National Nutrition Week | Tips for healthy cooking

Healthy eating requires choosing the right ingredients, combining them reasonably, and cooking them healthily.

The significance of cooking, on the one hand, is to kill food safety hazards such as pathogenic microorganisms and reduce anti-nutritional factors that affect digestion and absorption; on the other hand, it is to make the texture and taste of food easier to accept, speed up the digestion and absorption of food, and improve the utilization efficiency of nutrients; at the same time, cooking can also change the flavor of food, remove its odor, increase its freshness and fragrance, and promote appetite.

No matter how good the food is, if it is cooked to be inedible, the nutrients in it cannot be fully utilized. At the same time, cooking will inevitably cause the loss of some sensitive nutrients. In addition, cooking will also introduce ingredients such as oil, salt, sugar, and flavor enhancers, making the food contain more calories and more sodium.

The goal of healthy cooking is to achieve food safety goals and bring good taste and flavor while minimizing the loss of nutrients, ensuring that the digestion and absorption rate of food meets human needs, and avoiding the introduction of too much oil, salt, sugar and other ingredients, so as not to hinder the prevention of obesity and various chronic diseases.

1. How to retain more nutrients in food

Not all nutrients in food are afraid of heat. Protein, fat and carbohydrates are relatively heat-resistant, and dietary fiber and minerals will not be lost by heat. Only some vitamins and some ingredients are sensitive to cooking. Therefore, it cannot be said that nutrients no longer exist after cooking.

The factors that cause nutrient loss mainly include heating destruction, oxidation destruction, enzymatic destruction, water-soluble loss and oil-soluble loss.

Fat-soluble vitamins such as vitamin A, vitamin D, vitamin E and vitamin K, as well as fat-soluble bioactive ingredients such as lycopene and carotene, are mainly afraid of oxidation loss and oil dissolution loss. They are lost more after deep frying, large-scale frying, and stir-frying followed by stewing. Not only do they oxidize during heating, but they also dissolve in the cooking oil, remain in the pot and plate, and are finally flushed into the sewer. However, cooking or adding some oil to make soup (such as tomato and egg soup) will increase the bioavailability of these fat-soluble vitamins, that is, increase absorption. The main principle is that these fat-soluble vitamins will be freed from plant cells when cooking with cooking oil. But they are not afraid of steaming and cooking.

Various B vitamins and vitamin C, as well as water-soluble antioxidant ingredients such as polyphenols, are prone to water loss. When boiling and blanching vegetables in large quantities, these healthy ingredients will dissolve in large quantities in the water. Unless you drink the water used to cook the vegetables, the longer the cooking and blanching time, the greater the loss of nutrients and plant compounds.

Cereal food, also known as staple food, has the largest loss of vitamin B1 when cooked. Over-washing, discarding the water used to soak grains, frying in oil, and adding alkali to porridge are the main reasons for increased loss of vitamin B1. On the contrary, adding whole grains such as brown rice, millet, and beans to rice, and frequently eating steamed yams, sweet potatoes, potatoes, and other potatoes to replace part of the white rice is a good way to increase the number of B vitamins.

For vegetable foods, the nutrients that are most lost during cooking are vitamin C and folic acid, which are afraid of heat and oxidation, and are easily lost when dissolved in water. Vitamin B2 and some polyphenols are also easily lost when dissolved in water. In addition to eating them raw, steaming vegetables and stir-frying them quickly will result in less loss of vitamins. In addition, using half a bowl of water with a small amount of oil to replace a large amount of cooking oil, adding the vegetables to the pan and stirring them evenly, and then simmering them for one or two minutes, that is, the "water and oil stewing" cooking method, is also conducive to the preservation of multiple vitamins, and the preservation rate of vitamin C can reach 80%~90%.

The nutrient that is lost the most when cooking fish and meat is vitamin B1. But more importantly, it is necessary to avoid the oxidation of unsaturated fatty acids and proteins during cooking, and to avoid overheating to produce carcinogens. Therefore, steaming and stewing are good cooking methods, and stir-frying meat without a lot of oil smoke and baking wrapped in tin foil and controlled temperature are also acceptable. Deep-frying and charcoal grilling are the most unhealthy cooking methods. They not only cause nutrient loss, but also produce a large number of oxidation products and carcinogens. Many studies have shown that overheating meat can promote diabetes and cardiovascular and cerebrovascular diseases, and is not conducive to the prevention of colon cancer.

2. How to make staple food easier to digest

For staple foods, if the food is too hard, it will lead to slow digestion, which is not conducive to people with gastrointestinal diseases and indigestion. Therefore, for people with weak digestive ability, whole grains should be soaked in the refrigerator for 12 to 24 hours, paired with white rice, and then cooked in the "grain rice" or "grain porridge" mode of the electric pressure cooker. They can also be baked and ground into powder and then washed into paste with boiling water, or beaten into rice paste with a wall-breaking machine to fully obtain the nutrients in them.

3. How to control blood sugar after meals

The cooking method of staple food is related to the rate of increase in blood sugar response after a meal. If the food is too soft, it may increase the blood sugar response after a meal, which is not conducive to people who are losing weight and diabetic patients.

For those who need to control blood sugar, the proportion of whole grains can be slightly larger. After soaking in the refrigerator overnight, put it directly in the rice cooker for cooking. Do not add too much water to maintain a certain chewiness. It is best to eat less super-fine grain paste made with a wall-breaking machine, because it digests too quickly and is not conducive to controlling the rate of blood sugar rise.

4. How to avoid too much oil and salt

Adding too much oil during cooking will significantly increase the calorie value of staple foods and dishes. Therefore, people who need to control body fat and weight need to cook with less oil. It is best to control the amount of cooking oil consumed daily to within 25 grams (including the oil used in fried dough sticks, scallion pancakes, etc.).

Avoid eating various "colorful staple foods" with added oil, eat less snacks, avoid fried dishes, and increase the proportion of steamed, boiled, stewed and cold dishes, which can effectively reduce the amount of cooking oil intake. For example, eat one stir-fried dish, one stewed dish, one steamed dish or cold dish for each meal, and a bowl of whole grain rice or white rice, which can not only reduce fat intake, but also increase nutrient preservation rate.
Reducing sodium in cooking is very important for preventing cardiovascular and cerebrovascular diseases such as hypertension. When making cold dishes, do not add salt in advance, add salt before cooking, drink less salty soup, eat less pickles, use less salad dressing, use less "rice sauces", replace ordinary salt with low-sodium salt, and use less salt if you use chicken essence and MSG... These measures can effectively reduce sodium.

Learning these tips for healthy cooking can make your diet both healthy and delicious!

Author: Fan Zhihong | Vice Chairman of the Dietary and Culinary Nutrition Branch of the Chinese Nutrition Society Professor of China Agricultural University

Reviewer: Li Duo | Chairman of the Dietary and Culinary Nutrition Branch of the Chinese Nutrition Society, Vice President/Chief Professor of the Institute of Nutrition and Health, Qingdao University