While vitamin C plays a crucial role in immune support, it is not a one-stop-shop for preventing or alleviating cold symptoms. That depends on your health, immune system and vitamin C dosage. Some studies suggest that vitamin C supplements may reduce the duration and severity of cold symptoms. This is especially the case for stressed out people or those who don’t have a lot of vitamin C in their diet. Other research indicates vitamin C may not prevent or treat the common cold.18 Having a nutrient-dense diet that includes vitamin C can be a great foundation for immune support. That said, it’s not a guarantee that you won’t get sick.