Prebiotics are compounds in food that induce the growth or activity of beneficial microorganisms, the probiotics. Most types of soluble fiber are prebiotic, as is resistant starch, HMO (Human milk oligosaccharides), polyphenols and certain omega3 fatty acids, like the one that is for example present in walnuts. In a healthy gut, a gut that is in homeostasis, the good bacteria (probiotics) keep the ¨bad¨ bacteria under control.
The most well-known of the ¨bad¨ bacteria are Salmonella, E-coli, and the Campylobacter bacteria, these are all a part of your microbiota but only in small numbers. The whole idea of getting lots of prebiotics in your diet, is to nurture your probiotics so they produce postbiotics, the short chain fatty acids.
Postbiotics
When the microbes in your gut digest the prebiotics they produce SCFA’s (short chain fatty acids). These short chain fatty acids bring lots of health benefits. As their name suggests (acids), they make the colon more acidic which prevents the growth of the inflammatory, bad bacteria like the Salmonella & E-coli bacteria. These SCFA are used by the body as an energy source, and in a healthy body they provide 10% of your daily caloric requirement and are the main energy source for the cells lining your colon, the colonocytes. There are 3 types of SCFA, butyrate, acetate, and propionate, of which butyrate repairs a leaky gut by increasing the expression of tight junction proteins and decreasing the release of endotoxins. Butyrate also inhibits certain enzymes that cancer cells need to multiply. The SCFA regulate the root cause of inflammatory conditions as 70% of your immune system resides in the gut. They inhibit the most powerful inflammatory signals (NF-kB, IFN-ỵ, TNF-α). They also make your immune cells more tolerant to your food and in this way, help prevent food allergies and sensitivities. Another benefit of the SCFA are that they improve your blood sugar regulation. This effect is often called the lentil or second meal effect, when you have a bean or lentil dish for lunch, your dinner will give you less of a sugar spike than if you didn’t have the beans for lunch. SCFA also have the ability to lower your cholesterol level because they control a critical enzyme in cholesterol formation, they increase the excretion of cholesterol in the bile, and SCFA activate receptors in fat cells that decrease the fatty acid uptake. They also promote the release of satiety hormones which makes foods with prebiotics (plant foods) the ideal foods for weight loss. Beyond the gut these SCFA’s influence your brain as well. The SCFA can cross the blood brain barrier where the offer protection against Alzheimer’s disease by interfering with the formation of amyloid plaques that characterize Alzheimer’s disease. SCFA have also been associated with an improvement in learning and memory capability in several studies. Thus, you can say that these postbiotic SCFA’s are vital for gut health and beyond.
TMAO
The antithesis of the SCFA’s is TMAO which is a compound produced when our microbiota digests foods that contain carnitine and choline. The main sources of carnitine in our diet are meat, poultry, fish and dairy products. Carnitine is also found in several supplements that are used in the fitness, bodybuilding world. The main sources of dietary choline are eggs and refined grains. If we eat a lot of these foods, we foster the growth of bacteria that convert the choline and carnitine in these foods into TMA, which gets oxidized into TMAO in the liver. This TMAO wreaks havoc on our cardiovascular system, increasing our risk of heart attack and stroke. There have been studies done where they feed a beef steak to a person on a plant-based diet and one on a standard Western diet and measured their TMAO levels after the meal. This showed that the person on the plant-based diet did not have the bacteria that produce the TMA and had no rise in their TMAO levels while the person on the Western diet saw their TMAO levels shoot up. The best way to lower our levels of TMAO is to minimize the foods that contain carnitine and choline in our diet
The more fiber in your diet, the more you feed the healthy bacteria. These bacteria will produce more and more SCFA from the fiber in your diet. They become more efficient as you train them. When you experience some discomfort like gas or bloating when consuming a fiber rich meal, the best thing is to take it slow and easy. Same as in the gym, you don’t immediately start with the heavy weights. The plant foods that cause distress in people with a damaged gut are paradoxically also the foods we need the most to get our gut stronger. When you eliminate a food group from your diet your ability to digest these foods dwindles. So, eliminating a food than give you some respite in the short term but in the long term it’s going to haunt you.
One example nowadays that you hear a lot is that many people are eliminating gluten from their diet. This can be beneficial in the short term, as the biggest source of gluten in our diet are processed foods, but in the long term you will lose your ability to digest the grains wheat, rye, and barley properly. These grains when eaten in their whole form are consistently being associated with lots of health benefits. It’s like throwing the baby out with the bathwater.
The one exception on this people with celiac disease. People with celiac disease cannot tolerate gluten in their diet. When gluten is present in their small intestine the immune system attacks the intestine. Celiac disease is genetically motivated disease, which means that you must carry the gene for celiac to get the disease. It is estimated that about a third of Western people carry the gene but only 1% of them manifests the disease. People with celiac should not consume any gluten as continued exposure can lead to small intestine lymphoma, a universally fatal disease. There are 3 criteria to develop celiac disease, presence of the gene, exposure to gluten and an alteration or damage to the gut microbiota. In the last 50 years we saw a 500% increase in celiac disease which is not due to a shift in genetics but most likely due to an increase in people with a damaged gut wall.
The key to healthy microbiota is the diversity of plants that you have in your diet, but this diversity can look different for each person as everyone has a unique microbiota with their own strengths and weaknesses.
