A new DNA analysis of hot dogs and sausages in the US has revealed a few harsh realities about everyone's favourite street food. Not least, the fact that 10 percent of the vegetarian mock-meat products tested actually contained meat.

In light of the news that the World Health Organisation (WHO) has officially listed processed meats such as bacon and sausages as cancer-causing, this is probably the least of your worries if you're an avid hot dog lover. But it's definitely disconcerting news for all those who are trying to cut down or avoid eating meat products by buying vegetarian options.

The study was conducted by Clear Food, a consumer guide that makes its recommendations based on DNA analysis. The goal wasn't to freak everyone out about eating hot dogs - let's face it, most of us already assume our sausages contain a few wildcard ingredients - but to give us more scientific information with which to make our dietary decisions.

While some of these substitutions, hygienic issues, other variances, or off-label ingredients may be permitted by the FDA [Food and Drug Administration], our scientific disclosure allows you, as the consumer, to decide whether the variance or problems meet your personal standard in your buying decision," Clear Food explains.

The genomic analysis involved 345 different hot dog or sausage products from 75 brands, purchased at 10 different retailers in the US. Molecular biologists at Clear Labs then extracted the DNA from samples of these products and matched them to the genetic code of different animals.

What they found was that 14.4 percent of the items tested were problematic in some way, either as a result of contamination - which means that a non-harmful contaminant was found, most often human DNA - or substitution, which is where another food ingredient that's not on the label has been added.

Ten products tested contained chicken that weren't meant to, four contained beef, three contained turkey, two contained lamb and, worryingly, nine contained pork. That may not bother a lot of people, but it means that 3 percent of the sausage and hot dog products tested contained a type of meat that's often excluded for religious reasons.

"In most cases, pork found its way into chicken and turkey sausages," said Clear Food. Pork substitution was an issue in products across the price spectrum being sold at a wide variety of retailers."

Human DNA was found in 2 percent of the samples, which doesn't mean that there were traces of human meat in the sausages, but simply that there was some kind of contamination, so that could be through a stray hair or skin cells, or potentially even saliva.

Vegetarian hot dog products surprisingly fared the worst in this regard, with four out of the 21 products tested containing human DNA. And, yep, 10 percent of them contained meat. "We found chicken in a vegetarian breakfast sausage and pork in a vegetarian hot dog," the report explains.

There were also issues with the nutritional content listed on labels, with the analysis showing that protein content could be exaggerated up to 2.5 times. 

But the good news from the report (yes, there is some!) is that the scientists found no correlation between price and quality. 

Check out the full report for more information about the brands in the US that did well on the test. But a word of warning - the scientists only looked at one sample of each product, so it's hard to get a clear picture from that limited information about the overall safety and accuracy of an entire product line or brand.

Still, it's always nice to use a little science when making your shopping decisions, so go forth and gorge yourself on hot dogs. Just try to think a bit more about DNA testing while you're doing so.