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TalkingNutrition

Providing perspectives on recent research into vitamins and nutritionals

fishmarket

The Trick is Getting Nutrients, like the Book “George”, to as Many People as Possible

By Michael McBurney

To be frank, I am still perturbed by quotes in The Washington Post surrounding the secondary analysis of the AREDS2 randomized controlled trial (RCT) which was so aptly summarized by Dr Eric Ciappio yesterday.

While it is entirely correct to say “We don’t know whether these supplements might be beneficial at an earlier age”, the AREDS2 study design and results do not support the statement “A much better bet for all-around brain and heart health is eating foods naturally high in omega-3 fatty acids, such as salmon, flaxseed, and walnuts.” Show me the evidence from RCTs to justify this statement. It doesn’t exist. There aren’t any placebo-controlled RCTs with salmon, flaxseed, or walnuts.

Why recommend eating more fish? Are fish a more sustainable protein source? Or is it because of an inherent property, such as n-3 fatty acids? What about the risk of mercury contamination?

Some fish do contain more n-3 long-chain polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), than other foods. In their 2003 recommendation to increase fish consumption, the American Heart Association Nutrition Committee was probably more interested in shifting the types of dietary fat being consumed away from saturated/trans fatty acids found in red meat and dairy products towards long-chain polyunsaturated fatty acids in fish than encouraging the consumption of marine versus animal protein sources. But did they have RCTs with salmon, flaxseed, and walnuts? No.

Arterial stiffness, measured by carotid-femoral pulse wave velocity (cf-PWV), may contribute to cardiovascular disease (CVD) risk. Today’s featured article elucidates the challenge of food-based studies. Reinders and colleagues failed to find an effect of regular fish consumption on their CVD risk factor - arterial stiffness. A likely contributor is a lack of precision associated with self-reported dietary intake data.

However, plasma total n-3 PUFAs, EPA and DHA, are associated with lower arterial stiffness (P – 0.007). Each increment in plasma total n-6 PUFAs and linoleic acid (LA) was associated with higher arterial stiffness. This study demonstrates the importance of n-3:n-6 fatty acid balance in the body. It is futile to attribute health outcomes to the dietary intake of a single food (or nutrient or fatty acid) when the health of our body depends on the milieu of nutrients bathing each and every cell.

Dietary supplements are not a panacea for health. However, supplements, like foods, contribute to nutrient intake and nutritional status. Just as author of ‘George’, Alex Gino is trying to help children accept that gender pronouns may not apply to everyone, scientists need to help people accept that nutrition status is more important than judging people on their nutrition choices.  

Main Citation

Reinders I, Murphy RA, Song X, Mitchell GF, Visser M, Cotch MF, Garcia ME, Launer LJ, Eiriksdottir G, Gudnason V, Harris TB, Brouwer IA. Higher plasma phospholipid n-3 PUFAs, but lower n-6 PUFAs, are associated with lower pulse wave velocity among older adults. 2015 J Nutr doi: 10.3945/jn.115.212282

Other Citations

Chew EY, Clemons TE, Agron E, et al. Effect of omega-3 fatty acids, lutein/zeaxanthin, or other nutrient supplementation on cognitive function: the AREDS2 randomized clinical trial. 2015 JAMA doi: 10.1001/jama.2015.9677

Kris-Etherton PM, Harris WS, Appel LJ, for the AHA Nutrition Committee. Omega-3 fatty acids and cardiovascular disease: New recommendations from the American Heart Association. 2003 Arterioscler Thromb Vasc Biol 23:151-152

Gebaurer SK, Psota TL, Harris WL, Kris-Etherton PM. n-3 fatty acid dietary recommendations and food sources to achieve essentiality and cardiovascular benefits. 2006 Am J Clin Nutr 83:S1526-1535


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