Burnt Food: Is It Bad For You?

If you like your campfire marshmallows burnt to a crisp, you need to read this.

Emily Lachtrupp is a registered dietitian experienced in nutritional counseling, recipe analysis and meal plans. She's worked with clients who struggle with diabetes, weight loss, digestive issues and more. In her spare time, you can find her enjoying all that Vermont has to offer with her family and her dog, Winston.

A slice of toast with burnt edges, smeared with jam. Charred vegetables from the grill. Burnt-to-a-crisp marshmallows smooshed between graham crackers along with a square of dark chocolate. Burnt food may not sound the most appetizing…but in these circumstances? Burnt food is desirable. Tasty. And…not safe for you?

There's no denying the fact that some foods can increase the risk of chronic diseases, including cancer. For many years now, burnt foods have been classified as a carcinogen—a substance capable of causing cancer in the tissue. Yet experts say that the evidence isn't clear enough about whether humans should worry about their burnt toast in the morning or not.

So what should a burnt-food lover believe? We break down the specifics of the chemical process behind burnt food and whether or not you should stop sticking your marshmallow directly into the fire.

Whether a food has a few burn marks from the grill or a slice of bread is full-on charred from the toaster, that food is still going through the same process of burning no matter how it's cooked.

Burnt foods undergo a chemical process called non-enzymatic browning, a chemical process food undergoes when it is being cooked. There are two major types of non-enzymatic browning: caramelization, and the Maillard reaction.

Caramelization occurs when carbohydrates or sugar are heated and water is removed, then followed by a process known as isomerization (when a compound or food is transformed into a different form) and polymerisation (combining molecules, giving food a brown color and nutty flavor—like caramelized onions).

The Maillard reaction occurs when the amino acids of the food react with the reducing sugars as a food cooks, giving that item a distinct flavor as well as a darker color.

Nevertheless, when cooked food reaches past the point of caramelization, it will become black and charred. And foods that have been cooked in a high-temperature process will likely contain the chemical acrylamide, heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs).

While acrylamide is a chemical found in manufactured goods like paper, dye, or industrial products, it can develop when plant foods like fruits and vegetables are cooked at a high temperature. A prime example is when starchy foods are fried, baked, or roasted—the most common being potatoes, like french fries or chips.

This chemical is formed when the sugars in the food (glucose or fructose) react with a free amino acid called asparagine, which forms acrylamide. This happens during the Maillard reaction and can contribute to the color and taste of cooked food. And if a food is cooked at a higher temperature for a longer period of time, it will likely contain more of it—meaning if food is burnt to a crisp, it contains more acrylamide compared to a non-burnt starchy food.

So if acrylamide is a chemical, does that mean it's bad for you?

Currently, research is up in the air on whether acrylamide in high quantities is dangerous or not for the body. Some rodent animal studies show that acrylamide exposure can increase the risk of several types of cancers. Another review in the American Journal of Lifestyle Medicine makes a link between a specific family of compounds(acrylamide being one of them) and links to several chronic diseases.

However, many of the rodent studies used as citations for the dangers of acrylamide are older, some dating as far back as the 1980s and 1990s. Since this research, many experts have mixed feelings about whether acrylamide can increase the risk of cancer. Cancer Research UK denies that eating foods with acrylamide cause cancer and points out that there isn't enough evidence to prove this. The American Cancer Society says that while nothing can overtly cause cancer, acrylamide has been determined to be "reasonably anticipated to be a human carcinogen" by the US National Toxicology Program. The National Cancer Institute says that while rodent studies have made the link and institutions have warned about acrylamide, a large number of epidemiologic studies on humans have found "no constant evidence that dietary exposure is associated with the risk of any type of cancer."

HCAs and PAHs are chemicals that can form when meat is grilled, and these chemicals are created in different ways. HCAs are found in the char marks created when meat is cooked at high temperatures, such as grilling or pan frying. PAHs, on the other hand, are found in the smoke that's created when fat drips onto the coals or the heating element of the grill, which then rises up and clings to your food. According to the American Cancer Society, studies linking HCAs and PAHs to an increased risk of cancer in humans is mixed.

With no evidence to establish a risk yet with many institutions voicing caution, what does that mean for the eaters at home? Is it bad to order your fries extra-crispy, or to char zucchini on the grill? Many experts—including Chef Eva De Angelis, LDN—have come to the same conclusion: It's all about moderation.

"It's more important [to focus on] your overall dietary pattern than isolated foods," says De Angelis. "As a general rule, if you have a balanced diet rich in foods high in fiber, protein, and healthy fats with a reduced intake of processed and red meat, and foods high in sugar, fat, and salt, having the occasional burnt food is okay."

De Angelis says it's more important to focus on how frequently you are eating burnt foods. "There's no denying that charred food tastes good, and it's part of many flavorful dishes and meals," she says. "Yet, I try to eat them only on occasion. This way I can enjoy them without putting myself at risk of increasing the chances of chronic diseases."

While there are some previous animal studies that have linked acrylamide, HCAs and PAHs with an increased risk of developing chronic diseases like cancer, there isn't enough evidence to prove that the same is true for humans. And the National Cancer Institute Experts say that while it is considered safe to eat burnt food, with so much research still unknown around the topic, it is best to consume it in moderation in small quantities.

Needless to say, you can enjoy that crispy black marshmallow on your s'mores. It's all good.