Effect 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 typically 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 impairment, and visual impairment.

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

In England, there are eight to 11 new cases of MS per 100,000 people each year. Compared with 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 can influence CNS health via 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 the prevalence of MS.

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

This study used data from the UK Biobank cohort study to examine the association between diet and the occurrence of MS. The UK Biobank is one of the largest available healthcare resources used to identify genetic, environmental and behavioural 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, the Scottish Disease Records and the Wales Patient Database were used to assess MS diagnoses and outcomes.

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

The median long-term follow-up 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 was identified as a modifiable risk factor increasing the risk of MS, with current smokers, but not former smokers, being at greater risk of developing MS. Notably, previous studies have predicted that smoking cessation could reduce the incidence of MS by at least 13%.

People who smoke, have 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, as well as genetic determinants of obesity, increased the risk of MS. The combined effect of chronic low-grade inflammation, elevated leptin levels, decreased vitamin D bioavailability, and obesity may contribute to the development of MS.

Moderate fish consumption, particularly weekly consumption of oily fish, was associated with a small protective effect against MS incidence compared with more frequent consumption. Oily fish consumption during adolescence and later in life was inversely associated with MS risk, with these benefits particularly applicable to people living in areas with low sun exposure, which contributes to poor vitamin D synthesis.

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

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

This study used the UK Biobank database to assess the role of diet in MS. Based on FFQ data, moderate consumption of oily fish and alcohol was associated with a reduced risk of MS. Further studies are needed to identify the types of alcohol that may influence MS.