By Rosie Eyerman
Community Dietitian, Refugee Health Program & Resource Center
I recently read an article from the Academy of Nutrition and Dietetics on how certain cooking methods and additives can contribute to the progression of diseases such as diabetes and heart disease. This happens through compounds called Advanced Glycation End-products, or AGEs. Often, we hear that we should avoid high-fat cooking methods, such as frying, in order to avoid chronic disease, or that we should avoid high heat to prevent nutrient loss. But are some of our other favorite methods of cooking unhealthy for us too?
What are AGEs?
During the heating and cooking process, carbohydrates react with amino acids and fat to produce a browning effect known as the Maillard Reaction, or glycation. The end products of the Maillard process are the Advanced Glycation End-products or AGEs. We can visually see this browning effect on foods such as a roasted marshmallow or baked potatoes.1
This Maillard Reaction is the process that turns our food brown and, in turn, also creates a different smell, taste, appearance and texture which can make our food tastier. Methods of cooking, time, temperature and marinades can inhibit this formation while still making our food delicious. While I am a big fan of grilled foods, whether a lean venison burger or vegetable kabobs, browning our foods should not be the most common way to prepare meals.
As we age, our tissue proteins accumulate AGEs. Research shows people absorb 10 percent of all AGEs consumed.1 Over a lifetime, this can significantly affect our health. AGEs are associated with higher inflammation, which can contribute to the worsening of chronic illnesses such as heart disease, kidney disease, and diabetes. A reduced amount of AGEs in the body can reduce complications and improve health relating to lower inflammation.2
Classifications of Cooking Methods
Not only do our food choices matter, but how we cook matters too. Did you know that boiling broccoli releases nutrients into the water, but steaming keeps all the nutrients intact? How can different cooking methods also impact AGE formation in our foods?
AGEs form when a food begins to brown or burn from heat. During the high-heat process, our food cooks at a quicker rate so more AGEs occur in a shorter period of time. Table 1.0 walks us through the different varieties of preparing foods and how your AGEs component changes with each method. Raw food items will always yield the least amount of AGEs, moist food will have moderate AGEs and dry heated food will create the most amount of AGEs.
Let’s take a look at Table 1.0 for a glimpse of AGEs and cooking methods:
DRY HEAT: High amounts of AGE formation.
|METHOD||DESCRIPTION||LOW AMOUNTS OF AGES?|
|Sautéing||Cooked over stovetop with pan on high heat and little oil. Meat, vegetables, and vegetable proteins are commonly cooked in this manner||NO|
|Pan Frying||Cooked over stovetop with pan this method involves medium high heat and more oil than sautéing||NO|
|Roasting or Baking||Cooked using traditional or convection oven. This method uses heated air to transfer heat to cook food. Uses little oil, if any. Used for breads, cookies, meats, and vegetables||NO|
|Grilling||Cooked with rapid convection heat from below the food using gas flames or charcoal on a grill. Common foods are meats and vegetables during warm weather and picnics||NO|
|Broiling||Rapid heat is applied to food using an oven from the top of the food. Used to brown food quickly||NO|
|Deep Frying||Oil is heated to high heat of up to 400 degrees F then food is submerged. High temperature cooks the food quicker and allows it to be browned in the process||NO|
MOIST HEAT: Low amounts of AGE formation.
|METHOD||DESCRIPTION||LOW AMOUNTS OF AGES?|
|Poaching||Food is submerged in lowest temperature method at 160-180 degrees F. Liquid is calm with slight movement||YES|
|Simmering||When food is submerged in liquid at 185-205 degrees F. Liquid will have small bubbles. Common in cooking grains, stews, meat, and soups||YES|
|Boiling||Cooked when food is submerged in liquid at 212 degrees F. Liquid will have large vigorous bubbles. Not recommended for vegetables and fruit due to high nutrient loss. Common in cooking noodles||YES|
|Steaming||Cooked from the steam released when water reaches past boiling. Nutrient loss is low, food is cooked rather rapidly||YES|
|Microwaving||Uses energy waves to cook foods. No association with loss of nutrients. Commonly used to reheat foods||YES|
|Braising||Uses both dry heat and moist heat methods. Commonly used for vegetables and meats first sautéed or pan-fried to caramelize; then liquid is added by simmering to become tender and moist||YES|
How much of an impact on AGE content does the method of preparation actually have?
A skinless chicken breast is low in fat, high in protein and low in calories. However, this can change when we cook it. In Table 1.1 that raw chicken has 769 kU/100 mL compare to the moist heat of steam at 1,058 kU/100 mL, which is a 38% increase from the original product. In comparison, the dry heat method of broiled chicken at 450°F yields 5,828 kU/100ml of AGEs, which is a 658% increase from the original product. If we retain about 10% of the AGEs from the dry heat method of cooking, we would retain 583 kU compared to only 106 kU of the moist heat method.
|CHICKEN BREAST COOKING METHOD||AGE kU/100ML||SERVING SIZE (mL)||AGE kU/serving|
|Skinless, microwave, 5 min||1,524||90||1,372|
|Boiled in water, 1 hour||1,123||90||1,011|
|Boiled with lemon||957||90||861|
|Roasted, 45-minutes with skin||6,639||90||5,975|
|Breast, boiled in water||1,210||90||1,089|
|Skinless, poached, 15 minutes||1,076||90||968|
|Steamed in foil, 15 minutes, medium heat||1,058||90||952|
|Strips, stir fried with canola oil, 7 minutes||4,140||90||3,726|
|Strips, stir fried without canola oil, 7 minutes||3,554||90||3,199|
|With skin, 450°F, 45 minutes||8,244||90||7,420|
|Skinless, broiled, 450°F 15 min||5,828||90||5,245|
*Adapted from Uribarri, Jaime, Sandra Woodruff, Susan Goodman, Weijing Cai, Xue Chen, Renata Pyzik, Angie Yong, Gary E. Striker, and Helen Vlassara. “Advanced Glycation End Products in Foods and a Practical Guide to Their Reduction in the Diet.” Journal of the American Dietetic Association 110.6 (2010): 911-116. Journal of the American Dietetic Association. American Dietetic Association. Web. 20 Nov. 2015.
Fat Related to AGE
What we add makes a big difference. Adding too much fat to any diet can increase cholesterol but it can also increase AGE formation. You may notice in Table 2 that with the addition of canola oil, the AGEs increase by 16.5 percent. Similarly, high fat and aged cheeses have higher amounts of AGEs. Even though cheese isn’t necessarily cooked, heat during pasteurization and curing creates exposure to air and dry conditions which forms the AGEs. We see this increase in AGEs related to fat since carbohydrates not only react with proteins during the Maillard Reaction but with fats as well.
In contrast, we can add items to reduce the formation of AGEs in cooking. Acidic marinades such as citric fruits and vinegar prevent formation through the reduction of the pH. Table 2 shows that boiled chicken with lemon compared to boiled chicken has a reduction of AGEs by 15%. Marinades not only reduce AGE formation but also act as a meat tenderizer and can give the foods more flavor.
Low and Slow
The temperature and time of the cooking method can further reduce the amount of AGEs accumulated. Ideally, one should cook food on low and allow more time for the food to cook to desired consistency. A scrambled egg cooked on high for 1 minute with olive oil compared to medium high for 2 minutes results in a 62% reduction of AGEs. This shows how simple changes in heat and addition of time can alter the amount of AGEs.
AGEs and Vegetarian Food Choices
Vegetarian proteins and fats include legumes, nuts, seeds, eggs, oils, avocado, butter, cheeses and milk. Do these choices have reduced amounts of AGEs? While some choices like legumes, avocado, milk, eggs, and oils are lower AGE vegetarian choices, others such as nuts, seeds, aged cheeses, and butter have higher AGE content.
Although food choice matters greatly for the protein and fat that vegetarians can add to their diet, there are options that produce fewer AGEs. In general, high consumption of vegetables, grains and fruits (rather than high fat and protein foods) reduce the amount of AGEs absorbed due to the low content in these food groups, in combination with raw consumption or low temperature cooking techniques.
Burmese Coconut Squash Soup
A common squash found in Burma is buttercup squash, a cousin to our own butternut squash found in the United States. While it is possible to find buttercup in grocery stores in fall, butternut squash is significantly higher in Vitamin A at over 200% of the daily value, compared to buttercup at only 47% of the DV per ½ cup serving. Personally, I also find butternut squash to have a creamier and more palatable taste.
This recipe is the perfect seasonal soup with an intriguing taste – this is a definite addition to your normal fall recipe routine!
- 1 butternut or buttercup squash
- 2 carrots
- 1 cup coconut milk
- 3 cups vegetable broth
- 3 cloves garlic, minced
- 2-3 Tbsp. curry paste
- 2 tsp. coriander
- ½ tsp. turmeric
- 1/8 tsp ground red pepper
- 1 tsp cumin powder
- 1 Tbsp. lime juice
- 4 Tbsp. canola oil
- 1 onion
- ½ cup fresh basil, chopped
- Remove seed and skin from squash. Chop into ½ inch pieces. Chop carrots into ½ inch pieces.
- In a large pan or pot, add 2 Tbsp. oil. Heat then add squash, carrots, garlic, curry paste, coriander, turmeric, cumin, and red pepper to skillet with ½ cup of broth to mixture and steam from 20 minutes or until squash tender.
- While squash is cooking thinly slice onion and sautée in pan until browned.
- Mash squash using potato masher or hand mixer until pureed.
- Add in coconut milk, remainder of oil, and remainder of both to pureed squash mixture. Stir well. Bring to small boil until desired temperature. Add lime juice at end.
Serve and top with caramelized onion and basil. Serve over pad thai noodles if desired.