We can ward off a lot with a functioning immune system, but we become vulnerable when it weakens. However, a weak immune system can be restrengthened:
Sleep enough
Make sure you get enough sleep, as the body is detoxified during sleep.
Enjoy fruits and vegetables
Eat raw or steamed fruits and vegetables. Raw fruits and vegetables are rich in cell-protecting antioxidants. Eat as many different-coloured fruits and vegetables as possible. Berries, cabbage and broccoli are especially good, as are nuts, seaweed and spirulina. Spirulina is a nutrient-rich blue-green algae that is a natural, exceptionally digestible and wholesome food. To support this, you can additionally take vitamin B12.
Water, water, water
Remember to drink a lot of water because it flushes toxins out of the body.
Take in the fresh air
Stay outdoors for long periods and exercise in the fresh air.