Orange juice is often promoted as a beverage of choice if you're trying to fight off a cold or flu virus, and there is significant scientific support to drink citrus juice for your immune system.
According to a study published in Frontiers in Immunology, the vitamin C and folate in citrus juices sustain the integrity of the immune barriers and protect many types of immune cells, including natural killer cells and T-cells. What's more, the bioactive compounds in citrus have anti-inflammatory effects to support immunity.
Both orange and grapefruit juice are nutrient-rich and provide more than 100% of the total vitamin C you need a day in one serving. These 100% fruit juices also provide vitamin A and folate. When buying orange juice, you can even find options that are fortified with vitamin D, a nutrient long known to be essential for healthy immunity.