Skeptical Raptor's Blog hunting pseudoscience in the internet jungle

Does bacon harm your sperm quality and quantity? Doubtful!

whipped-vodka-candied-baconDuring the past couple of days, there have been a half dozen news articles (they all make the same claims) that have flown across my news feeds recently. They all say, “bacon is associated with lower semen quality,” or variations on that theme.

This can’t be so, because it’s BACON!!!

Bacon is the perfect combination of fattiness and saltiness, and has moved from a strictly breakfast food into mainstream high-end cooking, possibly promulgated by the reverence it’s given by Food Network chefs. There’s a whole subculture of bacon desserts, including bacon cheesecake. Bacon ice cream. Bacon chocolate dipped roses. Let’s not even salivate over all of the savory dishes made better by bacon; and until you’ve had bacon mac & cheese, you’re missing an important part of your life. OK, I might be exaggerating, but not by much.

So, does bacon really have an effect on a man’s sperm quality, and as a result, on his fertility? The answer isn’t as clear cut as these so-called science journalists are claiming, and certainly not as definitive as is claimed in some of the bad science websites.

First thing, the article about bacon and sperm has not been published in a peer-reviewed journal. It is merely an abstract being presented at the 2013 American Society of Reproductive Medicine Annual Meeting. As I’ve stated before, meeting abstracts rank near the bottom in quality as a source for science. Why? Well, as I wrote:

These are presentations made at meetings/conventions of a scientific society. There are hundreds made every year, and preliminary research is presented in poster sessions or formal presentations. Usually, there is a lot of question and answers, that of course doesn’t show up in a link to the abstract or poster, that can help explain data. Moreover, these types of presentations vary from nearly ready for publication to pure speculation. They have not been peer-reviewed (although peer review can unintentionally happen through tough questions). They are not published formally. And they often do not contain enough explanation of methods, data, analysis, and other issues to evaluate properly. I would not consider this type of information as anything but “observational” in a scientific sense, though, as mentioned above, only around half are published.

They aren’t peer reviewed. They present preliminary information. And frankly, about 50% either never get published (because the results are never confirmed) or are only published in low quality, non-peer-reviewed journals. In other words, you have no scientific critique of what is written in a meeting abstract, and it could vary from really interesting to really bad. Thus, the fact that this study is simply a presentation at a science meeting doesn’t mean it’s bad, but it’s not really a sign of high quality either.

So let’s assume that this study has some validity (obviously, bacon consumers everywhere are waiting for my analysis). Let’s walk through the methods and results, as far as I can determine from the abstract:

  • This was a retrospective study, or an epidemiological study that looks at historical data, which has the unfortunate disadvantage of not being able to eliminate bias from selection of participants. For example, the group studied already had fertility problems and had presented themselves to the Massachusetts General Hospital Fertility Center for treatment. We have no idea of the bacon consumption (or any other food) in groups that had no fertility problems. I could propose the hypothesis that bacon, in fact, increased fertility, and this study could neither support nor refute that assertion.
  • Only 156 men were studied, a small number which causes much higher errors. The distributed the men into two huge groups, 78 who were in the upper half of bacon consumption amongst this group, and 78 who were in the lower half. 
  • Those men who ate bacon regularly had 1.4% fewer normal sperm morphology compared to the group that ate less bacon. The number was barely statistically significant, but is so small that you are then lead down the path of “what would a larger study tell us?”
  • The authors claim that the upper half group had 30% fewer sperm than those who ate less bacon. Except, that’s not how the study was powered. They compared the upper half bacon group with a lower quartile fish eating group (who may actually be a part of the upper half bacon consuming group). This information makes no sense, and is an improper way of comparing two populations. They aren’t two populations, they may be highly overlapping populations.
  • There is no dose-response study, which shows that as we climb the ladder of bacon consumption, we don’t know if the sperm count/morphology decreases concomitantly. 
  • There is an assumption made by the author (and frankly by those journalists who are covering this story) that bacon (or more generally, processed meat) is singularly correlated (and causal to) infertility. Yet, we have no clue if a balanced diet that includes frequent consumption of bacon has no effect. In general, even those of us who are bacon addicts, bacon is not the only food consumed. How do those other foods, or exercise, or fresh air modify bacon consumption.

This study provides little useful evidence to answer the question whether bacon is going to have a negative effect on your sperm quantity/quality. It’s not peer reviewed. The study design is horrible. And the results are questionable. 

Just to be clear, I’m not saying, “go eat bacon all day every day, you’ll be all right.” No. No. No. Eating a lot of processed meats may have some negative effects on us. Eating fatty processed foods can be detrimental to cardiovascular health. It could lead to some times of cancer. But at this point, I’m going to say there is no evidence that bacon harms your fertility.

 

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