It is acknowledged scientifically that very high cooking temperatures can initiate a chemical process called oxidation. This, in turn, causes foods to release what is referred to as free radicals, which are known to alter DNA function and can lead to disease processes that include inflammation and even cancer. Hence the eventual cooking temperatures achieved, and the duration of cooking are both associated with undesirable health effects.
Steaming and boiling appear to be the healthiest ways to cook. This is especially so for meats. The cooking temperatures are lower overall, reducing the risk of the foods releasing free radicals. It’s even better if only water is used, without adding oil or butter. Steamed vegetables will maintain more nutrients, boiling tends to dissolve some water-soluble vitamins into the water. Poaching is also quite a healthy cooking technique. It involves using moist heat from liquids like water, milk, or even oil. But make sure the foods are really cooked before eating them, especially the meats.
If you are a fan of deep-fried foods, you may want to temper that habit. Frying foods with oils heated at high temperatures produces harmful by-products. Fumes released from some overheated oils may contain compounds that can increase cancer risk. Furthermore, highly heated oils will oxidize quicker and release more free radicals. The way out is to keep cooking times short if using overheated oils. And to ensure that you are also getting a large intake of vegetables and anti-oxidants.
Roasting is an especially popular cooking method. But whatever you roast, be it plant or animal products poses a health risk. The risk is again linked to very high cooking temperatures, and over-doing the roast till it blackens. Overdone roasts could cause chemical reactions that can release harmful compounds. Roast or toast to a light brown color, and avoid getting to the point of blackening. The same goes for grilling. You could avoid exposure to very high grilling temperatures by pre-cooking in a microwave. Flip over the grilling pieces every so often, and cut away and discard the blackened portions.
Broiling involves placing your foods below the oven’s heat source. It too is linked with the potential release of harmful substances due to the high cooking temperatures. Marinating meats with vinegar, lemon, or herbs when broiling or grilling may create a protective barrier.
But you don’t have to avoid any of the cooking methods entirely. If you generally eat healthily, having a mix of cooking methods is unlikely to have a significant impact on your health.