, Fortier M, Dang MTM, Allard M-J, Tremblay-Mercier J, Zhang Y, Lawrence P, Vohl M-C, Perron P, Lorrain D, Brenna JT, Cunnane SC. Kinetics of 13C-DHA before and during fish-oil supplementation in healthy older individuals. 2014 Am J Clin Nutr doi: 10.3945/ajcn.113.074708