Charred Foods and Cancer: Ask A Nutritionist

June 6, 2024

As we enter the peak of grilling season, Brandy on Dishing Up Nutrition's Ask a Nutritionist tackles a burning question: Do burnt foods cause cancer? Learn about the chemical changes in overcooked foods and get practical advice to reduce risks while enjoying your BBQ favorites.

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BRANDY: Welcome to Dishing Up Nutrition's “Ask a Nutritionist” podcast, brought to you by Nutritional Weight and Wellness. We're thrilled to be celebrating 20 years on air, discussing the connection between what you eat and how you feel, while sharing practical, real life solutions for healthier living through balanced nutrition. Thank you all so much for your support and listenership over the years. Now let's get started.

On today's show, I'll be answering a nutrition question we received from one of our Dishing Up Nutrition listeners. So today we'll be discussing the topic of whether or not eating burnt food or smoked foods can increase your risk for cancer.

So the original question was, “I recently lightly burned my toast and my spouse told me not to eat it because that black char is an oxidant. I had not even thought about foods that were oxidants. We just always hear about antioxidants. So, do black charred marshmallows or charred vegetables also carry oxidants?”

So I thought this was a pretty interesting question, especially as we're entering grilling season. This might actually be on some of your minds lately. And along those same lines, another listener wrote, “Are smoked foods, like smoked salmon or smoked ribs, safe to eat?” So I'm going to try to tackle these questions today so that you can feel confident in how you're preparing your food and know that it is safe. And this time of year, as we're entering the summer, grilling and barbecuing is a lot more popular and I think it's a great way to cook and to spend time outside.

And I really want to encourage you all to do it. So I'm going to let you in on some tips, how to prevent food from being overcooked, which can damage the food and actually create some issues. And I know it can be visually appealing to see those little char marks or those grill marks on a nice piece of steak or some vegetables.

What happens chemically in burnt or charred food?

And I know a lot of people really love the flavor of those charred bits. Maybe, you know, for example, the burnt ends of a brisket. But let's talk about what happens chemically when you cook food to the point of it being overcooked, where you're actually seeing burnt or charred parts of that food. Because when it comes down to it, cooking is all about chemistry.

When a food is heated, it undergoes structural changes and different chemicals are formed. And this is a normal part of cooking, and really this is why cooked food looks different, tastes different, smells different, compared to before it was cooked. And I would say this is also how we make many foods edible and palatable.

It's that transformation of flavor and that visual transformation that might make it more appealing to us. However, when a food is overcooked past a certain point, that's when it's going to appear black and charred. And foods that have been cooked at very high temperatures for long periods of time will potentially contain harmful chemicals.

So the names of the three most common chemicals in overcooked food are acrylamides, heterocyclic amines, or HCAs, and polycyclic aromatic hydrocarbons, or PAHs. And the two most prevalent food groups that are affected are those starchy carbohydrates and meats. But first, I really want to just give you an overview of how these chemicals are formed in meats.

So, we're going to start with those polycyclic aromatic hydrocarbons, or PAHs. PAHs are formed when you're cooking meat on the grill, or over an open flame, or some other heated surface, and the fat and the juices from that meat can start to drip directly onto the fire, or on that heated surface and create smoke.

So the smoke that results will actually contain those PAHs and then when that smoke kind of drifts up towards the meat, it sticks to the meat and you can consume that. So this same process applies to smoking meat. So PAHs are going to be contained in meat that are exposed to the smoke from fat or juice dripping on the flame or the heat, and then you consume that. So that's all about PAHs.


What are HCAs and are they harmful?

BRANDY: Heterocyclic amines, or HCAs, are produced from a chemical reaction between proteins and sugar when they're exposed to high temperatures. So, HCAs are formed when meat is exposed to high temperatures for prolonged periods of time. So the longer it's exposed to those high temperatures, the more HCA's are formed.

So whether or not these chemicals can cause cancer in humans has not been determined yet. There are some lab studies showing that HCAs and PAHs have been found to cause changes in DNA that may increase the risk of cancer. And although these studies in the lab showed that burnt foods or fried foods can increase the risk of certain cancers, that connection between consuming those foods and increasing cancer in humans has not been proven yet. So this is an ongoing area of research, still more to learn, but at this point, there's not significant data showing that humans are significantly impacted by this.

Acrylamides: chemical formed from overcooking starches

Now let's discuss overcooking starches. Acrylamide is formed after a chemical reaction from cooking carbohydrate foods like bread, fruits, and those starchy vegetables like potatoes. So this includes basically any cooking method: baking, barbecuing, grilling, toasting, frying, or roasting. And really this is how food changes color and flavor after cooking.

The longer and hotter a food is cooked, the more acrylamide it contains. For example, a piece of toast that is burnt to a black crisp has much more acrylamide than a piece of bread that has lightly been toasted to a golden brown color.

How to reduce exposure to these chemicals

Now let's talk about how to reduce your exposure to those chemicals, the acrylamides, the PAHs, and the HCAs. So when you're roasting or pan frying meat, it is recommended to use a low to medium heat temperature. Avoid using cooking methods that use high heat temperature like deep frying foods or pan frying with very high heat.

And we still do want you to be able to enjoy grilling season, but not be overly worried about ingesting these potentially harmful chemicals. So there are some steps that you can take to reduce your risk of eating these chemicals. So when you're grilling, I recommend keeping the flame low and avoid direct contact of the meat with the flame.

So try to keep that flame low and try to keep the duration of cooking times as brief as you can, especially if you're using higher temperatures. So one thing you can do is partially cook that meat at a low to medium temperature in the oven ahead of time, then finish it on the grill to give it that nice grilled flavor. This way, it doesn't have to be on the grill that long. So it's not exposed to those higher temperatures quite as long, and it's not exposed to the smoke as long.

And here's another tip. If you do happen to overcook something on the grill, and you see bits of char, you can simply cut off any blackened part or those charred parts before you eat it, and if you have access to an organics disposal, you can just toss those overcooked scraps in there, that way you don't have to waste any food.

Another tip is that if you plan to marinate your meat before grilling it, use a marinade that contains very little or no sugar, and try something that's maybe citrus based or vinegar based. Because the sugar in marinade can result in those chemical reactions that form potentially harmful chemicals that we just talked about.

But you can still add a ton of flavor to your meat with a homemade vinaigrette by using maybe some citrus juice or vinegar, some avocado oil, and some spices rather than a store bought marinade that almost certainly will contain high fructose corn syrup or some other form of an added sugar.

What is the best way to grill vegetables to prevent burning?

Lastly, let's talk about the best way to grill vegetables. Before you grill vegetables, I suggest soaking them in water for a few minutes to help prevent that burning. And if you plan on making kebabs, you also need to soak the wooden skewers before skewing those vegetables. So I suggest soaking those wooden skewers for at least 30 minutes beforehand, because wood is obviously very flammable.

Does eating burnt food cause cancer?

So soaking them in water is going to help prevent them from lighting on fire, which in turn is going to set your vegetables on fire. So circling back to the original question here, does eating burnt food cause cancer? Well, the evidence suggests that eating small amounts of burnt food occasionally is not likely to significantly increase your risk of cancer.

However, we can still take a few steps to be as safe as possible. I think the main takeaway is that we want to focus on eating real, high quality foods, real animal proteins, real natural fats, and a variety of colorful vegetables. So I would say, above all, it is important to get those high quality real foods in your diet, however you prepare them.

For example, the powerful antioxidants in colorful vegetables is going to help fight any oxidants from any burnt part of that food. So let's say you grill some asparagus and a little bit of it gets charred . The benefit from eating that asparagus will outweigh the negative impact from eating a little bit of it that's charred.

And if you're able to scrape off that charred part, even better. It's always best to strive for a balanced diet high in fruits and vegetables that are loaded with those antioxidants to minimize your risk of cancer overall. Even if the vegetables are slightly charred, I'd say it is still better to get them in than to not eat them at all.

So I hope this answers your questions about safe ways to prepare your food, and that you're able to get out there and enjoy grilling season this summer. Thank you all so much for listening to Dishing Up Nutrition's “Ask a Nutritionist”. If you found this episode helpful, be sure to leave us a rating or a review on your favorite podcast app. So we can help even more people discover the connection between what they eat and how they feel.

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