Vitamins supplements are commonly taken by many people to treat a variety of health problems. Over time, however, vitamins can degrade, causing them to become chemically altered. Although维生素C降解，这是无毒的。维生素C降解的速度取决于许多因素，即使过期的维生素C也是“安全的”，尽管它可能不有效。
维生素C如何降解？
维生素C也称为抗坏血酸或抗坏血酸。它可以经历一种称为氧化的化学反应，从而改变其化学形式。维生素C的氧化产物被称为脱氢抗坏血酸或DHAA。Although this compound can be converted back into vitamin C, that chemical reaction does not occur naturally.
阅读更多：维生素C的毒性水平
产品质量影响货架寿命
Although DHAA isn't toxic, it does not function effectively as vitamin C, meaning that over time, vitamin C supplements become less potent. However, different vitamin C supplements turn into DHAA at different rates. One factor that controls this is the initial quality of the supplement. Supplements that are packaged with very little moisture and are mostly free of any oxidized compounds will break down more slowly than poor quality supplements. However, there are no large-scale studies that have tested the degradation of different kinds of vitamin C, so it is not known which brands are the "best" in terms of expiration date.
阅读更多：维生素C片的成分
存储条件很重要
影响维生素C补充剂分解的速度的另一件事是如何储存。一旦容器打开，补充剂将开始更快地降解，因此未开封的维生素C补充剂的保质期比开放的更长。将维生素保存在浴室或厨房中，湿度可以上升，can increase the rate at which they degrade。维生素应储存在房屋的凉爽干燥部分，例如卧室。
服用维生素C的考虑因素
并非所有的维生素C补充剂都已经打印了有效期，您仍然可以服用旧的维生素C片。但是，如果它们改变了颜色或开始溶解，它们将不会那么有效。但是，请勿服用更高剂量的补充剂来抵消这种失去效力的损失，因为您可能会意外地服用too much vitamin C。这可能导致腹泻和其他健康问题。
阅读更多：维生素C的最大剂量
将维生素C添加到饮食中
从均衡饮食中获取维生素C始终是最好的选择。这推荐维生素C的摄入量19岁以上的男性为75毫克；对于女性，DV为60毫克。您会发现各种水果和蔬菜中的维生素C，最高的浓度是葡萄柚，甜辣椒，猕猴桃，西兰花，辣椒和蔬菜，例如羽衣甘蓝，香菜和芥末菠菜。增加维生素C摄入量的一些方法是：
- 有一碗水果方便的水果，以便中间零食。芒果，猕猴桃和橙子都是维生素C的好来源 - 一杯芒果提供每日价值的100％。
- 吃原始的水果和蔬菜。由于维生素C是水溶性的，因此在加工和烹饪过程中很容易降解。发表的研究论文翡翠见解found that broccoli, spinach and lettuce lost their vitamin C content by 14, 11 and 8.6 percent respectively from steaming, and reduced vitamin C by 54.6, 50.5, and 40.4 percent, respectively from boiling.
- 吃发酵蔬菜。Sauerkraut几乎包含每杯35毫克维生素C。
- 不要传递冷冻蔬菜。据报道纽约时报。