Have you ever wondered why it’s important to have fibre in your diet? Even if you haven’t, you might find some eye-openers in this article.
Let’s start with a question. Do you look at food labels? Have you noticed what’s listed there? Carbohydrate, protein and fat are listed because the government has made recommendations about the proportions of these macronutrients for a healthy diet. And consumers like to know the breakdown. Saturated fat is listed because too much saturated fat has health implications. Sugar is listed because that also has health implications. And we all know that too much salt, which is also listed, is associated with high blood pressure.
But why is fibre on there? Well, it’s good for you, but does it really deserve its place on food labels? You probably make conscious decisions about your food choices based on their content of saturated fat, salt and sugar. You probably also make food decisions based on the protein, carbohydrate and fat content. But do you make conscious decisions about your food based on how much fibre is in it?
You probably should. If there is one food-label related recommendation I would make over and above reducing salt, saturated fat and sugar, it would be to get more fibre. In my view, increased fibre intake has enormous and broad health benefits.
Below I tell you all about fibre and why it’s my number one ingredient in a healthy diet.
What is fibre?
You can find science-based definitions of dietary fibre.
The definition boils down to fibre being
- Derived almost entirely from plants.
- Composed of relatively long molecules.
- Not digested in the part of our gut where we digest most of the other stuff.
On this last point, around 85% or carbohydrates, 66-95% of proteins and 100% of fats are absorbed before the large intestine, i.e., in the stomach and small intestine. Fibre passes on through to the large intestine, or colon.
Types of fibre
Fibre has traditionally been categorised as either soluble or insoluble. Cellulose, hemicellulose and lignin are insoluble whereas pectins, oligosaccharides, gums and waxes form gels in water and are considered soluble to varying degrees. The solubility affects the thickness of the resulting gel that is formed.
If you’ve ever used ‘Fybogel‘ and left it to stand after adding the water, you’ll know how soluble fibre behaves in water. Or if you cook oats, you’ll notice how it gets thick and sticky – that’s the soluble fibre, and it’s one of the properties of fibre that make oats a healthy choice.
The characteristics of fibre influence its physiological properties. For example,
- Particle size influences hydration and fat storage within the fibre gel.
- The surface characteristics of the fibre impact enzyme binding and microbe activity.
- The solubility affects the trapping of nutrients and subsequent digestion and absorption.
- Fibre can impair mineral absorption due to binding.
- Soaking and cooking can alter the structure of fibre and its characteristics.
- Milling removes most of the fibre, disrupts cell wall structure and changes particle sizes.
So you start to get the idea that there is more to fibre than meets the eye.
I’m going to list some of the benefits of fibre, then go into more detail on some of them. For now, though, be aware that both soluble and insoluble fibre have benefits and most foods contain both, so don’t worry about getting enough of a particular type.
Most fibre containing foods have around one-third soluble and two-thirds insoluble fibre. But because there are lots of different types of fibre within those two categories, and each has benefits for your health, you should try to get a varied diet including different types of fruit, vegetables, pulses and whole grains. Aim for at least 30g of fibre daily from various sources.
Ok, so here’s the list.
The soluble fibre gel traps carbohydrates and slows their passage into the bloodstream. That means you get a slower rise in blood sugar and a more moderate insulin response.
Carbohydrates are not the only thing that fibre traps. It can trap carcinogens and thereby reduce the risk of them causing cancer.
Reduces the risk of diabetes
Slower digestion will have a positive impact on blood sugar and, you’d expect, diabetes. This is indeed the case.
In one study, women who consumed 26g per day of fibre had a 22% lower risk of developing diabetes than those consuming 13g per day. The same study discovered the risk of developing diabetes was inversely associated with total fibre intake and consumption of whole grains. In other words, as fibre and wholegrains go up, the risk comes down. It’s also dose-dependent, so the more fibre you have, the more it reduces the risk.
Interestingly, in that study, fibre from fruit and vegetables was not correlated to the risk of developing diabetes. It was fibre from whole grains that was most associated with a reduction in risk.
Also, in the same study, total carbohydrate was not associated with a reduction of risk, but the type of carbohydrate was strongly related. That means the glycemic index and glycemic load of a carbohydrate is an important consideration when constructing your meals.
You can understand why the occurrence of type 2 diabetes has risen when you consider how much of the western diet is composed of refined grains, devoid of fibre and high on the glycemic index. We have written before about the importance of carbohydrate in the diet and why, when attempting to lose weight, the mantra should be right carb, not low carb.
Fibre not only reduces the risk of developing diabetes; it can improve the condition for those who already have it. Fibre leads to improvements in blood sugar control and insulin response in both mild and moderate diabetics.
Reduces the risk of heart disease
One of the findings of studies is that fibre lower total and ‘bad’ cholesterol. That’s got to be good for reduced artery furring and subsequent risk of a blockage. Soluble fibre was shown to reduce both cholesterol and circulating fatty acids. As you’d expect, just from this fact, fibre has been shown to reduce the risk of Coronary Heart Disease (CHD).
In fact, reduction in risk of CHD is one of two health claims approved by the US Food and Drug Administration (FDA). The other is cancer – more on that below. Regarding CHD, they state that diets low in saturated fat and high in fruits, vegetables and whole grains have a decreased risk of leading to CHD.
One study concluded that, for every 10g of fibre added to a diet, the mortality risk of CHD decreased by 17-35%.
Because it adds bulk to your diet, fibre will help you feel full more quickly, and stay full for longer. That means you’ll eat less at meals and not feel the need to snack on unhealthy nibbles. If you’re a fast eater, consume the fibre rich foods on your plate first to make sure you get full quickly.
This is important for individual weight loss and across society for combating obesity.
Fibre can speed the passage of foods through the digestive system. That’s a good thing. For a start, it will alleviate constipation. But it also means that any nasty substances – carcinogens, for example – have less contact time with the wall of the digestive system and so less opportunity to harm you.
Increases levels of nutrients
Fibre comes from foods such as fruit, vegetables, whole grains and pulses. These are all nutritional powerhouses and packed with vitamins and minerals. If you make an effort to increase your fibre intake, you’re going to benefit from more health-giving goodies. More goodness, especially in the form of antioxidants, means improved ageing and a reduced risk of diseases such as cancer.
Studies have shown the correlation between fruit and vegetable intake and a reduction in large bowel cancer.
Stimulates beneficial fermentation
Fibre creates a pH environment just right for your microbes to ferment the fibre. Microbes produce beneficial short-chain fatty acids (SCFAs) that have anti-cancer properties and may reduce the risk of colorectal cancer.
I’m going to discuss in more detail the role of your gut bacteria on health, so read on.
Reduces the risk of cancer
This is the second fibre claim approved by the FDA. Fibre has been shown to reduce the risk of several types of cancer, including breast, small intestine and colorectal.
Did you spot how many times I mentioned cancer in the previous set of benefits? Those benefits give some insight into some of the mechanisms by which cancer can reduce the risk of cancer.
Fibre and your microbiome
You’re probably familiar with the idea that you have bacteria in your gut and that fibre feeds your good bacteria. But what do they do that is so good? Or is it just that they are not ‘bad’ and so don’t cause stomach upsets?
In fact, they are critical to our health. In her book ‘10% Human’, Allana Collen tells us how our microbes and evolved with us and how our physiology influences, and is influenced by, our microbiome. There are 1000s of species in the human intestine, each one with a different specialisation, and each one affecting the physiology not just of our intestines, but of our entire body. Through their actions, our microbes can influence the way we express our genes and ultimately impact our health, and even our behaviour.
We have evolved with them in a symbiotic relationship. They help us; we help them. How do we help them? By feeding them the right stuff, for a start. We’ve evolved with a diet that is much more fibrous than the current standard Western processed diet. And that fibrous diet has cultivated a selection of microbes that serve us well.
The more genes, the better!
Our microbes also provide a whole load of genes over and above our own set. And those genes can do things that we can’t. For example, they can digest cellulose and other fibre that we cannot, and they can supply us with beneficial by-products of that digestion. They can:
- Make vitamins such as folates, riboflavin and vitamin K.
- Neutralise harmful chemicals.
- Coat the gut lining with mucus to prevent the inappropriate passage of molecules either in or out.
- Crowd out or neutralise harmful organisms.
But equally, if we encourage species to thrive in the wrong proportions, or simply promote the wrong species, it can have negative consequences. The microbiome has been implicated in several modern disease states, including obesity, type 1 diabetes, multiple sclerosis, irritable bowel syndrome and even autism, to name a few.
Human digestion and the microbiome
Almost all ‘human’ digestion occurs before the large intestine, in the stomach and small intestine. 85% of carbohydrate, up to 95% of protein and all fats are absorbed before the large intestine. But you’ll notice 15% of carbs get through and almost all of that is dietary fibre and indigestible starches.
Beyond the small intestine – in the large intestine – there is limited human digestive capability. In that part of your gut, the number of microbes rises by orders of magnitude.
Somewhere between 10% and 30% of ingested energy ends up in the colon, available to the microbes there for fermentation. Those microbes help us to salvage the energy from these indigestible carbs and proteins. That’s a handy function, especially when calories are scarce.
The mercurial microbiome
Your microbiome can change rapidly in response to changes in diet, health, medications and calorie intake. Studies have shown that the microbiome can drastically change in as short a period as three days, following a reduction in calories. Another study in mice showed how switching from a low-fat, high fibre diet to a high fat, high sugar ‘Western’ diet altered the microbiome structure and metabolic function in a single day.
A responsive microbe community is good news and bad. You may be able to improve your digestion, bowel function and general health quite quickly by increasing your fibre content. On the other hand, it means you can’t afford to deviate too much or for too long from a healthy fibre rich diet.
The benefits of a healthy microbiome
Here are some of the benefits of a healthy microbe community:
- Regular bowel movements. If you want to cultivate a healthy microbiome, then you’ll need to consume lots of fibre, of course. But did you know that 70% of the dry weight of your poo is bacteria? More fibre, more microbes, more bulk for regularity.
- Good bugs crowd out nasty bugs. Or put more scientifically, beneficial microbes provide competition for, or neutralise, pathogenic organisms.
- Your gut bacteria provide useful end products, such as short-chain fatty acids (SCFA), vitamins, mucus and so on.
- Your microbes help salvage energy from otherwise indigestible fibre.
- A healthy microbiome is associated with better health – lower weight, improved cancer risk and better gut health, for example.
Prevention is better than cure
But the benefits of a healthy microbe community aren’t just about what they contribute; it’s also about what they prevent. For example, a healthy microbiome
- Prevents protein fermentation. If you eat too much protein and not enough carbohydrate to cultivate those beneficial bugs, it’s more likely that you’ll ferment protein in your colon. The by-product of this fermentation is the production of ammonia, indoles, phenols, sulphides, amines and thiols. These by-products have been linked to colon cancer and Crohn’s disease. Protein fermentation tends only to occur if there is insufficient fibre intake to encourage the good bacteria in sufficient numbers.
- Prevents chronic inflammation. Conditions such as type 2 diabetes and obesity tend to come with chronic low-level inflammation. This is thought to be caused by microbe-derived lipopolysaccharide (LPS). It is believed that a lack of healthy mucus-producing bacteria can allow LPS to pass from the colon into the bloodstream, where it can then impact our physiology and cause inflammation.
- Reduces the risk of cancer. Beneficial bacteria can neutralise hazardous molecules, prevent harmful reactions and provide cancer-fighting end products, such as antioxidants and short-chain fatty acids.
Short-chain fatty acids, particularly butyrate, acetate and propionate, are the main products of bacterial fermentation, and they have numerous benefits. For a start, acetate can provide us with energy. Propionate can inhibit cholesterol synthesis and has been shown to stimulate feelings of satiety, and so influence food intake. Butyrate is the preferred nutrient for the cells of the gut wall and is involved in a reduced risk of colon cancer.
A diet that has plenty of fibre will encourage more of the right microbes and more diversity. In turn, this will lead to the presence of a greater variety of enzymes that can produce different beneficial SCFAs.
Weight loss, fibre and your microbiome
Health is of paramount importance to us, but what we offer at Life Force Fitness is first and foremost a weight loss service. But, to be clear, we do not advocate unhealthy weight loss or faddy diets. That’s why we write blogs like this one. Healthy weight loss – that’s our thing. So with that in mind, it seems appropriate to include a section relating fibre intake to weight loss.
You probably knew this already, but a higher fibre intake is associated with leaner individuals. And there are lots of very good reasons why this is the case. Here are some:
Fibre helps you eat less
For a start, fibre is bulky; it will swell your stomach leading to feelings of fullness. What’s more, when fermented by your microbe allies, it increases production of the SCFA propionate and two hormones GLP-1 and PYY, all of which induce satiety. That means you’ll keep full for longer and not experience cravings.
Of course, eating more fibre means you’ll naturally reduce your intake of refined carbohydrates. That means you are less likely to develop poor eating habits consisting of regular ups and downs and hunger-induced sugary overconsumption.
Weight loss appears to have a dose-dependent relationship with fibre. In other words, the more you eat, the more you lose. One study found that for every 8 g increase in dietary fibre per 1000 kcal, participants lost 4.4lbs.
Another study on US men reported that for every 40g per day increase in whole grain intake, weight gain over eight years was reduced by 1.1lbs.
Fibre helps you absorb less energy
The ‘metabolisable energy’ (ME) of your food decreases with increases in fibre intake. What does ME mean? It means the total energy you consume minus that lost in your poo. So, in other words, you evacuate more ingested energy when you eat more fibre.
What’s more, the digestibility of fat decreases when fibre intake increases. And with increased transit times associated with fibre intake, there is less time to ferment and absorb energy from the colon.
Fibre encourages a ‘lean’ microbiome
The community of microbes in obese people is substantially different from that in leaner people. Does a different diet cause that difference, or does a different microbiome cause obesity? You’d think the former, wouldn’t you? But there is evidence it works both ways round.
There’s a school of thought that has observed the spread of obesity, tracing it from the Southern States of the US and tracking its spread, like a disease, throughout the rest of the world. A person’s microbiome can be transferred to other people who live in the same house. There’s a 175% greater likelihood of you being obese if you live with others who are obese. Is that simply a shared diet and shared habits, or does it have a lot to do with sharing an ‘obese’ microbiome?
In a study of probiotics, certain microbe species were shown to reduce the fat content of mice adipose tissue based on their ability to produce conjugated linoleic acid (CLA). Another study showed that the transfer of microbes from conventionally raised ‘fattened’ animals to germ-free animals resulted in dramatic increases in body fat levels and insulin resistance. Another study found that a particular microbe called Akkermansia muciniphila reversed high-fat diet-induced metabolic disorders such as fat gain, fat tissue inflammation and insulin resistance.
Your microbes contribute to your Resting Metabolic Rate
Your whole-body metabolism – calorie burn – is the sum of your own and your microbes’! How significant is this? Some calculations show that the gut microbes might contribute as much as 22% of the energy turnover of the average human. This is a lot more than is required to explain the obesity crisis. It could be an avenue of future research to look at ways in which your microbiome can contribute to your overall calorie burn.
In the meantime, if there is indeed a contribution from your microbes, your best bet is to feed a sizeable healthy community of them with good amounts of fibre-rich, healthful foods.
As always with the human body, the science of simple things turns out to be enormously complex. But I hope I’ve shown you that the benefits of a high fibre diet are varied and substantial.
If you’re trying to lose weight and you’re considering a diet that restricts fibre, such as the Atkins diet, please think again. It might get you a short term drop on the scales, but it could lead to longer-term health consequences.
Keep the carbs in your diet, but do ensure the carbs you choose are unrefined, fibre rich and packed with nutrients. You’ll get all the varied benefits of fibre, a better blood sugar and insulin response, a healthy diverse microbiome and lots of nutrients. If there’s one thing you change in your diet, make it to consume more fibre.