The vitamin abundant in citrus fruits that helps boost the immune system is vitamin C. Citrus fruits such as oranges, lemons, limes, grapefruits, and tangerines are excellent sources of vitamin C, which plays a crucial role in supporting immune function. Vitamin C supports various immune cells, including white blood cells, enhancing their ability to fight infections. It also acts as a potent antioxidant, protecting immune cells from oxidative damage during immune responses. Additionally, vitamin C helps maintain the integrity of skin and mucosal barriers, which are important first lines of defense against pathogens

. Vitamin C is essential because the human body cannot produce or store it, so it must be obtained regularly through diet. A deficiency in vitamin C can lead to weakened immunity and increased susceptibility to infections. Regular consumption of citrus fruits can help reduce the risk of infections and promote healthy immune cell function. For example, a medium-sized orange provides about 70-83 mg of vitamin C, which meets or exceeds the daily recommended intake for most adults

. In summary, vitamin C is the key immune-boosting vitamin abundant in citrus fruits, supporting immune defense mechanisms and overall health.