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Another study suggests that diet may influence the risk of multiple sclerosis. Image credit: Painted Wood/Stocksy.
  • Experts have yet to understand why multiple sclerosis (MS) develops, but current research suggests that genetic and environmental factors may influence its onset.
  • Italian researchers used datasets from the UK Biobank, one of the largest available databases, to conduct a study exploring how diet and other lifestyle factors may affect MS development.
  • The study’s authors say that ‘evidence encourages the study of diet as a modifiable risk factor for the neurological disease.’

Multiple sclerosis (MS) is a chronic, autoimmune inflammatory illness of the central nervous system (CNS) with rising prevalence. It is a progressive condition, which means that it will likely worsen over time.

MS is the most common debilitating neurodegenerative disease among young adults. Symptoms often appear between the ages of 20 and 40, but they can present at any age.

Some experts believe that genetic and environmental factors, such as smoking, obesity, and exposure to ultraviolet B (UVB) light may increase the likelihood of MS onset.

Scientists at the Università del Piemonte Orientale in Novaro, Italy scoured the vast UK Biobank for clues linking diet and lifestyle factors with the condition.

Their findings appear in the journal Nutrients.

Multiple sclerosis (MS) is a neurodegenerative disease which causes the immune system to attack myelin, a substance that coats nerve fibers.

The illness is marked by lesions in the central nervous system, or CNS, which can cause physical or cognitive impairment. Such issues can lead to sensory disturbances, visual impairments, lack of coordination, and paralysis.

Disease subtypes include clinically isolated syndrome, primary progressive MS, relapsing-remitting MS, and secondary progressive MS. Female MS patients outnumber male counterparts two to one.

Researchers have been studying this condition for a long time, continuously looking for interventions that could help people lower their odds of developing MS. One lifestyle factors that researchers have been looking at in relation to MS risk has been diet.

Prior research conducted by some of the present study’s authors had suggested that gut health may influence the CNS.

In their current paper, they state that “the existence of a gut–brain axis supports the importance of considering diet as an important modulator of gut homeostasis and, consequently, of CNS health.”

The scientists further note that a pro-inflammatory gut environment may elevate neuroinflammation and MS risk.

The study’s authors used data from the UK Biobank, one of the largest biomedical databases currently available. They did so to address “a paucity of large-scale prospective studies regarding […] dietary exposures that are focused on the general population,” as they explain in the paper.

At its start, this study cohort included 502,507 residents of the United Kingdom aged 40–69 years. The presence of MS was determined by hospital admissions with MS diagnoses or self-reported diagnoses of MS.

At the study’s baseline, in 2006, all participants answered a food frequency questionnaire (FFQ), through which they reported their usual consumption of 29 different food groups and alcohol over the previous year.

Participants answered questions about their daily intake of cooked vegetables, raw vegetables, fresh and dried fruits. They also reported their weekly intake of fatty fish, processed meats, beef, lamb, poultry, cheese, salt added to food, and other foods.

A subsample of participants also completed online interviews that recalled the previous 24 hours of dietary choices. The results were based on investigating 200 different foods and beverages.

“Since it [the online interview tool] automatically calculated the energy and nutritional contents of the reported food items, we were able to evaluate the impact of single micro- or macronutrient intake on the disease risk,” the study authors write.

They also used the dietary data to calculate the participants’ Mediterranean Diet scores.

After exclusions due to participant retractions or missing information, the final cohort included 499,563 people.

The present study also considered the role that additional lifestyle factors may play in MS onset. The authors combed through data on body mass index (BMI), smoking, and physical activity.

An average of 12 years of follow-up data identified 478 MS cases developing among the study cohort. This indicates a prevalence rate of 7.78 MS cases for every 100,000 person-years.

People who face an increased MS risk included those who smoked, had a vitamin D deficiency, or who had a history of Epstein-Barr virus infection. Genetic determinants for obesity and for obesity during childhood were also linked to an elevated MS risk.

The study’s authors observed an inverse correlation between adherence to a Mediterranean diet type and MS onset, suggesting that a healthy, plant- and whole-food-rich diet that included moderate fatty fish consumption may help protect against this chronic condition.

To the study authors’ knowledge, their work is the first to observe a “slightly protective” effect of moderate fish intake.

Eating fatty fish once weekly appeared to be more protective than more frequent consumption.

Medical News Today discussed the study findings with Kelsey Costa, MS, RDN, and Sarah Hormachea, MS, RD, BC-ADM, CDCES, both of them registered dietitians not involved in this research.

Costa commented that “[a] key strength of this study is its use of the UK Biobank database, a comprehensive resource that offers a vast amount of data from a large cohort.”

However, both dietitians expressed concerns about the study’s limitations.

Hormachea noted that “[t]he UK Biobank cohort consists of volunteers [including mostly white and high-income individuals], which may not be representative of the general population.“

She cautioned that:

“Participants who choose to join such studies often have different health behaviors and socio-economic statuses compared to those who do not participate.”

Costa also said that ethnic minority groups are underrepresented in the Biobank database, which may limit the generalizability of the study’s findings to those populations.

The potential for recall bias also stood out to Hormachea, as study participants might not have accurately remembered or reported their food intake.

In turn, Costa felt that the small number of MS cases “may reduce the statistical power of the analysis.“

“In other words,“ she said “it can be hard to accurately observe small effects unless you have very large sample sizes.”

Potential confounding factors, such as the nutrient density of the participants’ diets, might have influenced the findings, Costa remarked. She pointed out that “the study did not assess cooking methods, food processing, and the nutrient composition of specific food items or types of alcoholic beverages.”

Lastly, she cautioned that due to the study’s observational nature, causality cannot be established. Hormachea furthermore suggested that reverse causality could be an issue, as people diagnosed with MS might have changed their eating habits subsequently.

MNT asked Costa if she has seen positive results from dietary adjustments among people with MS.

She noted that different types of diets are likely to have different effects ion people living with this condition:

“Broadly speaking, hypercaloric diets can be problematic for multiple sclerosis, and conversely, low-calorie diets and diets high in fruits, vegetables, and other plant-based foods may improve signs and symptoms of multiple sclerosis.”

Nevertheless, she hypothesized that a Mediterranean diet may be able to help lower the risk of MS, especially compared to a typical Western diet.

The study’s authors believe that their “validated approach” of using 24-hour recall data has provided novel insights “insights into the role of complex dietary patterns, instead of single foods, in disease onset.”

Their data forms a basis for more specific studies which may help formulate evidence-based protocol for MS prevention and management.

Considering the various disease subtypes and phenotypes, they say, “may lead to new insights useful for personalizing dietary approaches in the context of precision nutrition.”