Sperm and salt
Sperm count fall blamed on salt is the headline on the BBC's web site and elsewhere. They report a study conducted in Michigan which found that rats starved of iodine grew larger testicles and had increased sperm production. (See also 'Salty secrets of shrunken testicles' in the New Scientist.) They claim that the alleged fall in sperm rates in the US in the 1960s is due to the introduction of iodine in salt there in 1924. Before you are tempted, however, to forego that bag of salted nuts with your beer in the pub, read on.
There are two things wrong with this study. Firstly, as the report's author James Crissman himself acknowledges, iodine is important for the development of the thyroid. If your intake is too low, mental development is impaired. That is precisely why it is added to salt in the first place.
Secondly, who says sperm counts are declining? The day before the salt alarm was raised, a Reuters report claimed that "the overall quality of semen in the US male population is the same today as it was 50 years ago." The study's author Dr. Rebecca Sokol, of the University of Southern California , said "… everything in our study indicates that … the average man's sperm count is not changing." Richard Sharpe of the Medical Research Council's reproductive biology unit also emphasises that sperm count data are very variable and that it would be unwise to assume that iodine, and therefore, salt, had any impact.
So – maybe that iodine-rich nibble with your favourite tipple is not going to wreck your manhood at all. And everybody knows that women love brainy men.