In addition to diseases like diabetes, cancer and cardiovascular disease, we need to avoid getting taken out by infectious diseases, such as influenza, COVID-19 and pneumonia. And as people get older and their immune systems weaken, it becomes more of a challenge to avoid succumbing to those infectious diseases. So how do we strengthen our immune systems, as we get older? Well surprisingly, one way to prevent your immune system from weakening as you get older is to avoid calorie-restriction (CR). Calorie-restriction has long been touted as the #1 key to living longer and slowing the aging process, based upon studies done using lab animals. But the researchers don't tell you is that calorie-restriction has been found to weaken the immune systems of those lab animals, which are raised in sterile environments. So if calorie-restriction also weakens the immune systems of humans, theoretically it would increase a person's risk of dying from an infectious disease.