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For Hypertension, Fish Is Better Than Supplements

Omega-3 fatty acids found in oily fish may have diverse health-promoting effects, potentially protecting the immune, nervous, and cardiovascular systems. But how the health effects of the fatty acid DHA work remains unclear, in part because its molecular signaling pathways are only now being understood.

Toshinori Hoshi, PhD, a professor of physiology at the University of Pennsylvania Perelman School of Medicine in Philadelphia, and his colleagues showed in two papers recently published in the Proceedings of the National Academy of Sciences how fish oils help lower blood pressure via vasodilation at ion channels. In vascular smooth muscle cells, such as those that line blood vessels, ion channels that span the outer membrane of a cell to let in and out ions such as sodium, calcium, and potassium are critical to maintaining proper vessel pressure.

The researchers found that DHA rapidly and reversibly activates these channels by increasing currents up to 20-fold. DHA lowers blood pressure in anesthetized wild-type mice but not in mice genetically engineered without a specific ion channel subunit.

In comparison, the team found that a dietary supplement, DHA ethyl ester, which is found in most fish oil pills, fails to activate the same channels and even antagonizes natural source DHA’s positive effect on the cells. The DHA ethyl ester seems to compete with the natural form of DHA for binding sites on the ion channel.

The team concluded that these channels have receptors for long-chain omega-3 fatty acids, and that DHA, unlike its ethyl ester cousin, activates the channels and lowers blood pressure.

The findings have practical implications for the use of omega-3 fatty acids as nutraceuticals for the general public and also for critically ill patients who may receive omega-3–enriched formulas as part of their nutrition.

Coauthor Michael Bauer from Jena University Hospital in Germany, who studies sepsis in a clinical setting, says the findings may encourage physicians to look more closely at the specific formulations given to sepsis patients, as they may contain either the free omega-3 acid or the ester.

The findings also underscore the importance of obtaining omega-3 fatty acids from natural food sources such as oily fish.

— Source: University of Pennsylvania School of Medicine