Multiple sclerosis: sunlight, diet, immunology and aetiology

Area of Science:

• Immunology
• Environmental Health
• Neuroscience

Background:

• Multiple sclerosis (MS) exhibits a higher prevalence in temperate latitudes.
• Migration studies suggest an environmental etiological factor influencing MS development before puberty.
• The exact environmental factor contributing to MS remains unidentified.

Purpose of the Study:

• To propose a novel explanation for the latitude gradient observed in multiple sclerosis (MS) epidemiology.
• To investigate the potential role of sunlight exposure and melatonin suppression in MS pathogenesis.
• To explore the influence of dietary fatty acids and sunlight on MS and its precursor conditions.

Main Methods:

• Review and synthesis of existing epidemiological data on multiple sclerosis.
• Hypothesizing the mechanism of sunlight's immunosuppressive effects via melatonin pathway.
• Examining the link between dietary fatty acids, sunlight, and retinal metabolism in relation to MS.

Main Results:

• Sunlight exposure may suppress melatonin secretion from the pineal gland, leading to immunosuppression relevant to MS.
• Dietary fatty acids and their anti-inflammatory eicosanoids are implicated in MS pathogenesis.
• Geographical exceptions to the MS latitude gradient, like in Japan, may be linked to dietary factors rather than solely genetics.

Conclusions:

• Sunlight's immunosuppressive effect on melatonin secretion offers a plausible explanation for the MS latitude gradient.
• Dietary influences, particularly fatty acid metabolism influenced by sunlight, may account for variations in MS prevalence.
• A re-evaluation of MS epidemiology is warranted, considering the immunological impact of retinal light exposure.