Your body hosts trillions of bacteria, viruses, and fungi, collectively known as the microbiome. While some bacteria are linked to disease, many play essential roles in supporting your immune system, heart health, weight management, and overall well-being. This article delves into the significance of the gut microbiome and its impact on health.

What Is Gut Microbiome?

Interestingly, bacterial cells outnumber human cells in the body, with approximately 40 trillion bacterial cells compared to 30 trillion human cells. With up to 1,000 species of bacteria present in the gut, each plays a distinct role. While most bacteria contribute positively to health, some can be harmful. Together, these microbes weigh around 1–2 kilograms, functioning almost like an additional organ essential for overall well-being.

How Does Gut Microbiome Influence Your Health?

The relationship between humans and microbes has evolved over millions of years, with the gut microbiome playing a crucial role from birth. Initial exposure to microbes occurs during birth, and some evidence suggests that exposure begins in the womb. As the microbiome diversifies, it starts influencing key bodily functions:

Digestion of breast milk: Beneficial bacteria like Bifidobacteria help break down essential sugars in breast milk, supporting infant growth.

Fiber digestion: Some bacteria process fiber into short-chain fatty acids, which contribute to gut health and reduce risks of obesity, diabetes, and heart disease.

Immune system regulation: The gut microbiome interacts with immune cells, influencing how the body responds to infections.

Brain health: Emerging research suggests a link between the gut microbiome and brain function, potentially affecting mental health and neurological processes.

Gut Microbiome And Weight Management

An imbalance between beneficial and harmful microbes, known as gut dysbiosis, may contribute to weight gain. Studies on identical twins—one with obesity and the other without—suggest that microbiome composition plays a role in body weight independent of genetics. Additionally, animal studies indicate that gut bacteria can influence weight gain, even when calorie intake remains constant.

Probiotics, beneficial bacteria found in supplements and certain foods, can help restore gut balance and support weight loss, though their effects may be modest.

Gut Health And Disease Prevention

The gut microbiome plays a vital role in preventing and managing conditions like irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). Imbalances in gut bacteria may lead to bloating, cramps, and digestive issues. On the other hand, beneficial bacteria like Bifidobacteria and Lactobacilli help strengthen the intestinal lining, reducing the risk of gut-related disorders.

Impact On Heart Health

Research suggests that the gut microbiome influences heart health by affecting cholesterol levels and blood pressure. Certain harmful bacteria produce trimethylamine N-oxide (TMAO), a compound linked to blocked arteries and heart disease. However, probiotics, particularly those containing Lactobacilli, may help reduce cholesterol levels and promote cardiovascular health.

Blood Sugar Regulation And Diabetes Risk

The gut microbiome also plays a role in regulating blood sugar levels. Research on infants genetically predisposed to type 1 diabetes indicates that gut microbiome diversity declines before disease onset. Furthermore, individual variations in gut bacteria may explain why people experience different blood sugar responses to the same foods.

Connection Between Gut And Brain

The gut is physically connected to the brain through nerves, and certain bacteria help produce neurotransmitters like serotonin, which influence mood and mental health. Studies indicate that people with mental health disorders often have different gut bacteria compared to those without such conditions. Additionally, some probiotics have shown promise in alleviating symptoms of depression and anxiety.

Tips For Healthier Gut Microbiome

Maintaining a balanced gut microbiome is crucial for overall health. Here are some strategies to support gut health:

• Eat a diverse range of foods: A varied diet rich in fiber, legumes, and fruits promotes microbial diversity.
• Consume fermented foods: Yogurt, kefir, and sauerkraut contain probiotics that enhance gut health.
• Limit artificial sweeteners: Some artificial sweeteners can encourage the growth of harmful bacteria.
• Include prebiotic foods: Bananas, oats, and asparagus contain fibers that nourish beneficial bacteria.
• Breastfeed infants when possible: Breastfeeding promotes a healthier gut microbiome in babies.
• Choose whole grains: Whole grains contain fiber and beneficial compounds that support digestive health.
• Opt for a plant-based diet: Vegetarian diets may reduce inflammation and support a healthier gut microbiome.
• Consume polyphenol-rich foods: Green tea, dark chocolate, and olive oil contain compounds that foster beneficial bacteria.
• Take probiotics if needed: Probiotic supplements can help restore gut balance after disruptions, such as antibiotic use.
• Use antibiotics cautiously: While antibiotics can be life-saving, overuse can harm beneficial gut bacteria.

While dementia is generally associated with older age, its onset can begin much earlier, including in middle age. A new study led by an international team of researchers found that muscle loss as people age may be an important warning sign for dementia risk.

The study, published in the International Journal of Food Sciences and Nutrition, also found a surprising difference in how obesity was linked to dementia depending on a person’s age.

What Did The Study Find?

Researchers analyzed more than 80 studies examining the links between body weight, body fat, muscle health and dementia.

They found that people with sarcopenia — the loss of muscle mass and strength — had a 42 per cent higher risk of dementia.

People with obesity in middle age, or before 65, had a nine per cent higher risk of dementia. In contrast, obesity in people aged 65 and over was linked to a 17 per cent lower risk.

The findings showed that body weight alone did not tell the full story when it came to dementia risk.

“It’s not just about how much you weigh – maintaining muscle strength and function also appears to be important as we age,” said lead researcher Dr Uraiporn Booranasuksakul from Burapha University, Thailand.

“Our findings suggest losing muscle could be an important warning sign for dementia risk.”

Why Muscle Health Matters

Sarcopenia is a condition where people lose a greater amount of muscle mass, strength and physical function, often as they get older.

Dr Booranasuksakul said the findings highlighted the importance of looking after muscle health throughout life.

“Maintaining muscle is an important part of healthy ageing, and regular physical activity and good nutrition can help support muscle strength and function,” she said.

Obesity And Dementia Risk Change With Age

Corresponding author Professor Mario Siervo from Curtin University’s School of Population Health said the findings also challenged the idea that dementia risk could be understood simply by looking at a person’s weight.

“We found that obesity in middle age was linked to a higher risk of dementia, but this relationship changed in later life,” Professor Siervo said.

“This does not mean people should gain weight as they get older. Rather, it shows us that the relationship between body weight, ageing and dementia is complex.”

What About Sarcopenic Obesity?

The researchers also looked at sarcopenic obesity, where a person has both low muscle mass or function and excess body fat.

Only four studies met the criteria for this part of the analysis, and researchers found no statistically significant link between sarcopenic obesity and dementia.

Professor Siervo said more research was needed to understand whether the combination of muscle loss and excess body fat affected dementia risk.

“There is still a lot we don’t know about how changes in muscle and body fat interact over time,” Professor Siervo said.

“More long-term research is needed to understand whether having both low muscle mass and excess body fat increases dementia risk.”

A Lifelong Approach To Healthy Ageing

The researchers said the findings reinforced the importance of taking a lifelong approach to maintaining healthy body composition, including preventing unhealthy weight gain during middle age and maintaining muscle strength and function as people get older.

India has a target to eliminate dog-mediated rabies by 2030. It has strengthened access to post-exposure prophylaxis for people exposed to rabid animals, but controlling transmission among dogs still remains a challengge.

India's National Action Plan for dog-mediated rabies elimination rests on human-health component, which focuses on post-exposure prophylaxis and awareness among bite victims, and the animal-health component, which focuses on vaccinating and sterilising stray dogs.

In a conversation with HealthandMe, Dr Hanul Thukral, Veterinary Epidemiologist, South Asia Field Epidemiology & Technology Network (SAFETYNET), formerly with the Centre for One Health, National Centre for Disease Control (NCDC), Ministry of Health & Family Welfare, Government of India, says that the human-health side of the programme is strong. The bigger challenge lies in giving the animal-health side enough resources, coordination and accountability.

The Gap Of Animal Health Component In Rabies

Dr Thukral talks about an unusual problem at the heart of India's rabies-control efforts. He speaks about the ownership of stray dogs and that they do not fall under any single ministry.

“Stray dogs also do not come under a particular ministry. They do not come under the animal husbandry ministry, the health ministry or the wildlife ministry. They are under the purview of local bodies, including municipal corporations and rural local bodies,” he said.

This is a larger issue as the animal-health component of rabies elimination depends on sustained vaccination and sterilisation campaigns. Dr Thukral said the country currently lacks dedicated funding and resources for this part of the effort.

For India to move faster towards the 2030 goal, he said local bodies need to be given greater financial and operational support, including resources to capture rabid dogs, sterilise stray dogs and vaccinate them.

He added, “There should be an incentive-based model for local bodies like Swachh Bharat. Financial or non-financial incentives could be offered to local bodies for their rabies efforts, including recognition for those that prevent the majority of deaths.”

Also read: 18-Year-Old Dies From Rare Measles Brain Complication As Pennsylvania Death Toll Hits 4

Treatment Is Available But The Patient May Seek Treatment Late

India's human-health response is strong. Dr Thukral said the health ministry has increased access to rabies vaccination and rabies immunoglobulins, with a goal of making vaccines available up to the PHC level and immunoglobulin available up to the CHC level.

Yet the first break in the prevention chain can occur before the health system even knows a bite has happened.

“The prevention chain breaks down where it actually starts. It starts with the awareness of dog-bite victims,” Dr Thukral said. “A person bitten by a dog has to recognise the danger and seek care before the health system can intervene. According to a recent estimate cited during the interview, only around 20-25% of dog-bite victims receive post-exposure prophylaxis, while 60-65% do not. Of those who receive it, only 50% complete it.”

Dr Thukral stressed that these are not definitive figures. “These are just estimates based on a subset of the population,” he said.

That gap can lead to delayed treatment. “In rabies, time is everything,” he said, adding, “If we don't get post-exposure prophylaxis immediately after the dog bite, after 10 hours or after 24 hours, it has virtually no use.”

The 70% Dog-Vaccination Challenge

Human treatment can prevent death after exposure, but elimination requires the transmission cycle to be interrupted among dogs. Around 70% vaccination coverage among dogs is needed to interrupt the transmission chain.

The problem, Dr Thukral said, is that India does not have reliable nationwide data showing what proportion of its stray-dog population is actually vaccinated.

He said, “A nationwide stray-dog census was only recently conducted, counting almost 1 crore 50 lakh stray dogs across the country. Local bodies and panchayats conduct surveys and organise vaccination campaigns within their jurisdictions, but the current effort is very scattered and very non-uniform.”

He added, “If I achieve 70% vaccination in a particular block, the dogs of that block are protected. But there is always a chance that unvaccinated dogs from the periphery or neighbouring blocks can enter that block.”

Also read: Chile Eliminates Dog-Transmitted Rabies: What Other Countries Can Learn

Treatment Alone Can Prevent Deaths, But Not Eliminate Rabies

Dr Thukral says saving people from rabies and eliminating rabies are not the same goal. He said, “One estimate suggests that if India continues increasing post-exposure prophylaxis coverage while carrying out suboptimal dog vaccination, around 400 deaths could be prevented over the next 10 years.”

Another estimate cited by Dr Thukral puts the figure at about 400-500 deaths over the next 10 years, with spending about 5 to 10 crores. But preventing those deaths would still fall short of elimination. “That’s it. We cannot achieve elimination,” Dr Thukral said.

“Humans are not the source of the infection,” he explained. “In this case, dogs or other animals are the source of infection. Unless we target them, we do not move closer to elimination.”

India Does Not Have Reliable Data For Vaccinated Stray Dogs

The same data problem extends to the Animal Birth Control programme, which combines sterilisation with anti-rabies vaccination. The expert says that there is no nationwide figure showing how many stray dogs have been vaccinated or sterilised. The information exists, but it sits across individual municipal corporations and panchayats rather than in one comprehensive national dataset.

“Vaccinating stray dogs doesn't come under the purview of the health ministry or the animal husbandry ministry,” he said. That makes it difficult to answer a seemingly basic question: what proportion of India's stray dogs is vaccinated at any given time? “We do not have nationwide data,” Dr Thukral said.

Also read: DRC Says Ebola Outbreak Has Peaked, UN Warns It’s Still Growing

Reliable 'One Health' Approach

Rabies is not a problem that can be solved by hospitals alone. At the district level, Dr Thukral said an effective One Health system would require health departments, municipalities, animal husbandry authorities, veterinary services and welfare bodies to have clearly defined responsibilities, adequate resources and a mechanism to coordinate.

He said, “The health department would focus on post-exposure prophylaxis, animal-bite management and awareness. Local bodies would handle dog vaccination, sterilisation and solid-waste management. The animal husbandry department could provide technical support, while welfare bodies could promote responsible dog ownership. Let every department do its job and establish coordination among them.”

That coordination also becomes important after an individual bite. Municipal or animal-health authorities need to communicate with the health department because one reported bite may indicate that additional people have been exposed.

How To Recognise A Rabid Dog?

Another challenge is recognising rabid animals. Dr Thukral said that after a dog is bitten by another rabid dog, it can take up to three months for symptoms to develop. However, he stressed that this does not mean the animal transmits the virus throughout that entire period.

“It will transmit the virus about 10 days before it starts showing symptoms,” he said. He also described several behavioural and neurological changes that can raise concern.

A dog that suddenly becomes aggressive, unusually quiet, or behaves differently from its normal pattern may warrant attention. Other signs described by Dr Thukral include seizures, excessive drooling, and changes in vocalisation.

“The basic thing we need to look out for if we get a dog bite or exposure from a potentially rabid animal is, most importantly, change in the animal's behaviour,” he said.

Also read: World Leaders Call For Obesity & NCD Prevention At BRICS 2026 Summit: Why Focus Is Growing?

India’s Surveillance Gaps

India's surveillance recorded 54 rabies deaths in 2024, according to the Press Information Bureau. But an independent study cited during the discussion put the number at more than 5,700, and estimated that India may have between 3,000 and 7,000 deaths annually.

Dr Thukral said that India's human rabies surveillance system is well equipped to detect, diagnose and report suspected and confirmed cases. But the bigger vulnerability, he said, may occur before a suspected case enters the health system.

“If there are scattered cases, such as one bite or a couple of bites, unless that patient reports to a health facility for potential post-exposure prophylaxis, the health system will most probably fail to capture it,” he said.

In other words, surveillance can only record what comes into contact with the system. Community awareness and care-seeking behaviour therefore remain critical.

The Biggest Challenge In India’s Rabies Elimination Goal

Dr Thukral believes the health component of India's rabies programme is comparatively strong. Post-exposure prophylaxis is accessible, almost free and cost-effective, he said. But it becomes more difficult when the focus shifts to dogs.

“Sterilising and vaccinating a dog currently takes around Rs 1,500 per stray dog to vaccinate it and sterilise it,” he said.

With a stray-dog population of around 1.5 crores, the scale of resources required becomes enormous. According to Dr Thukral, local bodies generally do not have that kind of money to dedicate to rabies control.

“So, yes, our system is very much in place and very strong to detect human rabies cases and treat them and provide them with the necessary care,” Dr Thukral said. “But for elimination, we need to target the source of the infection, which is obviously these stray dogs.”

For India to reach its 2030 goal, he said, the pace needs to pick up in terms of resources, manpower and political intention.

India's rabies challenge is therefore not confined to what happens after a person is bitten. It begins much earlier. With awareness, timely care-seeking, dog vaccination, sterilisation, waste management, reliable data and coordination between agencies working across the human and animal-health systems.

The country can continue expanding access to post-exposure prophylaxis and prevent more deaths. But, as Dr Thukral emphasises, that alone cannot deliver elimination. The question for the next four years is whether India can move from responding to individual exposures to systematically interrupting transmission at its source. As the expert said, “We need to target the source.”

You can feel fine and still have a heart that is slowly changing. Researchers at Imperial College London and the MRC Laboratory of Medical Sciences say millions of people could be living with hidden inflammation that does exactly that. They say the changes can start years before any symptoms show up.

"Our study, which is the largest of its kind, suggests that millions of people could be living with hidden inflammation, which is slowly changing their heart and causing long-term damage," said Professor Declan O'Regan, British Heart Foundation Chair of Cardiovascular AI at Imperial College London.

What The Study Found

The study was published in the European Journal of Preventive Cardiology. The team looked at data from nearly 480,000 adults in the UK Biobank, a large health database, Imperial says. They measured a blood marker called glycoprotein acetyls, or GlycA for short, which the paper uses to measure chronic inflammation. They also used heart scans and genetic data.

People with the highest levels of inflammation, the top 20%, had a 43% higher risk of heart attack and stroke than those with the lowest levels, the bottom 20%, according to Imperial.

Imperial adds that higher levels also went with changes in the heart itself. These included thicker heart walls, smaller heart chambers and poorer filling of the heart. The researchers say such changes can build quietly for years before possibly leading to heart failure.

Read More: Childhood Vaccine Rates Decline Across Europe, Lancet Study Finds

Where The Inflammation Comes From

Chronic inflammation is a long-term, low-level activation of the immune system, Imperial explains. It has been linked to cancer and diabetes, and is increasingly seen as a driver of heart disease.

According to Imperial, higher inflammation was strongly linked to poorer social and economic circumstances and to mental distress, as well as to smoking and excess body fat.

"The surprising thing was how much social factors and mental health are linked to inflammation and damage to the heart, as well as more well-known risk factors like smoking and inactivity," O'Regan said. He added that there was also a strong genetic factor, "with some people being naturally more resilient or susceptible to the inflammatory damage that comes from different lifestyles."

What Could Come Next

The study named proteins from the interleukin-1 and TNF families as likely drivers of the damage, Imperial says. Several are already targeted by drugs in clinical trials, which Imperial says raises hopes that anti-inflammatory treatments could help prevent heart disease before symptoms begin. The researchers say combining inflammation blood tests with genetic risk scores could help find the people who would benefit most from early action.

There is earlier proof that this idea can work. In the 2017 Canakinumab Anti-inflammatory Thrombosis Outcomes Study, or CANTOS trial for short, led by Paul Ridker and published in the New England Journal of Medicine, 10,061 people who had already had a heart attack, and had high inflammation, were given canakinumab or a placebo. The paper concluded that at the 150 mg dose, given every three months, canakinumab led to fewer repeat cardiovascular events than the placebo, independent of any drop in cholesterol. But those were heart attack survivors, not people without symptoms.

What to keep in mind

The study reports links, and the researchers describe inflammation as one possible pathway to heart damage. They also stress that being genetically susceptible, or living in hard circumstances, does not mean a person will develop heart disease, and that much can be done to prevent long-term inflammation.