Eating mussels can make your semen radioactive!

mmm….radioactivity. Image via Wikipedia.

They say you are what you eat and, according to new research, eating foods high in radioactive polonium-210 will make your semen radioactive, too. The work was published in the Journal of Environmental Radioactivity by Alphonse Kelecom and Ridta de Cássia dos Santos Gouvea. They measured the polonium-210 (Po-210) levels in the semen of 5 vasectomized non-smoking men before and after eating a meal of mussels.

Before eating the mussels, all the men had very low levels of Po-210 in the seminal fluid. This amount tripled (though was still fairly low) after eating the shellfish, but returned to normal by 4 days.

Polonium-210 is a radioactive derivative of uranium-238. It is widespread in the environment, but at low levels, and mostly comes from the natural decay of radon in the atmosphere. It can be toxic to humans if inhaled (eg: through smoking cigarettes) or eaten, but in general it’s pretty hard to get enough of it to kill you. That said, Po-210 has killed at least one person: the Russian spy Alexander Litvinenko, who was poisoned with tea laced with the radioactive isotope in 2006.

Most of the Po-210 that gets into the human body is flushed down the toilet. But, a small amount does remain in the body, mainly in the muscles and specific organs. It is estimated that the human body is exposed to an internal radiation dose of about 37Bq from Po-210. In contrast, our bodies contain about 5,000Bq of a radioactive isotope of potassium, K-40. However, Po-210 can do much more damage than K-40 because it is an alpha-emitter, whereas K-40 is a beta-emitter. Either way, these normal doses of radiation aren’t dangerous.

The authors of this study have been studying the amounts of Po-210 in people who may have high exposures to it: uranium mine workers, farmers who use phosphate fertilizers, and cement workers. They have also studied many sources of Po-210 contamination: cigarettes, cigars, aquatic plants, and seafood. They previously showed that eating a single meal of mussels leads to an increase in Po-210 in feces and urine for several days (I can’t find the article online…and I wouldn’t be able to read it, anyway; it’s in Portuguese).

Anyway, the point is this: eating seafood leads to a spike in Po-210 being excreted from the body. So, the implication is that eating seafood should also lead to higher levels of Po-210 in the body. But where does it go?

Here, the logic of the study gets a little confusing. Po-210 is often cited as a dangerous component of cigarette smoke. Some studies have found a link between cigarette smoking and male infertility. So, maybe Po-210 is bad for fertility. Thus, they decided to look at a link between eating seafood and Po-210 levels in semen.

How did they do this? Easy! They found 10 guys they knew to volunteer for the study (only 5 made it the whole way through). Requirements: they had to be vasectomized (the authors didn’t want to deal with sperm…maybe that will be a later paper?), they had to abstain from sex for the three weeks of the experiment, eat no fish or seafood except the one meal of 200g of mussels provided after the second week, and they had to provide a semen sample every morning for 10 days. Plus one semen sample before the experiment started.

First, they compared the pre-experiment sample to the sample collected after eating no fish for 2 weeks. The authors saw that the semen contained about half as much Po-210 when no fish or seafood was eaten than when there were no restrictions on diet. So, seafood is a source of Po-210.

The next sample was collected the morning before they ate a big batch of mussels. At this point, all of the men had very low levels of Po-210 in the semen: about 0.11mBq (a mBq is 1/1000th a Bq). After eating the mussels, their levels jumped to about 0.42mBq, and most returned to baseline two days later. Now, while the authors quote this as a “300% increase” in Po-210, it’s obviously still a very small amount.

(Compare these amounts to that used to kill Livitenko: 2GBq. That’s right, 2 billion Bq. That’s more than 200 times the lethal dose. Someone really wanted him dead).

But, who knows, it might be enough to cause damage to sperm DNA. While none of the samples in this study contained any sperm, an older study using fertility clinic patients did find that the amount of Po-210 in the sperm fraction of the ejaculate was more than 40 times the amount in the rest of the seminal fluid.

I doubt that a one-time exposure to mussels will hurt you (so dig in!), but if you eat a seafood-rich diet, it may be something to think about.