The influence of diet on the occurrence of multiple sclerosis

In a recent study published in the journal Nutrients, scientists determined whether diet influences the occurrence of multiple sclerosis (MS).

Multiple sclerosis is a chronic autoimmune inflammatory disease that usually affects people between the ages of 20 and 40. MS is characterized by damage to the central nervous system (CNS), which can cause cognitive or physical impairments such as loss of coordination, paralysis, sensory disturbances, and visual disturbances.

MS is classified into several subtypes based on different phenotypes, including clinically isolated syndrome, relapsing-remitting, primary progressive and secondary progressive MS.

In England, between eight and 11 new cases of MS are registered annually for every 100,000 people. Compared to men, women are twice as likely to be diagnosed with MS.

MS is a multifactorial disease that can develop due to genetic and environmental factors, such as exposure to ultraviolet B (UVB) radiation, Epstein-Barr virus (EBV) infection, obesity and smoking.

Diet is an important moderator of gut homeostasis, which may influence CNS health through the gut-brain axis. Several studies have shown that frequent consumption of dietary supplements can lead to "leaky gut" or gut dysbiosis, which increases the risk of developing Alzheimer's disease (AD).

A pro-inflammatory gut environment has also been reported to increase the risk of developing MS. In this context, a recent UK cohort study found that a healthy lifestyle, including regular physical activity, healthy body mass index (BMI) values and a healthy diet, was inversely associated with MS prevalence.

Accordingly, another study observed the positive effects of eating vegetables, fish, seafood, nuts, dairy, and whole grains on improving MS symptoms. Although several studies have reported the beneficial effects of a healthy diet on MS symptoms, the relationship between individual foods and MS risk remains unclear.

The present study used data from the UK Biobank cohort study to examine the association between diet and incident MS. The UK Biobank is one of the largest health resources available, used to identify genetic, environmental and behavioral factors for a variety of diseases.

At baseline, study participants completed a food frequency questionnaire (FFQ), which provided relevant information about their diet. National Health Service (NHS) records for England, incidence records for Scotland and a patient database for Wales were used to assess MS diagnoses and outcomes.

The current study used a prospective and multivariate approach to elucidate the role of diet in MS. Data from 502,507 people aged 40 to 69 years were available from UK Biobank, of whom 70,467 were selected for the study based on inclusion criteria.

The average long-term follow-up period was twelve years, during which 478 cases of MS were identified in the study cohort. This reflected an incidence rate of 7.78 MS cases per 100,000 person-years.

Smoking has been identified as a modifiable risk factor that increases the risk of MS, with current smokers, rather than former smokers, being at greater risk of developing MS. Notably, previous studies predicted that quitting smoking could reduce the incidence of MS by at least 13%.

People who smoke, have a vitamin D deficiency, a history of EBV infection, or human leukocyte antigen (HLA) DR15*1501 are at increased risk of developing MS. In addition to smoking, both childhood and adolescent obesity and genetic determinants of obesity increased the risk of MS. The combined effect of low-grade chronic inflammation, elevated leptin levels, decreased vitamin D bioavailability, and obesity may contribute to the development of MS.

Moderate fish consumption, especially eating oily fish once a week, was associated with a small protective effect against MS incidence compared with more frequent consumption. Consumption of fatty fish during adolescence or later life is inversely associated with the risk of MS, with these benefits particularly applicable to people living in areas with low levels of sun exposure, which contributes to poor vitamin D synthesis.

One previous study found that fatty fish, a good source of omega-3 polyunsaturated fatty acids (PUFAs), promotes the immunomodulatory functions of vitamin D. PUFAs have a preventive effect against AD and inflammatory diseases. Moreover, supplementing with four grams of fish oil daily also reduces relapse rates and inflammation in MS patients.

According to previous studies, the Mediterranean diet has a positive effect on preventing non-communicable diseases. An inverse association between weekly alcohol consumption and MS risk was also found.

The present study used the UK Biobank database to assess the role of diet in MS. Based on FFQ data, moderate consumption of fatty fish and alcohol reduced the risk of developing MS. More research is needed in the future to identify the types of alcohol that affect MS.