Fish is one of the best things you can eat on keto because of the omega-3 content, but some fish–like marlin–are high in mercury. We’ve always been told to stay away from mercury, but why?
Mercury in one of the deadliest heavy metals and, in large amounts, can cause damage to the nervous, immune, and digestive systems, as well as the kidneys and lungs. Ideally, there should be no mercury in the human body, but most people have trace amounts, mainly through the consumption of fish that contain high levels of mercury.
You can easily avoid this issue by having variety in your diet — don’t stick with these high mercury fish every single day.