If you eat seafood frequently, you should consider upping your selenium intake. Most seafood is contaminated by mercury from commercial waste or has naturally absorbed it from its environment. Not only can selenium counteract mercury poisoning, but it’s also important for certain bodily functions. Increase your selenium intake by eating seafood containing high levels of selenium, or take a daily supplement.

The National Resources Defense Council lists seafood by mercury content. Although the lowest mercury seafood category seems to contain harmless levels of mercury, recent research discovered that bodily mercury levels deemed safe can cause autoimmune diseases which are among the top 10 causes of death for women.

The good news is, since mercury is attracted to the selenium in your body, the selenium neutralizes mercury by binding to it. Your body normally uses selenium to produce antioxidant enzymes, which aid in preventing cancer and heart disease, support your immune system, and regulate thyroid function. But when too much of your selenium is tied up with mercury, your body won’t have enough left to produce your daily amount of antioxidant enzymes.

Selenium deprivation could lead to serious health problems. Studies involving rodents deprived of all their selenium via intentional mercury poisoning experienced thyroid hormone disruption. Newborn rodents experiencing thyroid hormone disruption developed permanent neurological damage.

How can you increase your daily selenium intake? You can eat selenium-rich seafoods like young albacore tuna (63 mcg per 3-ounce serving) and cod fish (32 mcg per 3-ounce serving). The adult recommended selenium dosage is only 55 mcg, but keep in mind that selenium-rich seafood contain mercury too, so you’ll end up with less selenium.

The purest selenium source you can take daily is through a supplement. These are relatively inexpensive, but experts debate their efficacy in raising blood selenium levels. Some studies show that eating just two Brazil nuts daily raises blood selenium levels by 5 to 10 percent more than a selenium supplement.

Given these studies, Brazil nuts are an equally good and far cheaper source of selenium (approximately 544 mcg per 1-ounce serving) than are supplements. They’re even safer to eat than selenium-rich seafood, since they aren’t usually contaminated with mercury.

Seafood lovers beware: safe low levels of mercury (like those in seafood) can still cause autoimmune disorders. You can protect yourself by increasing your selenium intake via eating selenium-rich seafood, Brazil nuts, or a daily supplement.