Ask the RD

Question: I use chia seeds and flaxseed in smoothies. How do they compare to fish as sources of omega‐3s?

Answer: The difference lies in the type of omega‐3 fatty acids. Plant sources like chia seeds and flaxseed contain alpha‐linolenic acid (ALA), while fish contain eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). ALA is an "essential fatty acid," meaning it must be obtained from food because the body can't make it. Our bodies produce only negligible quantities of EPA and DHA from ALA, so we must get them from food as well (Weylandt et al. 2015).

Research on EPA and DHA, the fish fatty acids, has shown that they help reduce cardiovascular disease risk, probably through a combination of lowering blood lipids, reducing inflammation and decreasing platelet aggregation (or clotting) (Papanikolaou et al. 2014). They may also protect against inflammatory diseases and some types of cancer. The benefits of ALA from seeds and nuts aren't nearly as clear, but some studies suggest a link to lower cardiovascular disease risk (Anderson & MA 2009; Rodriquez‐Leyva et al. 2010).

Recommended intake of ALA is 1.6 g per day for men and 1.1 g per day for women (IOM 2005). That's less than a tablespoon of flaxseed or walnuts (Rodriquez‐Leyva et al. 2010). While Americans don't come close to meeting recommendations for EPA and DHA intake, women tend to meet ALA recommendations (Papanikolaou et al. 2014). Consuming more EPA and DHA from fish—especially fatty fish like salmon, mackerel, sardines and anchovies—may be a higher priority than increasing ALA intake.

That said, sources of ALA include nutritious foods like flaxseed and flaxseed oil, walnuts and walnut oil, chia seeds, canola oil, soybeans and soy oil, and even dry beans (Rodriquez‐Leyva et al. 2010). Because flaxseed and chia seeds have that fibrous seed coat, you do need to grind them, as in your smoothies, to get the most ALA out of them.