What is Multiple Sclerosis?
Multiple Sclerosis is an autoimmune-mediated disorder that affects the central nervous system (CNS). Chronic inflammation causes destruction to myelin sheaths, a protective layer surrounding nerve fibers within the brain and spinal cord. This results in the formation of CNS plaques, lesions that impair nerve impulses which lead to neuronal dysfunction. This disruption between nerve fibers within the CNS can lead to symptoms such as fatigue, pain, changes in sensation and strength, vision changes, and changes in mood and memory.
The exact cause of Multiple Sclerosis remains unclear, however the literature suggests that the cause of MS is multifactorial and includes genetic predisposition combined with environmental factors. These factors trigger a cascade of events in the immune system, causing one's own immune system to attack the brain and spinal cord leading to neuronal cell death accompanied by nerve demyelination and neuronal dysfunction.
The abnormal immune response in the body causes inflammation and damage to the CNS. Various cells are involved in this abnormal response and much of the research looks at the response of T and B cells. T cells become activated in MS and enter the CNS through the bloodstream. Once within the CNS, chemicals are released causing inflammation and damage to myelin, myelin producing cells, and nerve fibers. T regulatory cells (a type of T cell) do not function correctly in MS and thus do not turn off the inflammatory response and “Killer” T cells directly attack cells causing damage. The activation of T cells activates B cells which produce antibodies and additional proteins in MS which create damage to the CNS.
Environmental factors including exposure to viral and bacterial agents, smoking, vitamin deficiency, diet, and exposure to UV radiation have been documented and associated with the onset of MS.
- Infectious agents: Exposure to viral and bacterial agents such as Epstein Barr virus (EBV), human herpes virus type 6, and mycoplasma pneumonia are being further investigated to determine their involvement in the development of MS. It is thought that these foreign agents may have a nuclear antigen that is structurally the same with myelin sheet components. When immune cells are activated by these agents, myelin sheath lesions will form.
- Geographical location: MS is known to occur more frequently in people who live further from the equator.
- Smoking: Current evidence suggests that smoking, due to nitric oxide (NO) and carbon monoxide (CO) production, plays an important role in MS. NO is a toxic gas that can damage neurons and myelin producing cells in the CNS. Studies have shown that stopping smoking prior to or after the onset of MS is associated with slower progression of disability.
- Vitamin D deficiency: Vitamin deficiency (especially vitamins D and B12) are considered risk factors for MS. Vitamin D plays an important role in cell proliferation and has a role in gene expression and regulation of immunity.
- Low-term sunlight: Low-term sunlight exposure has been identified as a potential risk factor for MS. Studies have demonstrated a reverse association among exposure to ultraviolet radiation and the incidence of MS.
- Diet: Studies report a significant negative association between MS risk and high fish intake and a positive significant association between high animal fat-based caloric intake. In addition to obesity in adolescents, particularly in girls and MS risk. Other studies have shown that obesity in early adulthood may also contribute to an increased risk of developing MS. Obesity may also contribute to inflammation and more symptoms in those already diagnosed with MS. The Mediterranean diet is a suggested diet for individuals with MS.