Most people, Americans in particular, need to eat more fiber. The evidence suggests a high-fiber diet can help manage your weight1 which impacts over two-thirds of the population. Even more importantly, researchers have discovered that short-chain fatty acids produced by bacteria that feed on plant fiber are major epigenetic communicators. In other words, they actually communicate with your DNA, thereby providing protection against a number of different diseases.2,3,4
Studies have also confirmed that high-fiber diets help reduce your risk of premature death from any cause5— a side effect linked to a reduction in chronic disease risk. When it comes to boosting your fiber intake, be sure to focus on eating more vegetables, nuts and seeds, not grains, as grains tend to promote insulin and leptin resistance.
Also, research confirms that in order to work, the fiber must be unprocessed.6,7 Processed supplement fiber such as inulin powder does not provide gut bacteria with what they need. It’s far better to use a supplement that is processed from sunchokes (Jerusalem artichokes) that inulin is typically extracted from.
Organic whole husk psyllium is a great fiber source, as are sunflower sprouts and fermented vegetables, the latter of which are essentially fiber preloaded with beneficial bacteria. Flax, hemp and chia seeds are other excellent fiber sources.
Different Types of Fiber
There are two main types of dietary fiber: soluble and insoluble. Ideally, you need both on a regular basis. Digestive-resistant starches can be considered a third type of fiber, differentiated from insoluble fiber by the fact that many of their benefits result from the fermentation process that occurs as they move through your large intestine.8
• Soluble fiber, found in cucumbers, blueberries, beans and nuts, dissolves into a gel-like texture, helping to slow down your digestion. This helps you to feel full longer, which can help with weight control. Soluble fiber also hinders the breakdown and digestion of dietary cholesterol, which can help normalize your cholesterol level.
Likewise, it slows down the rate at which other nutrients are digested, including carbs, so they're not as likely to raise your blood sugar. Some foods rich in soluble fiber also help feed good bacteria in your gut.
• Insoluble fiber, found in foods like dark green leafy vegetables, green beans, celery and carrots, does not dissolve and stays basically intact as it moves through your colon. By adding bulk to your stool, it helps food to move through your digestive tract more quickly for healthy elimination.
Insoluble fiber is also sometimes called roughage, a term that, to a degree, describes its function. As it moves through your colon, it helps move along food particles that may tend to adhere to the sides. Food that remains stuck to your colon may cause bloating, pain and constipation, as well as other problems.
• Digestive-resistant starch. To this we may also add digestive-resistant starches, found in chilled, cooked potatoes,9 seeds, tapioca starch and unripe tropical fruits such as banana, papaya and mango. These naturally occurring resistant starches are basically low-viscous dietary fibers. Like insoluble fiber, digestive-resistant starch is not broken down as it travels through your digestive tract and therefore adds bulk to your stool. They’re also powerful prebiotics.
By slowly fermenting in your large intestine, they feed gut bacteria that support optimal health. Best of all, they don't spike your blood sugar the way the completely ripened fruit would do, so they're also much more likely to improve insulin regulation.10,11
Why Add More Fiber to Your Diet?
Dietary fiber basically slows down your digestion and fills up space in your stomach and intestines, both of which will help manage your portion sizes and help you feel fuller longer. But that’s hardly the sole reason to eat more fiber. More importantly, all three types of fiber help nourish a healthy gut microbiome and serve to decrease your risk of several health-compromising conditions, including heart disease and diabetes, along with a number of gut-related health problems.
One study showed that for every 10 grams of fiber you add to your overall fiber intake, you lower your risk for all-cause mortality by 10 percent.12 Another study13 published in 2014 produced similar results. Here, every 10-gram increase of fiber intake was associated with a 15 percent lower risk of mortality, and those who ate the most fiber had a 25 percent reduced risk of dying from any cause within the next nine years compared to those whose fiber intake was lacking.
A report14 funded by the Council for Responsible Nutrition Foundation found that were U.S. adults over the age of 55 with heart disease to take psyllium dietary fiber daily, it could save nearly $4.4 billion a year. These cost savings are largely related to an 11.5 percent reduction in coronary heart disease-related medical events.
Researchers have also found that low-fiber diets can have generational effects by passing on an impoverished gut flora to your children. The study15,16 in question found that low-fiber diets cause “waves of extinction” in the gut of mice, and that this altered gut flora gets passed on to offspring. As much as 60 percent of the microbe species suffered severe decline in the low-fiber group.
In some cases, their numbers remained low even after the mice were again given high-fiber meals, suggesting it can be quite difficult to repopulate certain gut bacteria once they’ve been severely diminished. Each successive generation of offspring in the low-fiber group also ended up with less diversity than their parents, suggesting the problem is compounded over generations.