20 May 2018 - Forbes - New Advisory: Eat Fish Twice A Week To Lower Risk Of Heart Attack And Stroke -- What You Should Know

Two servings of oily fish per week can significantly reduce risk of heart attack and stroke, even for those who aren’t eating an especially healthy diet, according to a new science advisory from the American Heart Association (AHA).

Sixteen years after first releasing a recommendation to eat more fish, the AHA is doubling down on its advice. A wealth of credible studies have bolstered what at the time was an adequate if not entirely fleshed-out advisory made at the beginning of a new wave of research on fatty acids found in seafood. Now, say the researchers, there can be little doubt.

“The amount of research and science has grown so much since the last advisory came out that it was time to come up with a new statement on the beneficial effects of seafood in preventing not just heart disease, but stroke, heart failure, sudden cardiac death and congestive heart failure,” said Eric Rimm, a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health in Boston and chair of the group that wrote the advisory.

Specifically, the recommendation calls for eating two 3.5 ounce servings of non-fried fish per week, ideally chosen from oily varieties of fish highest in omega-3 fatty acids. The best options include wild salmon, albacore tuna, mackerel, lake trout, herring and sardines.

As an example, a four-ounce tin of sardines has between 1.3 - 1.8 grams of omega-3 fatty acids per serving, which breaks out to around 800 mg of DHA (docosahexaenoic acid) and 500 mg of EPA (eicosapentaenoic acid).

Research has focused largely on the anti-inflammatory influence of omega-3s, which counters the hardening and narrowing of arteries that characterizes heart disease. Diets higher in omega-3s are also linked to lower triglyceride levels and fewer fatty deposits that clog arteries. (A high level of omega-3 fatty acids is mainly why the Mediterranean Diet is thought to be such an effective inflammation reducer.)

According to the research team that released the latest advisory, science of the last couple of decades has also borne out the vital role omega-3s play in fostering cell communication (how our cells talk to each other to manage responses to nutrients and toxins, for example). “Omega-3s get into cell membranes, which is important for signalinginside and outside of cells. Cell communication is very important for a properly functioning heart,” Rimm said.

But don’t think a Friday night plate of fried catfish and slaw will fill the need. Eating fried seafood doesn’t provide the same benefits, and likely contributes to the very problem eating non-fried fish helps improve. The results of one study suggested that people who ate fried fish at least once a week were nearly 50% more likely to develop heart failure than those who rarely ate fried seafood.

While the AHA advisory was focused on heart health, research has also shown a significant correlation between eating higher levels of omega-3 fatty acids and improved brain health—and the same mechanism is likely at play: reduced inflammation.  Increasingly, the connection between inflammation and neurodegenerative diseases and disorders–from Alzheimer’s to Parkinson’s to depression–is becoming clearer. Upping the omega-3 density of our diets could be one of the most important things we can do for our brains as well as our hearts.

The AHA's advisory and the research supporting it leads to a few questions. For instance, can taking fish oil supplements provide the same benefits as eating fish? Recently, the efficacy of taking fish oil for heart health has been called into question. According to one study review, supplements may not measure up to eating fish when it comes to protecting the heart, but the research continues.

Do farm-raised fish provide the same benefits as wild fish?  While farm-raised fish are a more sustainable option than wild fish, the diets of many farm-raised fish—cornmeal, for example—may undermine the benefits by increasing the omega-6 fatty acids in the fish and lowering omega-3s. On the other hand, some farm-raised fish with diets tailored to enhance omega-3s actually have higher levels of EPA and DHA than wild fish. Here again, the research continues.

And should we be concerned about mercury levels? In short, yes—but not enough to make us not want to eat fish. The researchers note that mercury levels in fish high on the food chain, such as tuna, are a concern, particularly for pregnant women and young children, but say the benefits of ingesting more omega-3s far outweigh the mercury risks for most of us.