Vitamin C is extremely vulnerable to heat, light and oxygen. To minimize the loss of vitamin C in food, please note:
1. The longer the fruits and vegetables are stored, the more vitamins are lost. Therefore, try to eat the freshest fruits and vegetables as much as possible. To preserve, store them in the refrigerator as much as possible.
2, when cooking foods rich in vitamin C, the time is as short as possible, and tightly cover the lid to reduce the destruction of high temperature and oxygen. The soup is rich in vitamin C and should be consumed as much as possible.
3, vitamin C toxicity is very small, but taking too much can still produce some adverse reactions.
Reports have pointed out that adult vitamin C intake of more than 2 grams, can cause permeability diarrhea, this time the vitamin accelerate intestinal peristalsis, resulting in abdominal pain, diarrhea and other symptoms.
When the intake is less than 1 gram, high uric acid is generally not caused, and when it exceeds 1 gram, the uric acid clearance is significantly increased. The study found that excessive use of vitamin C, the vast majority of decomposition by the liver metabolism, the final product is oxalic acid, oxalic acid excreted from the bladder and urethra to oxalate, 4 grams of vitamin C daily, in 24 hours, urinary oxalic acid The salt content will increase from 58mg to 620m (more than 10 times). If you continue to take long-term overdosing, oxalate increase, it is easy to form urinary stones.
4, research shows that: long-term excessive use of vitamin C, can reduce the absorption of vitamin B12 in the intestine, leading to worsening of the condition of megaloblastic anemia. If the patient is congenitally deficient in glucose-6-phosphate dehydrogenase, daily intake of more than 5g of vitamins will cause red blood cells to rupture and hemolysis, resulting in anemia.
5, infertility, excessive vitamin C can also cause changes in disulfide bonds of glycoprotein in cervical mucus, prevent sperm penetration, resulting in infertility. Women of childbearing age who have long-term excessive use of vitamin C (a daily dose of more than 2g) will reduce fertility and immunity.
6, taking excessive vitamin C during pregnancy, may affect the development of the embryo, resulting in the fetus after birth on the vitamin C-dependent role, if you do not continue to use vitamin C to the newborn baby, there may be scurvy.
7, withdrawal response: long-term excessive use of vitamin C, resulting in the body "overload", regulatory mechanisms change, vitamin C decomposition and excretion accelerated, if suddenly stopped, leading to vitamin C deficiency,
8, when the daily intake of vitamin C in 2--8 grams, there may be nausea, abdominal cramps, sputum absorption, red blood cell destruction and urinary stones and other adverse reactions. Long-term overdose in children is prone to bone disease.
9, according to the Chinese Nutrition Society recommended indicators, normal daily intake of vitamin C dose of 100m g is sufficient. The maximum human tolerable dose is 1000 mg, which exceeds the maximum tolerated dose of 1000 mg. Excessive VC breaks down into oxalic acid. Oxalic acid is one of the causes of high urinary calculi, and the incidence of kidney stones, ureteral stones, and bladder stones is several times that of normal people. The human body intake of more than 2000mg, will also cause diarrhea permeability, easily lead to human dehydration.
10. It is forbidden to use with alkaline drugs at the same time. Vitamin C can enhance immunity and prevent colds. When the weather turns cold, many people will consciously eat vitamin C. However, patients with gastric ulcer should pay attention, vitamin C and ulcer drugs should not be the same service, but should be staggered for two hours to take. This is because gastric ulcer patients have more stomach acid, Weishuping, Wei Xi and other drugs for the treatment of ulcers are mostly to neutralize stomach acid, and taste sour and sweet, vitamin C is acidic, if the two are taken at the same time, naturally occur acid Neutralization of the reaction caused both drugs to lose their efficacy.
11, can not be used together with sulfa drugs, because vitamin C can promote the formation of sulfa drugs in the kidney stones.
12, oral contraceptives will accelerate vitamin C metabolism, so often use contraceptives due to increase vitamin C supplement dose.
Vitamin C is extremely vulnerable to heat, light and oxygen. To minimize the loss of vitamin C in food, please note: 
