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.

GLP-1 receptor agonists have established themselves as one of the most sought-after treatment methods to manage type 2 diabetes. Conversations around these drugs often focus on their ability to improve blood sugar control, promote weight loss and support metabolic health. However, what happens after a patient takes the first dose deserves equal attention.

These medications, which include semaglutide, liraglutide and dulaglutide, mimic a naturally occurring hormone called GLP-1. They stimulate insulin release when blood glucose is high, suppress glucagon, slow stomach emptying and promote a feeling of satiety to reduce cravings.

While there are plenty of benefits, GLP-1 medications are not suitable for everyone. Existing digestive conditions, other diabetes medications, kidney function and even retina health can influence how safely a patient responds to treatment.

On World Diabetes Day, doctors explain why starting GLP-1 therapy requires more than checking blood sugar levels, and what patients should know about its complications. They also discuss lesser-known side effects a patient may face after the first dose.

Who Can And Cannot Take GLP-1 Drugs To Manage Diabetes?

Also read: Why Does Type 2 Diabetes Increase The Risk Of Alzheimer’s Disease? Neurologist Explains

Before initiating GLP-1 treatment, doctors need to understand a patient's overall health, diabetes as well as medication history. This includes checking HbA1c levels, blood glucose patterns, kidney function and any history of pancreatitis, gallbladder disease or gastrointestinal problems.

Dr Bibhu Anand, Internal Medicine Specialist at Sir Ganga Ram Hospital, told HealthandMe that treatment decisions must be made according to the patient’s history.

He said, "We see the patient's HbA1c, blood glucose profile, kidney function, medicine history, and medicine prior to the first dose in detail. We specifically identify patients already receiving insulin or sulfonylureas, as these doses may require modification to reduce the risk of hypoglycemia.”

Patients with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2 are generally advised against using these medications.

Dr Anand said that those with a history of pancreatitis, severe gastrointestinal disease or gallbladder problems may also need assessment. The objective is generally to establish whether the benefits outweigh the risks.

GLP-1 GI Side Effect Or Diabetic Gastroparesis?

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Nausea, bloating, vomiting, constipation and diarrhoea are among the commonly reported gastrointestinal effects of GLP-1 medications. These symptoms are expected in the initial weeks of treatment or after an increase in dose. However, constant digestive discomfort in someone with diabetes should not be neglected.

Dr Richa Chaturvedi, Senior Consultant and Endocrinologist at Indraprastha Apollo Hospitals, Delhi, told HealthandMe that diabetic gastroparesis can cause symptoms that closely resemble gastrointestinal side effects due to GLP-1 drugs.

Gastroparesis develops when nerve damage related to diabetes affects food movement through the stomach. Patients may experience frequent nausea, early fullness, vomiting food consumed several hours earlier and unpredictable blood glucose levels. Unlike discomfort due to medicines, these symptoms may already exist before treatment begins.

"The key difference lies in the onset and pattern of symptoms. GLP-1 medications slow gastric emptying, meaning food remains in the stomach longer. This can cause nausea, bloating, belching and early fullness, particularly when treatment begins or the dose increases. These symptoms may settle as the body adapts."

Dr Chaturvedi emphasises that gastrointestinal symptoms should be assessed before starting treatment, especially in patients with chronic diabetes.

A gastric emptying study can be done if symptoms suggest gastroparesis. GLP-1 medications are generally not recommended for patients with severe gastroparesis, as they can further delay stomach emptying and affect nutritional intake.

Pancreatitis, Gallstones And Dehydration Risk

Also read: Semaglutide May Lower Fetal Oxygen Levels During Pregnancy, Sheep Study Finds

Although mild digestive discomfort may improve as the body adjusts to treatment, certain symptoms require immediate attention.

Severe pain in the upper abdomen or pain radiating towards the back, can indicate pancreatitis. Repeated vomiting, an inability to retain fluids, significant dizziness, reduced urination and upper-right abdominal pain accompanied by fever are other warning signs.

Dr Chaturvedi explains that pancreatitis has been reported during GLP-1 treatment, although it is uncommon and a causal relationship has not been established.

She said, “Gallbladder complications, including gallstones and inflammation, have a more established association with GLP-1 treatment. Rapid weight loss is an important contributing factor, as it can increase the likelihood of gallstone formation. Changes in gallbladder emptying may also play a role.”

Another concern is kidney injury due to dehydration. Persistent nausea and vomiting can reduce fluid intake, potentially affecting kidney function, particularly in patients who already have kidney disease.

Patients should therefore not dismiss severe abdominal pain or prolonged vomiting as routine side effect of the drug.

Diabetics Need Eye Testing Before Starting GLP-1 Therapy

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Digestive complications are not the only concern after starting GLP-1 medications. For patients with diabetes, retina health also warrants attention.

Dr Parul Maheshwari Sharma, Principal Director and Head of Ophthalmology at FMRI Gurgaon, told HealthandMe that a rapid improvement in blood glucose levels can sometimes cause an initial, temporary worsening of diabetic retinopathy. This phenomenon is known as early worsening of diabetic retinopathy.

Dr Sharma explained, “When blood sugar levels fall substantially over a short period, changes in retinal blood flow and vascular regulation may affect blood vessels that are already damaged. The concern is particularly relevant for patients with poorly controlled diabetes, high baseline HbA1c levels or pre-existing retinopathy.”

Patients with long-standing or poorly controlled diabetes, existing retinopathy or high HbA1c levels should ideally undergo a dilated retinal examination before initiating treatment, especially when substantial glucose reduction is anticipated.

Rare Vision Complication Patients Should Know About

Another emerging area of concern is non-arteritic anterior ischaemic optic neuropathy (NAION), a rare condition caused by reduced blood supply to the optic nerve that can result in sudden, permanent vision loss.

Some observational studies have reported an association between GLP-1 medications, particularly semaglutide, and NAION. However, a direct cause-and-effect relationship has not been established, and the evidence is still evolving.

Dr Sharma explains that this condition is different from diabetic retinopathy. While retinopathy affects the blood vessels in the retina, NAION involves damage to the optic nerve due to reduced blood supply.

Patients should be aware of warning signs such as sudden, painless blurring or loss of vision, particularly in one eye. Patients experiencing sudden visual changes should not wait for symptoms to resolve on their own.

She said, “Other symptoms include dark patches or blind spots in the visual field, distorted colour perception and difficulty seeing centrally. Sudden flashes, floaters or a curtain-like shadow across the vision also warrant urgent ophthalmological assessment. These symptoms could indicate conditions such as NAION, retinal complications or other sight-threatening emergencies.”

HbA1c, also known as hemoglobin A1c or glycated hemoglobin, is a widely used blood test to diagnose and monitor diabetes. However, ahead of World Diabetes Day, experts have warned that the test may not be accurate for everyone.

HbA1c measures how much glucose is attached to hemoglobin in red blood cells, providing an estimate of average blood sugar levels over the previous two to three months.

Certain medical conditions and blood disorders can affect its accuracy, making readings appear higher or lower than actual blood sugar levels.

Who May Get Inaccurate HbA1c Results?

Conditions such as anemia and hemoglobin disorders can affect HbA1c readings by altering the lifespan of red blood cells.

"HbA1c can be misleading when conditions alter red blood cell lifespan. Iron, B12 or folate deficiency may falsely elevate HbA1c. Conversely, hemolytic anemia, certain hemoglobinopathies, chronic blood loss, recent transfusion and some kidney conditions can lower it falsely," Dr Manisha Arora, Director of Internal Medicine at CK Birla Hospital, Delhi, told HealthandMe.

Dr Sandeep Kharb, Senior Consultant – Endocrinology at Asian Hospital, added that iron-deficiency anemia can also lead to falsely high HbA1c readings.

Experts also cautioned that HbA1c is not a direct measure of insulin resistance. A person may be insulin resistant even before their HbA1c reaches the prediabetes threshold.

What Medical Conditions And Medications Can Affect HbA1c?

Iron, vitamin B12 and folate deficiencies, chronic alcohol use, high-dose aspirin and severe hypertriglyceridemia may contribute to falsely elevated readings.

Falsely low results can occur with hemolytic anemia, hemoglobin disorders, blood loss, transfusions, pregnancy, kidney disease and erythropoietin therapy.

Certain medicines, including dapsone, ribavirin and some antiretroviral drugs, can also affect HbA1c interpretation. The direction of the error depends on the underlying condition and the testing method.

Can Fasting Blood Sugar Be Normal While HbA1c Is High?

Dr Himika Chawla, Senior Consultant, Endocrinology and Diabetology at PSRI Hospital, told HealthandMe HbA1c reflects average blood sugar over two to three months, while fasting blood sugar measures glucose at a particular point in time.

A person may have normal fasting glucose but experience repeated blood sugar spikes after meals, pushing their HbA1c higher. The reverse mismatch can also occur.

Doctors therefore consider both results and the patient's overall clinical picture before making a diagnosis.

What Test Should Be Used To Diagnose Diabetes?

When HbA1c may not be reliable, doctors can use blood glucose-based tests, including fasting plasma glucose and the oral glucose tolerance test (OGTT).

"First test it should be oral glucose tolerance test," Dr Anoop Misra told NDTV.

For the test, a person eats their usual meals for three days and then fasts for eight to 10 hours before their fasting blood glucose is measured. They then drink 75 grams of glucose mixed in water, followed by another blood test two hours later.

Misra explained that fasting glucose below 100 mg/dL and a two-hour reading below 140 mg/dL are normal. Fasting levels of 100–125 mg/dL or two-hour readings of 140–199 mg/dL indicate prediabetes. Fasting glucose of 126 mg/dL or higher, or a two-hour reading of 200 mg/dL or higher, falls in the diabetes range.

A new review of studies has found that people living with type 2 diabetes have a significantly higher risk of developing Alzheimer's disease.

Researchers from Curtin University conducted a systematic review and meta-analysis of 40 studies. They estimated that if 1,000 people with type 2 diabetes were followed for a year, an average of 4.7 would develop Alzheimer's disease.

Published in Alzheimer's Research & Therapy, a separate analysis found that type 2 diabetes was associated with a 53% higher adjusted relative risk of Alzheimer's disease compared with people without the condition.

How Does Blood Sugar Affect Memory?

Ahead of World Diabetes Day, Dr Sudhir Kumar, neurologist at Apollo Hospitals, Hyderabad, in a post on X, explained that several overlapping mechanisms may link type 2 diabetes to Alzheimer's disease. These include:

• Brain insulin resistance: Brain cells become less responsive to insulin, potentially impairing their ability to use glucose for energy and clear amyloid and tau proteins.
• Vascular damage: High blood sugar can damage large and small blood vessels in the brain, increasing the risk of strokes and vascular dementia.
• Chronic inflammation: Peripheral inflammation and lipid abnormalities can weaken the blood-brain barrier and trigger neuroinflammation.

How Does Diabetes Increase The Risk Of Dementia?

According to Alzheimer's Society UK, diabetes is an established risk factor for dementia. The risk also increases with the duration and severity of diabetes. However, having diabetes does not mean a person will necessarily develop dementia.

With diabetes and Alzheimer's disease cases rising globally, understanding the link between the two conditions is becoming increasingly important.

Insulin helps regulate blood sugar by enabling the body's cells to use glucose for energy. In people with diabetes, the body either does not produce enough insulin or cannot use it effectively, causing blood sugar levels to rise.

Studies have linked type 2 diabetes to an increased risk of dementia. In people with type 1 diabetes, severe and repeated episodes of high or low blood sugar have also been associated with a higher risk.

Diabetes and Alzheimer's disease may share certain underlying mechanisms. In both conditions, brain cells can become less responsive to insulin, potentially affecting brain function and contributing to the accumulation of amyloid and tau proteins associated with Alzheimer's disease.

How Can People With Diabetes Protect Their Brain Health?

Dr Kumar recommended the following measures for people living with type 2 diabetes:

• Maintain blood sugar levels: Aim to keep glucose within your target range.
• Avoid extreme fluctuations: Prevent prolonged high blood sugar (HbA1c of 7% or higher) and severe, repeated episodes of low blood sugar (hypoglycemia).
• Manage other health conditions: Keep blood pressure and cholesterol under control.
• Prioritise a healthy lifestyle: Eat whole foods, including vegetables, fruits and whole grains, and engage in regular physical activity to improve insulin sensitivity.

"Early detection, consistent blood sugar management, and working closely with your healthcare team can help safeguard your cognitive future," he said.