Mediterranean diet changes gut bacteria, boosting memory and cognition

 

A new Tulane University study suggests the Mediterranean diet's brain-boosting benefits may work by changing the balance of bacteria in the gut.

In a study published in Gut Microbes Reports, researchers at Tulane University School of Medicine found that subjects following a Mediterranean diet developed distinctly different gut bacteria patterns compared to those eating a typical Western diet. These bacterial changes correlated with better memory and cognitive performance.

"We've known that what we eat affects brain function, but this study explores how that could be happening," said lead author Rebecca Solch-Ottaiano, PhD, neurology research instructor at Tulane’s Clinical Neuroscience Research Center. “Our findings suggest that dietary choices can influence cognitive performance by reshaping the gut microbiome."

The study found that rats fed a Mediterranean-style diet rich in olive oil, fish and fiber over 14 weeks showed increases in four beneficial types of gut bacteria and decreases in five others compared to rats eating a Western diet high in saturated fats. These bacterial changes were linked to improved performance on maze challenges designed to test memory and learning.

Specifically, higher levels of bacteria such as Candidatus Saccharimonas were associated with better cognitive performance, while increased levels of other bacteria, such as Bifidobacterium, correlated with poorer memory function.

The Mediterranean diet group also showed better cognitive flexibility — the ability to adapt to new information — and improved working memory compared to the Western diet group. They maintained lower levels of "bad" LDL cholesterol.

This study is the first to assess the effects of the Mediterranean on microbiota and cognitive function outcomes relative to the Western diet in a rodent model. The researchers used young rats approximately equivalent in age to 18-year-old humans to model the effects of diet during a critical developmental period. The diets were based on human consumption and used ingredients reflecting the complexity of human diets. The Mediterranean diet (MeDi) showed clear benefits for cognitive flexibility, memory, and gut health, suggesting potential parallels in young adults whose brains and bodies are still maturing.

“Our findings suggest that the Mediterranean diet or its biological effects could be harnessed to improve scholastic performance in adolescents, or work performance in young adults,” said corresponding author Dr. Demetrius M. Maraganore, Herbert J. Harvey, Jr. Chair of Neurosciences. “While these findings are based on animal models, they echo human studies linking the Mediterranean diet to improved memory and reduced dementia risk.”

The researchers emphasize that larger human studies are needed to confirm these effects and better understand the complex relationship between diet, gut bacteria, and brain function in young people.

For those interested in following a Mediterranean eating pattern, key components include:
- Olive oil as the primary fat source
- Abundant vegetables, fruits and whole grains
- Fish and lean proteins
- Limited red meat and saturated fats
- High fiber intake from various plant sources

Loneliness linked to higher risk of heart disease and stroke and susceptibility to infection

Interactions with friends and family may keep us healthy because they boost our immune system and reduce our risk of diseases such as heart disease, stroke and type 2 diabetes, new research suggests.

Researchers from the UK and China drew this conclusion after studying proteins from blood samples taken from over 42,000 adults recruited to the UK Biobank. Their findings are published today in the journal Nature Human Behaviour.

Social relationships play an important role in our wellbeing. Evidence increasingly demonstrates that both social isolation and loneliness are linked to poorer health and an early death. Despite this evidence, however, the underlying mechanisms through which social relationships impact health remain elusive.

One way to explore biological mechanisms is to look at proteins circulating in the blood. Proteins are molecules produced by our genes and are essential for helping our bodies function properly. They can also serve as useful drug targets, allowing researchers to develop new treatments to tackle diseases.

A team led by scientists at the University of Cambridge, UK, and Fudan University, China, examined the ‘proteomes’ – the suite of proteins – in blood samples donated by over 42,000 adults aged 40-69 years who are taking part in the UK Biobank. This allowed them to see which proteins were present in higher levels among people who were socially isolated or lonely, and how these proteins were connected to poorer health.

The team calculated social isolation and loneliness scores for individuals. Social isolation is an objective measure based on, for example, whether someone lives alone, how frequently they have contact with others socially, and whether they take part in social activities. Loneliness, on the other hand, is a subjective measure based on whether an individual feels lonely.

When they analysed the proteomes and adjusted for factors such as age, sex and socioeconomic background, the team found 175 proteins associated with social isolation and 26 proteins associated with loneliness (though there was substantial overlap, with approximately 85% of the proteins associated with loneliness being shared with social isolation). Many of these proteins are produced in response to inflammation, viral infection and as part of our immune responses, as well as having been linked to cardiovascular disease, type 2 diabetes, stroke, and early death.

The team then used a statistical technique known as Mendelian randomization to explore the causal relationship between social isolation and loneliness on the one hand, and proteins on the other. Using this approach, they identified five proteins whose abundance was caused by loneliness.

Dr Chun Shen from the Department of Clinical Neurosciences at the University of Cambridge and the Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, said: “We know that social isolation and loneliness are linked to poorer health, but we’ve never understood why. Our work has highlighted a number of proteins that appear to play a key role in this relationship, with levels of some proteins in particular increasing as a direct consequence of loneliness.

Professor Jianfeng Feng from the University of Warwick said: "There are more than 100,000 proteins and many of their variants in the human body. AI and high throughput proteomics can help us pinpoint some key proteins in prevention, diagnosis, treatment and prognosis in many human diseases and revolutionise the traditional view of human health.

"The proteins we’ve identified give us clues to the biology underpinning poor health among people who are socially isolated or lonely, highlighting why social relationships play such an important part in keeping us healthy.”

One of the proteins produced in higher levels as a result of loneliness was ADM. Previous studies have shown that this protein plays a role in responding to stress and in regulating stress hormones and social hormones such as oxytocin – the so-called ‘love hormone’ – which can reduce stress and improve mood.

The team found a strong association between ADM and the volume of the insula, a brain hub for interoception, our ability to sense what's happening inside our body – the greater the ADM levels, the smaller the volume of this region. Higher ADM levels were also linked to lower volume of the left caudate, a region involved in emotional, reward, and social processes. In addition, higher levels of ADM were linked to increased risk of early death.

Another of the proteins, ASGR1, is associated with higher cholesterol and an increased risk of cardiovascular disease, while other identified proteins play roles in the development of insulin resistance, atherosclerosis (‘furring’ of the arteries) and cancer progression, for example.

Professor Barbara Sahakian from the Department of Psychiatry at the University of Cambridge said: “These findings drive home the importance of social contact in keeping us well. More and more people of all ages are reporting feeling lonely. That’s why the World Health Organization has described social isolation and loneliness as a ‘global public health concern’. We need to find ways to tackle this growing problem and keep people connected to help them stay healthy.”

Physical activity reduces chronic disease risk

 

University of Iowa researchers are recommending all patients be surveyed about their physical activity levels, after a new study underscores the link between physical activity and chronic disease.

The study, led by Lucas Carr, associate professor in the Department of Health and Human Physiology, examined responses from more than 7,000 patients at University of Iowa Health Care Medical Center who noted their level of physical activity in a questionnaire. 

From patients’ answers to the questionnaire, the researchers found that those who reported the highest level of physical activity — meaning they exercised moderately to vigorously at least 150 minutes per week — were at statistically significant lower risk of having 19 chronic conditions, including cardiovascular disease, cancer, respiratory disease, and diabetes.

The findings further suggest patients who are least active — meaning they reported little to no exercise in a given week — are at increased risk to develop a chronic disease.

Based on those results, the Iowa researchers also recommend health care systems provide information on health and wellness services for physically inactive patients who are at most risk.

“In our health care environment, there's no easy pathway for a doctor to be reimbursed for helping patients become more physically active,” says Carr, the study’s corresponding author. “And so, for these patients, many of whom report insufficient activity, we need options to easily connect them with supportive services like exercise prescriptions and/or community health specialists.”

Most hospitals in the United States do not ask patients about their physical activity, and no hospital system in the Midwest has done so, according to the researchers. In this study, Carr partnered with Britt Marcussen, a family medicine physician in UI Health Care, to offer the questionnaire to patients visiting for annual wellness exam appointments. The study period was from November 2017 to December 2022.

The Exercise Vital Sign survey, as the questionnaire is called, asked patients two questions that they answered on a tablet:

• “On average, how many days per week do you engage in moderate to vigorous exercise (like a brisk walk)?” (0-7 days) 
• “On average, how many minutes do you engage in exercise at this level?” 

Carr and his team propose making the survey available to all patients.

“This two-question survey typically takes fewer than 30 seconds for a patient to complete, so it doesn’t interfere with their visit. But it can tell us a whole lot about that patient’s overall health,” Carr says.

The researchers also compared results from patients who completed the surveys with more than 33,000 patients who weren’t offered the survey in other areas of the hospital. The researchers found patients who took the survey were younger and in better health than the patient population who weren’t given the questionnaire, based on analyzing all patients’ electronic medical records. 

While the link between physical activity and reduced risk of chronic disease has been known, the researchers say the study underscores the value of surveying patients about their physical activity levels.

“We believe this finding is a result of those patients who take the time to come in for annual wellness exams also are taking more time to engage in healthy behaviors, such as being physically active,” Carr says.

In a related study, published this month in the Journal of Physical Activity and Health, Carr’s team found that when healthcare providers billed for providing exercise counseling to patients, those invoices were reimbursed by insurance providers nearly 95 percent of the time. 

“Our findings suggest the recommended physical activity billing codes are reimbursed at a high rate when providers submit them for reimbursement, which reinforces the idea to make physical activity surveys and counseling services available,” Carr says.

Cole Chapman, assistant professor in the College of Pharmacy, is the first author on the study. Chapman, who joined the Pharmacy faculty in 2019 after earning bachelor’s and doctoral degrees at Iowa, collected and analyzed the data from the patients’ electronic medical records.