* Change the food you eat to include fresh raw fruit and vegetables because they have a vitally important role in boosting the immune system.
* Always choose whole grain versions of rice, pasta and flour.
* Avoid refined and preserved processed foods as these have had most of their nutritional potential removed.
* Avoid refined sugar as it's been shown to significantly suppress the immune system.
* Taking some regular aerobic exercise is an essential ingredient in any plan to boost the immune system.
* Stop smoking and avoid passive smoke which is smoke from other people.
* Emotional health can play a key role in weakening the immune system so seek help if this might be part of the problem.