The cause of the disease is unclear, and most researchers believe that the immune system plays an important role, and perhaps the disease stems from a genetic problem with the immune system. Perhaps a virus stimulates the body to produce an active immune response – a process in which the immune system develops damage to its own tissues, which it mistakenly perceives as foreign. It has also been envisioned that some kind of extreme mood swing or physical trauma that affects the immune system can trigger multiple sclerosis. It has also been suggested that dietary factors may be the causative factor. Some scholars’ explanations for the high incidence of MS in the north have documented a preference for baked meats, dairy products, and foods high in saturated fats. MS patients are less able than normal to absorb unsaturated fatty acids, which play an important role in the muscle’s processing of all foods, especially saturated fats. The result is an excess of saturated fats in their system. Many therapeutic diets have been devised to correct this imbalance and some dietary regimens have been successful, but none has yet been used as a treatment (see the section on nutrition and diet). Some scholars suspect that environmental factors are the cause of the disease. Among the factors cited are mineral veins, pesticides, diesel engine gas, chemicals in tap water, chemical solvents, household gas, gas from water heaters, and carbon monoxide pollution.