Our Wise Guide: Author Dr. Will Bulsiewicz (or "Dr B" as he is known) says forget about the fiber your grandmother used to take--the cutting-edge science on fiber is incredibly exciting. As Dr. B explains, fiber energizes our gut microbes to create powerhouse postbiotics called short-chain fatty acids (SCFAs) that are essential to our health. SCFAs are scientifically proven to promote weight loss, repair leaky gut, strengthen the microbiome, optimize the immune system, reduce food sensitivities, lower cholesterol, reverse type 2 diabetes, improve brain function, and even prevent cancer. Restrictive fad diets starve the gut of the critical fiber we need, weaken the microbes, and make our system vulnerable.
Key idea 1: Meet your gut microbiome.
Whatever you think you know about the importance of your microbiome is probably only the tip of the iceberg. Research in the field is growing at an exponential rate with 12,900 papers published in the last five years – that’s 80 percent of all the papers published about the gut microbiome in the last 40 years. And in the last 15 years or so, we’ve gone from knowing about 200 species of bacteria in the human gut to 15,000. It’s believed that there may even be as many as 36,000 species.
So what exactly is your microbiome? Well, the collection of microorganisms living inside you which includes bacteria, viruses, fungi, parasites, and archaea, is usually referred to as the gut microbiota, and the term microbiome is reserved for its genetic makeup. Let’s look a little closer at each of the microbes.
Bacteria are single-celled organisms that most people associated with illness. It’s true that some are bad – E. coli, for example – but most of them are good for us.
Fungi, on the other hand, are multicellular. Just as with bacteria, some are bad and some are good. Bacteria and fungi often compete, so while one flourishes the other withers.
Viruses are simply particles of DNA or RNA. And yet again there are bad ones that cause illnesses like hepatitis B, HIV, and, indeed COVID-19, but there are also good ones that work to keep your bacteria in harmony.
Parasites in your microbiome are like thieves – they steal energy from you and try to remain undetected. Some, like worms that can grow to 80 feet long, are – thankfully – rare in the Western world but others, like Toxoplasma gondii currently infect 60 million Americans – again, thankfully, mostly asymptomatically.
And then there are the archaea, ancient organisms that have been around for billions of years. Not only are they found in your colon, but also in ocean rift vents and volcanoes. They’re incredibly resilient and, right now, barely understood at all.
Your own gut microbiota is quite unique and diverse. For example, it contains from 300 to over 1,000 of the bacteria species possible from the 36,000 that are thought to exist.
So what does your gut microbiota do and what happens when it goes wrong?
Your microbiota is critically important to your digestive function, allowing you to extract nutrients from your food. Your food is also the food of the microbes in your microbiota and they thrive on different things. Remove a food group completely and the microbes that live on that starve to death. Not only that, your food choices in any 24 hours affect the evolution of the next 50 microbe generations. Effectively, this gives you a particular set of microbes that’s as unique as your fingerprint.
The importance of your microbiota has a reach far beyond the colon. Think of it as a kind of command center for your health. It’s involved in your immunity, metabolism, hormonal balance, cognition, and gene expression. Things that happen in your body or brain can often be traced back to the work of your gut microbes.
Disharmony and a lack of balance in your gut is known as dysbiosis and can lead to a loss of diversity of species which, in turn, can lead to a greater proportion of microbes that cause inflammation. When the wall of your colon is no longer protected by good microbes, this can lead to what’s called bacterial endotoxin entering your bloodstream. This bacterial endotoxin is produced by the likes of E. coli and Salmonella. Although the resulting inflammation can be quite low-grade it can also lead to life-threatening sepsis and even organ failure. It’s also linked to autoimmune diseases, obesity, coronary artery disease, type-2 diabetes, Alzheimer’s, and many other diseases. Bad news indeed.
Key idea 2: Overfed, undernourished, and hyper-medicated.
Kristen was one of Dr. B’s patients. Struggling with chronic abdominal pain and diarrhea for years, she was overweight, anxious, depressed, took antibiotics three or four times a year for sinus infections, and had migraines and polycystic ovary syndrome. She was taking “shed-loads” of medicines. She’d eliminated gluten and beans from her diet as she thought she had a sensitivity to them and had also tried following a Paleo diet. But nothing worked. She was now considering switching to a Keto diet to try and lose weight.
Kristen’s not alone. A massive 72 percent of Americans are overweight with 40 percent carrying an extra 14 kilos or more around their waists and hips. Alarmingly, 60 percent of Americans over the age of 19 are on prescription drugs and in the last 12 years, the number using five or more drugs has doubled. Life in the twenty-first century has led to us experiencing problems associated with being overfed, undernourished, and hyper-medicated. We’re simply destroying our gut and our health.
Dr. B sees many Kristens at his clinic – patients with irritable bowel syndrome, acid reflux, chronic diarrhea, abdominal pains, wind and bloating, and constipation in various combinations. Some are also experiencing side effects from the medications they’re taking. Others have a hormonal balance, have gained weight, have an autoimmune disease, have a mental illness, have heart problems, diabetes, or any one of a plethora of associated concerns. Many of these problems are associated with the patient’s lifestyle.
The use of prescription drugs – especially antibiotics – decimates our gut microbiota. For example, a five-day course of ciprofloxacin kills off around one-third of gut bacteria! Some of the bacteria species recover in just four weeks. Others don’t even reappear after six months. And with some drugs, the effect is even more evident: four years after taking them, the bacteria still haven’t recovered.
When it comes to diet, according to the US Department of Agriculture, an average American obtains approximately 32 percent of their calories from animal sources, 57 percent from processed plants, and a mere 11 percent from wholegrains, fruit, veg, nuts, and beans.
Diets that include high animal protein content are associated with increased numbers of the bad inflammatory microbes whereas plant protein actively encourages the good anti-inflammatory species and suppresses the destructive ones. Is it any wonder, then, that in the five regions of the world where people live longer than the rest of us, the populations have diets that are at least 90 percent plant-based with an emphasis on seasonal fruits, veg, beans, nuts, and wholegrains?
And we shouldn’t forget sugar and refined carbohydrates. A staggering 69 kilos of sugar are, on average, consumed by Americans and 4.5 kilos of highly refined grains every year. Most of the fiber has been stripped away from these which means they’re rapidly absorbed in the intestine rather than digested slowly. This leads to a loss in diversity of our gut microbes and a rise in carbohydrate-loving inflammatory bacteria.
When it comes to all the preservatives, additives, and colorants in processed food, would you be surprised to learn that they may be destroying our microbes, too? Many of them most certainly are, and the effects of a staggering 99 percent haven’t even been studied.
The solution to all of these problems? We need to get to the root cause of the problem not treat the symptoms. You’ve probably guessed it already: what we need to do is heal our guts.
Key idea 3: Keeping your gut healthy.
Would you be surprised to learn that if you want to heal your gut and keep it healthy you need to start with fiber? The reason is that fiber is amazingly good for your gut microbiota. In fact, it’s probably the most powerful solution to restoring the health of your microbiota. Right now, though, most people are completely fiber starved – less than 3 percent of Americans get their recommended minimum daily intake. That means 97 percent are walking around with a dietary-fiber deficiency!
Fiber is a complex carbohydrate that comes from plants. They have a monopoly on this food source. You’ve probably been taught that the fiber you eat goes in, and basically, comes back out again unchanged. In actual fact, that’s way too simplistic. Your microbiota contains more than 60,000 enzymes that are capable of processing fiber as opposed to your own measly 17 which can break down some complex carbs, but not fiber. And what happens when fiber is broken down is that short-chain fatty acids or SCFAs are released.
These SCFAs make your colon more acidic which very importantly prevents the growth of inflammatory bacteria. Additionally, the SCFAs suppress dangerous bacterial strains like E. Coli and Salmonella. Your dietary fiber feeds your healthy microbes, which produce more and more SCFAs in a virtuous circle.
So what can you do to alleviate your dietary fiber deficiency? A quick trip down to the health food store to pick up some of those fiber bars should do the trick, right? Well, perhaps unsurprisingly, no. What you really need to do for your gut microbiome to be healthy is to diversify your plant intake, or “eat the rainbow.” You should also aim for your diet to be at least 90 percent plant-based.
Dr. Rob Knight – or as Dr. B likes to call him, “the god of gut health” – found that for maximum gut microbial diversity, you should really be eating 30 different plants each week. That’s not as impossible as it might sound. The acronym F GOALS can help you remember what you need to eat. Each letter of the acronym represents a fiber-fueled food group.
F is for fruit and also for fermented foods. Don’t worry about the sugar in fruits – it’s not your enemy as it’s not processed, and besides, fruits are packed with vitamins, minerals, phytochemicals, and, of course, fiber. For fermented foods, try some sourdough bread, sauerkraut, tempeh, kimchi, miso, and kombucha.
G is for greens and wholegrains. Greens such as kale, spinach, arugula, bok choy, and romaine are packed with nutrients. And when it comes to grains, you can consider them as being the foundation of your healthy gut due to their high fiber content.
O is for Omega-3 super seeds such as flax, chia, and hemp. Both omega-3 and omega-6 are needed in your diet as your body can’t make them itself. But omega-6 is usually plentiful enough and the seeds and walnuts will provide you with the omega-3 you need.
A is for aromatics which include onions, garlic, shallots, and leeks – all very flavorsome and full of nutrients. Add in some nutrient-dense fresh herbs too, like basil and chives.
L is for legumes, which are both healthy and cheap. Another foundation for your healthy gut due to their high fiber content.
S is for sulforaphane which is found in cruciferous vegetables such as broccoli, sprouts, kale, cabbage, and cauliflower. Sulforaphane is known to protect us from some cancers, is a powerful antioxidant, and may also help with some other conditions such as Parkinson’s and Alzheimer’s. It’s also known to help with anxiety and depression amongst many other benefits.
And as a bonus, there are two more S’s. The first bonus S is for ’shrooms – mushrooms, which contain nutrients that are known to strengthen the immune system and help protect against cancer. In particular, eating one button mushroom per day reduces the risk of breast cancer by 64 percent. And the second bonus S is for seaweed which is high in fiber and contains nutrients not found in land plants.
You should also note that combining many plants can create a powerful synergistic effect. For instance, kale and lemon. Kale’s a great source of iron, but it’s what’s called “non-heme” and is less bioavailable than the iron you can get from meat. Although “heme-iron” from animals is more bioavailable, it’s also more inflammatory and associated with heart disease, colon cancer, and type-2 diabetes. Adding vitamin C from the lemon to the kale greatly increases absorption of the iron. The benefit to you is a source of iron without the increased risk of heart disease, colon cancer, and diabetes!
So by now you know some of the benefits of increasing the fiber in your diet and how you can do that, but here’s one final tip to ensure you maintain a healthy gut microbiota: share your microbes! Meet other people. Spend time with them. Shake their hands or give them a high five. And if you’re with your partner and the mood is right, share a kiss. Yes, it’s an expression of love, but what you’ll also be doing is exchanging 80 million microbes with each other!