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Roughly 3 grams of omega-3 fatty acids each day, in food or supplement form, may be the optimal amount needed to help lower blood pressure, a review of the research shows.

The analysis of dozens of studies, published Wednesday in the , looked at the relationship between blood pressure and two omega-3 fatty acids – docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) – which are found in seafood such as salmon, tuna, sardines, trout, herring and oysters. DHA and EPA can also be taken together in supplement form.

While previous research suggests omega-3 fatty acids might help lower blood pressure, the amount needed to do so has been unclear.

"According to our research, the average adult may have a modest blood pressure reduction from consuming about 3 grams a day of these fatty acids," study author Dr. Xinzhi Li said in a news release. Li is an assistant professor and program director of the Macau University of Science and Technology School of Pharmacy in China.

Analyzing data from 71 clinical trials published between 1987 and 2020, researchers examined the relationship between DHA and EPA – individually and combined – and blood pressure in nearly 5,000 adults with and without high blood pressure or cholesterol disorders. Study participants, who came from around the world, ranged in age from 22 to 86. They consumed omega-3 fatty acids through diet and/or prescription supplements for an average 10 weeks.

The analysis showed overall, people who consumed 2-3 grams daily of a combination of the two omega-3 fatty acids reduced their systolic blood pressure (the top number) and diastolic blood pressure (the bottom number) by an average 2 mmHg, compared to those who did not consume EPA and DHA.

Those whose blood pressure was high to begin with benefited more and could benefit from consuming higher amounts of omega-3 fatty acids, the review showed. For people with high blood pressure, 3 grams of omega-3 fatty acids a day lowered systolic blood pressure by an average 4.5 mmHg. In those with normal blood pressure, the systolic number fell by 2 mmHg.

When people with hypertension consumed 5 grams a day, systolic blood pressure fell by an average of nearly 4 mmHg, while those without hypertension experienced a less than 1 mmHg average decline.

The National Institutes of Health suggests consuming 1.1-1.6 grams of omega-3 fatty acids a day, while the ÃÛÑ¿´«Ã½ recommends eating two servings of fish (3-4 ounces) a week as part of a heart-healthy diet. It takes about 4-5 ounces of Atlantic salmon to provide 3 grams of omega-3 fatty acids. Fish oil supplements typically provide about 300 milligrams per pill, though doses vary.

"Most of the studies reported on fish oil supplements rather than on EPA and DHA omega-3s consumed in food, which suggests supplements may be an alternative for those who cannot eat fatty fish such as salmon regularly," Li said. "Algae supplements with EPA and DHA fatty acids are also an option for people who do not consume fish or other animal products."

According to the Food and Drug Administration, evidence that omega-3 fatty acids can help reduce high blood pressure or the risk for heart disease remains inconclusive. However, the in June 2019 it did find the evidence sufficiently credible for it to allow these claims on food and dietary supplements containing EPA and DHA.

"Our study supports the FDA guidance that EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease by lowering high blood pressure, especially among people already diagnosed with hypertension," Li said. "However, while our study may add a layer of credible evidence, it does not meet the threshold to make an authorized health claim for omega-3 fatty acids in compliance with FDA regulations."

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