It is very important to practice good hygiene, hand-washing, and food safety practices. Here are some things which can help prevent low immunity and keep white blood cell counts high: - Avoid sugar and keep sweet stuff to a minimum. Sugar prevents white blood cells from being their strongest - Eliminate unhealthy trans fats. - Drink plenty of water to flush out toxins - Exercise is a proven immune system booster. Exercise is best in moderation, however, since too much exercise may wear the body down and create immune system problems. - Avoid stress and try to relax. Too much stress invariably leads to a lowered immune system. Carrots and other red, yellow, orange, and dark-green leafy vegetables contain beta carotene which helps protect the immune system .