9. Tea
Regularly drinking tea throughout the day can help strengthen your immune system and your body’s ability to fight off germs and infections. Both green and black teas contain a beneficial amino acid called L-theanine, which can increase the infection fighting capacity of gamma delta T cells. L-theanine also promotes a sense of relaxation, calmness and well-being by influencing the release and concentration of neurotransmitters (like dopamine, serotonin and GABA) in the brain.