The common phrase, “you are what you eat”, has been around for centuries, but it is more than just received wisdom – today, there is molecular proof that food directly impacts one’s health and immunity.
A study [1] published in Nature showed that what mice consume initiates the release of a metabolite or metabolic byproduct that modulates the immunity of the mice’s gut. This study explains the relationship between the gut’s microbiota, diet and immune function.
The gut’s microbiota, diet and immune function
The research investigators conducted a series of experiments that identified how the gut microbiota breaks down specific molecules and improves the immune system in the gut.
In the experiment, the researchers found that once the mice consumed food that had branched-chain amino acids, these amino acids were then taken up by Bacillus fragilis. These microbes are naturally found in the gut.
Once taken in by the B. fragilis, the branched-chain amino fatty acids are converted into sugar-lipid molecules that have branched chains through a specific enzyme.
These branched sugar-lipid molecules are then released and picked up by antigen-presenting cells, which are immune-signaling cells.
The antigen-presenting cells induce natural killer (NK) T cells to up-regulate immune-regulatory chemicals and inflammation-controlling genes. The NK cells are involved in various inflammatory conditions and immune regulation.
Interestingly, the experiments revealed that the chained and branching structures of the molecules initiated these changes inside the gut.
Dennis Kasper, one of the senior authors of the study and a professor of immunology at the Blavatnik Institute at Harvard Medical School, observed that “we have shown how diet affects the immune system through a microbial mediator in the gut, and this is a striking example of the diet-microbiota-immunity triad at play,”.
He continued, “what this work does is provide a step-by-step pathway from beginning to end that explains how and why this triad works and how diet ultimately affects the immune system.”
The main question is, what types of foods or supplements are rich in branched-chain amino acids?
Prebiotics
The bacteria present in your gut are called the microbiota. It has been reported that there are trillions of resident microorganisms in the intestine and colon. Most of these bacteria reside in the colon. These microorganisms are mostly anaerobes and are crucial for human health.
The more diverse the microorganisms in your gut, the healthier your gut is. In contrast with the common belief that ‘germs’ are harmful to the body, many helpful microorganisms aid in the digestion of the food we eat.
These beneficial microorganisms digest and break down food to help with inflammation and enhance the immune system.
However, what keeps these microorganisms alive? And how can these bacteria work more efficiently? Microorganisms are kept alive by our food, most notably by prebiotics.
Prebiotics are food sources of the gut’s microorganisms that need to bypass the body’s acidic environment and reach the small and large intestines to function as food sources of the microbiota.
After arriving in the colon, the microorganisms ferment and metabolize the prebiotics to stay alive. This process is crucial to the gut’s health since it produces a variety of byproducts that boost overall health and immunity.
Different short-chain fatty acids are produced following the breakdown of the prebiotics. These short-chain fatty acids are essential since they provide energy to the colon cells, aid in immunity and inflammation and assist in mucus production.
It is important to remember that not all microorganisms metabolize the same prebiotics. Specific microorganisms metabolize or ferment certain prebiotics. Hence, not all prebiotics will have the same health benefits or effects.
Are prebiotics different from probiotics?
The simple answer is yes. While prebiotics acts as food for the microorganisms, probiotics are live microorganisms that must survive stomach acidity to reach the colon.
Once in the colon, they join the organisms in the gut to boost immunity and fight inflammation – the more diverse the probiotics, the better for your health.
What is the role of prebiotics in promoting gut health and the immune system?
About 70% of the immune system is found in the gut. To have healthy immune system, evidence from published studies has shown that nutrition modulates the functions of the immune system.
The immune system cells in the gut directly interact with the microorganisms or microbiota present in the colon. Lifestyle and diet directly influence these microorganisms. One’s diet affects the composition and diversity of the gut’s bacteria, affecting the immune system cells.
These microorganisms are the healthiest when the host or individuals consume a plant-based diet high in fiber. When these beneficial microorganisms are healthy, they also boost the host’s immune system.
A fiber-rich diet reduces inflammation and supports the microbiome. In a review [2] published in the Trends in Food Science & Technology journal, dietary fibers were shown to play a significant role in boosting immunity and improving health.
However, it should be noted that nutritional fibers and their impact on human health have been well-established for many years.
The review also affirmed that dietary fiber controls viral infections and chronic diseases. Diets high in fiber have been shown to have protective effects against type 2 diabetes, cardiovascular diseases and obesity.
Notably, dietary fibers are thought to control diabetes through their fermentation with the gut’s microbiota to short-chain fatty acids. These short-chain fatty acids help prevent the development of type 2 diabetes.
Fibers in preventing obesity
Meanwhile, beta-glucans in dietary fibers have been linked to reducing low-density lipoprotein and total cholesterol. In addition, nutritional fibers help prevent cardiovascular diseases by controlling or preventing obesity.
Once ingested, these dietary fibers increase feelings of satiety since their transit time to the lumen of the intestine is prolonged.
In contrast, digestible and simple polysaccharides in sugar-rich food are easily digested. This leads to increased feelings of hunger compared to eating food rich in fiber.
Another mechanism related to dietary fibers in preventing obesity involves its low energy bulk, which in turn could influence the palatability of the foods. In turn, this can lead to a lower intake of calories.
Eating a diet rich in fiber boosts the immune system by improving the gut’s overall health. Once the gut’s health is optimized and the diversity of the microorganisms is increased, this leads to better interaction with immune system cells.
In contrast, eating a diet high in saturated fats and sugar, animal meat proteins and processed foods, which often represent the western diet, results in less diverse-gut bacteria. This increases the risk of chronic diseases since this diet promotes inflammation. In addition, diets high in saturated fats increase the risk of obesity.
Current studies show that fat cells secrete chemicals and hormones known to increase inflammation. Hence, fatty tissues are now recognized as metabolically active endocrine organs.
Being overweight or obese affects immune function. Obesity stimulates low-grade inflammation, which is an immune system response.
Eating a plant-based diet and maintaining a healthy weight is critical in boosting the immune system and maintaining healthy microbiota.
What are the sources of prebiotics?
Considering the importance of prebiotics in boosting a healthy immune system by maintaining a healthy gut, here are some excellent sources of prebiotics:
- Bananas – are rich in vitamins, minerals and fiber.
- Asparagus – this green vegetable can be added to soups, salads or grilled.
- Whole grains – are rich in fiber, vitamins and minerals.
- Soybeans are high in protein and good sources of fat and carbohydrates.
- Raw onions can be sauteed, grilled or caramelized to flavor dishes. Raw onions can also be added to salads, dips and sandwiches.
- Garlic – raw garlic can be used as part of salad dressings.
- Artichoke is similar to ginger root and can be added to salad or soup. It can be roasted, boiled and sauteed.
- Dandelion greens – blanching this plant in boiling water for approximately 20 seconds will help reduce its bitter taste. This can be added to salads, stews, soups, casseroles or herbal teas.
Prebiotic supplements are also excellent sources of food for microorganisms. Keep in mind that there are many prebiotics supplements.
Always consult your doctor when planning to take prebiotics supplements to boost your immune system and improve your gut health.
The type of bacteria and the amount present in supplements vary by brand. Hence, it is essential to always do your research when planning to take these supplements.
You can talk to your doctor to determine which prebiotics supplement works best for your current health condition.
Take-home message
Prebiotics serve as essential food sources for bacteria present in the gut. The best sources of prebiotics include vegetables and fruits. Hence, a plant-based diet is highly recommended to improve the gut’s health and immune system function.
In contrast, a western diet high in saturated fats, sugar and animal meat has been associated with inflammation and the development of chronic diseases.
The gut’s health is highly interlinked with the immune system’s function. Since the diversity and health of the microorganisms are intertwined with the optimal functioning of the immune system, it is best to eat foods rich in prebiotics to boost the health of the microbiota.
Apart from naturally occurring prebiotics, supplements are also good sources of prebiotics. Like any supplement, always consult your doctor before deciding which prebiotic supplement to take.
[1] https://www.nature.com/articles/s41586-021-04083-0
[2] https://www.sciencedirect.com/science/article/pii/S0924224420305112
