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You may have seen posts online warning you about the dangers of eating burnt toast, but how much will that actually affect your health?

Hosted by: Hank Green

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Sources:
https://www.theguardian.com/science/2017/jan/27/how-burnt-toast-became-linked-to-cancer-acrylamide
https://www.ncbi.nlm.nih.gov/pubmed/25403648
https://www.livescience.com/57612-acrylamide-cancer-risk.html
https://www.cam.ac.uk/research/discussion/opinion-how-dangerous-is-burnt-toast
https://www.cnn.com/2017/01/23/health/burnt-toast-cancer-risk-roast-potatoes-acrylamide-bn/index.html
http://www.who.int/foodsafety/publications/acrylamide-food/en/
https://scienceblog.cancerresearchuk.org/2017/01/23/its-too-soon-to-say-browned-toast-and-crispy-roast-potatoes-cause-cancer/

Images:
https://commons.wikimedia.org/wiki/File:Acrylamide-MW-2000-3D-balls.png
[♩INTRO].

Most people don’t really like the taste of burnt toast, but sometimes, it’s your only option. Like, maybe, in your morning rush to get ready for school or work, you cranked the timer on your toaster too far, and your bread popped out all black and crispy.

You don’t have time to make more toast, you’re a busy person! And you’re really hungry! But how risky was it to chow down on that blackened bread?

Your mom did share that Facebook post about burnt toast causing cancer. Well, short answer: not very. Long answer: probably not very.

When starchy foods like bread or potatoes are heated to high enough temperatures, like by baking or frying, a chemical reaction takes place that produces a compound called acrylamide. In many cases, the reaction is similar to, but distinct from, the Maillard reaction between amino acids and sugars, which also causes food to brown during cooking. In really large doses, acrylamide totally is toxic.

Some industrial workers who are regularly exposed to the chemical have suffered neurological damage. And other work on rats has also shown that acrylamide could attach itself to parts of red blood cells, and ultimately damage DNA. But all of that is when acrylamide is used as a sealant, not when it’s a byproduct of toasting your bread for too long.

It wasn’t even until 2002 that the chemical was definitely discovered in food. Regardless, the UK’s Food Standard Agency eventually recommended that people should avoid eating singed starches even though they acknowledged they didn’t have enough scientific evidence to conclude exactly how dangerous these foods were for humans. And the International Agency for Research on Cancer also listed acrylamide as a “probable carcinogen”.

But given that IARC also lists a bunch of other stuff as carcinogens, including working as a hairdresser and hot drinks, it’s not as scary as it sounds. So far, based on the research, it looks like acrylamide isn’t very likely to cause cancer in humans. Remember those industrial workers?

While neurological damage is very much not a good thing, studies of that group have also found no increased risk of cancer in almost all organs, except for pancreatic cancer in only the most heavily exposed workers. In 2015, a meta-analysis of 32 studies was also unable to find any causal link between acrylamide and an increased risk for a variety of cancers… including pancreatic. And while some studies do show an increased risk in kidney and ovarian cancer, there are plenty others that contradict them.

One of the problems with these studies looking at acrylamide is that the animals used are exposed to way more of the chemical than any human ever would be in day-to-day life. Like, you’d need to eat 75 kilograms of fries every day for 2 years to be comparable to one study done in rats. And while all those fries sound amazing, it’s just not going to happen.

So, eating the occasional burnt piece of toast isn’t going to kill you. If you’re worried about your health, you can always talk to your doctor and focus on things like having a healthy diet and getting some exercise. Because if french fries are going to kill you, it’s probably not the acrylamide… and also, research shows that those things are definitely good for you.

Thanks to patron Tori Walsh for asking this question, and to all of our patrons on Patreon who voted to have it answered. We love the questions you come up with and, as always, we are really thankful for your support. Thanks for helping us make stuff like this.

If you’d like to support SciShow and free science education on the Internet, you can go to patreon.com/scishow. [♩OUTRO].