Is excessive intake of vitamin C harmful to health?

The extensive beneficial effects of vitamin C on human body are gradually known to everyone, especially its anti-cancer effect, which is easily misunderstood. Since vitamin C has so many benefits, you should eat more every day, and the more the better. From the point of view of nutrition, this understanding is incorrect. Reasonable nutrition requires that the intake of various nutrients should meet the physiological needs of the human body and there should be a certain balance between nutrients. Excessive intake of a certain nutrient alone will affect the functions of other nutrients, and even have harmful effects, including vitamin C. A large dose of vitamin C is harmless to the human body, and it will cause many side effects. Taking a large amount of vitamin C (more than 1 ~ 2g per day) for a long time, because vitamin C is ultimately metabolized into oxalic acid in the body, oxalate in urine can be greatly increased, stones can be formed, and uric acid content in blood and urine can be increased, leading to a sudden attack of gout. Taking a large dose of vitamin C will also reduce the contents of trace elements copper and zinc in the body, and will also cause the deficiency of vitamin b 12, leading to anemia. Vitamin C can also accelerate the dissolution of calcium into the blood, leading to hypercalcemia and hyponatremia. Some people will also have rash, edema, blood pressure drop, nausea, diarrhea and so on.

Normal children and teenagers can get the vitamin C they need as long as they eat a certain amount of fresh vegetables and fruits every day, without adding vitamin C tablets. When there is a special need to increase the supply of vitamin C, it should be done under the guidance of a doctor. It is necessary to avoid blindly taking large doses of vitamin C to avoid unnecessary harmful effects.

Why is vitamin C the most delicate vitamin?

Vitamin C, also known as ascorbic acid, is a water-soluble vitamin. It is the most fragile vitamin for the following reasons:

(1) As far as its physical and chemical properties are concerned, it is sensitive to oxygen, so it is easy to be oxidized, especially in the presence of copper plasma. Alkali can do a lot of harm.

(2) Vitamin C mainly comes from fresh vegetables and fruits, but in higher plants, as far as we know, at least five enzyme systems can catalyze the oxidative damage of vitamin C, such as ascorbic acid oxidase and peroxidase. Therefore, during the storage of vegetables, vitamin C will be destroyed and lost.

(3) The cleaning and cooking of vegetables are unscientific, and some of them are destroyed in the cooking process. For example, before and after cooking, the vitamin C in mung bean sprouts decreased from 10 mg/ 100 g to 5.6 mg/ 100 g, and that in Chinese cabbage decreased from 16.5 mg/ 100 g.

Knowing the above situation, we can take necessary measures to reduce the loss of vitamin C in real life. If vegetables and fruits are fresh, they should be washed first and then cut to avoid the loss of vitamin C with water. Stir-fry quickly and avoid using copper pots; It is best to eat vegetables once after burning, and try not to eat leftovers, so as not to destroy a lot of vitamin C. As long as you can eat enough fresh vegetables regularly and pay attention to the above points, generally speaking, there will be no vitamin C deficiency.