How can we improve our immune system? what is the diet we should follow? which. food increase immune s ytem

No sure way.: Staying in good physical shape with regular exercises (not extreme exercises) and a healthy diet may be helpful. Make sure your plasma vitamin d3 level is optimal since vitamin d3 has been shown to be an important immune regulator. I would like to see the 25 oh vitamin d3 level to be around 50 to 60 ng even though the recommended level is around 30 ng. More fruits & veggies.

Balanced immunity: Nutritious diet: limiting processed sugar, fats, along with probiotics; maintain ideal body weight with restful sleep, drinking plenty of water, & regular exercise (brisk walking, 3 times/week, e.g.) helps maintain a balanced immune system= no hypersensitivity/ allergies, the ability to fight off infections. Good diet = needed minerals. Vit. D supplement if you can't get daily, safe sun exposure.