How Robert F. Kennedy Jr. Ended Up With Mercury Poisoning (And How To Prevent It Yourself)

Controversy and Robert F. Kennedy, Jr., seem to be constant companions. For instance, he's made comments against vaccines — although he said he wasn't anti-vaccination during his 2025 confirmation hearings for the position of Secretary of the Department of Health and Human Services. However, some of what Kennedy has said remains unquestioned, such as his admission of having had mercury poisoning during a 2012 deposition he gave.

While speaking, he said that he struggled cognitively due to ingesting significant amounts of tuna fish sandwiches over an unspecified period of time. Indeed, tuna usually contains mercury, and mercury ingestion has been known to lead to cognitive problems, as well as eyesight concerns and balance issues. But can eating a lot of canned tuna actually make you so sick that you end up with mental dysfunction?

The answer, unsurprisingly, is that it depends. That said, the mercury levels in commercially canned tuna might surprise you.

Both freshwater and saltwater fish come in contact with mercury regularly. As they feed, they systematically bring mercury into their bodies. When they're caught and eaten by humans, the mercury gets passed along in the process.

Some fish and shellfish contain very little mercury on average (per FDA). Scallops, clams, and sardines fall into this category. Tuna, on the other hand, has relatively significant amounts of mercury by comparison. And all kinds of tuna (especially the bigeye tuna) are relatively high in terms of their mercury content because a tuna is a large fish that has more time to eat smaller fish (that have mercury in their systems) as it grows.

This means that when you dive into a can of tuna fish, you're getting trace amounts of mercury. Yet most people who enjoy occasional tuna fish sandwiches, casseroles, and salads don't have mercury poisoning. Why? They likely avoid eating canned tuna every day and opt for a more moderate level of tuna consumption.

The amount of mercury in tuna fish varies widely based on the type of tuna and the brand, per 2023 data from Consumer Reports. In general, tuna called "chunk light" or made from skipjack tuna contained less mercury than albacore tuna. Consequently, the advised weekly ration of canned tuna for healthy adults who are not pregnant is around two or three five-ounce cans.

Is there any way you can tell whether or not your favorite tuna fish is more or less toxic? According to marine expert Dr. Nicholas Fisher, you can try to find out the source of your tuna — and aim for fish from the Atlantic Ocean. Explained Dr. Fisher, "In China and India, they burn a lot of coal for electricity, and when you burn coal, you release a lot of mercury into the air, which eventually rains down; so mercury levels have been increasing somewhat in the Pacific. Whereas in the Atlantic, we've shown that the levels have declined a little bit."

Overall, you don't have to stop eating tuna fish. After all, tuna offers up nutrients: A 3-ounce serving contains 20.1 grams of protein, 11.9 grams of calcium, along with heart-healthy omega-3 fatty acids. Just be careful about eating tuna too frequently, and avoid serving it often (especially albacore varieties) to infants or young children who may be more susceptible to lasting side effects from mercury poisoning.