As we all know, many nutrients are afraid of heat, high temperature cooking will accelerate their loss. What is less known is that there are some nutrients that are afraid of light, so you should pay attention to "sun protection" when storing.

Vitamin K.

Also known as coagulation vitamins, it can promote the normal coagulation of blood. Without it, the blood clotting function may be weakened, and the bleeding may not stop in severe cases, and even death. Vitamin K can also promote bone metabolism and effectively reduce the risk of fractures. In addition, studies have found that adequate intake of vitamin K is beneficial to cardiovascular health and can reduce the incidence of coronary heart disease. The main food sources of vitamin K are vegetable oils (such as rapeseed oil, soybean oil and safflower seed oil, etc.), green leafy vegetables, soy products, offal, egg yolks and dairy products. Vitamin K is a fat-soluble nutrient. It is not particularly afraid of heat or water loss, but it has a particularly big weakness-afraid of light. Studies have shown that when rapeseed oil rich in vitamin K is packed in a transparent bottle, more than 90% of the vitamin K content is lost in less than 10 days; and when it is packed in a dark bottle, vitamin K is lost about half after 36 days. Therefore, it is recommended to buy vegetable oil in dark bottles first, and do not put it in a light place such as a stove after returning home. Other foods rich in vitamin K should also be kept away from light.

Vitamin B2.

Also known as riboflavin, it is an essential substance in the metabolism of protein, fat and carbohydrates. Vitamin B2 deficiency can cause inflammation and dysfunction of the mouth, lips, skin, and genitals, such as seborrheic dermatitis, oral ulcers, angular cheilitis, and dizziness. Its main food sources are dairy products, egg yolks, dark green leafy vegetables and so on. Vitamin B2 is resistant to alkali and light. When milk stored in a transparent glass bottle is exposed to sunlight for 30 minutes, 28% of vitamin B2 will be destroyed, and 50% will be destroyed after 90 minutes of irradiation. Therefore, the popular transparent milk bag in recent years is not conducive to the preservation of nutrients such as vitamin B2. In addition, porphyrins and other substances in milk will produce active oxygen under the excitation of light, and then react with proteins, vitamins and fats to produce ingredients with poor flavor and affect the taste of milk. It is recommended that you prefer milk in opaque plastic bags or cartons.

Vitamin C.

Also known as ascorbic acid, it is one of the most demanding nutrients for the human body. It has many health benefits, such as antioxidant, increase human immunity, and improve the utilization of iron, calcium and folic acid. The main source of vitamin C is fresh fruits and vegetables, such as kiwi, fresh dates, bitter gourd, peppers, spinach, grapefruit, strawberries and oranges. Vitamin C is more delicate. It is afraid of heat, light, oxygen, and alkali, and is easily lost with water. Generally speaking, the fresher the fruits and vegetables, the more vitamin C content, the longer it is stored, the less the content, especially in a light environment, will accelerate its loss. Avoid sunlight as much as possible when storing fruits and vegetables, and keep them in the refrigerator for better results. (Ma Yueqing, a registered dietitian in China)