Photo: Randy Mayor
Not a coffee drinker? Try green tea. It’s rich in L-theanine, an amino acid that makes you feel alert and invigorated without the jitters that some people get from coffee. L-theanine may also protect against energy-robbing illnesses like the common cold or the flu according to a 2007 Journal of the American College of Nutrition study. When volunteers took a green tea supplement twice daily for three months they were 23 percent less likely to be sidelined by either of these illnesses for more than two days.