When it comes to health, it’s not just what you eat, but the cooking methods that are used. Foods can have drastically different effects depending on how much heat is used in the cooking process.
Sweet potatoes are a classic example. Boiled sweet potatoes have a glycemic index (GI) of about 46. GI is a measure of the extent to which foods raise blood sugar levels.
The higher the GI, the faster and higher your blood sugar goes up after a meal, and the harder it will crash. It’s very difficult to match a high-GI food with your medications or to walk off the spike in blood sugar, so you want lower-GI foods. At 46, boiled sweet potatoes are considered low GI.
But baked sweet potatoes have a GI of 94. Baking has effectively turned them into candy. When foods are subjected to the high heat of baking or frying, the starches break down into sugars, instead of remaining in a more complex form that takes longer to digest.
White potatoes are the same way. Boiled, their GI runs about 50. Baked, they’re around 85. You see similar variations with squash and other starchy vegetables.
GI isn’t the whole story, of course. Maybe more important is the glycemic load (GL), which takes the total amount of glucose you will get from a food into account. Starchy vegetables are high in carbohydrate, no matter how you cook them. But by breaking them down at high heat, we make them less healthy for us.
You can see a list of the GI and GL of 750 foods, prepared different ways, in this American Journal of Clinical Nutrition article.
One of the differences between baked and boiled is the temperature. When boiled, the temperature can’t go above 212°F or 100°C, the boiling point of water. Baking usually is done at 350°F (177°C), which breaks down the starches more completely. That’s why baked foods are usually sweeter.
Frying also heats foods far above the boiling point. They might taste good with the added oils and the broken-down starches, but they are not good for you.
I’m not saying you absolutely shouldn’t bake or fry, or that any foods are completely off limits. It’s about learning new, better ways to cook for taste and health. It’s better to sauté your foods (cooking them quickly in a bit of fat) or parboil them (partially cooking them in boiling liquid).
The liquid doesn’t have to be water. You can use tasty broths of various kinds. Broths make foods come alive. You can see a variety of broth recipes here.
You can also season food while sautéing. It’s worth learning how to do this, because there are other problems with super-high heats. Foods cooked with high-heat methods seem to increase the cancer rates of people who eat them.
Cancer risks of burnt carbs
Acrylamide, a chemical produced by certain cooking methods, has been shown to increase the risk of cancer in rats and mice. According to an article on CNN, “Acrylamide is what makes bread and potatoes turn golden in color when fried, baked, toasted, or roasted. The compound is formed from simple sugars, such as glucose, reacting with an amino acid, known as asparagine, when these foods are cooked at temperatures above 120°Celsius [248°Fahrenheit]. Asparagine is found naturally in starchy foods.”
According to the National Cancer Institute, acrylamide is considered a probable cause of cancer in humans by the National Toxicology Program and the International Agency for Research on Cancer. Women with higher levels of acrylamide in their blood have been found in research to have increased risk of some breast cancers. A Dutch study found higher rates of endometrial and ovarian cancer associated with higher levels of acrylamide exposure.
According to the Food and Drug Administration (FDA), “Acrylamide is found mainly in foods made from plants, such as potato products, grain products, or coffee… Generally, acrylamide is more likely to accumulate when cooking is done for longer periods or at higher temperatures…such as [in] frying, roasting, or baking… Boiling and steaming do not typically form acrylamide.”
What about meats?
The FDA says, “Acrylamide does not form, or forms at lower levels, in dairy, meat, and fish products.” But there are other ways high heat can make meats carcinogens.
The National Cancer Institute reports that meat that is cooked at high temperatures often contains dangerous chemicals.
The chemicals are called heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). They have been shown to cause cancer in rodents. With people, it’s harder to tell, because it’s hard to know how much HCA or PAH people are eating.
According to the National Cancer Institute, “Researchers found that high consumption of well-done, fried, or barbecued meats was associated with increased risks of colorectal, pancreatic, and prostate cancer.”
These risks are significant for people with diabetes. An Australian study found that people with Type 1 or Type 2 diabetes have an increased risk of cancer of the pancreas, liver, and most other sites, and are more likely to die from these cancers than people without diabetes.
So you might want to reduce cancer risk and the glycemic index of your diet by not cooking too hot. More salads, sautés, sauces, more boiling and steaming. See some recipes here.
I’m leading a webinar on sex and kidney disease, which is quite a similar topic to sex and diabetes. It’s Thursday, March 23, at 4 PM ET. It’s free and will cover issues that most people don’t talk about. You can read about it and sign up for it at http://www.dpcedcenter.org/march.