4 Types of Toxins that Form When You Cook Your Food at High Temperatures
byCathe Friedrich
Cooking can enhance the bioavailability of some nutrients. However, cooking to high temperatures, especially frying and grilling, can cause the formation of four toxic compounds. Here’s what they are and how to reduce your exposure to them.
One reason the experts recommend not cooking food too long is exposure to heat destroys some nutrients. Losses are greatest for some B-vitamins, including riboflavin, thiamin, and folate. Vitamin C is another vitamin that’s destroyed by exposure to heat and light. However, it’s not just the loss of nutrients that makes cooking foods at high temperatures a concern, it’s compounds that form when you take the temperature too high. Some of these compounds are linked with premature aging and cancer. Let’s look at these compounds and how you can reduce your exposure to them.
Advanced Glycation End-Products
Advanced glycation end-products, also known as AGEs, form when proteins combine with sugar and fats. Therefore, it’s not surprising that processed, heat-treated protein and fat-rich foods contain these compounds, including hot dogs and bacon. AGEs form complexes that bind to cells and other proteins in the body and form cross-links that change how the protein’s function. AGEs are associated with oxidative damage and inflammation, two driving forces behind aging. Most animal-based foods have AGEs in their uncooked state and cooking to high temperatures creates more. Margarine, mayonnaise, and cream cheese are significant sources of AGEs too.
In contrast, fruits, vegetables, and whole grains are low in advanced glycation end-products. Therefore, one way to reduce your exposure is to eat more plant-based foods. You can also reduce your body’s AGE burden by not frying, grilling, or using other high-temperature cooking methods. It’s important to cook the meat long enough to avoid food poisoning, so strike a balance. Cooking foods with dry heat also increases AGE formation. Stick to steaming or poaching whenever possible. Nuts and seeds may also contain significant quantities of AGEs if they’re dry roasted.
Acrylamides
Acrylamides form when starchy foods are cooked without moisture, such as frying or baking. Foods that contain some of the highest levels of acrylamides are bread, fried potatoes, and potato chips. Coffee and dry roasted nuts also have a fair quantity of acrylamides too. These compounds form when an amino acid called asparagine reacts with sugars. The concern is that acrylamides are a carcinogen that increases the risk of cancer. One study found a link between consuming more acrylamides and damage to hemoglobin inside red blood cells in humans.
What about healthy foods that contain acrylamides? Nuts are a healthy snack, but roasted ones contain moderate quantities of acrylamides, but raw ones do not. It’s only when you heat food beyond 250 degrees F. that acrylamides form. The type of nut matters. Roasted almonds have higher levels relative to other nuts. In contrast, hazelnuts have little or no acrylamides. Quantities are lower in peanuts and cashews too. Since nuts have other health benefits and studies show they may reduce inflammation, snack on them judiciously but avoid dark or burnt almonds!
Heterocyclic Amines
Heterocyclic amines (or HCAs) form when you cook beef, pork, or lamb to high temperatures and meats until well-done. An example is the grill marks you get on a steak. Those marks are heterocyclic amines that form when creatine in meat encounters high temperatures.
What’s so bad about them? According to the National Institutes of Health, rodents exposed to heterocyclic amines develop malignant tumors in a variety of organs at a higher rate. The link between heterocyclic amines and human cancers is still unclear, although HCAs is a probable carcinogen.
Poultry, such as chicken, also forms HCAs when you cook it at a high temperature or grill it. Other foods don’t contain HCAs in appreciable amounts, but you find heterocyclic amines in cigarette smoke and car exhaust fumes.
How can you avoid these chemicals?
Limit the amount of grilled and charred meat you eat and choose leaner cuts of meat.
If you grill meat, marinate the first in an acidic solution such as balsamic vinegar for 30 minutes. Studies show this can reduce the quantity of HCAs in grilled meat.
Cut off any charred or darkened areas of the meat.
When you grill out, add veggies to the grill! Vegetables don’t form HCAs.
Add some spices to your meat. A study found that the spice rosemary can reduce HCAs by almost 90%.
Polycyclic Aromatic Hydrocarbons
Polycyclic aromatic hydrocarbons, or PAHs, are another chemical that forms from the reaction of creatine in meat with high heat. Like PAHs, they’re a probable carcinogen and something you should avoid as much as you can. You can reduce your exposure by following the same guidelines as for heterocyclic amines–limit grilled or fried meat, marinate the meat before grilling, remove charred areas, and consume more fruits and veggies!
The Bottom Line
Cooking destroys some nutrients such as vitamin C and certain B-vitamins, and it also produces some undesirable compounds you’d rather not have in your diet. However, you better absorb the nutrients from some foods when you cook them. For example, your body takes up more lycopene from tomatoes that have been cooked or processed than from raw ones.
Plus, cooking reduces the anti-nutrient content of some plant-based foods that interfere with mineral absorption. For example, some plants contain anti-nutrients, like oxalates, tannin, and phytate, that hinder the absorption of calcium, iron, and zinc. So, there are pros and cons to eating foods raw and eating them cooked. With meat, you must cook it a certain amount to kill bacteria that could cause food poisoning. So, don’t switch to raw meat to avoid HCAs and PAHs!
All in all, eat a diverse diet so you won’t get concentrated quantities of these compounds. Also, eat a variety of cooked and raw fruits and vegetables. Also, avoid highly processed foods as, no matter how you cook them, they have ingredients you don’t want.
References:
Nutrient Digest. “The Hidden Toxins in Cooked Food”
Tufts University Health and Nutrition Letter. “Are There Carcinogens in Roasted Nuts?”
com. “6 Grilling Tips to Avoid Carcinogens”
National Cancer Institute. “Chemicals in Meat Cooked at High Temperatures and Cancer Risk”
Food Chem. 2016 May 15;199:632-8. doi: 10.1016/j.foodchem.2015.12.017. Epub 2015 Dec 8.
Science Daily. “To Block The Carcinogens, Add A Touch Of Rosemary When Grilling Meats”
Could you please tell me what is considered a high temperature (in degrees Farenheit)? Can I regulate the formation of these compounds in meats by using a meat thermometer to regulate how high the interior temperature rises? Thanks.
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