A healthy immune system can clearly differentiate between a foreign invader and your own body. Infections, exposure to toxins, hidden allergens or stress and sleeplessness can increase one's body to illness.
Studies suggest that a healthy lifestyle can help maintain balance in the immune system, while less healthy situations can cause it to overreact. For example, low levels of vitamin D were demonstrated to be a risk factor for multiple sclerosis. Obesity is associated with many autoimmune illnesses, including rheumatoid arthritis and psoriasis. The stress and anxiety have been demonstrated to cause all types of illnesses. On the other hand, rheumatoid arthritis can be reduced by anti-inflammatory dietary choices. The right nutrients, a healthy weight, low stress, and regular sleep can help prevent unnecessary ailment.
My focus here is mainly on foods. Whatever you put in your body is one of the most important determinants of your health. As a Registered Nurse, I can say this: about 75% of many illnesses can be contributed to what you eat. For example, diabetes, hypertension, high cholesterol, cancer, gouty arthritis which is also known as the king's disease, it's due to the food that one consumes. Sugar is known to cause inflammation in the body, it also causes blood sugar to go up leading to diabetes.
I prefer organic food because I believe it is safer for our body. The other non-organic foods may be cheaper but they have been spray with pesticides, manure for fertilizer, genetically alter fruits, antibiotics on animals and other chemicals. So what we put into our bodies can make us feel better or can make it worst. It is common knowledge that people should eat only 80% full only and then stop. When you eat until you are really full before you are satisfied before you stop then it could have some adverse reaction on your body in the long run. Fewer or less calories it is believed to have an effect on longevity and weight loss. Exercise will make you stronger and have more energy but to lose weight, one must decrease one's calorie intake.
Some foods are known to cause inflammation are: sugar, trans fats, omega-6 fatty acids, refined carbohydrates, process food and meat, alcohol, caffeine, fatty acids, and food dyes.