Personal Growth
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Personal Growth

Fibre — the anti-nutrient

When we consider the nutritional benefits of food, we think about the vitamins, minerals and nutrients they contain. We think about components in the food that nourish the body. Fibre is completely different. The key to understanding fibre’s effect is to realize that the benefit lies not as a nutrient, but as an anti-nutrient. If you have a disease of excess nutrients, as in obesity or type 2 diabetes, then anti-nutrients are useful therapeutic options.

In contrast to most food, fibre has the rare ability to reduce absorption and digestion. Fibre subtracts rather than adds. In the case of sugars and insulin, this is good. Soluble fibre reduces absorption of carbohydrates, which in turn reduces blood glucose and insulin levels. In one study, type 2 diabetic patients were given liquid meals containing 55% carbohydrates with or without the addition of dietary fibre.

Fibre reduced both the glucose and the insulin peaks, despite consuming exactly the same amount of carbohydrates. Fibre acts as an anti-nutrient. Because insulin is the main driver of obesity and diabetes, reduction is beneficial. In essence, fibre acts as a sort of ‘antidote’ to the carbohydrate, which, in this analogy, is the ‘poison’. Carbohydrates, even sugar, are not literally poisonous in normal amounts, but this comparison is useful to understand the effect of fibre.

It is no coincidence that virtually all plant foods, in their natural, unrefined state contains fibre. Mother Nature has thus pre-packaged the ‘antidote’ with the ‘poison’. This is how traditional societies may eat diets high in carbohydrate without evidence of obesity or Type 2 Diabetes. The Okinawans, for instance, base their diet upon the sweet potato, and consume an estimated 80% of their calories as carbohydrate. High fibre protects against obesity. Until recently, they were one of the longest-lived peoples on earth. The Kitavans of New Guinea followed a diet estimated to be close to 70% carbohydrate with no evidence of ill health. The one critical difference is that these carbohydrates are all unrefined. The toxicity lies in the processing.

Western diets are characterized by one defining feature. It is not the amounts of fat, salt, carbohydrates, or protein that distinguishes the Western diet from all other traditional diets in the world. It is the high levels of processing of foods. Typical Western supermarkets are filled with highly refined foods in boxes, cans or frozen — refined carbohydrates, but also refined oils and refined proteins. Traditional Asian markets are instead full of fresh meats and vegetables. Many Asian cultures buy fresh food daily so processing to extend shelf life is neither necessary nor welcome. North Americans will buy groceries for weeks or even months at a time. The large volume retailer Costco, for example depends upon this.

Fibre and fat are two key ingredients removed in the refining process. Fibre is removed to change the texture, and make food taste ‘better’. However, the satiating effect is lost. When fibre bulks up the foods we eat, this activates stretch receptors in the stomach that signal the body (via the vagus nerve) that we should stop eating. When you eat too much at the buffet, all the food is not yet digested and sitting in your stomach. So, your body doesn’t yet have any idea how many calories of food you’ve eaten. But your stomach is overdistended like a ripe melon, and you feel full and perhaps slightly sick/ nauseated.

Natural fats are removed to extend shelf life since fats tend to go rancid with time. For example, white flour has virtually all the natural fibre and fat removed during processing. This exposes us to the full danger of the naked carbohydrate, which causes the ensuing high insulin levels. The ‘poison’ is ingested without the ‘antidote’. The protective effect of the fibre and fat are removed.

Where whole, unprocessed carbohydrates virtually always contain fibre, dietary proteins and fats contain almost no fibre. Our bodies have evolved to digest these foods without the need for fibre. The ‘antidote’ is unnecessary without the poison. Here again, Mother Nature has proven herself to be far wiser than us.

Natural foods have a balance of nutrients and fibre that we have evolved over millennia to consume. The problem is not with each specific component of the food, but the overall balance. For example, suppose we bake a cake with a balance of butter, eggs, flour and sugar. Now we decide to remove completely the flour and double the eggs instead. The cake tastes horrible. Eggs are not necessarily bad. Flour is not necessarily good, but the balance is off. The same holds true of carbohydrates. The entire package of unrefined carbohydrates, with fibre, fat, protein and carbohydrate is not necessarily bad. But removing everything except the carbohydrate may destroy the balance and make it harmful to human health.

Removing protein and fat may lead to overconsumption. There are natural satiety hormones (Peptide YY, cholecystokinin) that respond to protein and fat. Eating pure carbohydrate does not activate these systems and leads to overconsumption. For example, a glass of orange juice requires 4–5 oranges. It is difficult to eat 4–5 oranges, with all the associated pulp. However, by only drinking the carbohydrate portion, and discarding the rest, you may over-consume that carbohydrate. Another problem arises because the relatively pure carbohydrate results in increased speed of digestion. The rapid rise in blood glucose will result in the rapid rise in insulin.

The toxicity lies not in the food, but in the processing.

Nutritionism, where foods are considered based on their macronutrient content hid the dangers of refining for many years. Whole grains, vegetables as well as sugar were all considered similar because they happened to all be classified as carbohydrates. But the refined and unrefined carbohydrates were not alike.

Fibre and Type 2 Diabetes

Both obesity and Type 2 Diabetes are diseases caused by excessive insulin. Insulin resistance develops over time, with persistently high insulin. If fibre can protect against elevated insulin, then it should protect against Type 2 Diabetes. That is exactly what the studies show.

The Nurse’s Health Studies 1 and 2 monitored the dietary records of thousands of women over many decades. Overall, the risk of Type 2 Diabetes increases as the glycemic index increases. This is no surprise. This study was also able to confirm the protective effect of cereal fibre intake. Women who ate a high GI diet but also ate large amounts of cereal fibre are protected against Type 2 Diabetes. In essence, this diet is high in ‘poison’ but also high in ‘antidote’ at the same time. The two cancel each other out with no net effect. Women who ate a low GI diet (low ‘poison’) but also low fibre (low ‘antidote’) was also protected. Again the two cancel each other out.

But the deadly combination of a high GI diet (high ‘poison’) and a low level of fibre (low ‘antidote’) increase the risk of Type 2 Diabetes by a horrifying 75%. This is the exact effect of processing carbohydrates — increased glycemic index and decreased fibre.

The massive Health Professionals Follow-up studied 42,759 men over 6 years, with essentially the same results. A high GL and fibre diet confers no extra risk of type 2 Diabetes. A Low GL and low fibre diet also has no increased risk. But the diet high in glycemic load (poison) and low in fibre (antidote) increases the risk of disease by 217%. Yikes! The Insulin Resistance Atherosclerosis study confirms that fibre is an important protective factor against insulin resistance.

The Black Women’s Health Study demonstrated that a high glycemic index diet was associated with a 23% increased risk of Type 2 Diabetes. A high cereal fibre intake, by contrast was associated with an 18% lower risk of diabetes.

One of the key steps in weight loss is the addition of fibre. Even better, do not remove fibre from the natural foods that contain it.

The toxicity lies in the processing.

Carbohydrates in their natural, whole, unprocessed form, with the exception of honey, always contains fibre. This is precisely why junk food and fast food is so harmful. They are the very definition of highly processed foods. The processing of foods and addition of chemicals changes the food into a form that our bodies are not evolved to handle. That is exactly why they are junk.



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Dr. Jason Fung

Nephrologist. New York Times best selling author. Interest in type 2 diabetes reversal and intermittent fasting. Founder