Every cold and flu season, you’ll stand in the supplement aisle staring at a $40 bottle of something that promises to support your immune health, and you’ll probably buy it. The wellness industry will sell you mushroom tinctures and zinc lozenges. Science, however, would like to suggest something more fun. Research has linked orgasms to measurable immune benefits, and the case is more solid than it sounds. A 2004 study found that arousal and org…