Mercury Exposure from Tuna vs. Thimerosal in Vaccines

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Once upon a time, routine childhood vaccinations used a preservative containing mercury called thimerosal. I was always surprised by parents who didn’t want to vaccinate their kids for fear of exposing them to mercury, yet went on to feed them tuna. Each thimerosal-containing shot would inject roughly the same amount of mercury that’s in a can of tuna fish. And while a child may only get a half dozen or so mercury-containing shots, they could be eating tuna salad sandwiches year after year. So, it’s evident that kids would be exposed to less mercury from vaccines than they would if they ate fish. Though when the mercury is injected, the absorption is like 100%, whereas if we just eat it some passes right through.

We used to think the gastrointestinal absorption of mercury was close to 100% following ingestion of the mercury in fish, though more updated estimates are consistently less than 100%. On the other hand, the form of mercury in fish is worse than the form of mercury used in vaccines, which is excreted from the body much more quickly. The mercury in fish represents the greater threat to children. But because any potential risk is of concern, in 1999 the Public Health Service, the American Academy of Pediatrics, and vaccine manufacturers agreed that thimerosal-containing vaccines should be removed as quickly as possible. And by 2001, thimerosal was removed from all vaccines in the recommended childhood immunization schedule.

Currently, in the United States, only multidose vial flu vaccines contain thimerosal, and thimerosal-free flu shots are widely available. Flumist, the nasal spray vaccine, is mercury-free, as well as most of the single dose vials used for pregnant women, which anyone can request.

Of course, thimerosal is still used in infants’ vaccines in developing countries. If the mercury load is deemed unacceptable in North America and Europe, why should it be given to infants in other parts of the world? We could also ask: if we want to play it safe and not expose kids to that much mercury, should we be feeding them fish, since kids are constantly getting that much mercury in their meals, and it’s methylmercury, which is even worse than the mercury in vaccines.

Now, there are ways to mitigate the mercury if you can’t beat some tuna craving. Drinking green tea with a meal may help block some of the absorption of mercury when eating fish. Normally, the recommendation is to not drink tea with meals, because it can also block the absorption of iron. But that’s better than the other way to protect yourself, shooting up with heroin. For some reason, the activation of opioid receptors protects nerves from mercury toxicity.

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Motion graphics by Avo Media

• children
• fish
• green tea
• mercury
• tuna
• vaccines