By Dr. Mercola

Dietary fiber is at the heart of what archeologists have found at digs from the Paleolithic era. Fiber promotes better health by improving the health of your gut microbiome, or the 100 trillion or so bacteria that live in your intestinal tract and help regulate your immune system.

Very few people eating a Western diet get the recommended 30 to 35 grams of fiber per day, and that is well below the estimated 100 grams per day that your ancestors were eating.

Without adequate amounts of fiber, the beneficial bacteria in your gut begin to starve, starting a downward spiral in your health and wellness. From the day you are born until the day you die your health is dependent upon the variety and health of the bacteria living in your gut.

What Your Ancestors Ate Can Improve Your Health

Although most archeological digs from the past completely ignored fossilized bowel movements from the Paleolithic era, researchers are now discovering the important links between the health of these individuals and what they ate.

The fossilized Paleopoo, as it has become known, is an incredible storehouse of information about the plants and food types eaten centuries ago.

The types of food found in fossilized human excrement undeniably demonstrate that, for at least 99 percent of human existence, the gastrointestinal tract has been home to a high-residue diet of plant material, also known as fiber.

Role of Fiber in Appetite Control

Taking a scientific perspective on the types of foods most naturally digested and used by a mammal, researchers measured and compared both the functional body size and the area of absorptive mucosa in the gut.

When mapped out, mammals that eat mostly fruit and those that eat mostly foliage and green plant material fall along distinct lines.¹

Interestingly, when the same comparison of functional body size to absorptive mucosa of the intestinal tract is measured in humans, the results reveal we are more naturally frugivores, or mammals that more naturally survive on fruit, although I would still caution most people against eating too much fruit.

The amount of fiber you consume has significant impact on your health and wellness.² For instance, eating close to 100 grams of plant-based fiber meant eating a diet largely consisting of low-energy, low-calorie foods for those living during the Paleolithic era.

This helped control the appetite. One hypothesis for the increased number of individuals who suffer from obesity today stems from a lack of appetite control the low-fiber western diet perpetuates.³

Your Gut Flora Metabolizes Fiber Into Short-Chain Fatty Acids

Fiber is metabolized by your gut flora into short-chain fatty acids, which bind to and activate receptors on the surface of the cells, altering your metabolism.

Non-digestible complex carbohydrates, or insoluble fiber, can activate the receptors on fat cells that increase the amount of leptin secreted. This hormone helps to stabilize your blood sugar and reduce your appetite.⁴

Authors from the Department of Investigative Medicine at the Imperial College London hypothesized fiber and free fatty acids play a role in the production and maintenance of energy in your body.

Until diets changed to include processed foods and higher amounts of meat, you were likely to enjoy a high-fiber meal virtually every time you sat down to eat.

This resulted in the production of short-chain fatty acids that activated cell receptors and triggered the release of hormones. This activation reduced your appetite, which also reduced your food intake.⁵

Once the fiber had been digested and expelled, the amount of fermentation in your colon and production of short-chain fatty acids declined. This triggered a reduction in the production of specific hormones, which in turn triggered your appetite. And the cycle repeated itself once more.

However, in the standard western diet, the amount of fiber is greatly reduced and you no longer get signals to reduce your intake. Instead, the signal to keep eating is produced and your caloric intake skyrockets.

Problems With Low-Fiber Diets

What you eat has an impact on your daily health, but it also has an impact on the health of your children and your grandchildren.

In a study published in Nature, researchers looked at the microbiome of mice over several generations and found those mice fed a low-fiber diet suffered from a reduction in the variety of microbes in their intestines, as did their children and their grandchildren.⁶

Although the problem was compounded over generations when the mice were bred on a low-fiber diet, researchers found the bacterial variety and strength appeared to improve when the mice were once again fed a high-fiber diet.

However, the strength of the recovery of bacteria was reduced from one generation to the next.⁷ Low-fiber diets do more than damage the variety of bacteria in your gut and the microbiome of your children.

The Many Health Benefits of Fiber

Fiber fuels the beneficial bacteria to produce short-chain fatty acids, regulating your immune system and your appetite control. The products of metabolism from the beneficial bacteria feed the cell lining in your intestinal walls, reducing the potential for leakage of food molecules into your body.

Also referred to as leaky gut, this invasion of molecules not meant to be inside the sterile environment of your body increases the potential for allergic reactions and may predispose your child to neurological disorders.

It has also been associated in research studies with obesity, inflammatory bowel disease, celiac disease, autoimmune disorders, type 1 diabetes, cardiovascular conditions, chronic depression and chronic pain.⁸

On the other side of the same coin, eating a diet high in fiber can help reduce the potential for suffering from these very same diseases and some cancers, stroke and type 2 diabetes.

Fiber improves your skin health, reduces your risk of diverticulitis and helps stabilize your blood sugar. In fact, research points to the fact that a diet rich in soluble fiber can reduce your chances of death from any cause.⁹

How Much Fiber Should You Eat?

According to the Food Research Group of the U.S. Department of Agriculture, the average male American eats 18 grams of fiber per day and the average female 15 grams.¹⁰ 

The U.S. National Library of Medicine reports that the recommended amount is a range between 20 and 35 grams per day, and the American Heart Association recommends between 25 and 30 grams of fiber per day.^11,12 I believe about 25 to 50 grams of fiber per 1,000 calories consumed per day is probably a better goal.

Although also containing fiber, grains will break down in your body as sugar, driving your insulin and leptins levels higher. This increases your risk of obesity and diabetes. The majority of your fiber should come from vegetables, not grains. Soluble fiber, or fiber that is easily dissolved in water, is found, for example, in cucumbers, berries, nuts and beans.

This type of fiber helps to slow down your digestion, helping you to feel fuller longer. Organic psyllium is one of the best sources to radically increase your intake of soluble fiber. I shoot for 50 grams of fiber per 1,000 calories consumed daily and personally take about 6 tablespoons of organic psyllium a day, which supplies 75 grams of soluble fiber, about half of my daily fiber intake.

Insoluble fiber can be found in dark green leafy vegetables, carrots and celery, for instance. It adds bulk to your stool and doesn’t dissolve at all. Many of the fruits and vegetables in your diet are rich in soluble and insoluble fiber, both of which are necessary to the health of your gut. The discovery of the link between short-chain fatty acids and cell receptors signaling hunger has excited the pharmaceutical industry.

On the horizon are drugs that may be able to alter those cell receptors and reduce your hunger. These pharmaceutical solutions will likely come with a list of side effects and dangers to your health. Instead, it’s time to eat a diet high in fiber to enjoy the benefits without the additional risks of popping pills.