The largest fish in the world is the 40-foot-long whale shark, which can weigh more than 40,000 pounds — all from ingesting plankton and small fish.

But it's the 4- to 15-inch-long anchovy and herring, along with tuna, that are the best sources of omega-3 fish oil that delivers oversized heart health benefits.

A recent study reveals some new ways this essential fatty acid can keep your life going swimmingly. For three years, researchers from Switzerland tracked older folks and found that those who had an active lifestyle and no preexisting conditions showed unexpected benefits from omega-3s.

If those participants took 1 gram of omega-3s a day, their overall risk of infection fell by 11%. Upper respiratory infections specifically were reduced by 10%, and the risk of a urinary tract infection decreased by 62%.

Interestingly, the research also found that for those people, omega-3s did not protect against broken bones, strengthen muscle function, or lessen memory problems — possibly because the study participants were already doing well in those areas to begin with.

To make sure you're getting the omega-3s you need to stay healthy, indulge in salmon, sea trout, anchovies, and sardines. Flaxseed, chia seeds, avocados, and walnuts also provide some, as can a fish or algal oil supplement.

But ask your doctor about taking a daily supplement first, because they can interact with medications such as aspirin, blood thinners, blood pressure drugs, and certain chemotherapies.