The Important Role of Gut Bacteria in Human Health

The human gastrointestinal tract contains trillions of bacteria that play a vital role in overall health and wellbeing. These gut microbes interact with the immune system, nervous system, and endocrine system to influence many aspects of physiology. This article summarizes how gut bacteria affect inflammation, atherosclerosis, diabetes, obesity, and even neurological conditions.

19. Kale

Kale is hailed as one of the world’s healthiest vegetables. One cup of chopped, cooked kale has only 4 grams of net carbs without any sugar.

It provides a megadose of antioxidants like quercetin and kaempferol to reduce oxidative stress and inflammation in the body. Kale’s high fiber content also promotes digestion and gut health.

How Gut Bacteria Influence the Immune System

• The gut contains lymphoid tissue with immune cells like T cells and B cells. Dendritic cells extend processes into the gut lumen to sample bacteria.
• Regulatory T cells are informed by dendritic cells whether bacteria are pathogenic or commensal. Regulatory T cells then regulate the immune response to commensal bacteria to prevent inflammation.
• With a lack of gut microbiome diversity, there are not enough Regulatory T cells produced. This leads to unchecked inflammation against commensal bacteria.
• Regulatory T cells function needs to develop from a young age when the infant first starts eating foods and establishing a gut microbiota. This “tames” the immune system and prevents hyper-reactivity later in life.
• Many modern inflammatory diseases may be linked to lack of early Regulatory T cells development due to factors like C-section delivery, formula feeding, and antibiotics. The immune system overreacts instead of properly regulating itself.
• Beneficial gut bacteria secrete chemicals that stimulate Regulatory T cells development locally in the gut and systemically throughout the body. These help prevent inflammatory and autoimmune diseases.

The Role of Short Chain Fatty Acids

• Key healthy bacteria like Bifidobacterium and Lactobacillus produce short chain fatty acids like butyrate, propionate, and acetate.
• Butyrate provides energy for colonocytes, increasing mucus production and improving the gut barrier. More mucus prevents bacterial translocation across the epithelium.
• Butyrate is also absorbed into the bloodstream where it has anti-inflammatory effects systemically, reducing blood pressure and improving the blood-brain barrier.
• Overall, short chain fatty acids are very anti-inflammatory. Higher levels are associated with better health outcomes.

Fostering a Diverse Gut Microbiota

• Humans should harbor thousands of commensal bacterial species in the gut. The greater the diversity, the better.
• compare native Africans eating fiber-rich traditional diets vs Westerners. Africans have far more fecal bacteria by weight and more species diversity.
• To increase diversity: eat diverse fiber sources like tubers, vegetables, whole grains. Not just one type of fiber supplement.
• Take care not to kill bacteria unnecessarily through lifestyle factors:
  • Avoid unnecessary antibiotics
  • Avoid artificial sweeteners that disrupt bacterial metabolism
  • Eat foods containing phytochemicals and polyphenols that feed gut bacteria
  • Ensure adequate omega-3 intake which helps maintain gut barrier

The Gut-Brain Axis

• The vagus nerve forms a direct communication pathway between gut and brain in both directions.
• Gut microbes produce neurotransmitters that activate the vagus nerve and signal to the brain.
• Stress hormones released in the brain travel down the vagus nerve to the gut. This can exacerbate gastrointestinal issues like IBS.
• Improving gut health through diet and microbiome modulation can ameliorate gastrointestinal problems and conditions like vasovagal syncope, orthostatic hypotension, and rapid heart rate.
• This is because the vagus nerve regulates parasympathetic activity, heart rate, blood pressure, and digestive function via the enteric nervous system.

Gut Bacteria Affect Obesity, Metabolic Disease, and More

• Gut bacteria metabolize dietary components that the human body cannot digest. This impacts energy harvest and metabolism.
• Artificial sweeteners disrupt bacterial metabolism and lead to glucose intolerance and insulin resistance promoting obesity and diabetes.
• Short chain fatty acids like butyrate improve insulin sensitivity and may reduce weight.
• Alterations in gut bacteria have been linked to diverse disorders:
  • Obesity and metabolic syndrome
  • Type 2 diabetes
  • Cardiovascular disease like atherosclerosis
  • Autoimmune conditions like multiple sclerosis
  • Neurological conditions like autism
• Further research is needed on how gut microbial gene expression and bacterial secreted metabolites influence human physiology and pathology.

Gut Microbiota Interact Closely With The Immune System

• The gut microbiota interacts closely with the immune system to prevent inflammation against commensal bacteria via immune cells like Regulatory T cells. Short chain fatty acids from bacteria are powerfully anti-inflammatory.
• A diverse gut microbiome is healthiest and requires eating a diversity of whole, unprocessed plant foods. Lifestyle factors like antibiotics disrupt diversity.
• The gut and brain signal bidirectionally via the vagus nerve. Improving gut health can ameliorate issues like vasovagal syncope.
• Gut bacteria influence many aspects of human metabolism and physiology. Alterations to the gut microbiome are linked to conditions ranging from obesity to autoimmunity.

Further research should focus on bacterial gene expression and secreted metabolites to clarify mechanisms relating the gut microbiota to human health. But we already know that optimizing the gut microbiome through diet and lifestyle confers tremendous benefits to overall wellbeing.